A Waste of a Storm System for Southeast Snow Lovers

Snow accumulations this weekend

As a nasty, cold rain falls, have you ever pondered what would’ve happen if all of that rain had been snow? As a snow-lover born and raised in the Southeast, it’s hard not to get a little frustrated when one or two minor yet significant ingredients don’t come together at the right time to bring a few inches of snow. We snow lovers usually upset those who dislike snow by talking about how much we want snow. It’s not like we can help that we like snow. When snow accumulates in the South outside of the mountains, it usually melts within a day or two anyway. Wow, I’m saying the word snow a lot, aren’t I?

Weekend Setup

Let’s talk about why a number of you will be disappointed by what happens late this weekend into early next week. A shortwave will continue pushing across the southern and central Plains today. This feature has induced the development of a surface low, now sitting on the Kansas/Missouri border. It will continue on a northeastward trajectory toward the Great Lakes region into early to mid-weekend. As a result, a cold front will push down to the Gulf coast from Texas to the Florida panhandle. This front will bring colder temperatures by mid to late weekend to most of the South, outside of areas at/near the Southeast coast and Florida.

Projected surface conditions on Sunday morning, December 13, 2020

A secondary shortwave will move into the Pacific Northwest today. Early to mid-weekend, the wave will trek southeastward across the Rockies, into the Four Corners region, and then eastward into the Southern Plains. As with the first shortwave, a surface low will develop. This feature, however, will move across the lower Plains and then across the Gulf coast states late Sunday into Monday. And, here’s the thing. This low will move into the Southeast behind the cold front. This sort of setup favors winter storms impacting parts of the Mid-South, Southeast, and Tennessee. Yet in this case, snow will fall across the Cascades, much of the Rockies, the Southern Plains, and even into parts of the Mid-Atlantic, but NOT across the Southeast and most of Tennessee.

12z NAM’s projected snowfall accumulations through Monday afternoon (using 10:1 snow/rain ratio)

Why Some Will Get Snow When Others Won’t

The problem is the lack of cold air. Though the cold front will have already pushed through much of the Southeast, there won’t be enough time for sufficiently cold air to spill into the region. Earlier in the week, the European model had a couple of runs that indicated a winter storm would occur, but at the time, it depicted a stronger system. In this case, the low would’ve advected sufficiently cold air as far south as Tennessee, northern Mississippi and Alabama, far northern Georgia, and central North Carolina. Given the projected surface low track, Atlanta would’ve likely missed out anyway, but places like Memphis, TN; Nashville, TN; Chattanooga, TN; Huntsville, AL; Birmingham, AL would’ve had a significant winter event. Oh well!! Instead, get ready for more rain over the weekend.

Projected rainfall amounts from Sunday evening to Monday evening

Comments on 2020-21 Winter Forecast

Throughout much of this winter, the coldest air will have a tendency to remain locked away in western/central Canada and Alaska, oftentimes only spilling into northern parts of the U.S. (check out our winter forecast for specifics). Despite this fact, much of Tennessee and the northern third of the Southeast should have a few decent chances to get wintry weather this season. However, the rest of the Southeast likely won’t fare as well. The currently active pattern across the Southeast likely won’t persist much past December, and a tendency for above average temperatures will lower those snow/ice probabilities further.  

Christopher will post an article later today on potential snowfall accumulations for this Sunday and Monday across the Southern Plains and Mid-Atlantic.

Download Firsthand Weather’s Southern Snow App Today

Curious to know how much snow you will receive? Download Firsthand Weather’s newFREE app: SOUTHERN SNOW (Link). This app has you covered this winter and will let you know how much snow is in your forecast and notify you of any winter weather alerts for your area!

Download Southern Snow

Active Pattern To Bring Anomalous Warmth East And Heavy Precipitation from Four Corners to New England

When a ridge of high pressure stubbornly sits over the same region, it generally brings dry weather and above average temperatures. A ridge causes sinking motion in the atmosphere, preventing deep clouds and precipitation from developing. However, along the edges of the ridge, or what I sometimes refer to as the periphery of the ridge, embedded disturbances in the flow will induce precipitation, some of which can be moderate to heavy. Notice the latest 72-hour rainfall totals (March 14-17 at 8am ET). Aside from localized convection, Florida and areas near the Gulf and Southeast coasts have remained dry through the period, due to sinking motion caused by the ridge. On the other hand, parts of the Southern Plains, Mississippi Valley, Tennessee Valley, Ohio Valley, and Mid-Atlantic have experienced wet conditions along the ridge’s periphery.   

Rainfall totals over the last 72 hours (March 14-17 at 8am ET)

Another hotspot for heavy precipitation over the last few days has been across California and other western regions. An upper-level low pressure system developed this past weekend and continues to slide southeastward along the West Coast. When a low becomes detached from the main flow, they tend to meander for a while and not move all that much. Eventually though, they get absorbed back into the main flow and make their way eastward/northeastward, which will happen by mid-week.

The evolution and track of the upper-level low will have an effect on the weather for the remainder of the week nationwide. As the feature approaches the Four Corners region on Wednesday, precipitation will develop and spread across the region. Mountainous regions across the Colorado Plateau have a high probability of picking up at least 4 inches of snow from Wednesday into Thursday, but accumulations will likely exceed at foot across the higher elevations. As the upper low moves northeastward into Colorado and then into the central Plains on Thursday, a surface low will develop just east of the Colorado Rockies. As the surface low moves across the central Plains and into the upper Midwest/Great Lakes region, a swath of accumulating snow will fall from Nebraska and the Dakotas into the far upper Midwest on Thursday going into early Friday.

The probability of snowfall accumulations exceeding 4 inches from late Wednesday into late Thursday

Also, the eastward progression of the upper low will amplify the ridge across the eastern U.S., which will drive up the temperatures substantially as the rest of the week progresses. Across the Southern Plains, Mid-South, Southeast, and Tennessee, temperatures will surge well into the 70s and into the 80s across parts of the area on Wednesday. The first round of moderate to heavy rain/storms associated with an embedded weaker disturbance will move across parts of the Southern Plains, Missouri Valley, Ohio Valley, and Kentucky/northern Tennessee on Wednesday. The rain will continue spreading northeastward into the Mid-Atlantic and lower half of New England later Wednesday into early Thursday. Some accumulating snow could fall across higher elevations regions in New England. The warm front will continue advancing northward on Thursday and Friday, expanding the warmth as far north as the Ohio Valley and Mid-Atlantic on Thursday and into the Great Lakes region/New England by late Thursday/early Friday. In fact, temperatures will probably increase overnight going into Friday across part of the Great Lakes region and western New England. Another round of rain/storms will move across similar regions in the Thursday/Friday timeframe ahead of an approaching cold front.

Green/yellow shaded regions have the high probability of having flash flooding on Wednesday or Wednesday night
Green/yellow shaded regions have the high probability of having flash flooding on Thursday or Thursday night

The cold front will sweep across most of the eastern U.S. by Friday/early Saturday, which will briefly usher in winter-like temperatures. Unfortunately, the cold front will take it sweet time fully moving through the Southeast; thus, expect Saturday to bring another day of 70s/80s across most of the Southeast outside of the Tennessee Valley and parts of the Mid-South. In fact, the cold front will likely stall out somewhere close to the Gulf Coast and northern Florida, so Florida and possibly surrounding regions just north may not experience much relief from the anomalous warmth.

Projected departure from average temperatures on Saturday morning

Major Early-Season Winter Storm Becoming More Likely But Uncertainty Remains

In my last article, I primarily discussed the big picture and detailed the regions that could be at risk for wintry precipitation this weekend. We’re now getting to the point that we can begin discussing precipitation-type; however, we won’t be releasing accumulation maps until later in the week. Let’s get right into things.

The surface low will develop and trek across southern Texas Friday into early Saturday. This feature will strengthen as it moves across the lower Gulf coast states over the weekend and then off or along the East Coast late weekend/Monday.

The models have recently begun to project another shortwave feature swinging across the Great Plains and then phasing (combining) with the southern stream system moving eastward from California. This could result in a stronger surface low, especially as it approaches the East Coast, and given these trends, I fully anticipate that most of the southern right quadrant of the U.S. will receive heavy precipitation this weekend. The Weather Prediction Center graphic below shows this quite well in their days 4-5 forecast that covers Friday night through Sunday night. Of course, some of these areas will be getting snow and/or ice (or a combo), so for example, an inch or two of rain equates to quite a lot of snow if an all-snow event occurs for a given location. For the regions that manage to be on the snowy/icy side of this system, I expect a significant, early-season winter storm event.

weather prediction center forecast

Let’s start from the Four Corners region and the Southern Plains and then work our way eastward. I’ll reference the latest operational European model, and then tell you what I agree and disagree with.

The swath of snowfall accumulations shown to occur from New Mexico to the Texas panhandle and over northern and central Oklahoma and Arkansas look well-placed. Most of Texas (outside of the panhandle), Louisiana, and most of Mississippi (expect possibly the northern part of the state) should only experience a cold rain.

Southern Plains winter storm forecast

Tennessee, the northern third of Alabama/Georgia, and the Carolinas poses the greatest forecast challenge. Strong high pressure will be located to the north, as discussed in my last article, but the low pressure system will deepen as it crosses the Gulf coast states. Additionally, cold air damming will establish itself along the east side of the Appalachians, which will allow cold air at and near the surface to spill into western and central North Carolina, northern South Carolina (including the Upstate), and northeast Georgia. Places such as Atlanta, GA and Chattanooga, TN will likely be placed relatively close to the cold rain/frozen precipitation line.

Given the latest trends in surface low strength, warm air will likely get advected over the colder air at the surface; thus, a transition from snow to ice (sleet/freezing rain) will probably eventually occur across some locations. Since I anticipate the presence of this warm nose aloft, I currently am not ruling out the possibility of an ice storm somewhere across northeastern Georgia, South Carolina, and across central parts of North Carolina. Colder air will be deeper across western North Carolina and into Virginia; thus a significant snowstorm will be more probable across those locations. The latest European model depicts this well. It has the heavier snowfall totals across northern Upstate SC, western and central NC, and southern Virginia. The European model is a bit more bullish on snowfall totals south of I-85 across northeast Georgia and the Carolinas than I would be at this point, but that’s because I believe ice could cut back on total snowfall amounts in those areas. The Atlanta area needs to cautiously monitor the latest forecasts, even though I believe the main event will be to your north and northeast. BUT, it only takes a ‘little’ snow and ice to cause a big mess. That currently is my biggest uncertainty with this forecast.

Southeast winter storm forecast

The European model is a bit more generous with snowfall accumulations into southeastern Tennessee than the GFS model (and the Firsthand Weather forecast, for that matter) has been. I have higher confidence that snowfall accumulations will occur in northern Tennessee and southern Kentucky, due to the availability of colder air. However, I continue to monitor southern Tennessee closely. That’s still a very tough call.

I expect only rain along the southern half to two-thirds of all Gulf coast states from Mississippi eastward. In fact, there could be thunderstorms within the warm sector of this system.

To summarize, the big story will be the swath of snow that falls from parts of the Southern Plains/Southwest eastward into parts of Tennessee and Kentucky. The biggest story will likely be the significant winter storm that unfolds across parts of the Carolinas, northeast Georgia and Virginia. Determining the exact cut-off between frozen precipitation and cold rain remains extremely challenging. For those located along and near the southern edge of potential accumulations, please be aware that significant modifications to the current forecast may need to be made over the next couple of days.

Please continue to follow Firsthand Weather on Facebook, and please follow us on Instagram if you haven’t already. We will have an accumulations forecast later this week.

What’s All Of This Talk About A Southern Winter Storm Next Weekend?

Is it really that time of year again already? For most of us, we skipped fall and went straight into winter last month. Although wintry precipitation has already impacted parts of the United States, the first legitimate chance for a winter event farther to the south will come in about 6 or 7 days. The goal is never to address local-scale specifics in the long-range, but we can begin discussing the pattern that could support a winter storm. This allows us to establish an initial framework by looking at the big picture first, and then we can build upon that foundation with specific details in the coming days.

Will the mid and upper-level atmosphere support an early-season winter storm across portions of the South?

The first step, especially at this point, is to look at what’s currently going on well-above the surface and attempt to determine how that pattern will evolve over time. From this, it’s possible to infer what could occur at the surface without it being necessary to look at modeled surface output at this point. A closed mid-to-upper level low pressure system was located over the central U.S. yesterday (Saturday) and has now moved northeastward over the Great Lakes. A cold front, associated with a surface low that developed in response, will push all the way through Florida by mid-week. Broad troughing will remain established over the eastern U.S., keeping an anomalously cold air mass in place.

Now, here’s the main reason I made a post on November 29th about the possibility of a winter storm. A split-flow regime is expected to become established over the far western U.S. Let me explain what that means. With this setup, the jet stream splits into northern and southern components. The northern component (the polar jet) will extend well into western Canada and Alaska, while the southern component (the southern jet) will eventually dip into Baja California. Now, check out the map I posted under this paragraph. You can see the broad trough over the eastern U.S., ridging over western Canada and Alaska, and a shortwave extending into southern California and Baja California. I drew arrows to indicate mid and upper-level flow. Do you see how the flow begins to merge back together over the central U.S.? When this occurs, this is called confluence. As this confluence occurs, this will result in sinking motion over the Great Plains and will support the development/maintenance of strong high pressure over that area. Winds flow clockwise around a high pressure system in the Northern Hemisphere, and cold, Canadian air, will wrap around on the east side of this high. There’s your cold air source.

GFS 500 mb map

This will allow another cold front to push southward, and a surface low will develop in response to favorable dynamics just to the east of the shortwave over California. As this shortwave treks eastward late week into early weekend, so will the surface low, which will probably ride somewhere along the frontal boundary. This will result in rainfall across drought-stricken southern California and the Southwest and a swath of wintry precipitation that will extend somewhere from the Southwest/Southern Plains to the East Coast.

If you were to ask me how far to the south I believe frozen precipitation will occur, in short, I’ll tell you I don’t know. But, I’ll give you some insight on this. With conditions favoring high pressure over the central U.S., I’m comfortable saying that it wouldn’t be too difficult to get frozen precipitation (snow and/or ice) as far south as parts of Oklahoma, Arkansas, and Texas. Farther eastward into Tennessee and northern Mississippi/Alabama/Georgia, it becomes a bit more of a tough call. I’m especially paying close attention to northern South Carolina, most of North Carolina, and parts of Virginia, due to the potential for cold air damming to establish itself east of the Appalachians as surface high pressure moves eastward. That’s why in our ‘best chance for wintry precipitation’ map (shown below), we currently depict higher probabilities across those locations. Of course, it should go without saying that we will have to modify this map between now and next weekend, and keep in mind that wintry precipitation is not exclusively snow. We can iron out all of those details later.

southern snow/ice forecast

Conclusion:

Again, we’re simply trying to determine how this pattern will evolve. Any unforeseen changes in that would completely throw off my current expectations for next weekend. Have fun looking at all of the snowfall projection maps, but it’s important to understand the major limitations of accumulation projections this early in the game. And no, I’m not expecting nearly 3 feet of snow in parts of South Carolina like what the European model is showing.

european model snow forecast

Be sure to follow us on Facebook for numerous updates on this event throughout this week. Also, please give us a follow on Instagram. We’re really trying to grow that account. As always, continue to check back with us daily for new updates.

A special thank you to Kimberly Gnat for sharing a picture with us of the snowstorm near Chicago late last month, which we used as the featured photo.

2018-2019 Winter Outlook

Introduction

It is that time of the year. Days are getting shorter; temperatures are getting cooler; and, many have already seen their first freeze or snow of the season. October is an important month for climatologists and meteorologists to analyze certain trends and variables from August to present to obtain an idea of what may come during the winter season. Seasonal forecasting is difficult, and an inexact science, in which many meteorologists have varying methods to generate a seasonal forecast. There are certain areas around the world we can observe to assist in providing a ‘snapshot’ of what the winter season may look like for the United States. A handful of current or predicted teleconnections and variables around the globe can aid in providing the ‘snapshot’ of the upcoming winter. A few of these are: ENSO, QBO, snow and ice cover, NAO, AO, PDO, TNH, and solar activity. A few of these aforementioned variables will be included in the technical discussion later in the article, but first, here is the 2018-2019 Winter Outlook and Snow Outlook.

Regional Discussions

A (San Antonio, TX; Houston, TX; New Orleans, LA; Tallahassee, FL; Charleston, SC; Fayetteville, NC): This region will feature an active winter. Temperatures will be below average and precipitation will be above average. Wintry precipitation will be above average for this region outside of Florida. Either way, you want to make sure you are ready for the winter. It’s so simple. Just by doing a quick search into something like ac repair chandler if your heating is broken, you’ll be able to find a professional who can help resolve this issue and get you living in a warm environment for the winter months once again. You just never know what the weather is like, as it is so unpredictable, but it is best to be safe than sorry.

B (Dallas, TX; Oklahoma City, OK; Little Rock, AR; Jackson, MS; Birmingham, AL; Atlanta, GA; Greeneville, SC; Charlotte, NC): This region will be characterized by temperatures below average and precipitation above average. This region has the opportunity for several winter storms to provide snow and ice opportunities.

C (Kansas City, KS; Omaha, NE; Rapid City, SD; Casper, WY; Billings, MT; Fargo, ND; Des Moines, IA; Chicago, IL; Columbus, OH): This region will be characterized by temperatures well below normal and snowy conditions. Several winter storms and brutal cold are possible.

D (Philadelphia, PA; New York, NY; Boston, MA; Portland, ME): This region will be characterized by temperatures below average and snow well above average. A few potent Nor’easters are possible in this region over the winter.

E (Detroit, MI; Marquette, MI; Green Bay, WI): This region will be characterized by chilly temperatures and frequent snow opportunities.

F (Denver, CO; Salt Lake City, UT; Twin Falls, ID; Spokane, WA): This region will be characterized by temperatures slightly below average and near normal precipitation. A few winter storms moving in from the Pacific Northwest are possible in this region.

G (Albuquerque, NM; Phoenix, AZ; Los Angeles, CA; San Francisco, CA; Las Vegas, NV): This region will be very bland during the winter. The “Pineapple Express” will cease to exist, thus, temperatures near to above average with precipitation below average. Far eastern areas in this region may see precipitation near average.

H (Portland, OR; Seattle, WA; Boise ID): This region will be characterized by temperatures above average and precipitation near average to slightly below average. There will be a few winter storms that move in from the northern Pacific, thus, providing beneficial snow to ski resorts in the region.

Discussion/Method

The equatorial Pacific is an important region to analyze in October. The state of this region can play one of the puzzle-pieces (an important puzzle-piece) into how the winter will shape up. There are three very important variables to analyze when looking at the equatorial Pacific: I) sea-surface temperature (SST) anomalies, II) the positioning of the anomalously warm or cool SSTs, and III) the depth of the anomalously warm or cool SSTs. As of late-October, the state of the equatorial Pacific is trending anomalously warm which is signaling El Niño conditions developing. In fact, the trade winds (normally flow from east to west) in the central and eastern equatorial Pacific have started significantly weakening. This is only reinforcing the anomalously warm temperatures that have persisted for several weeks; another sign of a developing El Niño. This is supported and is expected to continue per the majority of the models. We are currently in a neutral condition (not El Niño or La Niña); however, due to this region continuing to warm since summer, the chances of El Niño developing are increasing. The Climate Prediction Center has increased the odds of El Niño developing in the winter to 70-75%.

Current SST Anomalies

ENSO Predictions Plume

So what is El Niño? El Niño simply put a climate pattern that occurs when SSTs (in the equatorial Pacific) are above-normal for a long period of time. This climate pattern is a cycle (ENSO) in which below-normal SSTs can occur, too. When SSTs are below normal for an extended period of time in this region, the development of La Niña can occur. This climate cycle play an important role in shaping weather patterns around the entire World. Of significance, are the impacts of this cycle on the winter in the U.S. El Niño is typically associated with an extended Pacific jet stream and amplified storm track for parts of the southern United States. This can cause an increase in cloud-cover and precipitation for the southern United States In return, due to the cloud-cover and precipitation, temperatures tend to be below-average in this region. With the hyperactive storm track across the south, the chances are increased that at some point a phase between the northern and southern jet stream will occur, leading to the possibility of southern winter storms. It can also lead to above-average temperatures in northern/northwestern parts of the United States. The impacts on temperatures and precipitation, however, are dependent upon the strength of the El Niño and the positioning of the warm SSTs.

El Niño winter pattern in North America (CPC)

Based on the current trends and available data, it appears a weak to moderate Modoki El Niño may develop this winter. I am sure you’re wondering what differences, if any, are there between Modoki El Niño and El Niño. And yes, there are differences. An Modoki El Niño is slightly different than the conventional El Niño. Modoki El Niño features stronger warming, and at a great depth, of the central equatorial Pacific and cooling in the eastern and western tropical Pacific. This is what is occurring based on the latest SST anomalies. Also, notice the cooler temperatures along the West Coast of South America. This is a signature, when paired with the central warming, of Modoki El Niño.

El Niño SST anomalies (JAMSTEC)

Modoki El Niño SST anomalies (JAMSTEC)

This type of warming and cooling pattern in the tropical Pacific alters the normal winter pattern in the United States and has different implications than the typical El Niño on temperatures and precipitation. Instead of the Southwest seeing an increase in rainfall, as expected with El Niño, Modoki El Niños can cause an increase in temperatures and lack of precipitation in this region. This is depicted in our winter outlook in which we are forecasting the Southwest to see a warm and dry winter. An increase in storminess and cool temperatures can occur for South-central and Southeastern parts of the United States during a Modoki El Niño. This active storm track from Texas across the Gulf Coast states and up the East Coast is also depicted in our winter outlook.

El Niño temperatures (JAMSTEC)

Modoki El Niño temperatures (JAMSTEC)

El Niño precipitation (JAMSTEC)

Modoki El Niño precipitation (JAMSTEC)

The North Atlantic Oscillation (NAO), the Arctic Oscillation (AO), are crucial teleconnections to take into consideration during seasonal forecasting–-especially during the cool months. The NAO, which can be hard to forecast outward more than a few weeks in advance, has large implications on winter seasonal outlooks—-especially for areas east of the Rocky Mountains. Throughout much of the year, the NAO and AO have been positive but the strong positive phase of these teleconnections has begun to relax and dipped to negative levels. A more neutral or negative phase of NAO allows a high to build near Greenland, which tends to lead to cooler temperatures for parts of the eastern United States due to a dip in the jet stream across this region. SST anomalies distribution across the North Atlantic Basin is looking increasingly favorable for the NAO to go neutral or negative during the winter. Research shows a link between SST anomalies and NAO in which a certain pattern of SST anomalies across the Atlantic Basin can increases the likelihood of the NAO dipping to a negative phase. A negative phase of the AO also aids in ushering chilly air for parts of the eastern and southern parts of the United States due to the circulation around the North Pole becoming weak, thus, can allow chilly air to move southward at times. When these two teleconnections (NAO and AO dip to negative values, the atmosphere will eventually respond, and very active weather will establish across parts of the South and the Mid-Atlantic/New England. Ensembles show the NAO and AO remaining neutral with negative dips at times during the winter, which will lead to large winter storms at times from the Southeast up the East Coast.

Current SST anomalies (North Atlantic)

Negative NAO Pattern Implications On Surface Temperatures

Negative AO Pattern Implications On Upper-Levels

The Pacific Decadal Oscillation (PDO) is important to analyze, too. The PDO has a warm and cool phase. What is unique about the PDO is that the warm and cool phases can last 20-30 years–-this is much longer than your ENSO cycles that last half a year or up to almost two years. The PDO also has an influence on the strength of ENSO. When the PDO is warm, higher heights develop over Alaska and the northwestern Pacific, which can dislodge cold air over Canada and usher it southward into central and eastern parts of the United States. The PDO is in a warm phase, which will have big impacts downstream–leading to lower heights across the eastern United States. Alaska has observed impacts from this “warm blob” so far this Fall. Many records have been broken across the state for the warmth and lack of snow that have occurred thus far. This will likely continue through the winter season.

Warm PDO SST anomalies

Another important factor to take into consideration is the snowcover across Siberia and other parts of the Eurasian continent, snowcover across western and central Canada, and the Arctic sea ice extent. While the snowcover was not abundant in parts of Siberia, it has begun to increase over the past couple of weeks, and the snow cover continues to build in eastern Canada and advance southward in central Canada. This will allow for cold air to build and become well established, followed by an eventual equatorial movement at times during the winter.

Current Snow and Ice Cover

Taking into consideration some of the phases of the aforementioned teleconnections and current global features, here are a few analog years that may give a good snapshot of what this winter could look like. Weak to moderate central based El Niño years were selected to generate temperature and precipitation anomaly composites to help form the framework of the winter outlook. Please note, no two years exactly parallel one another. This is what the analog years chosen showed for the winter:

Temperature Anomalies

Precipitation Anomalies

2018-2019 Winter Outlook Conclusion

The 2018-2019 winter will feature below average temperatures for southern and eastern parts of the United States. Above average temperatures are expected for the the Pacific Northwest. Precipitation will be above average for southern and eastern parts of the United States. The above average precipitation will lead to seasonal snowfall totals above average across the Southern Plains, Southeast, Mid-Atlantic and the Northeast. Please keep in mind, if your region is in an area with above average temperatures, this does not mean wintry precipitation will not occur.

Hurricane Willa’s Remnants Will Have Large Impacts From Gulf States And Up The East Coast

Hurricane Willa is getting closer to the west-central coast of Mexico and should make landfall within the next few hours (Tuesday evening). Willa should retain major status until landfall. Willa will begin to weaken and lose its tropical characteristics as it moves across the higher terrain of Mexico into Texas but the remnants will remain well established to have large impacts from mid-week through the weekend for parts of the United States.

As the remnants move into Texas, deep moisture will stream northward throughout Texas into eastern New Mexico and Oklahoma. This will aid in heavy rainfall for this region with the greatest flood threat occurring in central and southern Texas, which has recently been inundated with rain. Widespread 1-3″ amounts are possible in eastern New Mexico and central and southern Texas with isolated 3-4″ amounts in central Texas near the Hill Country (see Fig. 1).

Fig. 1: 7-day rainfall forecast

The remnants will move out of Texas on Wednesday, merge with a shortwave, and begin to slowly intensify across the northern Gulf by Thursday. This will aid in thunderstorms and heavy rain for the Gulf States (from Louisiana to Florida) for late week. The low will then move off of the Southeast coast by late Friday and begin a north-northeastward forward movement off of the coast of the Carolinas. At this point, the low will begin to interact with an approaching cold front and deepen fairly quickly by Saturday morning as it spins off of the coast of the Mid-Atlantic. Heavy precipitation (see Fig. 1), rough seas and strong winds up to 30-60 mph (see Fig. 2)) will be possible for parts of the Mid-Atlantic and Northeast through the weekend. While coastal areas will see heavy rain (2-4″ are possible), areas further inland may see snow.

Fig. 2: Wind forecast Saturday evening

That is right, snow is possible as the nor’easter wraps in enough cold air for a transition to a heavy, wet snow. The best chance for snow will occur in interior parts of the Northeast down into the higher terrain of West Virginia. These areas may see a few inches of wet snow with several inches possible in the higher elevations of the Appalachians. Please keep in mind, we are a few days out so the snowfall forecast will likely need to be adjusted. A couple degrees cooler or warmer will have large impacts on accumulations and precipitation type.

Flooding is possible in Texas from this storm, which will impact travel. Turn around, don’t drown. Travel implications are also likely in parts of the Mid-Atlantic and Northeast due to wind and precipitation. With trees still having leaves on them, this increases the likelihood of them being overwhelmed for either wind or snow. This will increase the chances of power outages in this region over the weekend.

2018-19 Winter El Niño?

October is an important month for climatologists and meteorologists to analyze trends and variables to aid in providing an idea of what may come during the winter season. There are certain areas around the world we can look to, to provide a ‘snapshot’ of what the winter season may look like. One area of significance importance is the equatorial Pacific. The state of this region is a large piece of the winter outlook puzzle. There are three very important variables to analyze when looking at the equatorial Pacific: I) sea-surface temperature (SST) anomalies, II) the positioning of the anomalously warm or cool SSTs, and III) the depth of the anomalously warm or cool SSTs.

As of mid-October, the state of the equatorial Pacific continues to trend anomalously warm, which is signaling El Nino conditions developing (see Fig. 1). In fact, the trade winds (normally flow from east to west) in the central and eastern equatorial Pacific have started significantly weakening. This is only reinforcing the anomalously warm temperatures that have persisted for several weeks; another sign of a developing El Niño. This is supported and is expected to continue per the majority of the models (see Fig. 2). We are currently in a neutral condition (not El Niño or La Niña); however, due to this region continuing to warm since June, the chances of El Niño developing are increasing. The Climate Prediction Center has increased the odds of El Niño developing in the winter to 70-75%.

Fig. 1: Current SST anomalies (Tropical Tidbits)

Fig. 2: Models ENSO predictions (IRI and CPC)

So what is El Niño? El Niño simply put a climate pattern that occurs when SSTs (in the equatorial Pacific) are above-normal for a long period of time. This climate pattern is a cycle (ENSO) in which below-normal SSTs can occur, too. When SSTs are below normal for an extended period of time in this region, the development of La Niña can occur. This climate cycle play an important role in shaping weather patterns around the entire World. Of significance, are the impacts of this cycle on the winter in the U.S. El Niño is typically associated with an extended Pacific jet stream and amplified storm track for parts of the southern U.S. (see Fig. 3). This can cause an increase in cloud-cover and precipitation for the southern U.S. In return, due to the cloud-cover and precipitation, temperatures tend to be below-average in this region. With the hyperactive storm track across the south, the chances are increased that at some point a phase between the northern and southern jet stream will occur, leading to the possibility of southern winter storms. It can also lead to above-average temperatures in northern parts of the U.S. The impacts on temperatures and precipitation, however, are dependent upon the strength of the El Niño and the positioning of the warm SSTs.

Fig. 3: El Niño winter pattern in North America (CPC)

Based on the current trends and available data, it appears a weak (to possibly moderate) El Niño may develop by winter. It should be noted, the strength of El Niño does not necessarily reflect its impacts on global weather patterns that develop. The type of warming and cooling pattern in the tropical Pacific alters the normal winter pattern in the U.S. and has different implications on temperatures and precipitation. Historical weak El Niños have produced these temperature and precipitation anomalies in the lower-48 (see Fig. 4 and Fig. 5):

Fig. 4: December-February temperature anomalies

Fig. 5: December-February precipitation anomalies

While the aforementioned figures show below-average precipitation across parts of the southern U.S. during a weak El Niño, El Niño that tend to be on the strong side of weak (close to moderate) lead to wetter conditions in this region.

Firsthand Weather is in the process of developing its 2018-2019 Winter Outlook but I wanted to give some insight into one of the pieces of the puzzle we analyzing for the winter season. Firsthand Weather’s 2018-2019 Winter Outlook tentative release date is October 26th, 2018!!

Snoklahoma: Snow In The Forecast For Parts Of Oklahoma, Texas And Kansas

It is only October but snow is in the forecast for parts of Oklahoma, Texas and Kansas by late this weekend. The strongest cold front of the season will move southward into this region by late-weekend. Behind this cold front, the temperatures with the Canadian airmass will be at or below freezing for much of Kansas, the Panhandle of Oklahoma and northwestern Oklahoma, and the Texas Panhandle.

A potent shortwave trough will dive south out of the Rockies, along with warm-air advection well-above the surface, will lead to the development of precipitation late Saturday into Sunday. Precipitation initially will fall as light rain but forecasted soundings show (see Fig. 1) a transition to snow is expected throughout the day on Sunday into early Monday (see Fig. 2 and Fig. 3).

Fig. 1: Forecast sounding in Texas Panhandle

Fig. 2: Future radar (Sunday afternoon)

Fig. 3: Future radar (Monday morning)
Guidance indicates frontogenesis developing Sunday, which will act to increase precipitation rates. This will lead to banded snow features in which moderate to heavy snow may fall at times late Sunday. Several inches may fall within this area of frontogenesis, which guidance indicates will be from southwest to northeast out of the Oklahoma Panhandle into central Kansas. Lighter snow amounts will fall to the east and south of this area (see Fig. 4).

Fig. 4: Forecast snowfall totals
Travel will likely become dangerous in areas that see the heaviest snowfall late Sunday into Monday morning.

Big Cool Down On The Horizon

A decent cold front will move through central parts of the country late this week into the weekend. The sub-tropical ridge that has kept temperatures across the Southern Plains and Southeast above average recently will begin to move eastward as a trough moves in from the west. This will send a cold front south on Thursday and the front will continue its southward progression into the weekend. The front should move through Nebraska and into Kansas on Thursday into Friday, and through Oklahoma and northern Texas on Friday into Saturday. Tomorrow, along the cold front, a few severe thunderstorms look possible due to forecasted instability and shear values (see Fig. 1).

Fig. 1: Thunderstorm outlook map for Thursday

The front should stall across northern Texas and western parts of the Mississippi and Tennessee Valleys as it feels the influence of the ridge. This will keep temperatures warm for much of the Southeast outside of Arkansas, northern Louisiana, northwestern Mississippi and western Tennessee (cooler temperatures are in the forecast for other parts of the South/Southeast later in the extended period so keep reading for details on the cooler temperatures). Temperatures behind the cold front will be well below average for much of the Southern Plains and Midwest late this week and weekend (see Fig. 2 and 3).

Fig 2: Friday afternoon temperature anomalies

Fig 3: Saturday afternoon temperature anomalies

It should be noted, deep moisture will move into New Mexico, Texas and Oklahoma from Thursday into Saturday as the trough nears. This moisture will stream into this region from the Gulf of California where a Tropical Depression is located this afternoon. The increase in moisture will lead to increased rainfall, which may lead to flooding in parts of New Mexico, Texas and Oklahoma. Isolated areas in Texas and Oklahoma may see 2-6″ (see Fig. 4). The increase in precipitation and cloud-cover should keep afternoon temperatures below average even before the front moves through on Friday (see Fig. 2 and 3). High temperatures late this week into the weekend should be in the 60s and 70s for Oklahoma and 80s for most of Texas.

Fig. 4: Rainfall forecast through 7 days

Looking ahead to next week, a more amplified trough appears to usher in a reinforcing shot of cooler air. The cooler air will first be felt across the Northern Plains early next week, followed by the Southern Plains by mid-week, then eventually parts of the Southeast by late week into next weekend. Far Southeastern parts of the United States (Florida, eastern Georgia, South Carolina, and eastern North Carolina) may miss out on the coolest fall-like temperatures from this front but temperatures should still decrease. For other parts of the South, this will be the first significant cold front of the fall season. High temperatures will be well below average (see Fig. 5). It is too early to forecast high and lower temperatures with much confidence but right now it appears highs may be in the 60s and 70s with lows in the 40s and 50s behind this front. Locations further north will see temperatures much cooler than this.

Fig. 5: Temperature probabilities days 8 through 14

First Winter Weather Advisory Of The Season Issued In The Lower-48

Winter weather will grace parts of the northern Rockies early this upcoming week as snow levels drop to around 9,000 feet. The Billings National Weather Service (NWS) issued the first Winter Weather Advisory (WWA) of the season for parts of southern Montana (see Fig. 1).

Fig. 1: Current WWAs for Montana

2-7″ with isolated higher amounts are likely for the Beartooth and Absaroka Mountains (see Fig. 2). This will cause hazardous travel conditions where the heaviest snow falls. Snow will not be limited to Montana. Northwestern Wyoming and Northwestern Colorado will see snow in the higher elevations (see Fig. 3).

Fig. 2: Latest message from the NWS

Fig. 3: NAM snowfall forecast

Late-August snow is not unheard of for the northern Rockies. The jet-stream begins to dip slightly southward this time of the year, which can cause snow levels to drop. It’s just a matter of time before more areas in the lower-48 pickup their first snow of the season.