Saturday Snow Update

Saturday Late-Morning:
Currently, a strong arctic cold front is moving into northwestern Texas and has moved through much of Oklahoma. This front will continue to advance towards the south and move towards the Texas Coast by late in the day. Temperatures behind the cold front will range from the single digits in the Oklahoma Panhandle to the 20s throughout the rest of Oklahoma behind the front, while temperatures ahead of he cold front (southern and central Texas) will get into the 70s and 80s. Parts of northern Texas have dropped into the 30s already, and the remainder of northern Texas will fall into the 30s by early afternoon. Windchills will range from below zero in western Oklahoma to the teens in northern Texas.

The majority of precipitation will not develop until the afternoon hours; however, light freezing mist is possible over the next hour or two in northern and central Oklahoma. The low-levels will significantly dry out thus decreasing the freezing mist potential by the afternoon hours.
slide03
NAM Composite Reflectivity: Saturday Morning

Saturday Afternoon-Evening:
Snow will begin to develop behind the cold front in northwestern Oklahoma as well as the Texas Panhandle as energy associated with the upper-level trough creates an area of lift. This thin band of snow will move towards the I-35 corridor in Oklahoma by the evening hours. The snow will begin to lessen in magnitude as it moves towards the southeast, but flurries are possible as far south as I-20 (DFW area) in northern Texas by Saturday night.
slide06
NAM 500mb Vorticity Map: Saturday Afternoon
slide04
NAM Composite Reflectivity: Saturday Afternoon
slide05
NAM Composite Reflectivity: Saturday Evening

The snow amounts will generally remain light for Texas and Oklahoma. Parts of northwestern Oklahoma and the Texas Panhandle may see upwards of 3” while the rest of Oklahoma sees .5-1.5” with a dusting for the Red River Counties (and flurries down towards the DFW-Metro).
slide01
Forecast Snowfall Totals: Saturday-Sunday Morning

Along with the cold temperatures and snowfall, the winds will be a big issue gusting upwards of 30mph. This will lead to windchills will be in the single digits, and below zero in some areas, as well as blowing and drifting of snowfall. Some areas in Oklahoma may see a brief period of close to whiteout conditions due to the light snow and gusty winds. This will make travel very dangerous due to low visibilities in parts of Oklahoma.
slide08
NAM Windspeeds: Saturday Evening

Sunday Morning:
Temperatures will be the coldest of the season by Sunday morning. Temperature will range from below zero in Kansas, northwestern Oklahoma, and the Texas Panhandle, while the single digits and teens are likely for the rest of Oklahoma; northern Texas will fall to the teens while 20s are likely for much of the rest of the state. Windchills will fall below zero for many areas north of the Red River.
slide07
NAM Temperatures: Saturday Morning

Weekend Snow

Tonight:
Currently, a strong arctic cold front is moving into northern Kansas. This front will continue to advance towards the south and move into northwestern Oklahoma by early tomorrow morning—before continuing its progress through Oklahoma and into Texas throughout the day. Temperatures behind the cold front tonight will be in the teens and 20s (single digits in northern Kansas), and in the 50s ahead of the front (60s in parts of Texas).
slide07
NAM Temperatures: Saturday Morning

Saturday Morning-Evening:
Snow will begin to develop behind the cold front in northwestern Oklahoma as well as the Texas Panhandle. As the cold front races southward, and lift increases due to upper-level energy, the snow will become more widespread.
slide06
NAM 500mb Vorticity Map: Saturday Afternoon

This will lead to much of Oklahoma and the Texas Panhandle seeing light snowfall throughout parts of the day on Saturday. The snow will eventually move towards the east, and eventually into parts of far northern Texas by Saturday night.
slide03
NAM Composite Reflectivity: Saturday Morning
slide04
NAM Composite Reflectivity: Saturday Afternoon
slide05
NAM Composite Reflectivity: Saturday Night

The snow amounts will generally remain light for Texas and Oklahoma. Parts of northwestern Oklahoma and the Texas Panhandle may see upwards of 3” while the rest of Oklahoma sees .5-1.5” with a dusting for the Red River Counties of North Texas (and flurries down towards the DFW-Metro).
slide01
Forecast Snowfall Totals: Saturday-Sunday Morning

Along with the cold temperatures and snowfall, the winds will be a big issue gusting upwards of 30mph. This will lead to windchills will be in the single digits, and below zero in some areas, as well as blowing and drifting of snowfall. Some areas in Oklahoma may see a brief period of close to whiteout conditions due to the light snow and gusty winds.

NAM Windspeeds: Saturday Evening

Sunday Morning:
Temperatures will be the coldest of the season by Sunday morning. Temperature will range from below zero to freezing for much of theslide09 Southern Plains. Make sure your elderly neighbors are checked on; protect your pets, pipes, and plants during this very hard freeze. I will have an update tomorrow morning.
slide08
NAM Temperatures: Saturday Morning

Several Shots At Wintry Weather (Southern Plains)

There’s a lot to talk about for the Southern Plains over the next week, so I will get straight into it. This discussion will update the Saturday-Sunday snow potential, the storm system I mentioned for early next week in the Southern Plains, and the chance for very light wintry precipitation as early as tonight in some areas.

Tonight:
A reinforcing surge of cool air has moved into Oklahoma today and is moving into Texas this evening. Temperatures with this airmass are in the 20s and 30s in Oklahoma with windchills well below freezing. While winds are from the north at the surface, bringing in this cool airmass, the winds about 1000 feet above our heads will shift towards the southeast overnight. This will force a warmer airmass over the cool airmass at the surface, which should lead to overcast conditions by morning and possibly light drizzle in some areas. This light drizzle, while spotty in nature, may fall into surface temperatures that are at or below freezing in parts of central Oklahoma by early tomorrow morning. Freezing drizzle amounts will be extremely light for Oklahoma and no travel issues are expected (remain alert on bridges and overpasses in case a slick spot were to develop). Luckily, much of the spotty drizzle appears to stay just east of the 32-degree line. Conditions should improve by late morning.
slide02
3km NAM Composite Reflectivity: Wednesday Morning

Wednesday Night and Thursday Morning:
Another round of very light freezing drizzle is possible overnight Wednesday. The precipitation will remain light, however, it is expected to be more widespread than tonight’s drizzle. This could lead to a few slick spots for the Red River Counties of north Texas, much of western Texas, and Oklahoma. I want to reiterate amounts will be very light and likely less than .01”, but we all know it doesn’t take much ice to cause travel issues on elevated surfaces. There could be a snowflake or two in parts of Oklahoma, but analyzing the entire atmospheric column at this points, doesn’t show a promising snow profile. Conditions should improve by late in the morning on Thursday.
slide03
3km NAM Composite Reflectivity: Thursday Morning
slide04
3km NAM Total Precipitation

Saturday afternoon-Sunday Update:
As a surface-low moves across southern Kansas on Saturday, an arctic cold front will move into Oklahoma and northern Texas throughout the day on Saturday. Temperatures on Saturday will be in the 20s/30s behind the front while areas ahead of the front will be in the mid to upper 70s! The movement of dense arctic airmasses is not particularly portrayed well by models, so the cold front may move at a faster pace than model depiction.
slide01
2m GFS Surface Temperatures: Saturday Afternoon

Behind the cold front passage, wintry precipitation may develop over parts of Oklahoma and northern Texas late in the day on Saturday into early Sunday morning. This band of snow is possible as the base of a trough approaches and strong lift occurs.
slide08
500mb GFS Vorticity Map: Sunday Morning
slide05
6-Hour GFS Precipitation Rate and Type: Saturday Evening
slide06
6-Hour GFS Precipitation Rate and Type: Sunday Morning

While adequate lift and cold temperatures will be present to support wintry precipitation, moisture will be limited. The cold front will act to scour out the low-level moisture, which would keep any snow very light if precipitation manages to develop. The GFS, and some of the other guidance, is hinting at a dusting for parts of Oklahoma and northern Texas. Please note, the map below is just showing you what the GFS is forecasting for snowfall totals this weekend. It’s entirely too early to accurately forecast snowfall totals if any at all.

slide07
Accumulated Snowfall GFS: Thru Sunday

Next Week:
Right now, the guidance is hinting at a strong upper-level low (ULL) ejecting into Texas. This scenario would create conditions favorable for increased precipitation chances, and potentially wintry precipitation under parts of this ULL. Such systems, while surface temperatures remain marginal at this time (32-35 degrees), have strong dynamic cooling. Such cooling would likely bring a wet snow to parts of the Southern Plains. It’s too early to determine the strength and track of the ULL, but I will continue to monitor this system and have updates as needed.

Again, this potential event is several days out, so a lot will change. One thing that is certain, temperatures Saturday night will be very cold across the area—windchills will be well below freezing so dress accordingly. I will continue to monitor this potential event and have updates as needed. Early next week needs to be monitored for Arkansas and northeastern Texas, but more on that later in the week.
slide10
500mb GFS Vorticity Map: Wednesday Afternoon
slide09
6-Hour GFS Precipitation Rate and Type: Wednesday Afternoon

Weekend Arctic Front And Snow?

As detailed in our 2016-2017 Winter Outlook, the Southern Plains is an area in which winter troubles are possible. The next potential winter weather event is several days down the road, so this is more of a discussion of what I am monitoring right now and not an official forecast. I am keeping a close eye on the upcoming weekend for the Southern Plains. A potent surface-low will move across southern Kansas on Saturday, which will allow for an arctic cold front to ooze into Oklahoma and northern Texas Friday night and throughout the day on Saturday. Temperatures on Saturday will be in the 20s/30s behind the front while areas ahead of the front will be in the 70s! The movement of dense arctic airmasses is not particularly portrayed well by models, so the cold front may move at a faster pace than model depiction.
slide02
2m Surface Temperatures: Saturday Afternoon (GFS)

The aforementioned surface-low will have precipitation associated with it. Parts of Kansas and Missouri will likely see rain, which will transition to snow as the low moves towards the northeast. Please note, since this event is several days out, the track of the surface low may change, which would cause southward or northward adjustments of wintry precipitation chances.

A second area of wintry precipitation that needs to be evaluated is for parts of Oklahoma and northern Texas late in the day on Saturday. Light snow showers may develop as an area of robust ascent occurs across Oklahoma and northern Texas as the base of a trough approaches this area.
slide04
500mb Vorticity Map: Saturday Evening (CMC)

It is important to note that while adequate lift and cold temperatures (throughout the entire atmospheric column) will be present, moisture will be limited. The cold front will act to scour out the low-level moisture, which would keep any snow very light if precipitation manages to develop.
slide03
6-Hour Precipitation Rate & Type: Saturday Evening (CMC)

Again, this potential event is several days out, so a lot will change. One thing that is certain, temperatures Saturday night will be very cold across the area—windchills will be well below freezing so dress accordingly. I will continue to monitor this potential event and have updates as needed. Early next week needs to be monitored for Arkansas and northeastern Texas, but more on that later in the week.

Southeastern U.S. Ice Storm Potential Discussion

After a very warm November across most of the United States, temperatures have gone in the opposite direction this month thus far, bringing below average temperatures to a large area. While the cold doesn’t look to be quite as expansive by the end of the month, most of us are going to have to deal with two to three more intrusions of Arctic air over the next ten days. An interesting pattern will begin to evolve by the middle of this week, which could set the stages for a potential ice storm across parts of the Southeast due to cold air damming (CAD) and a noteworthy winter storm that will trek from the Pacific Northwest to the Great Plains and eventually into the Great Lakes and interior Northeast regions. It wouldn’t even be out of the question for a changeover of frozen precipitation to occur on the backend of this system for parts of the Ohio Valley and Tennessee Valley later in the weekend, but we still have time to iron out details like that.

As I mentioned on social media yesterday and alluded to on Friday, the pattern by the end of the week into early next weekend is looking more favorable for an icing event to unfold, which would primarily impact a region stretching along the east side of the Appalachians. However, due to the progressive nature of the overall pattern, exact timing will be key, which makes this a relatively low confidence forecast. By the end of this article, I will have detailed the regions that should keep an eye on this possibility, but first, I want to discuss why the pattern could support such an event, along with what has to happen for an ice storm to occur.

The Pre-Existing Pattern:

An upper-level trough is going to begin digging into the Northern Plains early this week and will generally progress eastward as the week progresses. This trough will likely be centered over the Great Lakes/Ohio Valley region by Thursday, and an associated surface low pressure system will be near the Hudson Bay. You might be wondering what in the world this has to do with a potential ice storm this weekend east of the Appalachians, but it’s important because a cold front associated with this low pressure system is going to sweep across much of the U.S. this week, eventually making it to the Gulf Coast towards the end of the week. This will help to establish a cold and very dry air mass over the eastern two-thirds of the nation.

Surface high pressure is going to build into the central U.S. starting around mid-week, and that high is going to move eastward to the East Coast (centered over the northeastern U.S.) by the end of the week into early next weekend. This is a fairly classic way to get some form of a cold air damming scenario to set up east of the Appalachians. To put it simply, winds blowing from the northeast transports colder air southwestward, which gets jammed up against the mountains. The Appalachians act as a barrier, and the cold air basically gets stuck (jammed up against the mountains).

Take a quick look at what the latest GFS model (Figure 1) is showing for surface dew points early Friday afternoon. This is incredibly dry air with dew points down to minus 10 into South Carolina and northeast Georgia. It may seem counter-intuitive that such dry air would be necessary to set the stages for an extended wintry precipitation event, but it is necessary in some cases, which I’ll explain why in a bit.

Friday U.S. Dew Points

Figure 1: Projected Surface Dew Points On Friday Afternoon, December 16th

Figure 2 is a vertical profile of temperature (red line) and dew point (green line) over Greenville, SC from the latest GFS for Friday afternoon. I hope that this doesn’t seem overly complicated, but notice how the temperature and dew point lines are very much spread apart from the bottom of the image up to a certain point. This shows just how dry the atmosphere is from the surface to about a mile above the surface.

Sket t Greenville, SC

Figure 2: A Skew-T Profile Generated By The Latest GFS Model For Friday Afternoon, December 16th In Greenville, SC

Please bear with me. This is about to make sense in a minute, I promise.

The Low Pressure System That Could Bring The Necessary Precipitation:

The storm system that is going to be responsible for this possible madness in parts of the Southeast this weekend is going to move into the Pacific Northwest later in the week, and an upper-level trough off the West Coast will move inland, which will help to maintain a surface low pressure system as it makes its way to the Great Plains. The low pressure system is going to then move in a northeast direction from the Great Plains to the Great Lakes/Northeast region along a developing jet streak. Since this system will be taking such a track, a lot of warm air from the Gulf of Mexico is going to be transported over a large section of the Southeast and even get transported as far north as Tennessee Valley and over parts of the Ohio Valley this weekend.

Let’s Make Sense Out Of All Of This:

As all of that warmer air gets transported over the Southeast, it’s not simply going to push the cold air out of the way that is wedged east of the Appalachians. It’s going to just go over it. With time, temperatures are going to warm to above freezing above the surface and will begin to mix with and erode away that cold and dry air mass. However, with such a setup, that can take quite a while, and forecast models handle such scenarios horribly.

Also, remember how I kept going on and on about how dry the air mass will be beforehand? As precipitation begins to fall through that dry air column, a process known as evaporational cooling will occur. Although this would initially prevent precipitation from reaching the ground, this would actually lead to further cooling, even if the surface high pressure to the north began to move off the East Coast.

Who Needs To Keep An Eye Out For A Potential Ice Storm:

The biggest question mark right now is. . .how soon will precipitation begin developing and moving into the Southeast? If it moves in much later on Saturday into Sunday morning, that’s going to give more time for that warm, moist air from the Gulf of Mexico to erode away that cold air mass. That will also give more time for the surface high pressure to the Northeast to move off the East Coast, which is what will be responsible for the cold air wedging. If the precipitation begins to move in Friday evening into Saturday morning, then we’re going to have a bigger ice storm potential on our hands. Keep in mind though that forecast models often overestimate how quickly the colder air will move out.

Regions that could be impacted by this potential winter event will be northeast Georgia, Upstate and northern South Carolina, central and eastern parts of North Carolina (inland zones), a large region in Virginia and maybe a bit farther north from there. From that point, temperatures should be cold enough throughout the atmosphere to support more of a mixed bag of frozen precipitation farther north before making the change to freezing rain. Regions that should avoid icy weather includes locations like northwest Georgia, most of eastern Tennessee (Chattanooga for example), all of Alabama, etc. Some of the models do show a changeover to some frozen precipitation for parts of the Tennessee Valley and extending into the Ohio Valley late weekend, but if that occurs, that would be due to Canadian high pressure behind the system transporting cold air quickly enough southeastward to result a changeover. That’s highly uncertain at this point and is something that will have to be addressed in a couple of days.

If precipitation were to start early, regions farther south into Georgia and South Carolina would have to be monitored and included in the “threat zone”

Bullet-Point Summary:

  • A pre-existing cold air mass will initially be in place across the eastern U.S. with cold air damming setting up east of the Appalachians.
  • A storm system will help transport warm, moist air into the Southeastern U.S. and northward. However, this warm air will initially go over the colder air before mixing to erode away the cold air mass, which will take time.
  • However, the combination of cold air damming and evaporational cooling could result in an icing event that could impact northeast Georgia, Upstate and northern South Carolina, central and eastern parts of North Carolina, a large region in Virginia, and maybe a bit farther north from there.
  • The quicker precipitation moves into the area, the greater the chance this has to be an impactful event. This might make it necessary to expand the threat zone a little farther south into Georgia and South Carolina, if precipitation moves in too quickly. It would also mean that the onset of precipitation might involve sleet initially before transitioning to freezing rain.
  • If precipitation moves in much later, this decreases the ice storm threat quite a bit, but some icing issues could still occur. Again, forecast models often overestimate how quickly cold air will move out with such setups. This means that you should not rely on mobile weather apps during this period, as they may have temperatures warmer for Saturday than what might occur.
  • Regions that will avoid an ice storm include regions like northwest Georgia, most of eastern Tennessee (Chattanooga for example), all of Alabama, etc. However, some forecast models have rain changing over to frozen precipitation late weekend as cold air rushes to the southeast. That is highly uncertain at this time and will need to be addressed in a couple of days.
  • Christopher Nunley should be doing an article tomorrow on the winter weather threat across the Great Plains, which I didn’t address here.
  • As far as asking questions on how much wintry precipitation you’ll get in your backyard, I have NO clue. Right now, we’re trying to simply pinpoint locations that might get any amount of frozen precipitation late week into next weekend.

Overnight Snow In Texas

The well-advertised arctic boundary is pushing southward across the Southern Plains at this hour. Temperatures have fallen into the teens in northwestern Oklahoma/the Texas Panhandle with windchills close to zero. Overnight lows will dip into the single digits for some areas, while the majority of the Southern Plains is in the teens and 20s.
slide02
Temperatures When You Head To Work/School-Thursday Morning (HRRR)

Wintry precipitation chances will increase tonight through Thursday morning for parts of Texas (it should be noted flurries are possible across eastern Oklahoma and Arkansas). An upper-level jet streak will move into western Texas overnight. This will generate a band of precipitation, which will likely fall in the form of freezing/frozen precipitation. Precipitation should start out as light sprinkles/very light rain, transition into freezing rain as temperatures at the surface fall below freezing, and then transition into a light snow/sleet mixture under the most concentrated band of precipitation. The greatest chance for wintry precipitation will occur just south of I-20 in northern Texas out towards the Concho Valley of Texas. Accumulations do appear to remain light at this time in northern Texas, but an inch may fall out towards western Texas/the Concho Valley.
slide01
Wintry Precipitation Chances/Accumulations (Personal Forecast)

Since the jet-streak is not overly robust, and the low-levels are fairly dry, this should limit heavier amounts of precipitation. I should point out, latest short range guidance (the RAP and the HRRR) are indicating heavier precipitation amounts, which would lead to possibly a few areas seeing more than one inch in parts of Western Texas. I am not forecasting this scenario, yet, but will keep a close eye on the evolution of the precipitation trends. Travel may become slick for parts of Western Texas, and it is possible to see slick spots develop south of I-20 in northern Texas on bridges and overpasses. I will continue to monitor the latest guidance and have updates as needed.
slide04
Snowfall Accumulations Map (HRRR)
slide03
Radar Simulation-Thursday Morning (HRRR)

Texas Snow?

First off, I would like to apologize for the lack of updates as of late. As many of you know, I am super inundated with teaching, research, and wrapping up my PhD. With that said, I am enjoying every second of it.

I am keeping a close eye on cold temperatures and wintry precipitation chances for parts of the South from Wednesday afternoon through Thursday morning. An arctic cold front, which is currently oozing southward across central parts of the country, will move into the Southern Plains on Wednesday—and continue moving through southern parts of Texas on Thursday. This will usher in very cold temperatures—wind chills will be in the single digits and teens once the front moves through.
slide02
Thursday Morning Temperatures (NAM)

It is possible light wintry precipitation will develop behind this boundary during the day on Wednesday. The greatest chance will be across northern Oklahoma, southern Kansas, and northern Arkansas. A dusting to 1 inch is possible in these areas, but dry low-levels should limit higher amounts of wintry precipitation.

Another area of interest is parts of Texas late Wednesday into Thursday. An upper-level jet streak that will trek across Texas, which will aid in enough lift, combined with adequate mid-level moisture, to generate wintry precipitation.
slide03
500 hPa Relative Vorticity (NAM)

The precipitation will start out as light sprinkles, then transition into snow once the atmosphere moistens and cools. Accumulations do appear to remain light at this time, but an isolated dusting to (at the very most) 1 inch is possible. The greatest chance for snow will remain south of I-20 in northern Texas, the Texas hill country, and parts of western Texas.
slide01
Wintry Precipitation Chances Wednesday-Thursday

I will continue to monitor the latest guidance and have updates as needed.