A potent cold front will work its way through the eastern half of the country over the next 24 to 48 hours. This cold front will deliver the coldest air of the season to many areas, dropping temperatures below average from Thursday through Saturday. The most noticeably cool air will be felt during the overnight and morning hours with some areas experiencing a frost. See how low the temperatures will go!
Along with cooler temperatures, there will be a noticeable reduction in humidity, allowing for comfortable afternoons. This will set the stage for great high school and college football weather to end the week and this weekend.
A fall cold front will move across eastern parts of the country Wednesday and Thursday, delivering a chill to the air. Temperatures will fall well below average with a significant drop in humidity. The cooler air mass will be most noticeable overnight into the early morning hours from Thursday through Saturday.
Low temperatures across the South and Southeast will fall into the 40s & 50s Thursday through Saturday. Some 30s are also expected in parts of Tennesee, western North Carolina, and northeastern Georgia. These areas that fall into the upper 30s will have a chance to see a light frost Thursday night/Friday morning and Friday night/Saturday morning under clear skies and light winds. Protect your plants if you live in far northeast Georgia, western North Carolina, and central Tennessee.
The colder air won’t be confined to the Southeast. Temperatures farther north will also be chilly during the overnight and early morning hours. Widespread 30s & 40s are forecast across the Great Lakes, extending into the Ohio Valley, and Northeast.
Hurricane Larry is forecast to transition into a major winter storm, delivering feet of snow in Greenland. Larry will continue to rapidly move northeast into the weekend. As Larry continues on this journey, moving farther north, it will quickly transition into an extratropical cyclone by Saturday.
As the extratropical system approaches Greenland, it will pull in copious amounts of moisture. Temperatures will be cold enough for this moisture to fall in the form of snow.
The copious amounts of moisture will equal feet of snow for parts of Greenland. The heaviest snow will fall across eastern parts of the island, closest to the track of Larry, where up to 5 feet may fall in some areas over the weekend.
The snow will also be windblown. As Larry becomes extratropical, the already large wind field will expand. Winds of 60 to 80 mph are possible creating dangerous blizzard conditions.
Get the pumpkin spice coffee creamer from the store and dust off the light jackets. The first taste of fall arrives for many North Carolina, Upstate South Carolina, Tennessee, northern Mississippi, northern Alabama, and northern Georgia Thursday night and Friday morning.
Once Ida departs, a drier and cooler air mass will filter into the region. This will allow for a few days of pleasant conditions. The coolest temperatures arrive Thursday night and Friday morning when conditions will be perfect for optimized cooling. Lows will fall into the 50s and low-60s for many with parts of Tennessee and western North Carolina falling into the 40s–some mid-40s cannot be ruled out. Upper-50s will sneak as far south as far northern Georgia, Alabama, and Mississippi.
A rather cool storm system will bring the first flakes of the season to parts of the west over the next 36-hours. Peaks in Montana, Wyoming, Utah, and Colorado can expect snow, some of which will accumulate.
The first flakes will begin to fly tonight in Montana with the flakes eventually falling in Wyoming, Utah, and Colorado by Thursday. By the time the flakes stop flying, accumulations are expected. The best chance for accumulations will be above 10,000 feet where a few inches will fall. A light dusting is possible down to 9,000 feet with the rain/snow line as far down as 8,000 feet.
While August snow is not unheard of in August for these areas, it is not a frequent occurrence this early in the season. Snow becomes more common in September for these areas.
This is just an early reminder that fall and winter are right around the corner!
While we are in the Dog Days of Summer, you know fall is right around the corner when the Farmers’ Almanac releases its Winter Outlook. The 2021-22 Winter Outlook was released and shows a good chunk of the country experiencing a taste, or two, of Old Man Winter this season.
The Farmers’ Almanac is indicating most areas east of the Rockies will experience cold temperatures with a good shot for above-average wintry precipitation. If you’re a snow lover, this is good news. This outlook indicates the South and Southeast will also have a good chance for wintry precipitation. Areas west of the Rockies will experience a normal winter.
This is the Farmers’ Almanac’s winter forecast, not Firsthand Weather’s. Firsthand Weather’s official 2021-22 Winter Outlook will be released in the coming weeks.
A historic winter storm will cripple parts of the Rockies and Plains over the weekend. Some areas will experience feet of snow, which will create significant travel impacts, allow for power outages, as well as damage to trees. A few areas that will see the biggest impacts are Colorado, Wyoming, and parts of Nebraska.
A potent upper-level system is moving over the Southwest. This system will move northeast into the Rockies over the weekend, followed by the Plains early next week. Deep moisture is feeding north ahead of the system, which will contribute to the heavy snow as the moisture is forced up the Front Range of the Rockies.
Current Winter Weather Alerts
A plethora of winter weather alerts have been issued across Colorado, Wyoming, and parts of Nebraska. A blizzard warning is in effect for southeastern Wyoming and the northern Nebraska Panhandle where heavy snow and strong winds will lead to white out conditions. A winter storm warning has been issued for central Colorado, southern & central Wyoming, the southern Nebraska Panhandle, and South Dakota where heavy snow will fall. A winter storm watch has been issued for parts of northwestern Nebraska and southwestern South Dakota for heavy snow potential.
Snow Accumulations and Impacts
Heavy snow and strong winds are likely for the Front Range of the Rockies and the Plains, leading to whiteout conditions. 1 to 2 feet of snow will fall along the I-25 corridor in the region. The 1 foot totals will extend into the western Plains. Parts of the Front Range may see 3 to 4 feet of snow. Heavy snow accumulations of a foot will extend south into the northern mountains of New Mexico. Denver, Cheyenne, Fort Collins, and Boulder will see significant accumulations.
The winter storm is currently over the Southwest and will begin impacting all of the Four Corners states overnight Friday into Saturday. The snow will also begin impacting slight impacts from the system in the Plains and Front Range of the Rockies overnight Friday.
Bigger impacts will arrive for the Front Range of the Rockies and the Plains Saturday through Sunday. Heavy snow and wind will stick around through the entire weekend, continuing into early-Monday morning before shutting down.
All eyes are on an upper-level low over the Southern Plains. This upper-level low will race to the east overnight into Saturday and begin to open into a shortwave over the Mid-South tonight. Despite the upper-level system opening into a shortwave, it will be rather vigorous as it moves into the Southeast on Saturday.
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As the shortwave treks over the Southeast, strong lift, and a gradual moistening of the atmosphere will occur. This will lead to an uptick in cloud cover across the South & Southeast beginning tonight and continuing through Saturday morning. A light band of precipitation should develop with the increased lift ahead of the shortwave overnight into early-Saturday morning across northeastern Alabama, northern Georgia, far southeastern Tennessee, southeastern North Carolina, and far western Upstate South Carolina.
Initially, the precipitation from this band will fall into dry air at the surface; thus, the majority of the precipitation will evaporate before reaching the surface. This evaporation process will lead to a gradual moistening of the atmosphere, leading to precipitation reaching the ground Saturday morning. The precipitation band will increase in coverage and intensity throughout the morning hours Saturday. Here is where the forecast gets interesting. The temperature profile of the atmosphere is supportive of a rain/snow mixture. Almost the entire column of the atmosphere, from the ground to where the jets fly, will be below freezing. This will allow snow or a rain/snow to fall across the aforementioned regions.
High-resolution models are suggesting .05″ to .20″ of precipitation falling across northeastern Alabama, northern Georgia, far southeastern Tennessee, southeastern North Carolina, and far western Upstate South Carolina.
With temperatures supporting wintry weather, precipitation amounts of .05″ to .20″ would equate to a few areas seeing accumulating snow. Models are suggesting up to 1″ of snow possible.
Firsthand Weather is forecasting flurries from northeastern Alabama, northern Georgia, far southeastern Tennessee, southeastern North Carolina, and far western Upstate South Carolina Saturday morning with light accumulations possible across the higher terrain of northeastern Georgia. Within this area of accumulations, due to banding, isolated 2″ amounts cannot be ruled out but most areas will see lesser accumulations.
It should be noted: this event is marginal. Slight deviations in weather variables may significantly change the forecast so keep checking back for updates.
A strong shortwave approaching the Southern Plains has already resulted in a precipitation shield developing across much of Oklahoma and upper Texas. As the wave treks across the two states overnight, precipitation will fill in across the eastern half of Texas tonight before doing the same across Arkansas, Missouri, and Louisiana overnight into Wednesday morning. The Arctic air mass remains well entrenched over much of the Southern Plains and Mid-South. Surface high pressure over the Ohio Valley will begin departing eastward of Wednesday, but with recent snow/sleet cover, plenty of cold air will remain in place to help pull off another powerful winter storm across recently impacted areas.
In this article, I will focus primarily on the ice storm threat with the coming system. A mixture of freezing rain and sleet will likely lead to scattered to widespread power outages across parts of eastern Texas, lower Arkansas, Louisiana, and Mississippi on Wednesday/Wednesday night and across parts of North Carolina and the Virginias on Thursday.
Southern Plains & Mid-South Ice Storm Impacts and Timeline
Temperatures will continue to plummet overnight tonight across the Plains and Mid-South. Widespread 20s already overspread the region of interest, and many of those areas will drop into the teens overnight. Precipitation will reach Arkansas, far northern Louisiana, and northwestern Mississippi early enough Wednesday to fall mainly as snow at first. An associated surface low will skirt along the southeast Texas and then across the Louisiana coast on Wednesday. This low will transport warmer air overtop colder air at the surface. This warm nose will lead to a nasty freezing rain moving across eastern Texas, the northern two-thirds of Louisiana, lower Arkansas, and western/central/northern parts of Mississippi.
Due to strong, low-level warm air advection, the latest NAM guidance results in freezing rain/sleet transitioning to a cold rain more quickly across much of Louisiana and Mississippi later on Wednesday. Warm advection will partially be offset by melting on Wednesday, since the ice-to-liquid phase change is a cooling process. Plus, dry air in the low levels will result in evaporational cooling keeping colder air in place for longer. For these reasons, I favor the colder HRRR model guidance, which has an ice storm impacting areas farther to the south. The latest HREF ice accretion projections for Wednesday and Wednesday night provides some idea as to where the heaviest freezing rain accumulations will occur. A large swath of 0.5-1+ inch freezing rain accumulations could fall, resulting in widespread power outages. Due to the self-limiting nature of ice storms, freezing rain accumulations these high can be challenging to reach. However, surfaces already well below freezing will allow accumulations to occur immediately. To provide some perspective, amounts as little as 0.05-0.1 inches can cause major issues on roads, especially on bridges and overpasses.
Carolina and Mid-Atlantic Ice Storm Impacts and Timeline
The surface high across the Ohio Valley on Wednesday will shift into New England late Wednesday into Thursday. Surface ridging will build down the east side of the Appalachians, setting up a cold air damming setup. As mid-level ridging along the East Coast amplifies on Thursday, the surface low along the Gulf coast will take on a northeastward trajectory. As the feature moves across central Georgia and South Carolina during the day, rain will overspread much of the Southeast. However, enough cold air at the surface will allow a major ice storm to unfold across western/central/northern parts of North Carolina, much of Virginia, southeastern West Virginia, and into the Delmarva peninsula.
Strong warm air advection in the low levels will eventually result in a transition from sleet and/or freezing rain to a cold rain across upper South Carolina and lower parts of North Carolina. The timing on this transition will determine ice totals in that region. The latest HRRR guidance doesn’t depict any significant totals since it has sleet transitioning directly to rain, but HREF ensembles indicate a more prolonged period of freezing rain down to the North Carolina/South Carolina border. Ice totals in northern Virginia into the Delmarva peninsula should receive lower ice totals relative to areas to the south due to more snow in the beginning. For areas in between, the ice storm could bring totals reaching or even exceeding 0.25-0.5 inches.
A longwave trough with quite a broad base will remain almost stationary across the northern half of the U.S. this upcoming week into at least next week. A ridge will persist just off the West Coast, while a block sits over western Greenland. Another ridge will remain positioned over the southeastern quadrant of the U.S. This ridge will initially keep temperatures well above average across the Southeast; however, northern troughing will prohibit the ridge from amplifying unabated. A baroclinic zone will become established across the Southern Plains, Mid-South, Missouri Valley, Tennessee Valley, Southeast, Ohio Valley, and Mid-Atlantic. This setup will bring several opportunities for snow, ice, and rain across the mentioned regions over the next two weeks.
We discussed around a week ago how longwave troughing can suppress the storm track too far southward to bring any meaningful wintry precipitation. Instead, conditions are generally very dry and cold. If you recall, model guidance had a lobe of the tropospheric polar vortex digging as far south as the Tennessee Valley for early this week. Instead, we got a flatter trough with some Southeast ridging. In most guidance now, we’re stuck with a long-lasting broad-based trough that likely won’t keep the southern stream storm track suppressed.
Cross polar flow extending from Siberia over into western Canada has allowed Arctic air to pool over western Canada. That brutally cold airmass has already begun spilling into the upper Plains and Midwest. But essentially, we now have the available cold air to tap as numerous storm systems parade from the Southwest/Southern Plains in an east or northeastward direction. One major drawback to the expected pattern configuration is that ice (sleet/freezing rain) could become the more predominant frozen precipitation-type across the Southern Plains, Mid-South, Southeast, and even into the lower Ohio Valley and Mid-Atlantic. With broad troughing centered across the central U.S. and a Southeast ridge to the east, southwesterly flow will transport warm air above the surface. However, Canadian high pressure will wrap around very cold air at the surface. This will produce atmospheric profiles that support sleet/freezing rain versus snow.
Systems We’re Currently Watching
We have a slew of systems we’re currently watching that will bring impacts in the foreseeable future. We’re going to post articles and social media updates on each system individually, but we will introduce those threats here.
February 10-12, 2021 (Wed.-Fri.): Shortwaves embedded in mostly westerly flow will bring widespread precipitation across the Southern Plains, Mid-South, Missouri Valley, Southeast, Tennessee, along and south of the Ohio River, and the Mid-Atlantic. Canadian high pressure has continued to advect cold air at the surface across northern portions of where precipitation will develop. We expect a prolonged period of sleet/freezing rain to fall across northern Texas, central/eastern Oklahoma, northern/central Arkansas, lower Missouri, western Tennessee, upper Mississippi, and Kentucky. North of the Ohio River and areas across much of the Mid-Atlantic will experience mostly snow, although lower and central parts of the Virginias may get a mixture of snow/ice. For areas south, expect rain.
February 13-14, 2021 (Weekend): Forecast model guidance indicates HIGH uncertainty for this potential event. The outcome of this potential winter storm depends on the interaction of three features: a shortwave entering lower California late week, a shortwave entering the Pacific Northwest around the same time, and a lobe of the tropospheric polar vortex spinning over the northern Plains/Midwest. The European model continues to indicate that the California wave gets suppressed so far south that it passes across the Gulf of Mexico. This feature would bring rainy conditions to Florida and areas along and relatively close to the Gulf coast over much of the weekend. On the other hand, the GFS often has the California wave phasing with the Pacific Northwest wave somewhere over the central U.S. This scenario would result in the phased systems eventually taking on a northeastward trajectory. This scenario would potentially bring a significant winter storm to the central/southern Plains, the Mid-South, the Missouri Valley, the lower Midwest, the Ohio Valley, the lower Great Lakes, and Northeast over the weekend. I will admit that this is a tough forecast, and at the moment, I need additional time to study this event.
February 15-17, 2021 (Mon.-Wed.): A strong shortwave will enter the western U.S. later in the weekend and dig southeastward into the Four Corners region. As the wave continues eastward, the tropospheric polar vortex lobe will move eastward across the Great Lakes and Northeast. These two features will create a region of confluent flow across the Ohio Valley and Mid-Atlantic/New England, which will support Canadian high pressure moving eastward into the Northeast. This high will likely result in cold air damming as far south as the Carolinas and Georgia. A surface low will likely develop along the Gulf coast in response to the shortwave approaching the region. Cold air will already be in place across the Southern Plains, Mid-South, and much of Tennessee to support wintry precipitation. With cold air damming in place, the Carolinas, northern Georgia, and northeastern Alabama need to closely monitor the potential for an ice storm next week. This system could potentially bring an impactful winter storms to parts of the Ohio Valley, Mid-Atlantic, and (maybe) the Northeast. We have about a week to get into specifics. I advise against making any changes to current plans until confidence increases over the next two to three days.