Winter Storm Izzy - Major Mess for the East Coast!

Disclaimer *First of all, I apologize for formatting. I was not able to get the text to wrap around the images like I usually can, so things might look a little wonky on the mobile version of this post*...

The "What"

Models were hinting at a major winter storm this weekend around this past Monday or Tuesday, and now that we're within 48 hours models are aligning in their predictive calculations. If you just want totals, types of precipitation, and impacts expected, you can skip to the end. The 4 .gif files that I'm using are the surface and 850 mb model guidance temperature for the GFS and NAM weather models from the 06Z model run through 48-66 hours. I used these to show the differences in each model with respect to temperature at the surface as well as in the mid-atmosphere so that you can see where the model is getting it's guidance from.

The Setup

Synoptically we have the jet stream dipping quite far south, allowing for positive vorticity advection into the deep Southeastern United States, as well as much colder air temperatures plunging southward. The upper-level low is followed closely by the surface low, but the persistent Bermuda High is forcing the surface low to track northward more rapidly than initially modeled.  
The surface low will be moving up through the western Piedmont of NC, which will cause strong warm air advection from the Atlantic to heat the mid-atmosphere to temps above freezing for central NC, however the surface cold pool from the

 last two days of cold air damming from the

 Canadian High and northerly winds has locked in

 sub-freezing surface temperatures for the duration 

of this event until about 21Z Sunday or 00Z Monday (5-9pm Sunday night EST).

The region in which you reside will have a substantial impact on the type of weather you'll experience from this winter storm, named Izzy by The Weather Channel. Were the surface low tracking closer to the coast, this would be another winter storm like that of January 2000 for central NC (22" of snow in Raleigh for those of you who were here at the time). If it were tracking 

more over Fayetteville and up through VA Beach, we would have more of the '04 or '06 ice storm scenario. This time around, the low is tracking northward near Durham, and because of that we're getting a warm nose of air from the Atlantic in the mid-atmosphere (around 850 mb -750 mb, or roughly 1.5km - 3 km, which will quench all snow chances 

throughout the early afternoon to evening hours on Sunday. 

Types of Precipitation by Region:

Mountains

If you want to see snow, the mountains are where you'll 

want to go! Areas west of Pilot Mountain and north of Charlotte will be experiencing an all-snow event through even Monday

 afternoon and could see some pretty nice snow totals with some areas like Boone even topping 1 foot!

Foothills

Places like Hickory, Statesville, and especially further north like Mount Airy and Pilot Mountain will experience mostly snow through the event and due to surface temperatures should have some nice accumulation of up to 8-9 inches, especially areas further north which will benefit from additional accumulation on Monday morning as the low continues to track north. 

Western Piedmont

Getting into Winston Salem and down to Charlotte will experience still snow but less than foothills, however due to that pesky warm nose in the mid-atmosphere the temperature will rise above freezing by mid-afternoon on Sunday which will cause falling precipitation aloft to melt prior to coming into the surface air. The surface air, however, will still be below freezing and thus liquid precipitation will freeze on contact. This is freezing rain. After a few inches of snow (4-6" for this area), precipitation will transition to freezing rain before making a transition back to snow by dinner time for a short while before the precipitation ceases to fall. 

Central Piedmont into Sandhills

This is where things get really messy. Precipitation will begin as early as 4 am Sunday morning in the Sandhills but hold off until around 10-11:00 am as far north as Henderson. The reason behind this is because the cold air settling in on Saturday night is not only cold, but also very dry. Part of the cooling will come occur from a process known as "evaporative cooling", which is the short and sweet describing the process by which liquid moisture evaporates into dry air as it falls, working to saturate the air with respect to water vapor, absorbing heat from the atmosphere to do so. 

I'm expecting precipitation to start as snow prior to lunch in this area, transitioning quickly to sleet then freezing rain before early afternoon. 

Afternoon hours will experience a surface temperature rising above freezing, which will cause liquid rain to fall at the surface and work to reduce accumulations of all types of wintry precipitation. 

Getting into dinner time the temperature will drop back below freezing at the surface, and precipitation will make a shift back to freezing rain before ending around mid-evening on Sunday. 

Coastal Plains

The Coastal Plains will experience mostly liquid rain for the duration of the event, with the heaviest rain occurring mid-afternoon Sunday into dinner time (timing from south to north) as the low tracks northward. 

Types/Accumulations Summary:

Mountains:

Snow: Early Sunday morning - Sunday night: new accumulation 12-15"

Foothills:

Snow: Early Sunday morning - Sunday afternoon: new accumulation 6-8"

Sleet: Sunday afternoon - Sunday evening: new accumulation 1-2"

Western Piedmont

Snow: Early Sunday morning - Sunday afternoon: new accumulation 3-4"

Sleet: Sunday afternoon - dinnertime Sunday: new accumulation 1-2"

Freezing Rain: dinnertime Sunday through Sunday night: new accumulation 0.25-0.3" in spots (primarily eastern Charlotte suburbs/Goose Creek area through Wadesboro looking east and up through Asheboro looking north)

Central Piedmont into Sandhills

Snow: Mid Sunday morning: new accumulation 1-2" (higher totals expected closer to VA border)

Sleet: Late Sunday morning: new accumulation 0.5-1" (higher totals expected closer to VA border)

Freezing Rain: Late Sunday morning - early Sunday afternoon: 0.1-0.25" (more FZRA south into sandhills - Sanford, Lillington, Pinehurst, Fort Brag, and Rockingham and less FZRA north into the Triangle)

Liquid Rain: Sunday afternoon - Sunday evening: new accumulation 0.50-0.75"

*Liquid rain will transition back to freezing rain after dinner into the mid evening on Sunday.

Coastal Plains 

Liquid Rain: Sunday: new accumulation 2.0-2.5"

Impacts:

The major impacts will be to travel and power outages. 

Power Outages:

Since the winds will be picking up throughout the day Sunday and shifting from a northerly wind pattern to more of a westerly/southwesterly pattern and the ground will be wet, I expect downed branches, trees, and power lines. Make sure to have plenty of candles, backup batteries, and flashlights prepared and that you have the blankets you will need washed, because it will get cold on Sunday night and Monday night. 

Travel Impacts:

The roads will be treacherous on Sunday into Monday. Surface temperatures will drop below freezing on Sunday night and again on Monday night. I highly discourage Sunday and Monday travel, especially west of I-95. Tuesday we will likely experience a slick commute west of I-95, and things will likely be closed down between US-1 and I-40 due to ice accumulation on Sunday. 

Stay tuned to your local news stations for updates on the pattern as it may shift slightly in the next 36-48 hours, but this is what we're looking at for now. Be safe and keep your eyes to the skies!

*graphics credits to College of DuPage (weather.cod.edu), NWS, and NOAA for the .gif files and the 5 things to know*