A Tale of Two Cities (or Four P-Types in this case).

Winter weather is tearing across the eastern half of the United States, and it has come time again to analyze possibilities for an extreme winter precipitation event in the Carolinas! 

The Setup

This week has been filled with student hope and parent dread as another winter storm is working its way through the United States. A strong Miller Type-A synoptic pattern will be demonstrated by the Canadian High air mass over the Great Lakes propagating eastward funneling cold air down the coast while a Low originates in the Gulf and propagates along the eastern seaboard, providing ample moisture for significant precipitation. While there are a number of ways to achieve wintry precipitation in North Carolina, this type of system takes the cake in terms of providing both cold air and moisture. 

We've been watching this particular system for about a week, and it is turning out to be nothing less than a mess. A cold air damming wedge is providing cold surface temps while onshore flow from the SE is providing warming temps about 1000m off the ground. The Hurricane Hunters dropped dropsondes into the system earlier today to get the best possible reading of the atmosphere prior to the latest model run. 

General Expectations

The system is going to be messy. Subsequent model runs have hinted at a more northward shift of the center of low pressure which damages snow accumulation chances in the Carolinas. As it stands, this is looking like more of a sleet fest with some snow and freezing rain mixed in. Valid for the same operational time - 12Z on Sunday, January 25 (7:00 am Sunday) - the ECMWF (European model) and, the GFS, and the NAM (American models) seem to be aligned pretty well as to the dynamics playing out. Generally speaking, there will be a large area over the Carolinas and southern VA of sleet with freezing rain bordering the sleet and liquid rain closer to the coast and along the eastern side of the mountains. Snow will be far more prevalent the further north you live into VA, West VA, and especially Kentucky as this storm progresses. The mess is going to be determining how much of each precipitation type to expect. As is 'law' in the world of real estate - location, location, location. 

Specific Accumulation

Snow accumulation, while still possible in NC (likely less than 2 inches total accumulation) will be contained to the northern border of NC. The band of heaviest snow will extend from Missouri through Kentucky, and West Virginia where totals will likely exceed 1 foot with localized heavier snowfall totals exceeding 15 inches. 

Sleet accumulation is more difficult to nail in this instance as there are so many factors contributing to the precipitation type. I wouldn't be surprised if the Piedmont extending out to about I-95 experiences anywhere from 1-4 inches of sleet accumulation with a snow mix at times. Sleet will likely be the main p-type through this system even up into southern VA and Virginia Beach, so the accumulation from Danville, VA through Virginia Beach will likely be fairly mixed between sleet and snow. Particular to this storm, the further north and west in the state, the higher your accumulation of sleet and possible snow. 

Liquid Rain will be the main result for most of GA, southern SC, and the Outer Banks. Rain totals will hover around 1 to 1.5 inches of liquid. 

Freezing Rain will be the real kicker for this system. The pesky warm nose around 900 mb-700mb is going to really cut down on frozen precipitation totals and increase the likelihood for freezing rain accumulation as the storm progresses NEward. On the high end, which I pray does not come to pass, there is a possibility for over 0.75" of freezing rain in north central Georgia, 0.4" in SC and the NC Coastal Plains, and even 0.5"+ in eastern TN. Realistically might experience half of that, but nonetheless the hazard that poses for safety and power outages as we enter next week is frightening.

Timing

The system will organize over Texas on Friday overnight and begin propagating eastnortheastward. By Saturday afternoon, eastern TN and the Appalachian Mountains will begin receiving a mix but primarily sleet. Saturday overnight the system will cover the Carolinas and VA producing roughly the mix seen above in the 12Z model images. By sunrise on Monday morning, the system will be off affecting New England and largely out of our hair. I would imagine the GOES-16 visible image from Monday morning/afternoon will be quite impressive in terms of areal coverage of snow, sleet, and freezing rain. Behind the system conditions will be blustery... a terrible situation for heavy power lines. I will discuss hazards below. 

Hazards

Travel - The initial hazards with this system will include travel and accessibility to resources. Roads will be impassible and it will be best to stay home. Brine solution only provides so much protection against sleet and freezing rain as the first layer of melting precipitation frequently washes away the salt. 

Temperature - We may set some low temperature records behind the system. Current model output is showing bitterly cold temperatures in the single digits and possibly below 0 in some places on Monday night into Tuesday. This will largely depend on cold air advection within the system and cloud cover behind the system. The clearer and calmer the air, the more rapid cooling occurs. The temperature will not rise above freezing again until Wednesday of next week, and anything that melts will refreeze on Wednesday night with another night in the low 20s. Be careful of black ice and slippery bridges. 

Power Outages - There is a possibility of widespread power outages, if not in NC, then in SC and GA due to freezing rain on power lines and winds (verification-dependent). If you have a generator, now is a good time to get it gassed and greased up so that it is ready to go on Sunday and Monday if needed. 

Food - As travel will be highly limited for a few days, and the temperature will remain cold for so long, stores will likely be closed until Wednesday or later depending on infrastructure. My family and I have purchased a case of bottled water and some canned soups just in case the power does go out. We also restocked our battery supply so that we have plenty of flashlights available in the event of a power outage. 

Action Items (Precautions)

I am not telling you what to do here, rather providing some suggestions based on historical experience with winter storms. It would be prudent to:

1. Make sure batteries are ready to go for flashlights or other lantern-type equipment.

2. Charge any portable battery chargers in advance so that you can have cell phone power for longer.

3. Stock up on sufficient non-perishable items like bottled water and canned goods to be prepared in the event of power outages. This does not mean buy the whole store out of bottled water... it will only be half a week. 

4. If at all possible, stay off the road after precipitation starts falling. Roads are going to get very slick very quickly, and I would hate to see one of you in a ditch or next to a tree!

5. Mentally prepare to ride out the storm for a few days. Things will not return to near normal until Thursday of next week. 

That's about it! If you have any questions, you know where to reach me; and remember, keep your eyes to the sky!