Dec. 3: Warmth today, wintry weather this weekend?

Paul Heggen's Weather Blog


Our first winter storm of the season will approach central North Carolina over the weekend…but before that gets here, we get to enjoy another day of unseasonably warm weather today. Temperatures will reach the upper 60s and low 70s, with a mix of clouds and sunshine overhead:

The chilly air moves in from the northwest overnight — temperatures will drop about 30° from today’s highs to Tuesday morning’s lows:

Plenty of sun on Tuesday, but highs will only reach the low 50s, with some spots stuck in the 40s:

A very slight chance of rain will move through Wednesday morning, as the next wave of chilly air moves in. The North American Model’s radar simulation from midnight through noon Wednesday isn’t impressed with our chances of anything more than a trace:

Thursday and Friday will be dry but chilly, then the weekend gets…”complicated.”

It’s too early to have any confidence in the specifics of our wintry weather potential this weekend — the storm system that will head our way is still over the Pacific Ocean, over 3000 miles away!That said, it’s NOT too early to look at the possibilities. We’ll start with the model data — there are only a couple of models that look that far into the future, which simplifies things for the moment. The American GFS model shows cold rain moving in late Saturday, mixed with a few snowflakes…then a changeover to wet snow on Sunday, then more cold rain mixed with snow before everything wraps up late Monday. This animation runs from 7:00am Saturday through 7:00am Tuesday:This is the European forecast model’s simulation for the same time frame:The two models are actually pretty similar (which is remarkable enough by itself), but the European model shows 1) a later arrival of the precipitation on Saturday, and 2) cold rain during the daylight hours Sunday and Monday, with snow mixing in overnight and early in the mornings. That seems more reasonable to me, but our confidence in specific weather patterns more than five days in advance is tenuous at best. Any sleet/snow accumulations would be hampered by the fact that the ground is still warm, and air temperatures are likely to be a little above freezing. I’m not going to show you any model-produced snowfall forecasts at this point — not only are they 100%-guaranteed-to-be-wrong, but I’m not going to be the one to put that stuff out there for people to share on Facebook.What we CAN look at is the ensemble data — the models I showed above, but run dozens of times with slightly different conditions. That gives us a range of possibilities, and hopefully helps narrow down the “most likely” scenario. The European ensemble shows a 50-50 chance of even 1″ of snow/sleet accumulating in the Triangle through next Tuesday morning — higher chances to the northwest, much lower chances to the southeast:The Weather Prediction Center (a branch of NOAA that works in conjunction with the National Weather Service) is similarly cautious. WPC estimates a 30%-50% chance (I’ve rounded it to 40% on this map) from the Triangle to the north and west of “at least 0.25 inches of sleet/snow liquid equivalent”…which we can translate as, “enough sleet or snow to make a mess on the roads”:So at this point, it’s just something we’ll keep an eye on. If you have travel plans over the weekend, pay close attention to the forecast over the next several days as things come into focus. It’s WAAAAAAAY too soon to speculate on potential school closings, and you don’t need to clear out the grocery stores’ supplies of milk, bread and toilet paper.We’ll keep you updated — you can be certain there WILL be changes as we head through the week…it’s just the nature of winter weather forecasting, especially in the South. We’ll get some better model data once the storm system actually hits the West Coast and weather balloons can start sampling the upper atmosphere. In the meantime, I’ll be doing plenty of this over the next several days as we try to figure out exactly what’s going to happen.


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