Raleigh Weather Discussion
Of course the big weather story today is the unfolding winter storm later this evening and overnight. We are under a winter storm warning for this evening and overnight. I have already posted my latest thoughts and snowfall graphic but here is a link to it in case you missed it.
For the Triangle, the rain today will quickly transition to snow probably around 8-10pm. This could even be accompanied by some thunder and lightning as the dynamics aloft will be significant. The snow will likely last for 3-6 hours and probably fall pretty heavily. Literal model output is predicting 4-7 inches across the Triangle, but this assumes a 10:1 snowfall ratio. Actual ratios will likely be a little less than that, like 7:1, but we will see a significant amount of precipitation fall between 7pm and 1am tonight perhaps up to a inch of qpf or more. So depending on how quick the transition occurs, we could see a nice quick dump of snow. For now, I am going for 2-4 inches across the Triangle. I am looking at the hourly soundings from the latest 12z NAM. The model changes RDU from rain to snow between 9-10pm this evening. With moderate to heavy snow from then till 2-3am. The model shows probably 0.5 to 0.75 inches of the QPF falling as snow. A 10:1 ratio would suggest 5 to 7.5 inches, a 7:1 ratio would be 3.5 to 5.25 inches, and a 5:1 ratio would be 2.5 to 3.75 inches. So for now a 2-4 general call seems good.
The snow will quickly end between 2-4 am from west to east and tomorrow looks cold. Temps will struggle into the 30s but likely not out of it. There will likely be some slick/snow-covered spots on roads tomorrow morning, although I would anticipate with a 2-4 inch snow, that the main roads will be fine by mid-day and in the afternoon. However, I would anticipate some icy spots Friday night and Saturday morning though as we appear to be heading into the low 20s for Saturday morning. So be careful then out driving around.
We warm up ahead of a cold front back into the 50s by Sunday, but another shot of arctic cold comes in later Monday and Tuesday. Tuesday will be a cold day with temperatures struggling to get above freezing. We will moderate as the week progresses, as another cold front drops down into the Midwest and approaches the East. This will result in southwest flow and moderating temps. The models are differing on the timing of the cold frontal passage with the ECMWF earlier and the GFS later, for now I will go with a passage during the day on Friday and cooler temps for next weekend but it starts to warm up again by Sunday/Monday. For now, after tonight’s snow event, I don’t see any in the forecast through late next week.
National Extended Weather Discussion/Forecast
A new trough will dig into the interior West/Rockies early in the 11-15 day period (~1/28) which will result in the ridge re-forming in the East with a warm-up. However, the model data is pretty united in showing ridging building in the western US and the –NAO re-appearing by late in the 11-15 day period which would take us to the last few days of January and early February. We get a new run of the Euro weeklies tonight, but the CFS weeklies maintain a cold forecast for weeks ¾ which take us into the first half of February.
So I guess the bottom line is that after a cold week next week, the following week looks to warm up in the East for several days, but a colder pattern will likely re-establish itself by the end of January.