Thursday, December 22, Noon
Today’s rain was very close to being a surprise for the metro area as cold air hung on longer than expected. Unfortunately, unless you are west of Frederick, you likely saw a cold rain with an occasional pity sleet pellet. However, out near the Blue Ridge, a couple of inches of snow has fallen and with the arrival of ridiculously cold air tomorrow morning, there are some areas out there that might have a White Christmas.
For us, we hang our hopes on the frontal passage tomorrow morning to bring at least some mood flakes, definitely the coldest temperatures we’ve seen in several years, and possibly an ugly commute. There’s no doubt that the front means business. The temperature yesterday at 4PM in Denver was 42, and at 5PM it had fallen to 5; a 37 degree drop in one hour. Other cities out west had similar hourly changes, and although the mountains will ensure that we won’t have that kind of difference in an hour, I can easily see a 20 degree drop in two hours. Combine temperatures falling below freezing with any rain or snow that accompanies the front and the inability to pre-treat roads, and it’s a recipe for nasty travel conditions. Unfortunately, all of this will likely play out in real time because there is so much uncertainty.
The cold air is presently modeled to arrive tomorrow morning with temperatures falling below freezing between 8 and 10AM. There will be a lull in precip later today and tonight, but showers and possibly a thunderstorm will accompany the front. And it’s going to get windy. Like miserable windy. So, the obvious question is, will there be any moisture on the roads, and how much, when we fall below freezing? I still don’t want to make a guess as I want to wait for another model to come into range and then update this evening. So for now I’ll leave you with the most recent NWS discussion and their take.
.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... A strongly forced convective line of low topped showers and/or storms may form immediately along the front early on Friday morning. These showers/storms could be capable of bringing down very strong wind gusts from aloft. Strong winds will also ensue within the cold advection behind the front itself. Wind gusts in excess of 40 mph appear possible areawide Friday afternoon, with gusts up to 60 mph possible in the mountains. This could lead to downed trees and other wind damage, which could result in numerous power outages. An extremely cold air mass will follow this frontal passage, and it is going to come in quite fast on Friday. Main adjustment made to the forecast for this period was to speed up the arrival of cold air on Friday. Temperatures in the teens to low 20s likely arrive to the I-95 corridor during the early afternoon hours, if the recent trends in guidance are correct. This paired with some lingering moisture behind the front could spell trouble for the afternoon/evening commute. Any precipitation at this point would fall as snow, and given the rapid onset of cold temperatures, would likely flash freeze onto road surfaces. Still some uncertainty if that happens in the metros, but definitely an issue worth monitoring, especially given that this will occur on the Friday before Christmas.
The Weather Mill 