Sunday, December 17, 2017

Sunday Showers and an Unsettled Pattern Ahead

 Showers Today, Mid-Week Warm Up, Late Week Storm Chances, Uncertain Christmas 



We've got a showery Sunday across the region. NWS Louisville mentioned the dry mid-level air limiting the efficiency of rain reaching the surface and based on current analysis data and radar images showing scattered light rain I certainly agree with that. Interesting to note that there have been reports of sleet mixing in with rain as well, which is realistic given the current environment. No impacts are expected since surface temps are simply too warm. Expect a rainy day to continue through the afternoon with areas of light drizzle possible through the night. Lows tonight shouldn't drop too much since I don't expect the clouds to go anywhere so it looks like overnight temps should be around 40º.
  Monday: Highs should reach the low 50's across KY with southerly low-level winds advecting warm air into the area. I do think cloud cover will be hanging around tomorrow so that cloud keep highs down a little bit but warm air advection will still be the theme. Lows Monday night will be in the upper 30's-low 40's as stubborn cloud cover keeps things insulated. 
  Tuesday: Similar start to the day with warm air advection/southerly low-level winds ahead of a weak front. All in all I'm thinking we won't see much rain from this system but scattered showers are possible. Highs should reach the mid 50's before the front passes and West/Northwest winds bring in cooler air. Overnight lows should drop to the upper 30's and high-pressure will build in leading to clearer weather for the next day or two. 
  Wednesday: Despite Northerly low-level winds I think highs should reach 50 or so since it will be much sunnier than now and daytime heating should be maximized. Of course clear skies will also allow overnight lows to drop as well so lows should have no trouble dropping to near freezing/32º. 
  
Thursday into the weekend is where things really begin to get unsettled AND uncertain. Upstream developments across the central Plains on Thursday will play a key factor in our holiday forecast. I want to point out that I will definitely be posting updates frequently because, the truth is, we just don't know for sure how the small details will play out and things seem to change with every observation and model run. 

A strong low-pressure system will likely develop along the East side of the Rockies. This low-pressure system will slide eastward dragging a warm front across the region and a trailing cold front behind it. Thursday and Friday should be fairly warm and temps will flirt with 60º. I think we may see thunderstorms during the Thurs-Fri timeframe and I'm not willing to rule out strong-severe storms. Wind fields should be relatively amplified, providing sufficient wind shear, and if daytime heating & moisture return reaches the potential I expect then there could be some destabilization. Storm chances would be increased if the front is favorably timed (passes during max destabilization).

(Current model data showing different possible positions of upper air & surface features for Christmas. Notice the spread and inconsistency)

Then we move on to the Christmas weekend forecast, which is riddled with even more uncertainties. Honestly, there are too many possibilities right now for Christmas weather so, unlike some, I'm not going to pretend that I know what will happen. Model guidance isn't any help right now because there are so many inconsistencies you can find a model that suggests any type of weather you want that far out. What I do know is that colder air will stream in behind the front and will be deep enough to support wintry precip. Some models have been very consistent with snow chances for Christmas Eve/Day. Some have been very consistent keeping us dry. It's anybody's guess which to believe. I will say it's important to follow along closely as we get closer and confidence increases because there is a real possibility for winter weather affecting the holiday weekend, especially if you're traveling. 
DKK