Tuesday, October 29, 2019

Tuesday Night - Rain showers. Mixed precip late. Low: 29-33

 Wednesday - Rain showers. High: 33-37

 Wednesday Night - Rain, changing to mixed precip late. 
Low: 28-32
Thursday - AM snow. Mostly cloudy. High: 32-36
Friday - Partly cloudy and warmer. High: 44-48

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Tuesday night we will see rain showers with mixed precip later in the night hours with lows in the upper 20's to lower 30's. Wednesday will see rain showers with highs in the mid to upper 30's, the rain will continue into the night hours with mixed precip, lows in the upper 20's to low 30's. Thursday morning will see snow with clouds starting to clear late in the day, highs in the mid to upper 30's. Friday will be partly cloudy and temperatures will start warming up, with highs in the mid 40's.
Forecasters: Lujan, Savoy, Vanderpool, Heaven, Munley
Issued:  5:00 pm; October 29,  2019

Technical Discussion (The nerdy stuff we are discussing in class!) 

The WPC Model Diagnostic Discussion advocates to use ECENS mean with ECMWF/UKMET/CMC blend. However, the models are not handling the situation in our area very well. Previous model runs indicated that the high temperature this afternoon would be in the mid 40's and we did not get there. Currently we are at 37 in Columbia. This would indicate that there is a significant spread in temperature predictions among models, and that they do not have a good handle on the unfolding situation. With the observed temperatures falling well below the predicted values, our forecast shift has decided to go mostly with GFS and short-range models (HRRR and RAP), as well as guidance from the SREF. However, we will keep in mind the fact that actual temperatures will be slightly cooler than what models indicate. 

Tonight temperatures will be near freezing with with saturation from the sfc to 500mb. We may see liquid precipitation transitioning to mixed precipitation as the night wears on. Short-range models show Columbia right on the edge between rain and a sleet/snow mixture between 06-09z Wednesday, with soundings indicating a temperature profile that could go any way. Temperature changes of just 1 degree will make the difference between rain and a wintry mix. Therefore, have included mention of mixed precipitation later tonight, but this is not certain. 

Tomorrow, temperatures may manage to make it into the mid 30's. Rain will persist through the morning with a break possible in the afternoon. Tomorrow night low temperatures will range in the upper 20's to lower 30's. Rain in the evening will transition into mixed precipitation overnight. Thermal profiles will briefly support a mixture of sleet and freezing rain as precip transitions to snow. This window of mixed precipitation should only last an hour or two before the column goes entirely below freezing and we start to see snow. Only concern here is a lack of moisture in the DGZ, which could lead to inefficient snow production and possible freezing drizzle mixed in. 

Thursday, snow looks to continue until mid day. Model soundings from both the GFS and NAM show a saturated column through 18z, and possibly as far as 21z. Therefore, we will at least see clouds throughout most of the day Thursday in addition to the morning/mid-day snow. Temperatures look to max out in the lower to mid 30's by afternoon - much, much colder than seasonal averages. 

Friday temperatures may be in the mid to upper 40's. GFS and NAM soundings show mostly clear skies with weak lower-level WAA. Therefore, at least a seasonally cool Friday looks to be in store.

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