Wednesday, February 13, 2019

Wednesday Night - Clouds move in becoming partly cloudy. Low: 40-44.

Thursday - Windy, increasing cloud cover becoming mostly cloudy by the afternoon. High: 54-58.

Thursday Night - Cloudy, temperatures drop quickly Low: 23-27.

Friday -  Mostly cloudy with a chance for afternoon snow showers. High: 21-25.

 Saturday - Mostly cloudy chance for afternoon wintry precipitation.  High: 30-34.

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A nice mild day for weather here in mid-Missouri. Mild southerly winds helped our high temperatures reach into the lower 50's with pockets of sunshine. Overnight lows will not drop significantly remaining mild. Clouds will begin to move in this afternoon into evening becoming partly cloudy as moisture near the surface increases. Tomorrow early will be similar to today with above average temperatures and some periods of sun. However winds will increase overnight and conditions will be breezy throughout the day tomorrow, with gusts around 35-40 knots. Temperatures will fall quickly Thursday night into Friday morning as a cold front will make its way into the area. Friday will be cold and there is a chance for light snow from Friday afternoon into the overnight hours. Accumulations are only expected to be around 1 inch but could impact the evening commute. Saturday afternoon we prepare for the next system to move through bringing a possibility of a wintry mix. 
Forecasters: Bongard, Sumrall and Hirsch
Issued: 2:35 p.m., February 13, 2019

Technical Discussion (The nerdy stuff we are discussing in class!)
Warm temperatures Wednesday afternoon have a western CONUS ridge and a high pressure system over the Gulf Coast to thank for highs in the 50's during the afternoon. The northwestern flank of the high pressure is helping to strengthen southwesterly flow at 850 mb over the southern Plains into the Midwest. Thickness charts show textbook perfect celanoids developed over this region helping to bump temperatures up 20-30 degrees higher than yesterdays cold highs.

Overnight this evening temperatures will regulate back only into the 40's as warm air advection continues into the morning and mid day hours of Thursday. The forecast area will again warm up though change is quickly on the way. The ridge aloft out west will deamplify allowing for a large upper level trough to swing into the northern Rockies. This will create a high powered zonal flow aloft over the southern CONUS in the form of a 180-200 knot jet streak from California into the southern Plains. This jet will be the catalyst for a very active weather pattern over the end of the week. First up, a central Canadian trough will swing a shortwave down into the Plains dragging with it a cold front that will wipe out the warm air advection we have enjoyed. Passage of this cold front looks to take place between 20Z and 00Z Valentine's Day night. Some disagreement occurs with precipitation development as NAM allows for scattered showers over the region and east of Columbia while GFS keeps precipitation chances well east of central Missouri. A slight chance for rain is possible though unlikely Thursday night as behind the cold front a bitter cold northwest flow dries the area out very quickly.

Low's in the 20's will make warming temperatures difficult Friday as we set up for the next round of winter weather to impact the region. Large model divergence with this system occurs as the NAM keep influence from the previous days trough over the area in the form of low level northerly winds. This will sustain the dry layer inhibiting precipitation development. GFS on the other hand will swing low level flow around to the east and southeast allowing for some moisture from the northwest to interact with the atmosphere overhead eroding the dry layer over Columbia. This will allow for snow to develop and sublimate into the dry layer moistening up the profile by 18Z. Moisture models are modest so even know the second half of the Friday forecast will involve snowfall the accumulations look to be in the 1-3 inch range. At 48 hours out it is hard to decide out a likely outcome at this point though the upper level flow leads to a GFS outcome as keeping the eastern CONUS based trough's flow over the region seems unlikely at this time. We will definitely need to reevaluate this precipitation situation in future model runs.

Below freezing temperatures Friday night will coincide with snowfall that will end by mid morning Saturday over Columbia at the latest. A quick moving ridge will rip through the Plains allowing a short window of dry time for the forecast area from Saturday morning into late Saturday afternoon. After that, another quick moving system riding the vigorous zonal jet across the CONUS will impact the area with yet another chance for snowfall Saturday night into Sunday.

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