Friday, February 12, 2021

 Current Conditions at Sanborn Field

 Wind Chill Advisory from 9PM Friday night through 12PM Saturday...likely extended

Friday Night - Overcast. Wind Chill Advisory. Cold, windy. Low: -2-2.

Saturday-  Overcast and cold. Wind Chill Advisory in effect. High: 8-12.

Saturday Night -  Cloudy. Frigid and windy conditions. Low: -4-0.
Sunday - Cloudy. Cold with light snow beginning before noon. High: -2-2.

Monday - Overcast. Light snow. High: 0-4. 

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If you thought it couldn't get any colder here in mid-Missouri, it will. This weekend will bring with it frigid temperatures, blustery winds, and a chance for accumulating snow. The frigid arctic air mass that has kept temperatures in the teens will surge southward as a low pressure system travels eastward across the country. Temperatures will struggle to get out of the single digits for the remainder of the weekend. Winds from the northeast at 10-15 mph will bite. The National Weather Service has issued a Wind Chill Advisory and will likely extend it into this weekend. Wind chills could be as low as 20 below in the morning with daytime wind chills staying well below 0. The above mentioned low-pressure system will bring a chance for accumulating snow Sunday into Monday. There is still uncertainty as to the path of the system, but current thinking has the highest accumulation staying in Southern Missouri. Columbia will likely see up to 3 inches of snow by Monday evening. These totals are subject to change, so make sure you stay tuned to your local station or the National Weather Service for latest developments.

Forecaster: Bongard, Travis
Issued: 5:00 PM CST 12 February 2021
Technical Discussion (The nerdy stuff we are discussing in class)

GFS continues to verify as the model of choice as NAM trends too warm for initial conditions at the onset of the forecast period. The largest impacts of this forecast will be the potential record setting low temperatures Sunday and Monday as well as possible snowfall chances and accumulations on those days as well. A continental arctic air mass has always begun to creep further southward into the central CONUS this afternoon and is set up to send surface temperatures in central Missouri plummeting this weekend into the low single digits and even below zero at times.

Upper air analysis show a large long wave trough draped across the northern CONUS from the Rockies through the northern Plains into the Great Lakes region. Columbia finds itself in the axis of this long wave and due south of the upper level low spinning over central Canada this afternoon. A weak shortwave traversing the flow out of the Rockies will begin to amplify the long wave deeper into the CONUS Saturday before being swallowed of by the long wave flow. Amplification will increase especially to our west as a stronger shortwaves emerges in the flow. This will place mid-Missouri in the divergent right entrance region of a jet streak Sunday morning helping in potential precipitation development. The flow will continue to amplify considerably Sunday afternoon and overnight into Monday as a deep trough will bisect the CONUS in meridional flow. The trough will become positively tilted as its axis passes through the Midwest Monday afternoon and evening.

500-mb vorticity analysis confines most of the energy with the long wave trough to the northern CONUS flow. Vorticity associated with the first shortwave riding the long wave across the country will slowly advect into the region overnight tonight into Saturday. Most of the energy with the wave will dive south away from our region keeping precipitation chances minimal Saturday. The stronger of the two shortwaves will trek vorticity into Missouri again Sunday morning and keep circulation overhead through the remainder of the weekend into Monday. As the system associated with the shortwave passes through the Midwest the majority of energy associated with it will travel through southern Missouri missing the forecast region.

The low level moisture profile is saturated but holds small PWAT values of around 0.3 inches of water thanks in part to the bitter cold temperatures. Cold air advection at the low levels in the form of northerly 10-15 knot flow will help drive temperatures to near below 0 Sunday morning. There is a good likelihood that the low high temperature record for KCOU will be shattered as historic cold air entrenches itself over the region Sunday and Monday. Given that the low temperature records are -5 and -15F Sunday and Monday respectively it will be harder to topple those records though the Sunday record may be in jeopardy. Wind chills near -20 and -25F respectively will likely prompt additional Wind Chill Advisories and maybe even Warnings in Missouri as the weekend comes to a close.

Snow chances Sunday morning increase as the shortwave approaches from the west. Model soundings so a saturated profile by 15Z with temperatures and dewpoints well below zero just above the surface. With little moisture to work with in this bitterly cold atmosphere light but persistent snowfall is expected Sunday with accumulations of an inch in some locations expected. Snowfall persists through Monday afternoon according to model soundings though final accumulations totals only top out at 2.5-3 inches by the end of the forecast period Monday afternoon.

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