Current Conditions at Sanborn Field
Wednesday: Mostly sunny. High: 72
Wednesday Night: Clear and colder. Low: 46
Thursday: Clear skies. High: 75
Thursday Night: Clear. Low: 52
Friday: Partly cloudy. High: 80
Discussion: Fall weather is in full effect on campus after the frontal passage Monday night into Tuesday that brought cooler temperatures and much needed rainfall to mid-Missouri. Seasonal high temperatures will be the story for Wednesday and Thursday with the coldest temperatures seen since May returning to the area thanks to clear skies overnight tonight. A warming trend will begin Thursday and take a significant leap toward warmer temperatures Friday thanks to the presence of high pressure to the south. Fair will preside over the region to close out the work week.
-Bongard
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Forecasters: Kobielusz, Macko, Bongard
Date Issued: 09/22/21 10:00 AM CST
Technical discussion:
For this forecast period the 06Z run of the GFS was chosen based upon its consistency with current conditions, specifically surface temperature. The NAM was running significantly colder than what is being observed.
For Wednesday, upper level model charts at 250 mb reveal a ridge-trough pattern over the CONUS. Northwest flow in the Midwest is evident behind the frontal passage that occurred Monday night into Tuesday. Vorticity at 500 mb resides just to the east associated with the aforementioned fropa that will slowly erode to the east over the course of the day. The northwest flow is consistent with lower levels as well where a lack of moisture will keep skies mostly sunny today. The region is entrenched in post frontal weather regime.
Wednesday night will host continued northwest flow over the region though the ridge to the west over the Rockies will begin to push into the central CONUS by Thursday morning. A new trough just off the coast of the Pacific Northwest carrying with it plenty of vorticity at 500 mb will begin to make its way into the Intermountain West. The lack of moisture in the lower levels continues which will lead to plenty of radiational cooling overnight tonight dropping temperatures into the upper 40's; the coldest its been since May 31st.
The low pressure system that impacted the region earlier in the week meanders over the Great Lakes region as the upper level ridge finally pushes into the Midwest. This will prompt upper level flow to begin to shift from the northwest back to the west inducing zonal flow over the area by Thursday evening. The trough to the west slowly makes its way over the Rockies Thursday as the ridge begins to de-amplify thanks to the strengthening of a trough over central Canada. High pressure builds to the southwest which will be the impetus for warmer conditions to close out the forecast period.
Zonal flow aloft Thursday night takes over as the ridge dissipates and the trough to the north takes over the flow regime. A slight increase in low level moisture may add some cloud cover Thursday night stabilizing overnight lows to more seasonal levels. The high pressure system begins to migrate to the east promoting west-to-east surface winds overnight.
Friday will be significantly warmer than Thursday as the western flank of the high pressure to the south turns surface winds to a more southerly course. The trough to the west will make its way into the central CONUS but fall short of reaching Missouri before the end of the forecast period Friday afternoon. This system embedded in the trough is packing plenty of moisture and vorticity to potentially impact the region this weekend. Future forecasters should monitor this system closely.
-Bongard
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