Current Conditions at Sanborn Field
Wednesday: Partly cloudy. High: 75
Wednesday Night: Clear. Low: 43
Thursday: Mostly cloudy. High: 60
Thursday Night: Mostly cloudy. Low: 44
Friday: Clearing sky. High: 64
Discussion:
If you need some simplicity in your life, it's your lucky day! Mild conditions are forecasted through the end of this week. It's probably about time to get used to keeping that jacket with you as well--we're going to start seeing much cooler temperatures following the passage of the cold front on Wednesday. It'll stay a bit cloudy on campus after tonight, but the sun will make its return by Friday.
- Macko
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Forecasters: Kobielusz, Macko, Bongard
Date Issued: 10/20/21 10:00 AM CST
Technical discussion:
This forecast was built using the 06Z run of the NAM40. Both the GFS and the NAM were accurately modeling a closed low near the South Dakota, Nebraska, and Iowa borders but the GFS was running about 2 degrees warmer than what was being observed while the NAM was running less than a degree warmer that what was being observed.
The most prominent features at 250-mb are a closed low pressure system centered over the border of South Dakota, Nebraska, and Iowa along with a storing meridional flow over the CONUS. This closed low is associated with a negatively tilted trough and has a jet streak that is situated just south of the low in Kansas. Through Wednesday, this closed low moves east to Minnesota and Iowa and the jet streak from Kansas moves into Missouri around 18Z. By Thursday, the trough has moved to eastern Missouri and an upper level ridge has begun forming in eastern South Dakota leaving us in a transitional zone for the remainder of the forecast period.
The
500-mb chart shows weak vorticity at 12Z on Wednesday morning as early
morning showers continue to dissipate and push east. This vorticity
continues to decrease throughout the remainder of the forecast period in
Missouri, but strengthens around the outskirts of the low in Minnesota
starting Wednesday night into Thursday morning. The region remains in a post frontal regime beyond Thursday morning to the end of the forecast period Friday afternoon void of any vorticity worth mentioning.
At 700-mb during the day on Wednesday, moisture left over from early morning showers will dissipate as the sun comes out and by 21Z on Wednesday, RH will be low and Missouri dry for the remainder of the forecast period. Any moisture, along with negative vertical velocity, will remain north of Missouri and close to the low.
At 850-mb there is a LLJ and high RH over Mid-Missouri at 12Z Wednesday morning but remaining moisture will be swept away by the passage of a cold front between 18Z Wednesday and 00Z Thursday. Due to the lack of significant moisture associated with this system the fropa looks to be a dry one. The LLJ strengthens as the cold front passes and the axis of the trough moves over Mid-Missouri, shifting winds from a southwesterly component to a northwesterly component. On Thursday morning, the trough associated with the low, now centered in Michigan, now has a positive tilt indicating that the system is weakening. The LLJ continues to move east on Friday as well as an area of high pressure beginning to form over St. Louis. Friday is dry but as the day goes on moisture from Kansas begins to make its way into Missouri by Friday evening.
-Kobielusz
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