Current Conditions at Sanborn Field
Thursday Night: Partly cloudy. Low: 42
Friday: Partly cloudy. High: 63
Friday Night: Mostly cloudy. Low: 51
Saturday: Cloudy with showers in the afternoon. High: 65
Saturday Night: Cloudy with showers and thunderstorms. Low: 58
Discussion:
Another cool night is ahead with temperatures dropping to 42 degrees with a partly cloudy sky. The clouds will hang around throughout the day on Friday as temperatures warm to 62 degrees. Cloud cover will slowly increase into Friday night, becoming mostly cloudy by Saturday morning as a warm front moves overhead. Some rain expected after noon on Saturday persisting into Saturday night. Although you may hear a few rumbles of thunder overnight, severe weather is unlikely. Rain could be heavy at times with rainfall amounts up to 1" expected.
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Forecasters: Heienickle, Meyer, Orr
Date Issued: 10/21/21 5:00 PM CST
Technical discussion:
The 12Z run of the GFS20 was utilized Thursday afternoon. After comparing the current surface conditions with the GFS20 and NAM, GFS better modeled the present pressure systems. GFS also displayed more accurate current surface temperatures.
The 250-mb map shows a trough passing over Missouri with an accompanying jet streak. A ridge, moving in after the trough, allows for stable conditions. This jet streak allows for northerly winds 03Z Saturday and continues through the forecasting period. Future forecasters should watch for the incoming strong jetstreak moving over Colorado.
Circulation is present over Mid-Missouri Thursday afternoon displayed at 500-mb, but vorticity exits to the east by 15Z Friday. Small circulations, associated from a greater circulation moving over Illinois, allows for mixing in the atmosphere in Missouri. Vorticity will move in to Missouri by 18Z Saturday, increasing chances for precipitation. Light rain is possible throughout the afternoon.
At 700-mb, moisture values remain low Thursday night into Friday. Relative humidity begins to increase 03Z Saturday. This increased cloud cover and moisture will allow for greater potential for precipitation in the afternoon and evening Saturday. Vertical velocity values remain low until 18Z Saturday.
Thursday evening will see colder temperatures as supported by winds at the 850-mb level. These temperatures will remain consistent due to increased cloud cover. A warm front will move through Friday night supported by southerly winds, bringing moisture and temperatures in the mid 50s. Temperatures will remain warm with southerly flow Saturday.
The soundings from GFS show a shift in surface winds to southerly flow Friday at 0Z, indicating the warm front moving in. Temperature and dewpoint values remain similar, creating a saturated environment. Saturday at 03Z, moisture and negative omega values are increasing. A high K-Index of 35 and precipitable water values over an inch tell of convective potential Saturday afternoon, presenting a good environment for showers and thunderstorms.
Future forecasters should look to the incoming low pressure system to the east of Missouri, which will bring convection and continued showers.
- Heienickle
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