Thursday, November 18, 2021

Current Conditions at Sanborn Field

 Sunny. High: 46

Thursday Night
Mostly Cloudy. Low: 30

 Mostly Sunny. High: 48

Friday Night: 
Mostly cloudy. Low: 37


Partly sunny. High: 58



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 Ending the week before break much cooler than it started, after the passage of a cold front yesterday. Colder air behind the front and a breezy northwesterly wind will keep temperatures cooler on Thursday, but the good news is that a warm up is expected as winds will shift to the south on Friday and warmer air will move into Mid-Missouri. Along with the more seasonable temperatures will come some more clouds on Friday and Saturday, but no precipitation is expected. Enjoy the quiet and fall-like conditions as you are preparing for Thanksgiving break!

- Duff


Forecasters: Duff, McDaniel, Aldrich

Date Issued: 11/18/21 10:00 AM CST

Technical discussion:    

The 06z GFS was used for our forecast today, as it initialized current and recent conditions better than the NAM, especially in relation to early morning temperatures. 

At 250 mb we can see that Missouri is featured at the bottom of a weakening trough, transitioning from negatively to positively tilted. We continue to endure the backside of the trough until 03z Friday, when the system and it’s jet streaks move off to the Northeast. As soon as it departs, though, a different set of jet streaks enter Missouri from directly west. Zonal in nature, these streaks are not associated with any trough, but are similar in magnitude to the streaks seen previously. They will affect Missouri from roughly 15z Saturday to 0z Monday, where they weaken and are carried off to the northeast by an incoming shortwave. The continuity of moderate jet steaks, different in direction but alike in their strength, indicates that Missouri will see a steady pattern of higher winds in the upper atmosphere, keeping the region fairly cold. 

Vorticity measurements appear to be mostly barren. Marginal vorticity leftover from last night quickly exits to the east later today, and values remain at zero throughout the entirety of Friday. A brief flaring of vorticity is observed over North-Central Missouri at Saturday 03z, but it is likely just an anomaly due to it’s isolation from any neighboring areas of vorticity. Also, high pressure building in from the southwest begins to approach Missouri at this time, making any serious bouts of vorticity unlikely at best. It is not until Sunday morning that vorticity values become sizable, correlating with the advancement of a shortwave trough. 

700 mb relative humidity is low for all of Thursday and Friday, as the drier air from yesterday’s cold front is centered upon the midwest region. Values will stay at nearly zero until Saturday 06z, where moisture slowly builds in from the northwest before accelerating on Sunday. Omega values do not seem to increase with moisture, though, indicating that any active weather or serious precipitation is likely. In fact, any rain would probably be in the form of very isolated/brief showers. 

850 charts clearly define a high pressure system moving west, pushing into Arkansas at Friday 06z, where it’s influence is large enough to affect the entire state. This supports indications of quieter weather at higher levels, and the system is powerful enough to bring warmer air from the gulf and southwest. As we become placed on the backside of the system at 21z Friday, we can expect the combination of southerly wind flow and southwestern air to warm our temperatures up considerably. 

GFS soundings display little moisture availability, with only some present on Friday night. Even then the readings are only enough to support some scattered, high level cloud cover that will not produce precipitation. 

Future forecasters should pay attention to the trough expected to enter the Great Plains on Sunday afternoon, as vorticity, omega, and humidity values look to increase drastically with it’s arrival. 

- McDonald

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