Thursday, December 9, 2021


Current Conditions at Sanborn Field

Thursday Night:
Clear. Low: 42

Cloudy with chance for rain, breezy. High: 70

Friday Night:
Clouds with continued chance for rain, breezy. Low: 35

Clear. High: 47

Night: Clear. Low
: 32


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Your calendar might say it’s December 9th, but the weather certainly does not feel like it. The low tonight of 42 is only a few degrees shy of the average high for December (around 46). For Friday, the record high of 69 set only a year ago is in jeopardy as temperatures might make it into the 70s. Then a cold front moves through on Friday, dropping temperatures into the middle 30s, where they should be for December. Rain chances stay low with the front passing by, but a quick hit of rain cannot be ruled out. What will be noticeable will be the winds, cranking out of the south around 30mph with gusts approaching 40mph during the day on Friday. Saturday will feel more like winter, with highs in the 40s with a northwesterly wind around 20mph, lows might get near freezing Saturday night.  

- Meyer


Forecasters: Meyer, Heienickle, Orr

Date Issued: 12/9/21 5:00 PM CST

Technical discussion:  

This forecasting period was analyzed using a blend of the GFS and NAM models. When looking at the two models they both accurately depicted the low pressure system to our North. The NAM under forecasted the temperatures that were currently seen at Sanborn field. These variances from the actual forecast were considered when making this forecast. 

At the top levels, a jet streak moves through Northern Missouri Thursday night. Strong upper level winds push this weather through the CONUS. A strong jet streak will move through central Missouri around 18Z Friday. Missouri will see this jet streak with weaker winds throughout the day Saturday. 

Circulation shown at 500mb does not impact Missouri until Friday at 12Z. This vorticity quickly moves out of the area with another wave of circulation with strengthened values at 19Z Friday. Circulation continues to be present and significant values can be seen around 09Z Saturday. This circulation exits at 21Z Saturday. Small circulations renter at 00Z Sunday for a brief period of time.

High levels of relative humidity are not present Thursday night, giving way to clear conditions. Around Friday at 18Z, high levels of relative humidity enter the area and will remain until 00Z Saturday. This potential for rain is increased with the low pressure system moving through during this time. Late Saturday night increased values of relative humidity are seen.  

At 850mb, weak westerly winds allow for stable conditions Thursday night. Winds begin to shift southerly as a low pressure system forms over Kansas. This low pressure system moves to the East and moves just North of Missouri around Friday afternoon. There will be significant winds blowing in air from the southwest with winds up to 60kts. Around Saturday at 09Z, as a low pressure system to our North moves out, we see cold air move in. Winds shift to the Northerly and significant cold temperatures are seen. Cooler temperatures remain until the remainder of the forecasting period.

Thursday night, at the surface, will see average temperatures with weak warm air advection over Missouri. Strong southerly flow is seen just before it is interrupted Friday at 18Z from a low pressure system moving from Kansas to Northern Missouri. Significant warm air advection can be seen as the Low moves through. These warm temperatures exit with the low. Cold air and winds from the North are seen late Friday and into Saturday. Saturday will see cooler and more seasonable temperatures. 

The soundings for this forecasting period indicate multiple periods where rain could be a potential. 18Z Friday, when the low pressure moves through, sees potential for precipitation. Veering winds are present just before indicating there is warm air advection. There is moisture at the surface and aloft, but there is a dry layer around 850mb. This dry layer could be from the increasing southwest winds Missouri is receiving, but will prevent any significant rainfall. Later in the evening, 00Z Saturday, the NAM remains dry, while the GFS forecasts a slight potential for a thunderstorm with increased CAPE values and southwesterly winds.

- Heienickle

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