Wednesday, October 27, 2021

 

 

Current Conditions at Sanborn Field




Wednesday:
Overcast. Increasing rain chances throughout the day. High: 59
 

 


Wednesday Night:
Widespread showers. Low: 47
 



Thursday:
Steady rain. High: 50
 

 


Thursday Night:
Scattered showers. Low: 47

 


Friday
:
Overcast. Rain ending in the morning. High: 50


 
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Discussion: We have reached the time of year where you are going to need to start digging that heavy jacket or coat out of the back of your closet as temperatures will continue to drop and rain chances increase on Mizzou’s campus. Abundant moisture along with a low pressure system are going to bring us rain chances throughout the next few days. Scattered rain is expected to begin on Wednesday afternoon and increase to widespread, steady rain showers by Wednesday night, continuing into Thursday. Rain begins trailing off on Friday and the sky will begin to clear as we head into Halloween weekend. Severe weather is not expected, but there could be a rumble of thunder or two. Rain totals are expected to be around 1.5” throughout Friday afternoon.

 

-Kobielusz

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Forecasters: Kobielusz, Macko, Bongard

Date Issued: 10/27/21 10:00AM CST

Technical discussion:  

This forecast was developed utilizing the 06Z run of the GFS20. The same run of the NAM40 resulted in temperatures several degrees cooler than those that were observed. Additionally, the GFS modeled the low-pressure system in the Central Plains with greater accuracy. 

A deep upper-level trough near the Colorado-Kansas border is evident on the GFS 250-mb map. The strongest region of the upper-level jet is found to the trough's west. However, central Missouri will fall under the influence of the eastern portion of the jet stream by early afternoon on Wednesday. This region of the jet is expected to cross the Illinois border by Thursday. The jet streak initially described as being on the western side of the upper-level trough will start to round the trough as the trough deepens on Thursday. It is expected that this jet streak will amplify further south near the lower Mississippi Valley. Missouri will still fall under this deepened trough until it pushes further east towards the end of the forecast period. Upper-level divergence is also expected over the state during daylight hours on Wednesday before dissipating.

500-mb vorticity maps indicate that vorticity will be prevalent around the middle Mississippi Valley throughout the day on Wednesday into the overnight hours. By daybreak on Thursday, much less spin is anticipated. Vorticity is expected to return over central Missouri by Thursday night and into Friday.

The 700-mb layer, already moist at the beginning of the forecast period, is expected to become further saturated through the end of the week. Relative humidity values are expected to exceed 90% by Wednesday afternoon. This moist status will remain until the end of the day on Friday when the layer may begin to dry out. Positive omega values become prevalent over mid-Missouri after nightfall on Wednesday, but will become much less widespread by sunrise before becoming negligible. 

An extremely well-defined low-level jet is seen on the GFS 850-mb map. The jet, having a strong southerly component, will pull warm, moist air from the gulf into Missouri during the day on Wednesday. This will raise the dewpoint temperatures expected at 850-mb through Friday, indicating that this layer will be moist as well. The LLJ will begin to weaken slightly during the day on Thursday as it continues to track eastward. A well-defined low-pressure system will dominate the weather over Missouri though the end of the week. Due to the center of this low-pressure system being just to the south of Columbia, it will encourage rainfall to persist even after the passage of the cold front on Thursday.

At the surface, cooler temperatures are expected following the passage of the cold front mid-day on Thursday. Precipitation totals from this system are expected to range from 1" up to 1.25". A little over half of this precipitation is expected to fall on Wednesday night before the cold front passes through Columbia later on Thursday.

- Macko

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