Wednesday, November 10, 2021





Current Conditions at Sanborn Field

Overcast. High: 67

Wednesday Night:
Overcast with showers beginning late evening. Low: 48

Sunny. High: 56         

Thursday Night:
Partly cloudy. Low: 38


Building clouds. High: 43



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- Kobielusz


Forecasters: Kobielusz, Macko, Bongard

Date Issued: 11/10/21 10:00 AM CDT

Technical discussion:  

    This forecast was developed using 06Z GFS20 guidance. Both the NAM40 and the GFS20 verified when modeling MSLP across the CONUS, but the GFS was more accurate when predicting Wednesday morning's low temperature. Satellite imagery and GFS20 modeled soundings were also used in evaluating the atmosphere for this forecast period.

    Wednesday is off to a relatively boring start over central Missouri, but activity is to pick up in the evening hours. The day begins with zonal flow across the state before meridional flow takes over later this evening. Such a pattern will last through the end of the week. The 250-mb plot shows prevalent upper-level divergence extending from southern Iowa down into Texas, hugging the Kansas-Missouri border. This region of divergence will continue to track eastward overnight before weakening considerably around mid-Missouri. Once this weakening occurs, the jet will pick up in speed. A negatively-tilted trough with Canadian origins will begin to move to the southeast overnight on Wednesday. This will allow the jetstream to strengthen further during daytime on Thursday due the winds rounding the trough south of Missouri. By Thursday night, central Missouri will fall within the jet core. The deep upper-level trough previously mentioned will begin to tilt eastward as it changes directions, traveling to the northeast. In association with the recently acquired title of "positively-tilted trough", the jet will begin to weaken.

    500-mb plots also suggest that Wednesday night will be the most active. Considerable vorticity is to be expected around the same region with well-defined upper-level divergence. This circulation maintains its magnitude throughout the evening as it makes it into central Missouri. By early morning on Thursday, this vorticity will be a thing of the past for many mid-Missourians as any widespread vorticity will then be found along the eastern border of the state.

    The 700-mb level will be dry during the daytime on Wednesday. Around nightfall, much more significant moisture can be expected due to the frontal passage. However, this moisture will vanish by daybreak, and this layer will remain dry for the day and into the night. Friday will provide us with another opportunity for cloud cover, although the greatest moisture will be located in northern and southern Missouri. 

    The layer that begins Wednesday with moisture is none other than 850-mb. High dewpoint temperatures dominate this level throughout Wednesday night. The air at 850-mb is also expected to dry out considerably following the frontal passage. Such conditions will last through the end of the forecast period. The low-level jet will peak in intensity on Wednesday night before weakening before early morning. A shift in winds resulting from the frontal passage is evident, with southwesterly winds changing to northwesterly. The low-level jet will reinstate its influence over the region on Thursday night before becoming quiet once more.

    Very little convective potential exists with the precipitation moving through the area on Wednesday night. MUCAPE values fail to exceed 400 J/kg, and positive LI values prevail. K-Index values remain low in magnitude as well. Thus, heavy rainfall is not anticipated with this frontal passage. Rain accumulations could be anywhere between 0.25" and 0.5".

    Previous forecasting shifts suggested that Thursday night's low temperature would sit in the low 30s. However, updated model guidance suggests that the true low temperature will not be nearly as cool. It is recommended that future forecast shifts pay close attention to the factors that could possibly affect Thursday night's temperature and modify the forecast as they see fit.

- Macko

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