Current Conditions at Sanborn Field

Wednesday: Mostly sunny. High: 81
 

 

Wednesday Night: Clear. Patchy fog possible before sunrise. Low: 61
 

 

Thursday: Sunny. High: 83
 

 

Thursday Night: Clear. Low: 60

 

 

Friday: Sunny. High: 84

 

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Discussion:

September in mid-Missouri is off to a great start and will continue to be until the end of the week! Some patchy fog is possible in low-lying areas overnight Wednesday into early Thursday morning. This will likely be very localized and will burn off quickly after sunrise. Otherwise, high temperatures will remain close to average for early September with plenty of sunshine. Overnight lows will be cool in the low 60s.

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Forecasters: Russell, Travis, Shaw

Date Issued: 09/07/2022 9:00AM CDT

Technical Discussion:

 

Persistence is key for this forecast period as calm weather continues for the remainder of the work week. The main concern for this period was determining what effect winds will have on the region's daytime high temperatures as well as assessing the potential for patchy fog overnight Wednesday. A blend of the GFS and NAM was used as both models had remarkable consensus for the period with some discrepancies in low-level moisture.

 

A rather uneventful period has taken shape for the region and will continue to be as such to end off the week. A large, upper-level ridge over the western half of the CONUS is keeping the westerlies well to the north of the mid-Mississippi River Valley as the region remains in northwesterly flow in the upper and mid levels of the atmosphere. By Thursday afternoon, an upper-level, longwave trough will propagate southeast out of western Canada and begin to erode the ridge. As this happens, the ridge will elongate and flatten causing a low-pressure system currently centered over the ArkLaTex region to become cutoff over the Gulf Coast of LA and MS. Missouri will sit in the notably laminar flow between these two systems. By the Saturday morning, a shortwave rounding the base of the aforementioned longwave trough will help bring that cutoff low back into the large-scale flow westerly flow. As the low begins to move northeast, both the GFS and NAM are hinting at some moisture moving in from the SE that may make its way into mid-Missouri in the form of high- to mid-level cloudiness. Attention then turns to the shortwave that will have a slow-moving cold front associated with it that may impact the region this weekend, beyond the forecast period.

 

As mentioned above, model consensus breaks down in the handling of low-level moisture. The NAM is showing its usual bullish tendencies with a widespread saturated airmass where the GFS shows low relative humidity. While the GFS solution is more likely, NAM soundings do hint at the possibility for patchy fog overnight Wednesday into early Thursday morning. The inversion and calm winds are evident in both soundings, but as hinted at above, the NAM has a 2 degree dewpoint depression (DD) at the surface where the GFS has a 7 degree difference. Still, the thinking is (especially due to the presence of fog this morning) that very localized fog is possible combined to low-lying areas where the DD will be closer to the NAM guidance.

Additionally, due to a heavy emphasis on persistence forecasting and height falls associated with the eroding ridge, current thinking is trending cooler with daytime high temperatures. Nevertheless, surface winds will shift out of the SSE by late Thursday afternoon and into Friday. The late shift on Thursday will likely have little impact on its high temperature. Thus, lowered the previous forecast high for Thursday by 4 degrees. Depending on Wednesday's high temperature, this may need to be adjusted.