Current Conditions at Sanborn Field 

 

Monday: Decreasing clouds Mostly sunny by afternoon. High: 95

Monday Night: Mostly clear.  Low: 72

 

Tuesday: Partly cloudy. High: 95

 

Tuesday Night: Mostly clear. Low: 72

Wednesday: Partly cloudy. Increasing clouds in the evening. High: 90

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Discussion:

Prepare for some toasty weather as we head into this week! High temperatures will reach near record breaking numbers for Mid-September. Expect highs climbing into the nineties and plenty of sunshine as we go through the week. Then later on Wednesday a cold front will be passing through to bring the heat down for the end of the week to a more comfortable level.

Simmons

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Forecasters: Schneringer, Simmons, Travis

Date Issued: 09/19/2022 11:00 AM CDT

Technical Discussion:

 

Astronomical summer will end on Thursday, but it will certainly feel like the middle of summer this week. The main concern plaguing this forecast period is an upper-level ridge centered over the central CONUS resulting in near-record-breaking heat. Some relief looks to be on the way as a cold front will pass through the region Wednesday. Went primarily with NAM guidance as it better resolved the location of the disturbance w/r/t the GFS.

Strong upper-level ridging will keep things quiet and unseasonably hot for the end of summer. The westerlies are slowly but surely drifting further south, but still remain well to the north of Missouri. Going forward, any rain chances will likely come in the form of a ridge-running MCS. That said, any chance of this comes beyond the current period (a problem for the next shift) overnight Wednesday into Thursday. Until then, the 590-dm height contour at 500 hPa will park itself between the I-70, I-44 corridors, anomalously far north for the last week of summer... By Wednesday afternoon, a jet streak sags south and on its far south end, increased divergence (and associated circulation at 500 hPa) rounds the crest of the upper ridge in IA Wednesday afternoon. The GFS and NAM disagree considerably regarding the location of the greatest forcing for ascent. The GFS is notably further south, pushing the divergence and circulation along the MO-IA border and into NE Missouri. The NAM is further north, away from the center of the upper-level high, over north IA. Seeing as how greater forcing for ascent would logically occur further away from subsidence associated with the center of high pressure, the NAM looks to be the more likely solution. 

Some pesky mid- to low-level saturation sticks around through the period indicating that the sky will likely not be entirely clear. That said, clouds will largely be fair weather CU and sunshine will still dominate. By early Wednesday morning, moisture transport in the low levels is decently efficient, but certainly nothing to write home about and looks to converge further to the north in line with the upper-level forcing. Low-level WAA is prevalent ahead of the approaching front, invading the area after 00z Thursday. With all this in mind, chances for precipitation look to be greatest just beyond our period.

The biggest headache for this period comes with timing of FROPA. The difference between the GFS and NAM is a whopping 10-12 hours. The GFS favors surface FROPA occuring between 12z and 15z Wednesday while the NAM favors 21z Wednesday to 00z Thursday. As such, the high temperature for Wednesday will largely be dictated by the actual time of passage. As mentioned above, favoring the NAM solution and thus went with a later passage time. Future shifts should pay CLOSE attention to how subsequent model solutions line up and adjust the high accordingly.

Travis