916 FXUS63 KDMX 251722 AFDDMXArea Forecast Discussion National Weather Service Des Moines IA 1222 PM CDT Thu Sep 25 2025
...Updated for the 18z Aviation Discussion...
.KEY MESSAGES...
- Above normal temperatures and dry Thursday through at least early next week.
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.DISCUSSION... Issued at 215 PM CDT Wed Sep 24 2025
Visible satellite imagery early this afternoon shows plenty of cumulus clouds over the state and these will persist until shortly after sunset. Forecast soundings show a rather dry column, but with the steep low level lapse rates and what moisture there is, it may and has been enough to squeeze out sprinkles or a fleeting shower over southern Iowa/south of I-80. This chance of a sprinkle/shower is also shown in a few of the high resolution models, namely the ARW cores and the HRRR. Any showers will dissipate quickly after sunset. Into tonight, winds will become quite light or calm as the boundary layer decouples and surface high pressure pushes over the state. Moisture trapped beneath the near surface inversion should result in fog starting to form a few hours after midnight with the most widespread fog coverage around sunrise. 12z HREF shows the highest probability of visibilities under a mile over parts of northern Iowa with those chances at 40 to 70% depending on the location. While soundings do show that far south central into southeast Iowa have lower chances of fog formation, have broadbrushed the inclusion in the forecast. Areas of fog that do form will dissipate by around 9am.
The main weather theme Thursday afternoon into early next week will be mostly dry conditions with temperatures above normal for late September in the upper 70s or low 80s. This benign pattern is being drive by a somewhat slowly evolving upper level pattern, which will see an elongated, positively tilted trough shifting eastward from the central US leaving behind a closed low over the Deep South by late this weekend. Upstream of Iowa, a ridge will be advancing towards the state through the end of the week with another closed low off the California coast that moves to the Four Corners region by the end of the weekend. While a shortwave trough will ride overtop the ridge sending a cold front into the state this weekend, moisture from the Gulf will still be cut off with the forecast remaining dry.
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.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1222 PM CDT Thu Sep 25 2025
VFR conditions with winds below 10 knots will prevail through the period at all terminals. FEW to perhaps SCT FL035 have developed or will develop at ALO/DSM/OTM this afternoon before dissipating this evening. There may be a touch of high level smoke overhead, but not enough to include anything prevailing.
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.DMX WATCHES/WARNINGS/ADVISORIES... None.
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DISCUSSION...Ansorge AVIATION...Ansorge
NWS DMX Office Area Forecast Discussion