931 FXUS63 KDVN 151027 AFDDVNArea Forecast Discussion National Weather Service Quad Cities IA IL 527 AM CDT Mon Sep 15 2025
.KEY MESSAGES...
- Unseasonably hot conditions will continue for much of this week before moderating some by Friday.
- Mostly dry conditions are expected through mid week, with increasing chances (30-50%) of showers and storms by Thursday night into Friday area-wide.
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.SHORT TERM /THROUGH TONIGHT/... Issued at 230 AM CDT Mon Sep 15 2025
An upper level ridge will remain over eastern Iowa and northwest Illinois today resulting in a continuation of the unseasonably hot and humid conditions. It won`t be quite as hot as it was over the weekend due to slightly cooler 850mb temperatures into the upper teens (C). Forecast highs range from the mid/upper 80s north of Highway 30 to the lower 90s south. Dewpoints will hold in the mid 60s to close to 70 degrees, but with the slightly lower ambient temperatures peak heat indices should not be as high as yesterday, reaching the upper 80s to mid 90s for most areas today.
Isolated showers and thunderstorms could develop during peak heating this afternoon and evening across portions of eastern Iowa and west-central Illinois, mainly west and southwest of the Quad Cities along a corridor of subtle low-level convergence. Confidence is low on the areal coverage with the CAMs showing a wide variety in solutions. Latest thinking is for a lower coverage scenario due to limited forcing across the area. If a few storms do manage to develop, moderate SBCAPE (1500-2500 J/kg per HREF) and DCAPE (1000+ J/kg) could support locally strong wind gusts.
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.LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 230 AM CDT Mon Sep 15 2025
Tuesday through Wednesday will continue to see the hot air mass in place, although the 850 mb temperatures look to gradually decrease from this weekend in both the ECMWF and GEFS ensembles. High temperatures will generally be in the middle 80s to lower 90s per the latest NBM, so a slight moderation expected. Humidity will also remain elevated as well, with dew points during this period in the lower to middle 60s.
One change in the extended forecast is for a slower arrival of the trough late in the week. This translates to a continuation of the hot conditions on Thursday with much of the area likely to stay dry. The heat will eventually become scoured out by Friday as a longwave upper-level trough is progged to slowly move into the north-central CONUS region. Not only will this trough help scour out the heat, but it will also bring our next widespread chances of showers and storms to the area. The NBM has 20-50% chances for showers/storms beginning Thursday night and lasting into the weekend. There are no strong signals for severe weather with latest machine learning guidance showing low end probabilities (under 5% - 10%). High temperatures late in the period are forecast in the 70s and 80s.
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.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 522 AM CDT Mon Sep 15 2025
Quiet weather with VFR continues through today. Low coverage (10-20%) showers and storms may develop this afternoon and evening over portions of eastern Iowa. However, confidence is too low on placement and coverage to include a rain/thunder mention in the TAFs.
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.DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None.
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SHORT TERM...Uttech LONG TERM...Uttech/Schultz AVIATION...Uttech
NWS DVN Office Area Forecast Discussion