763 FXUS63 KLOT 151109 AFDLOTArea Forecast Discussion National Weather Service Chicago/Romeoville, IL 609 AM CDT Mon Sep 15 2025
.KEY MESSAGES...
- Warm and dry conditions are expected through the work week.
- Periodic shower and thunderstorm chances return toward the end of the week (20-30%).
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.DISCUSSION... Issued at 245 AM CDT Mon Sep 15 2025
An overall quiescent pattern is in place across the region with amplified upper ridging across the western Great Lakes region atop a closed upper low in the Southeast (a pseudo-Rex Block pattern). This will allow unseasonably warm temperatures to prevail through the rest of the work week with high temperatures in the 80s to near 90 (warmest toward western and central Illinois). Relatively weak surface flow amidst expansive surface high pressure should allow daily lake breezes to push inland holding temperatures mainly in the 70s near the lakeshore. This should also help keep any shower/storm activity west of the local area for the majority of the work week.
Ensemble guidance has also trended a bit slower with the break down of the upper ridge/blocking pattern later in the week with most of the area remaining dry through the day on Friday and further slowing could occur with later updates. Eventually the western trough (and/or potential cut-off low) will shift east toward and over the area leading to periodic shower and thunderstorm chances over the weekend into early next week. This will be paired with cooler more seasonable temperatures in the 70s.
Petr
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.AVIATION /12Z TAFS THROUGH 18Z TUESDAY/... Issued at 609 AM CDT Mon Sep 15 2025
No major forecast concerns are expected through the TAF period as a ridge of high pressure will remain in place over the Great Lakes. The current southeast winds will become more easterly later this morning with speeds remaining generally in the 5-8 kt range. However, there is the potential for a land breeze to develop tonight which may turn winds more north-northeasterly at ORD and MDW before they turn back easterly Tuesday morning. While most guidance keeps winds east of north tonight, cannot completely rule out a period of northwest winds especially at ORD. Otherwise, mostly clear skies will prevail aside from a passing cirrus cloud.
Yack
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.LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None.
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