288 FXUS63 KLOT 302310 AFDLOTArea Forecast Discussion National Weather Service Chicago/Romeoville, IL 610 PM CDT Tue Sep 30 2025
.KEY MESSAGES...
- Dry and unseasonably warm daytime conditions through the weekend.
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.DISCUSSION... Issued at 150 PM CDT Tue Sep 30 2025
An upper level ridge axis remains over the western Great Lakes this afternoon. Southerly winds on the west side of the ridge is pulling moisture from the Gulf northward for an impressive cloud shield spanning the eastern Great Plains. A shortwave trough over the Colorado front range will move northeastward tonight and Wednesday. The trough will weaken and phase with the longer wave pattern aloft, but it will help nudge the ridge axis southeastward toward the Ohio River basin. Cloud cover is expected to increase as the trough moves closer. Winds will slowly become more southeasterly on Wednesday before switching to the southwest into Thursday. Temperatures will remain in the 80s south of Interstate 80 tomorrow, but the southeasterly winds are expected to keep far northeastern Illinois in the 70s.
Wide spread 80s return on Thursday. An upper level ridge will try to build back over the area for high pressure to grow once again. Temperatures on Friday and Saturday will increase back into the mid to upper 80s and with southwest winds, even the city of Chicago will be in the low to mid 80s. With finer fuels being dry, there is a limited risk for fire weather concerns toward the end of the week. Luckily the winds should be light enough through the work week, but with the gradient flow increasing over the weekend it is possible forecasted wind gusts are being underrepresented in models which may increase the fire danger, particularly for more interior locations away from Chicago.
Models are still suggesting an upper level trough will move over the Great Plains early next week which will send a cold front toward the area increasing precip chances with it. However, models are still not showing great agreement in the overall pattern. For now, there was no need to change the PoPs that the NBM provided knowing the lower confidence in timing. The set up does not look conducive for severe weather and cool air advection behind the front should knock temperatures back down to more seasonable conditions by the middle of next week.
DK
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.AVIATION /00Z TAFS THROUGH 06Z THURSDAY/... Issued at 610 PM CDT Tue Sep 30 2025
VFR with no concerns through the period. Northeast winds this evening will become easterly on Wednesday. Speeds will likely be in the 10-15 kt range Wednesday afternoon with the potential for occasional gusts into the 15-20 kt range.
Castro
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.LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None.
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