099 FXUS63 KLOT 162320 AFDLOTArea Forecast Discussion National Weather Service Chicago/Romeoville, IL 620 PM CDT Tue Sep 16 2025
.KEY MESSAGES...
- Warm and dry conditions persist through the work week.
- Periodic shower and thunderstorm chances return this weekend into early next week (20-40%).
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.DISCUSSION... Issued at 233 PM CDT Tue Sep 16 2025
Quiet conditions will persist through at least Thursday as a somewhat blocked large-scale pattern with a strong ridge over the Great Lakes begins to break down. Cloud cover will remain quite low with only some cirrus filtering over the area from a pair of upper-level lows situated well to the west and southeast. Meanwhile, the southwest extent of a surface ridge will remain entrenched over the area through Wednesday before another ridge noses southward toward the area on Thursday. This will favor an extended period of generally E to NE winds.
Temps will continue to gradually warm each day with inland locations experiencing highs in the mid 80s and lows in the mid to upper 50s. Close to the lake, reinforcement of lake-modified air will result in highs in the mid 70s and lows in the 60s. While precip is unlikely during this period, the longer nights, light winds, and mostly clear skies could support shallow fog (primarily tonight) given marginally favorable dew points in the mid 50s. Have included patchy fog late tonight through sunrise for areas along the north of the Illinois River and west of the I-294/94 corridor in the Chicago metro.
Kluber
While quiet and dry weather will persist in this blocked pattern through the rest of the work week, the upper level ridge begins to break down heading into the weekend as a western trough (and/or potential cut-off low) begins to slide eastward towards the Great Lakes. This will lead to increasing chances for periodic showers and thunderstorms over the weekend into early next week.
KJB
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.AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 620 PM CDT Tue Sep 16 2025
VFR with easterly winds under 10 knots this evening. Winds will become light overnight. The only real impact that is being monitored is the potential for localized fog developing overnight. Chances are better toward daybreak and closer to Lake Michigan, but there is some uncertainty with just how light the winds get (more winds reduces fog chances). With guidance trending toward vis reductions, introduced a TEMPO at ORD/MDW for the chance for at least high MVFR with trends monitored through the overnight. Additionally, maintained the reduced vis at RFD/DPA/GYY.
VFR again on Wednesday with easterly winds up to 10 knots.
DK
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.LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None.
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