FXUS63 KLOT 271725

AFDLOT



Area Forecast Discussion

National Weather Service Chicago/Romeoville, IL

1225 PM CDT Mon Oct 27 2025



.KEY MESSAGES...



- A passing storm system may provide periods of rain across the

  area during the middle of the week, favoring areas south of

  Interstate 80. 



- Expect seasonable temperatures through next weekend.



&&



.DISCUSSION...

Issued at 310 AM CDT Mon Oct 27 2025



An upper-level low centered near the Bootheel of Missouri early

this morning will move ESE to the Carolinas through tonight as 

a strong ridge over Ontario remains mostly stationary. A deep 

reservoir of dry air advecting from the east and northeast will 

suppress precip well south of the area, with only some cirrus 

attempting to lift northward through the day.



A longwave trough over western Canada and the northwest U.S. 

will become considerably elongated across the Great Plains over 

the next 24-48 hours between the ridge over Ontario and a 

rapidly building west coast ridge. A narrow north to south 

oriented band of rain is expected to develop west of the 

Mississippi River late tonight into Tuesday in association with 

a modest area of mid-level moisture below a broad entrance 

region of a northwest pointed upper-jet maximum. Extensive low 

to mid-level dry-air advection from a pseudo-Hudson Bay high to

the northeast will steadily erode the eastern edge of the 

precip band Tuesday into Tuesday night before the main vorticity

lobe of the tough detaches and pivots southwest of the area. 

Expectations are that much of the area will remain dry on 

Tuesday, with rain potential ranging from low-end chance PoPs 

(30%) near the Wisconsin line to likely PoPs (up to 70%) toward 

central Illinois Tuesday night into Wednesday morning. It is 

highly likely that there will be a sharp north to south gradient

in precipitation somewhere over the forecast area, with a 

distinct possibility that much of northern Illinois remains dry 

with this event.



The newly formed low to the southwest, the original low over 

the Carolinas, and even the remnants of Hurricane Melissa will 

congeal into a longwave trough over the Northeast late in the 

week, with signals of a couple reinforcing waves crossing the 

area from the northwest this weekend into early next week. 

Ensemble guidance continues to depict a loose omega block 

developing as the west coast ridge amplifies. Our area would be 

situated on the western edge of the main longwave trough to the 

east, yielding sporadic bouts of scattered rain showers and 

perhaps some lake effect rain showers during this time. Temps 

will remain seasonable as arctic air remains well north of the 

area.



Kluber



&&



.AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/...

Issued at 1225 PM CDT Mon Oct 27 2025



No significant aviation weather concerns for the 18Z TAFs.



Forecast area sits between surface high pressure over eastern

Canada, and low pressure over the Plains. This will continue to

provide relatively dry, easterly low-level flow to the region 

through Tuesday. Surface winds near 15 kts with a few higher 

gusts this afternoon will diminish to around 10 kts with sunset 

this evening. Winds will increase again late morning to midday 

Tuesday, with some higher gusts around/a little above 20 kts 

possible in the afternoon. 



Otherwise, VFR conditions are expected through the period, with

increasing high cloud cover Tuesday. Spotty light rain is 

possible over eastern IA and eventually central IL by late 

Tuesday, though this is expected to remain south of the 

terminals. 



Ratzer



&&



.LOT WATCHES/WARNINGS/ADVISORIES...

IL...None.

IN...None.

LM...Small Craft Advisory until 7 AM CDT Wednesday for the IL 

     nearshore waters.



&&



$$



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