974 

FXUS63 KLOT 050557

AFDLOT



Area Forecast Discussion

National Weather Service Chicago/Romeoville, IL

1257 AM CDT Fri Jun 5 2026



.KEY MESSAGES...



- Trending warmer and more humid with periods of showers and

  thunderstorms starting early Friday and continuing into next

  week.



- Low (level 1 out of 5) severe weather threat Friday PM along

  with a threat for locally heavy rainfall.



&&



.DISCUSSION...

Issued at 217 PM CDT Thu Jun 4 2026



For Friday and Saturday the main forecast question is shower and 

thunderstorm trends, with greater emphasis on the showers given the 

overall marginal lapse rates and lack of strong forcing for 

convection.  CAM guidance normally wouldn't be relied on too 

closely, but several models show similar trends and align with the 

overall concept of how things appear likely to evolve, so elected to 

follow a blend of those that appeared to reflect this thinking.



A cluster of showers with some embedded thunderstorms is expected to 

make its way into the area from Iowa early Friday ahead of a diffuse 

cold front and weak shortwave aloft.  This activity should 

overspread the area through the morning into early afternoon at 

which point slight ridging aloft and movement away from the 

supporting surface boundary may allow for a decrease in coverage for 

later in the afternoon and evening.  The exception may be in the 

southern half of our forecast area where an outflow boundary from 

the earlier activity could provide the focus for additional 

development.  



Most locations on Friday and Friday night do not appear poised for a 

complete washout, but given an axis of PWATs exceeding 1.75" and the 

expected slow motion of this cluster, some areas could see some 

heavy rainfall. SPC also has us in a Day Two marginal risk but this 

would not appear to pose a widespread threat given the 

aforementioned marginal support for convection overall.



Later Friday night into Saturday the model guidance begins to 

diverge, but the general idea still appears to keep the best focus 

for continued showers in southern and western portions of the 

forecast area.  The exception could be along a developing lake 

breeze that might be able to tap into the moist airmass and support 

an additional area of showers Saturday afternoon.



For Sunday into the first part of next week, model guidance is 

showing a narrow mid to upper level ridge building overhead, with a 

stationary front at the surface extending east from the Plains into 

the Ohio Valley.  This boundary, wherever it happens to park, would 

appear to be the best focus for additional shower and thunderstorm 

activity, especially with support from afternoon heating and 

dewpoints in the 60s to occasionally lower 70s.



Lenning



&&



.AVIATION /06Z TAFS THROUGH 12Z SATURDAY/...

Issued at 1257 AM CDT Fri Jun 5 2026



Main Concerns:



- Potential for occasional SHRA/TS with associated VSBY 

  reductions today and again late this evening-overnight



- Lower CIG trends this morning through this afternoon



- Chance for a north-northeasterly wind shift associated with

  the SHRA/TS threat late this evening-overnight



The long stretch of mainly quiet flying weather will come to an

end over the next 24+ hours. Initial showers and possible embedded

TS in the pre-dawn through mid morning should generally favor 

northwest IL/RFD area (PROB30 for TS there), though spotty VFR 

showers could develop over the Chicago metro. The overall best

chance for on station TS impacts will be from mid morning 

through early to mid afternoon, earliest at RFD, and latest at

GYY. Maintained TEMPO TS mention with similar timing to

previous issuances. After the afternoon activity shifts east,

our next period of interest is late this evening and overnight.

There's some signal for showers and storms to develop north of

the terminals (possibly over WI) and sag south, accompanied by

an outflow driven wind shift to north or northeast. Introduced 

PROB30s at ORD, MDW, and GYY for this window. 



South-southwest winds early this morning will become gusty out

of the southwest after daybreak, with some potential for

occasional gusts as high as 25-30 kt in the early to mid 

afternoon. Lowest CIGs (lower MVFR to temporary IFR) during 

daylight hours today should focus into RFD area, though 2-3kft 

AGL CIGs appear probable at times at the Chicago metro 

terminals.



Castro



&&



.LOT WATCHES/WARNINGS/ADVISORIES...

IL...None.

IN...None.

LM...Small Craft Advisory from 10 AM this morning to 7 PM CDT this 

     evening for the IL and IN nearshore waters.



&&



$$



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