FXUS63 KLOT 191947

AFDLOT



Area Forecast Discussion

National Weather Service Chicago/Romeoville, IL

247 PM CDT Tue Aug 19 2025



.KEY MESSAGES...



- Dangerous swimming conditions expected at southern Lake 

  Michigan beaches today through early Thursday.



- A chance for sprinkles or very light showers tonight into

  Wednesday morning. 



- Patchy fog possible tonight into early Wednesday.



- Temperatures early to mid next week will likely be an early

  Fall preview!



&&



.DISCUSSION...

Issued at 246 PM CDT Tue Aug 19 2025



Conditions are quiet and rather comfortable out there this 

afternoon. The cold front that moved across late last night 

driving heavy showers and thunderstorms has since pushed away 

from our CWA into central IL. Advecting in behind this front and

overspreading the area is a thick stratocumulus deck. The cold 

advection and cloudy skies have kept temperatures largely in the

70s so far with only a couple of sites in our south reporting 

80 as of 2 PM.



Waves are building on southern Lake Michigan this afternoon as 

gusty northerly winds move over the water. The Michigan City 

buoy is already reporting wave heights greater than three feet 

and they're climbing quickly, with a beach hazards statement in

effect for our Indiana counties. The high swim risk will take 

hold of Illinois beaches this evening. Then expect dangerous 

swimming conditions to persist through tomorrow and stretch into

at least Thursday morning.



A very subtle low level wave/baroclinic zone will be pushing 

south across the region this evening into tomorrow. A number of 

model camps are resolving southward-moving pockets of very light

rain or sprinkles overnight while the wave moves across, mostly

over areas near the lake. Boundary layer moisture will stretch 

farther inland during the morning spreading light precip chances

west of the Chicago metro for the morning hours. As inversion 

heights lift, the shallow unstable layer may become supportive 

of true light showers for a period during the morning before 

drier air advects in for the afternoon.



Additionally, there is a good-looking signal for areas of fog 

to develop overnight with patches of dense fog even possible. 

This is primarily a concern across the outlying suburbs and 

outside of the Chicago metro. How much clearing skies see 

tonight will also play a role in the fog potential, but that's 

rather uncertain.



A large upper high will park itself over the Four Corners 

region for the back half of this week and spread a quiet upper 

flow regime over the Midwest. This should bring dry and largely 

sunny conditions to Thursday and Friday. Temperatures leading up

to this weekend should be seasonably warm in the upper 70s and 

low 80s. A cold front looks to move across the region Friday 

night and Saturday, but a lack of forcing and instability could 

keep precip coverage rather low. High pressure should then build

in behind the front and keep conditions dry for Sunday. 

Temperatures are expected to fall to the cooler side of average 

early next week behind that cold front.



Doom



&&



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

Issued at 105 PM CDT Tue Aug 19 2025



The cold front associated with the overall system has pushed

through the local terminals, lifting ceilings from IFR to MVFR.

Across much of the region, MVFR ceilings prevail and will

continue to hold throughout much of the TAF period. Winds start

the forecast northerly, with small variations expected on both

sides of north before a mainly north-northeast shift this afternoon.



Overnight, northerly winds continue while diminishing to around

4-6kts. Along the lake terminals, forecasting the stratus deck 

to increase which could lead to development of BR and slightly 

reduced visby's. Further out at RFD, the chance of clearing 

early overnight could bring about some morning patchy fog so 

dropped visby to 4SM, although it could be lower depending on 

clearing and winds. North-northeast winds take hold Wednesday 

morning, increasing to near 10-12kts through the morning, 

bringing the opportunity to gradually clear out in the 

afternoon.



Baker/Doom



&&



.LOT WATCHES/WARNINGS/ADVISORIES...

IL...Beach Hazards Statement from 8 PM CDT this evening through 

     Thursday morning for ILZ006-ILZ103-ILZ104.



IN...Beach Hazards Statement through Thursday morning for INZ001-

     INZ002.



LM...Small Craft Advisory from 1 AM Wednesday to 4 AM CDT Thursday 

     for the IL and IN nearshore waters.



&&



$$



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