FXUS63 KLOT 192326
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
626 PM CDT Tue May 19 2026

.KEY MESSAGES...

- Dry but cooler conditions Wednesday and Thursday, followed by
  increasing rain chances Friday.

- Intermittent shower/thunderstorm chances for Memorial Day 
  weekend, though much of the period should be dry.

- Several periods of moderate to high swim risk conditions
  possible through early next week due to persistent northeast
  winds over Lake Michigan.

&&

.DISCUSSION...
Issued at 237 PM CDT Tue May 19 2026

A cold front currently nearing the I-39 corridor across the 
western CWA will shift eastward across the forecast area through
the remainder of the afternoon. With the combination of an 
outflow boundary early this morning now east of I-57, increasing
low-level cloud cover, and 600-800 hPa warming, the potential 
for any storms or appreciable heavier showers appears to be 
confined to the extreme southeast CWA (south of a Paxton to 
Rensselaer line) for the next few hours. Otherwise, spotty 
shallow showers remain possible anywhere ahead of the cold front
through the daytime hours.

Though the front will track well south and east of the area 
tonight, modest low-level frontogenesis in response to a broad 
mid to upper- level jet may yield either a few light showers or 
a band of light rain across the far southern CWA overnight into 
mid-morning Wednesday.

High pressure will expand across the northern Great Lakes 
Wednesday through Thursday. Expect dry but cooler conditions 
amid persistent northeast winds through this period. 

A Pacific wave off the Baja of California will bring an area of
increased mid-level moisture across the central CONUS late this
week as low-level Gulf moisture is drawn northward toward the 
mid- Mississippi River Valley. Though stout low-level drying 
from the northeast over the Great Lakes will impede the initial 
northward extent of rain on Friday, the overall translation of 
deep moisture northward should overcome the low-level dry air 
and bring an area of rain across most of the area by late 
Friday. Poor mid-level lapse rates will greatly limit 
thunderstorm chances.

A gradual warmup appears in store this weekend into early next 
week as broad ridging builds over the north-central CONUS. 
However, there remains substantial model disagreement as to 
whether a larger southwest CONUS trough late this week becomes 
cut-off over the southern Plains/Texas or remains loosely tied 
to the western edge of the ridge. The latter solution would 
bring cooler and more unsettled weather to the area late in the 
weekend and delay any potential warm- up to next week.

As an added note, we are nearing the start of the Beach Hazards
season. Given the potential for multiple periods of northeast 
winds and higher waves this week/weekend into next week, swim 
risk messaging may need to increase in the next couple days.

Kluber

&&

.AVIATION /00Z TAFS THROUGH 06Z THURSDAY/...
Issued at 626 PM CDT Tue May 19 2026

Key Aviation Messages for the current TAF period:

- MVFR cigs may be observed at times through tomorrow morning

Gusty west winds will slowly diminish this evening and turn to 
the northwest in the wake of a cold front passing east of the 
area. Occasional gusts to 20 knots are possible through 3Z 
tonight, but not persistent enough for mention in the TAF. 
Isolated showers are still possible this evening, but the 
probability of any one of them passing directly over a terminal 
is too low for mention in the TAFs. Additionally, most of the 
development and movement should be to the south and east of any 
of the terminals, giving further confidence to keep the TAFs 
dry. Ceilings are expected to hover between 2500 to 3000 feet 
through this evening. There is a chance for higher level MVFR 
cigs to linger through the overnight period. There is high 
confidence in a return to VFR by Wednesday morning, but lower 
confidence in when/if MVFR cigs lift overnight. Winds will turn 
to the northeast tomorrow morning. Occasional gusts to 20 knots 
are possible.

DK

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from 10 AM Wednesday to 4 AM CDT Thursday 
     for the IL nearshore waters.

     Small Craft Advisory from 7 AM Wednesday to 4 AM CDT Thursday 
     for the IN nearshore waters.

&&

$$

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