380
FXUS63 KLOT 222308
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
608 PM CDT Thu May 22 2025

.KEY MESSAGES...

- Hazardous conditions at Lake Michigan beaches through
  this evening, particularly across NW Indiana.

- Below to well below normal temperatures are favored through
  the Memorial Day holiday weekend.

&&

.DISCUSSION...
Issued at 311 PM CDT Thu May 22 2025

Through Friday Night:

A pronounced shortwave trough continues to dive across the
western Great Lakes which will allow isolated to widely
scattered showers to persist through early evening. The bulk of
these showers should remain along and south of a Peru, IL to
Rensselaer, IN line with those north of this line likely staying
dry. Otherwise, partly to mostly cloudy skies to gradually
clear out overnight with temperatures cooling into the lower to
mid-40s. Additionally, winds and waves at area beaches will also
gradually subside this evening but in the meantime continue to
use caution if along the lake.

A surface high will build into the area on Friday resulting in
dry conditions. However, continued northwest flow aloft will
keep below normal temperatures around with highs in the lower to
mid-60s and lows Friday night in the lower to mid-40s. The
exception will be along the lakeshore where a lake breeze will
keep highs more into the mid to upper 50s.

Saturday through Thursday...

The aforementioned surface high is forecast to remain over the
Great Lakes through our Memorial Day weekend resulting in mostly
dry and below average conditions. Though, a stalled baroclinic
zone across the mid-Mississippi and Tennessee Valleys may allow
an isolated shower to brush our far southern CWA (south of
US-24) on Sunday and/or Monday. Regardless, highs will remain in
the 60s (50s near the lake) and lows in the 40s through the
weekend.

For Tuesday onward, the forecast become much more uncertain as
guidance shows an inverted upper trough developing over the
Great Lakes and getting blocked in place by a ridge to our west.
Depending on where exactly this trough sets up, our area could
see a warming trend with highs back towards the 70s and
increasing chances for showers and/or thunderstorms or another
period of below average temperatures with highs in the 50s to
60s. Given how global guidance tends to struggle with blocking
patterns, saw no reason to deviate from the NBM forecast which
is favoring the warmer and possibly wetter solution. That said,
this part of the forecast will likely change as we get closer to
be sure to check back for more details.

Yack

&&

.AVIATION /00Z TAFS THROUGH 06Z SATURDAY/...
Issued at 608 PM CDT Thu May 22 2025

- Lake breeze wind shift from northwest to northeast expected
  Friday afternoon

VFR conditions expected through the TAF cycle. Winds will become
light and variable this evening, then northwest Friday morning.
A lake breeze is expected to result in a wind shift to northeast
Friday afternoon. Some uncertainty exists with respect to timing
of the lake breeze. Potential exists for lake breeze to be later
in the afternoon than reflected in current TAFs, but opted to
not make any changes to timing from previous TAFs at this time
and will defer that to later TAF issuances.

- Izzi

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement until 10 PM CDT this evening for
     ILZ103-ILZ104.

IN...Beach Hazards Statement until 1 AM CDT Friday for INZ001-
     INZ002.

LM...Small Craft Advisory until 10 PM CDT this evening for Wilmette
     Harbor to Calumet Harbor IL.

     Small Craft Advisory until 1 AM CDT Friday for the IN
     nearshore waters.

&&

$$

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