821
FXUS63 KLOT 171123
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
623 AM CDT Tue Sep 17 2024

.KEY MESSAGES...

- Hot and dry conditions will continue through at least
  Thursday.

- Chances for rain will return to the area on Friday and through
  the weekend.

&&

.DISCUSSION...
Issued at 201 AM CDT Tue Sep 17 2024

Through Monday:

Over the next 72 hours, an upper-level trough diving southeastward
along the coast of British Columbia will "kick and replace" a trough
currently over central California toward the northern Plains.
Meanwhile, an upper-level low currently centered over the Carolinas
will gradually weaken while drifting eastward toward the Atlantic
Coast. Inbetween both large-scale features, the local weather
pattern in our neck of the woods will remain remarkably banal with a
persistence methodology remaining appropriate. Today through
Thursday will feature mostly sunny skies, low humidity levels, light
winds, and daily lake breezes. Highs will top off in the mid to
upper 80s each afternoon (cooler near the Lake Michigan shoreline),
and overnight lows will fall into the mid to upper 50s each
night. A few patches of ground fog may develop around daybreak
each morning in northeastern IL, as well (where locally higher
dew points off Lake Michigan should be somewhat "sheltered"
from the easterly advection of drier air elsewhere).

Thursday night into Friday, low-level humidity will begin to
increase as a remnant warm sector from an occluding cyclone moving
into Manitoba "sloshes" eastward into the Great Lakes. A few showers
and storms may develop along a weakening cold front overnight across
parts of Iowa and Wisconsin, though they should be in a weakening
state by the time they reach northwestern Illinois by daybreak
Friday. With forecast soundings depicting minimal capping by mid-
afternoon, a few showers or storms cannot be ruled out before
sunset, though coverage should be isolated given a dearth of large-
scale forcing (20% or lower chance areawide). In all, Friday is
looking relatively quiet with partly cloudy skies and highs in
the mid to upper 80s.

This weekend and beyond, EPS/GEFS guidance continue to depict a
pattern changes characterized by a return of regular chances for
showers and thunderstorms as well as gradually decreasing daily
temperatures.

Borchardt

&&

.AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 623 AM CDT Tue Sep 17 2024

No significant forecast concerns expected this period. Light/calm
winds to start will become east/southeast at 4-8kts by late
morning. A lake breeze will turn winds easterly at the Chicago
terminals early this afternoon with speeds around 10kts. Winds
will become light southeast again this evening and then likely
light and variable or calm again into early Wednesday morning.

There is a small chance for some shallow/patchy fog late tonight
into early Wednesday morning. cms

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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