886
FXUS63 KLOT 191904
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
204 PM CDT Sat Oct 19 2024

.KEY MESSAGES...

- Gorgeous (if you like warm and dry conditions in October) weather
  will prevail into early next week.

- A cold front will send temperatures back toward normal toward
  the end of next week. A few sprinkles may occur in the Tuesday
  to Wednesday time frame, as well.

&&

.DISCUSSION...
Issued at 204 PM CDT Sat Oct 19 2024

Through next Saturday...

A fitting way to describe our local weather today is undeniably
gorgeous. With the responsible surface high pressure system
parked just to our southeast expected to remain in place through
early next week, a persistence-based forecast of continued
gorgeous weather is appropriate. Highs tomorrow and Monday will
be unseasonably warm and in the upper 70s to lower 80s, and
overnight lows will be in the low to mid 40s. Aside from a few
mid-level clouds this evening, completely clear skies will be
the norm. It doesn`t get much better for this time of year in
the Great Lakes.

Tuesday, the upper-level low meandering in the desert
southwestern US will lift northeastward into the Great Lakes.
While forcing with the upper-level wave will be strong (500mb
heights dropping by about 1dam/12hr) and mid-level lapse rates
will be steep (7-7.5 K/km in the 700-500mb layer) as the wave
lifts overhead, low-level moisture will be decidedly scant. As a
result, ensemble model guidance advertises any upstream showers
and thunderstorms decaying as they move into Illinois during
the afternoon on Tuesday. With that said, if low-level moisture
profiles are even marginally better than currently forecasted, a
few high-based showers and thunderstorms cannot be ruled out
mainly south of I-80 and west of the Indiana state line. At this
point, will tuck in a "silent" 10% chance for sprinkles Tuesday
afternoon south of I-80. Precipitation or not, Tuesday should
feature increased cloudiness, keeping temperatures in the low
to mid 70s.

Wednesday, a deep low pressure system in southern Hudson Bay
will send a cold front through the Great Lakes. Similar to
Tuesday, low-level moisture profiles on Wednesday still appear
hostile to precipitation. However, steep mid-level lapse rates
(partially forced by similarly strong upper-level forcing) may
nevertheless afford a few showers behind the front. Perhaps more
noticeably should be a push of breezy northwest winds anchored
by robust CAA (850mb temperature dropping nearly 15C/24hrs).
Indeed, Thursday will be markedly cooler than the days before
with highs near 60 degrees.

Forecast confidence lowers toward the end of next week as
ensemble model guidance differs on the evolution of the upper-
level pattern. With that said, there is an emerging signal for a
return of above (if not much above) average temperatures
to close out October.

Borchardt

&&

.AVIATION /18Z TAFS THROUGH 00Z MONDAY/...
Issued at 1209 PM CDT Sat Oct 19 2024

There are no aviation concerns through the TAF period. Southwest
winds (occasionally gusting to 20kt during the afternoon hours)
and clear skies (save for a brief period of VFR cigs this
evening) will prevail.

Borchardt

&&

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

&&

$$

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