636
FXUS63 KLOT 201736
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1236 PM CDT Sat Jul 20 2024

.KEY MESSAGES...

- Wednesday will likely have the highest shower and thunderstorm
  coverage of the upcoming week.

- Near to a bit below normal temperatures through next work week.

&&

.DISCUSSION...
Issued at 255 AM CDT Sat Jul 20 2024

Through Sunday Night:

Surface high pressure will again remain in control of our
weather through tonight. There will be a bit more in the way of
cloud cover (daytime Cu and scattered to broken Cirrus).
Forecast highs are in the upper 70s to lower 80s, except a touch
cooler along the immediate lakeshore due to lake breeze
influence. Lows tonight will be a bit milder than those of early
this morning.

On Sunday, a weakening modest mid-level short-wave will
pinwheel near the MS River. While spotty high-based sprinkles
can`t be ruled out, the best chance for any isolated showers
(15-30% PoPs) will likely be across portions of interior far
northern Illinois and then west-southwest of the CWA in west
central Illinois. Model forecast soundings are largely capped
south of the WI state line, so continued to withhold any
thunderstorm mention in the official gridded forecast, as
chances appear to be less than 15%. High temperatures on Sunday
will likely be similar to a degree or two warmer than this
afternoon, and again a touch cooler near the lake due to onshore
flow. Sunday night will be a near carbon copy of tonight.

Castro


Monday through Friday:

Typical summer-like weather is in store for the upcoming week
as the upper level pattern remains relatively stagnant with
occasional mainly diurnal shower/storm chances and near normal
temperatures in the low to mid 80s for highs. Cooler
temperatures in the 70s are still anticipated along the
lakeshore due to daily lake breezes and/or prevailing onshore
flow.

Monday and Tuesday could very well be dry for most areas though
diurnal isolated to widely scattered garden variety showers and
storms can`t be ruled out (20% chance) as a weak mid-level
disturbance lingers over the region. Wednesday afternoon/early
evening still looks like our best potential for areawide showers
and storms (50-60% chance) as a shortwave dives southeast
across the western Great Lakes. A slightly slower arrival of
this feature could result in showers/storms persisting later
into the evening and potentially even into the day on Thursday
across northwest Indiana. There is a bit more flow aloft on
Wednesday so can`t fully rule out a locally stronger storm, but
the severe weather threat remains low. High pressure builds back
into the region late Thursday into Friday with dry conditions
returning to end the week.

Petr

&&

.AVIATION /18Z TAFS THROUGH 00Z MONDAY/...
Issued at 1228 PM CDT Sat Jul 20 2024

Concerns:

- Lake breeze boundary turning winds easterly at ORD/MDW this
  afternoon.

High pressure over the region is keeping VFR conditions in place
with generally light and variable winds. A lake breeze boundary
has developed, turning winds north to northeast at KGYY and
pushing inland across Chicago. Based on latest trends, have sped
up the arrival at KMDW to 1830z and arrival at KORD may be a bit
before the 20z time in the TAF. Speeds behind the boundary
should range from 8-10 kt. Light and variable to even calm winds
will return this evening and become light north to northeast
Sunday.

MDB

&&

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

&&

$$

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