433
FXUS63 KLOT 111113
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
613 AM CDT Sat May 11 2024

.KEY MESSAGES...

- Dry, seasonable, and breezy conditions this weekend.

- Periods of showers and a few thunderstorms are expected Sunday
  night through early Tuesday. There will be many dry hours.

&&

.DISCUSSION...
Issued at 319 AM CDT Sat May 11 2024

Through Sunday:

A cold front continues to advance across eastern IL and
northern IN this morning with an area of scattered showers
traversing ahead of the boundary. These showers will continue to
exit our area over the next hour or so leaving us with dry
conditions for the rest of the weekend. However, the combination
of cold advection in the wake of the front and a lingering
pressure gradient will promote breezy northwest winds this
afternoon. Gusts are expected to top out in the 20 to 30 mph
range today before gusts gradually subside this evening. Despite
the cold advection, temperatures will remain seasonable today
with highs in the upper 60s to lower 70s though onshore flow
across northwest IN will hold readings a few degrees cooler.

Heading into Sunday, mid-level ridging will build into the
Great Lakes which will turn winds out of the southwest and usher
in warmer temperatures. Therefore, highs on Sunday are forecast
to top out in the upper 70s to lower 80s. Though strong diurnal
mixing is expected again on Sunday which will promote breezy
winds, but this time in the 20 to 25 mph range. Additionally,
the deeper mixing should also lower dew points, despite the
warm-moist advection, which will make RH values dip into the
30-35 percent range Sunday afternoon. Thankfully, the recent
rains and greening vegetation should limit any fire weather
concerns.

Yack


Sunday Night through Friday:

Monday into Tuesday, the cut-off low currently meandering in the
southwestern United States will become "re-absorbed" into the upper-
level flow while drifting eastward toward the mid Mississippi River
Valley. As a result, waves of showers and a few thunderstorms are
expected to roam through the general region starting as early as
Sunday night and lasting through Tuesday. At this point, the Monday
afternoon-Tuesday morning period is favored for the highest coverage
of showers and storms locally, which may include swaths of locally
heavy rainfall (>1") given relatively slow storm motions, an
abundance of synoptic-scale lift, and PWATS nearing 1.4". Outside of
waves of showers and thunderstorms, temperatures early next week
will be like a tale of two seasons with highs in the mid 70s away
from Lake Michigan on Monday and only in the low to mid 60s on
Tuesday (thanks to expansive onshore flow off Lake Michigan).

Wednesday and at least the first half of Thursday, a surface high
pressure system and upper-level ridge will move over the Great Lakes
allowing for a rebound in temperatures into the low to mid 70s. With
the core of the surface high pressure system expected to pass north
of our area, the surface wind will maintain an onshore component. As
a result, temperatures will continue to be cooler near the Lake
Michigan shoreline. Ensemble model guidance continues to favor the
next opportunity for showers and a few thunderstorms to arrive
sometime in the late Thursday to early Friday timeframe.

A much-too-early look at the latter half of May suggests relatively
seasonable weather with highs in the 70s and regular opportunities
for showers and thunderstorms. (In other words, there are no signs
of much above or below normal temperatures, or for much above or
below normal precipitation).

Borchardt

&&

.AVIATION /12Z TAFS THROUGH 18Z SUNDAY/...
Issued at 612 AM CDT Sat May 11 2024

Northwesterly winds at press time will quickly increase in
gusto over the next few hours and remain gusty through sunset
(peak gusts of 25-30kt). After sunset, efficient surface
decoupling and the passage of a weakening lake breeze will lead
to light and variable winds. Southwesterly winds will become
established by daybreak Sunday. Clear skies will become dotted
by high-based cumulus by early afternoon.

Borchardt

&&

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

&&

$$

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