698
FXUS63 KLOT 290741
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
241 AM CDT Wed May 29 2024

.KEY MESSAGES...

- Dry and pleasant weather expected today through Friday.

- Periodic chances of showers/storms return over the weekend
  into early next.

&&

.DISCUSSION...
Issued at 241 AM CDT Wed May 29 2024

Through Friday:

A high latitude mid/upper-level ridge axis centered across the
Plains states early this morning, will build eastward across the
Midwest into the western Great Lakes through Friday. As it does,
the main belt of active northwesterly flow that has been providing
the area with daily rounds of afternoon storms will finally be
shunted to our east. A well deserved break in our period of
active weather is thus expected through weeks end as surface high
pressure sets up shop over the Great Lakes.

Water vapor imagery early this morning depicts the final impulse
in this active weather pattern quickly peeling off to the
southeast across northern IN. With its exit early this morning,
the lingering rain showers ongoing at press time near the
lakeshore will come to an end. While the lingering cloud cover may
also clear out of the area for a period this morning, it appears
that diurnal fair weather cumulus will redevelop this afternoon
across interior sections of northern IL, thus leading to a partly
cloudy/sunny afternoon. Temperatures will be pleasant today, if
not even a bit chilly near the lake. Expect inland highs to range
from the upper 60s to the low 70s, while onshore flow will keep
readings in the lower 60s along the lakeshore. Dangerous swimming
conditions are also expected along most Lake Michigan beaches
today due to enhanced wave action from the breezy northerly flow
down the lake.

Following a chilly night tonight, as temperatures bottom out in
the low to mid 40s, conditions on Thursday will be a couple of
degrees warmer than today. Mostly sunny skies Thursday will push
inland temperatures into the low to mid 70s, with mid to upper
60s expected along the lakeshore. Conditions will then begin to
gradually warm as we get closer to the weekend as the surface
flow turns back to a southerly direction following the eastward
passage of the Great Lakes surface high. This is expected to push
temperatures back into the upper 70s for Friday, though slightly
cooler conditions will persist near the IL shores.

KJB


Friday Night through Tuesday:

This weekend looks to start on a rather rainy note. A cold front
stemming from an occluding low all centered the way in the Hudson
Bay region of Canada will push across the region late Friday through
Saturday. A developing low-mid level wave will spin up a secondary
center of surface low pressure along the boundary in the central
Plains late Friday. As the low/front moves through the area, we can
expect a push of showers and possibly a few thunderstorms. There is
quite a bit of discrepancy on the path of the embedded low. However,
models can agree that, with poor mid level lapse rates overspreading
the region, just about all instability sufficient for thunderstorms
will be confined to near and south of the low track where low level
lapse rates will be notably steeper. The GFS and Canadian move the
low across southern IL leaving us with a mere wave of showers along
the front while the thunder potential appears low. The Euro brings
the low directly through the CWA bringing a marginal potential for
some embedded thunderstorms, especially in our south. The NAM
through 12Z Saturday, the end of its latest run, tracks the low to
our north which would provide a modest thunder potential area-wide.
The GEFS and EPS favor the solutions of their respective
deterministic counterparts, although both show at least some support
for all of the above-mentioned scenarios. Regardless, the consistent
signal is that we presumably shouldn`t have to worry about anything
more than general thunderstorms. The ideal timeframe looks to be
late Friday night through Saturday morning, although there is a
growing signal for rain to stick around later into the day,
especially if the southern solutions verify.

Temperatures should warm through the weekend and into next week when
we expect a return to the 80s for several days. Saturday will likely
be kept in the middle 70s while low 80s are forecast for Sunday.
Both days look to be noticeably cooler near the lakeshore, especially
on the IL side. Most of Sunday should be dry, but some models are
spitting out isolated pockets of rain during the day.

There`s been a strong and consistent signal for a cold front to pass
through the region sometime between Monday and Monday night with a
favorable thermodynamic environment to support thunderstorms
building out ahead of it. The GEFS, CIPS, and CSU severe prob
guidance are all highlighting Monday for a potential for severe
weather in the region. Luckily, the shear profile looks awfully
unimpressive and not generally favorable for organized convection.
However, if we can get enough instability built up, some stronger
storms are certainly conceivable. A lot of that will be dictated by
the time of day that the front decides to move through. A generally
unsettled pattern will keep intermittent rain chances alive through
midweek with another cold frontal passage and thunder potential
perhaps on the scope for around Wednesday.

Doom

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1232 AM CDT Wed May 29 2024

The primary aviation weather concerns through the 06Z TAF period
include:

* Continued intermittent showers and MVFR cigs through the middle of
  the overnight, mainly at the Chicagoland sites.

Light rain showers and MVFR cigs are now expected to hang around
through the middle of the night or even the predawn morning hours
over Chicagoland. At RFD, MVFR should clear out closer to 06 or 07Z
with no more rain expected. VFR is then expected through the rest of
the period.

Near-northerly winds, favoring a 340-350 direction, will stay up
near 10 kt through the night and Wednesday morning. Winds will veer
to NE around 18Z at the Chicago sites, closer to 21Z at DPA, and not
until mid-evening at RFD. Light near-northerly winds can be expected
Wednesday night.

Doom

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement through this evening for ILZ103-ILZ104.

IN...Beach Hazards Statement through this evening for INZ001-INZ002.

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

&&

$$

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