089
FXUS63 KLOT 092336
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
636 PM CDT Thu May 9 2024

.KEY MESSAGES...

- Period of quiet and warmer weather on Friday, followed by
  another chance of showers Friday night.

- Periods of showers and possibly some thunderstorms early next
  week.

&&

.DISCUSSION...
Issued at 239 PM CDT Thu May 9 2024

Through Friday night:

After our break in rainfall, our next batch of showers continues
to quickly shift/develop eastward into the area early this
afternoon in association with the next mid-level impulse now
shifting into northwestern IL. These showers will persist across
much of the area through the remainder of the afternoon before
gradually tapering off from northwest to southeast across the area
this evening. While the thunder threat with this activity will
remain low, we cannot rule out a few storms across our far
southern counties in central IL and IN late this afternoon. Either
way, no severe weather is expected.

Drier weather is expected during the day Friday as we await our
next weather maker shifting southward across the Upper Midwest.
Partly cloudy/sunny afternoon skies will allow inland temperatures
to rebound back into the mid to upper 60s. However, conditions
look to become favorable to allow an afternoon lake breeze to
develop along the northeastern IL shores. While the lake breeze
may not move more than 10 to 15 miles inland prior to sunset,
onshore easterly winds will keep conditions a few degrees cooler
along the lakeshore Friday afternoon.

Our next chance of rain will come Friday night as the next fast
moving and compact impulse digs southeastward across the western
Great Lakes. This looks to be a quick hit (2 to 4 hours) of
mainly some showery activity with an approaching surface cold
front, though steepening lapse rates could also support a couple
of embedded thunderstorms. The quick movement of the precipitation
should keep total amounts rather low, so we really do not look to
have any major hydro threats with this activity.

KJB


Saturday through Thursday:

The rain chances forecast for Friday night will clear the area by
daybreak Saturday. Surface high pressure building in from the south
and steady height rises aloft will then bring pleasant Spring
conditions to the area for the weekend. Temperatures will be rather
seasonable on Saturday with highs forecast in the middle and upper
60s, lower 60s closer to the lakeshore. A tight pressure gradient
behind the departing storm system will bring breezy NW winds to the
area on Saturday. As the surface high moves across the Tennessee
Valley Saturday night into Sunday, the mild return flow will pull
highs into the middle and upper 70s to close out the weekend, again
with a hefty breeze expected during the day.

An upper trough looks to move across the central Plains and lower
Midwest Monday into Tuesday. The surface response will be a low
pressure center that medium-range guidance can agree will pass to
our south. Nonetheless, broad upper forcing in a moisture-rich
profile will lead to rain chances across our domain early next
week along the storm`s northern flank. An ample amount of MUCAPE
north of the low could bring us some elevated thunderstorms as
well, although heavy rain may be the most appreciable concern. This
wave will hang out in the region through Tuesday with another wave
moving in right behind for midweek ushering in what could be a
somewhat active week ahead with lots of room for rain chances.
Luckily, nothing overly impactful appears on the scope through the
middle of next week.

Doom

&&

.AVIATION /00Z TAFS THROUGH 06Z FRIDAY/...
Issued at 636 PM CDT Thu May 9 2024

Key Aviation Impacts for the current TAF period:

- Isolated light rain with MVFR cigs through the overnight.
  There remains a 50 percent chance for terminals closer to Lake
  Michigan to have IFR cigs Friday morning.

- Potential lake breeze Friday afternoon. Mostly likely at MDW,
  but low confidence on it arriving at ORD

- Next round of rain arrives after 03Z on Friday night.

The main axis for rain stretches over KMDW and KGYY and is
gradually moving southeast of Chicago. IFR cigs are still
associated with this area of heavier rainfall, but behind it is
gradual improvement to higher MVFR around or above 2000 feet.
There are even pockets, like the one currently over KRFD, of
VFR skies. However, there remains some scattered cellular
development. Cells are not overly strong and thunder is not
expected. There should be more periods of drier conditions
through 03Z, so -SHRA mentions were converted to VCSH. These
higher MVFR cigs will continue through Friday morning. There is
a chance for IFR cigs that could develop, but confidence is low
so the TEMPO was left in place for cigs as down to 900 feet.

As the sun rises, mixing should be strong enough to start
lifting and breaking up cigs to provide VFR through the end of
the TAF. Winds will turn to the north. For the early part of
the morning the winds will favor more east of north, before
late morning and the afternoon they become more west of north
and eventually true northwest. Hi-res models are projecting a
potential lake breeze develop Friday afternoon. There was
stronger confidence in it arriving at KMDW and KGYY, so it was
added there, but some models have the boundary setting up right
over KORD with west winds over much of the terminal and east
winds just to the east. With confidence being so low, the lake
breeze was not added to the current KORD TAF, but will be
revisited in later forecast packages.

Much of the TAF should be dry, but the next front comes down
from Minnesota and Wisconsin Friday evening. There is a chance
that it arrives at KRFD before 00Z, but for now rain was kept
out of their TAF, though -RA was added to the Chicago terminals
with current projections arriving around 03Z.

DK

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 3 AM CDT Friday for the IL and IN
     nearshore waters.

&&

$$

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