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000
FXUS63 KLOT 250724
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
224 AM CDT Thu Apr 25 2024

.KEY MESSAGES...

- Periods of showers and thunderstorms expected starting Friday
  and continuing at times through the weekend, with some threat
  for severe weather, particularly later in the weekend. Locally
  heavy rainfall possible as well.

- Gusty southerly winds to 40 mph Saturday and Sunday.

&&

.DISCUSSION...
Issued at 224 AM CDT Thu Apr 25 2024

Through Friday:

After a cool start, temperatures will jump a few degrees compared
to Wednesday as high pressure begins to depart to the north and
east. A lake breeze will push inland towards midday resulting in
lake cooling with high temperatures for lakeside communities only
in the upper 40s to near 50 degrees. Tonight, temperatures will
fall into the upper 30s and lower 40s, with a smattering of mid
30s possible in the typical cool spots. Increasing low-level warm
advection and 5 to 10 mph surface winds will likely preclude much
of a frost threat.

Friday will be a transition day towards a more active period of
weather heading into the weekend. A tightening pressure gradient
will drive increasing southeasterly breezes through the morning
and afternoon. Eventually, shower and thunderstorm chances will
also increase, particularly during the afternoon, as a lead
impulse drives a more notable increase in warm advection overhead
although the severe threat during this period appears low.

Carlaw


Friday Night through Wednesday:

Showers and scattered thunderstorms are expected to be ongoing
Friday evening across much of the area and will be ending early
Saturday morning, from west to east. A warm front will be
lifting north across the area Friday night, shifting winds to
the south/southwest and they may gust into the 30-35 mph range.
This will likely allow temps to level off in the upper 50s to
around 60 in the evening and then possibly slowly rise into the
lower 60s during the overnight hours.

As the first surface low lifts north across the upper Great
Lakes on Saturday, there remains little focus for new
thunderstorm development during much of the daylight hours on
Saturday. There could be some lingering precipitation in the
east Saturday morning and perhaps an isolated storm across far
northwest IL along a cold front by evening. Lowered pops to low
chance for most of the area. Southerly winds may gust as high as
40 mph on Saturday and with the expected lack of precip and
warming temps prior to sunrise, highs should easily reach upper
70s for most areas and lower 80s are looking possible.

A second area of low pressure will move from the Plains Sunday
to the upper Great Lakes Monday along the cold front noted above
left behind from the first system. Convection is expected to
develop northeast of this second low and along the cold front
Saturday night. There remains quite a bit of uncertainty for
where exactly this will occur and how far into the cwa it may
move or develop. Nevertheless, increasing pops Saturday evening
through Sunday morning look reasonable, especially for the
northwest half of the cwa. There would be some severe potential
during this time as well as the potential for heavy rain.

Precip trends for Sunday become fairly uncertain and likely
dependent on what does or does not occur Saturday night. While
there will likely be some dry periods Sunday into Sunday night,
difficult to make any changes to the higher blended pops. There
will be a continued threat of severe weather and heavy rain on
Sunday, perhaps a better chance with any convection Sunday
afternoon. Assuming there is some dry hours and some sunshine,
highs on Sunday may be similar to Saturday, in the upper 70s
with 80 possible.

The slower evolution/movement of the second system has
continued, resulting in the cold front not moving across the
local area until Monday afternoon with a continued chance for
showers/scattered thunderstorms on Monday, mainly across the
eastern half of the area. Confidence is fairly low for how
convective trends will evolve on Monday. cms

&&

.AVIATION /06Z TAFS THROUGH 12Z FRIDAY/...
Issued at 1226 AM CDT Thu Apr 25 2024

Only forecast concern this period is a lake breeze this
afternoon. Light and variable winds overnight will become
southeast after daybreak and may briefly become southerly before
turning back to the southeast. A lake breeze will move inland
this afternoon shifting winds easterly at ORD/MDW/GYY with
speeds to 10kts. Winds will turn back to southeasterly this
evening with speeds under 10kts, though speeds are expected to
increase to 10-12kt by daybreak Friday with some gusts possible.
cms

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Freeze Warning until 8 AM CDT this morning for ILZ003-ILZ004-
     ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ103.

     Frost Advisory until 8 AM CDT this morning for ILZ019-ILZ020-
     ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ105-ILZ106-ILZ107-
     ILZ108.

IN...Frost Advisory until 8 AM CDT /9 AM EDT/ this morning for
     INZ001-INZ002-INZ010-INZ011-INZ019.

LM...None.

&&

$$

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