174
FXUS63 KILX 132325
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
625 PM CDT Sat Jul 13 2024

.KEY MESSAGES...

- Hot and humid weather will prevail Sunday and Monday...with
  afternoon heat index values peaking above 100 degrees both days.

- The primary focus for thunderstorms and potential severe weather
  will remain north of central Illinois for the next couple of
  days. As a cold front drops southward, the chances for storms
  will increase markedly by Tuesday.

- Below normal temperatures will return by the middle and end of
  next week as highs drop back into the upper 70s and lower 80s
  Wednesday through Saturday.

&&

.SHORT TERM...(Tonight and Sunday)
Issued at 247 PM CDT Sat Jul 13 2024

Isolated convection will develop across central Illinois over the
next couple of hours then linger until shortly before sunset.
After a period of warm/dry weather this evening, attention will
turn to developing thunderstorms well to the N/NW of the area
across Minnesota/northern Iowa. CAMs continue to be in
disagreement...with the HRRR keeping the convection to the north
across Wisconsin and perhaps far northern Illinois late tonight.
Meanwhile the NAM/WRF-ARW/HRW NSSL all suggest the storms will
take a more southerly trajectory and spill into the NW KILX CWA
shortly after midnight. Given the current synoptic pattern featuring
a prominent upper ridge centered over the Desert Southwest and
downstream weak troughing across the Great Lakes/Ohio River
Valley, the more southerly trajectory seems plausible. As a
result, have introduced 30-40 PoPs mainly for locations north of
I-72 late tonight into early Sunday morning.

The convection will track further E/SE and dissipate after
sunrise, followed by a partly to mostly sunny and hot day. Thanks
to at least partial sunshine and SW winds increasing to 10-15mph,
high temperatures on Sunday will top out in the lower to middle
90s. With dewpoints in the lower to middle 70s, corresponding heat
index values will climb into the 100-105 degree range by
afternoon. While there is still some uncertainty about early
morning convection potentially keeping the N/NE CWA slightly
cooler than forecast, think the prevailing SW winds during the
afternoon will cause temps to climb above 90 degrees even at
Bloomington/Champaign/Danville. Have therefore opted to issue a
Heat Advisory for all of central and southeast Illinois from
Sunday afternoon through Monday afternoon.

Barnes

.LONG TERM...(Monday through Next Saturday)
Issued at 247 PM CDT Sat Jul 13 2024

Another round of nocturnal convection will likely develop Sunday
night...this time across Wisconsin/northern Illinois into northern
Indiana. Will maintain low chance PoPs along/north of I-74
accordingly, but think the bulk of the activity will remain just
N/NE of the area. As thermal ridging develops ahead of an
approaching cold front, high temperatures on Monday will climb a
couple degrees higher than Sunday into the middle 90s. This will
result in afternoon heat index readings peaking in the 105-110
degree range, warranting the continuation of the Heat Advisory.

As a deep upper low currently over northern Saskatchewan/Manitoba
digs southward, it will push a cold front toward central Illinois
Monday night into Tuesday. Given high dewpoint air pooling ahead
of the boundary and increasing deep-layer wind shear associated
with the approaching upper wave, will need to keep an eye out for
potential severe weather...particularly Tuesday afternoon/evening
as the front sags southward. If frontal timing remains the same,
may also need to consider extending the Heat Advisory through
Tuesday afternoon for locations south of I-70.

Once the front passes, a significantly cooler and less humid
airmass will arrive for the middle and end of next week. High
temperatures will drop back into the upper 70s and lower 80s
while overnight lows will dip into the 50s and lower 60s Wednesday
through Saturday.

Barnes

&&

.AVIATION...  (For the 00z TAFs through 00z Sunday Evening)
Issued at 624 PM CDT Sat Jul 13 2024

Low pressure will remain west of the terminals through the period
with a modest S/SW breeze through the period, at least outside the
influence of any thunderstorms. Storms are ongoing across
portions of northern Illinois as well as a line of storms from SE
MN across central WI. This more northern line of storms may push
south into central Illinois late tonight into Sunday morning. It
remains unsure how far south the line will reach, but a prob30
accounts for the potential of it reaching the I-74 corridor in a
weakening phase. Expect SW winds to begin gusting around 20 kt mid
to late Sunday morning.

Deubelbeiss

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 1 PM Sunday to 8 PM CDT Monday for ILZ027>031-
036>038-040>057-061>063-066>068-071>073.

&&

$$