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991
FXUS63 KILX 202306
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
606 PM CDT Thu Jun 20 2024

.KEY MESSAGES...

- Hot and humid conditions will continue across central and
  southeast IL into the middle of next week, with brief relief
  from the heat Sunday into Monday. The hottest conditions of the
  upcoming 7 days look to be Friday, Saturday, and Tuesday when
  air temperatures climb into the mid 90s, and heat index values
  peak near or just above 100 degrees.

- Isolated thunderstorms will be possible this afternoon and
  evening north of I-72. A better chance for thunderstorms arrives
  Saturday night into Sunday morning as a cold front moves
  through Illinois.

&&

.DISCUSSION...
Issued at 237 PM CDT Thu Jun 20 2024

After some potential for scattered showers and thunderstorms this
afternoon and evening in the vicinity of a warm front lifting
into the upper Midwest, high pressure aloft will dominate the
forecast into Saturday. A strong cap is evident in forecast
soundings into Saturday owing to subsidence associated with this
high pressure. The 500 mb high pressure center will be close to
the Ohio Valley Friday, but then get suppressed into the Gulf
States by Saturday as a low amplitude but vigorous trough shifts
from the northern Plains into the Great Lakes, driving a cold
front into central IL Saturday night. A moderate CAPE/Shear
parameter space looks to accompany this front as it approaches
central IL, prompting a Marginal Risk for severe thunderstorms
from SPC, however unfavorable timing of a late night frontal
passage for most of central IL looks to bring a question of how
far southeastward strong to severe thunderstorms can continue.
Currently the Marginal Risk ends at the Illinois River. Another
front looks on track for late Tuesday or Wednesday, with the next
chance for thunderstorms. Rainfall amounts don`t look promising
for erasing the dry conditions that have crept up over most of the
area, with a quarter inch forecast south of I-70, up to around an
inch west of the Illinois River.

Hot and humid conditions remain on track for much of the upcoming
week. Heat and humidity will gradually build further until
Saturday as the cold front arrives, with highs peaking in the mid
90s, and heat index values around 100 to a few degrees about 100.
The cold front will bring some degree of temporary relief Sunday
and Monday, with highs suppressed to around 90 degrees. Heat
index will likely still be well into the 90s Sunday with lingering
humidity, but dewpoints are likely dry enough Monday that
afternoon heat index is only in the lower 90s. Heat looks to
rebound again Tuesday ahead of the next cold front. Lows only look
to fall as low as the lower to mid 70s until Sunday night.

Airnow.gov for Air Quality shows an orange category (Unhealthy for
sensitive groups) appearing over the Wabash river valley over
eastern/se IL today and tomorrow. An air quality alert is in effect
over much of Indiana from through midnight Friday night.

37

&&

.AVIATION...  
-- Changed Discussion --
(For the 00z TAFs through 00z Friday Evening)
Issued at 606 PM CDT Thu Jun 20 2024

VFR conditions will prevail at all TAF sites next 24hrs. Skies
should be mostly clear through the night with few to scattered CU
developing again tomorrow over the area. Winds will become light
and variable tonight, then become southwesterly tomorrow with
speeds less than 10kts.

Auten
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&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$