695
FXUS63 KILX 250441
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1141 PM CDT Fri May 24 2024

.KEY MESSAGES...

- Saturday will be dry and warm. Highs in the 70s, clear skies,
  and dry weather makes for a beautiful Saturday.

- There is a 80-100% chance of thunderstorms on Sunday. These
  storms have the potential to be severe, with an enhanced risk
  (level 3 of 5) for severe weather that day.

&&

.UPDATE...
Issued at 854 PM CDT Fri May 24 2024

At 8 PM an approaching cold front was just east of the Mississippi
River about to enter the central IL forecast area. An axis of
1000-1500 J/kg MLCAPE was maintained just ahead of the front,
which should gradually slip southeastward through the evening as
the front continues to move eastward. The front should exit the
forecast area to the east by a few hours after midnight,
eliminating the thunderstorm threat across central IL. Until then,
strong to severe thunderstorms ahead of the front should continue,
gradually weakening as they move into a region of weaker deep
layer shear. Corridors of repeated thunderstorms have produced
areas of flash flooding, especially south of the area where 6-7
inches have fallen. Amounts in excess of 3 inches have been
estimated through portions of Scott, Morgan, and Sangamon
Counties, mainly far south. Champaign County has received
estimated 4 inch amounts earlier. While current activity doesn`t
support much threat of new flash flooding imminently, this will
need to be watched the next several hours. A severe thunderstorm
watch until 9 PM has been expired. An isolated storm with large
hail has just pulsed up in Schuyler County moving eastward, but
this activity is expected to be too isolated to extend the watch,
as moisture transport into the area looks as if it will be cut off
by storm development toward the St. Louis area and southward.
Thunderstorms this far north will likely remain sub-severe.

Updates this evening have been to address areas of short term
thunderstorm activity associated with multiple disorganized
clusters of storms ahead of the front, as well as winds driven by
the thunderstorm clusters.

37

&&

.DISCUSSION...
Issued at 245 PM CDT Fri May 24 2024

The storms this afternoon continue to have a severe aspect to them,
with damaging winds, large hail, and an isolated tornado being
possible. They are quite chaotic in motion and where they are
initiating. There are multiple boundaries interacting with each
other. They are seemingly merging to create a linear formation and
will move off to the east towards the Indiana border this evening.
There is a flooding risk with these storms as they are moving slower
and the axis of higher PWAT values is across the CWA, east of I-55.
The severe risk should subside before midnight tonight.

Saturday a surface high pressure will set up over the area,
providing us a brief breather before the next round of active
weather arrives Sunday morning. There is a low pressure system
bringing frontal passages through the region on Sunday with a risk
of severe weather along with the cold front.

A warm front will quickly move north through central Illinois early
Sunday morning, placing us in the warm sector. This should allow us
to destabilize and break any cap that is in place ahead of the
cold front. Highs that day are in the upper 70s to mid 80s, with
dewpoints near 70. The GFS is showing about 3000-4000 J/kg of
SBCAPE, 40-55 knots effective bulk wind shear, and very steep mid-
level lapse rates of ~9 C/km by 18z Sunday. DCAPE is showing
around 1000 J/kg on forecast NAM and GFS soundings at that same
time. This round of severe weather will have an all hazards risk,
damaging winds, large hail, and a tornado or two.

Monday (Memorial Day) has a 20-30% of any showers that day but will
be mainly dry. However, it will be quite windy. So those on the lake
or tent camping should stay aware of any stronger wind gusts that
may occur Sunday night into Monday. There is a 50-70% chance of wind
gusts 40+ mph overnight. Temperatures look to be in the mid 70s for
the holiday.

Further passed Monday, highs slowly warm back up but stay in the mid
70s to low 80s through the week.

Copple

&&

.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1141 PM CDT Fri May 24 2024

A cold front will slowly work its way southeastward across the
central IL terminals overnight. Ahead of the front, scattered
showers and a remote possibility of a thunderstorm can be
expected. Winds will be S-SW around 10 kts. Behind the front,
winds will shift to NW around 10 kts, then high pressure will
settle into the area by mid morning bringing clear skies and light
and variable winds. Skies look to remain clear until high clouds
associated with the next storm system spread into the area
Saturday evening. Winds will return out of the SE 6-12 kts after
00Z.

37

&&

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

$$