602
FXUS63 KILX 270159
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
859 PM CDT Sun May 26 2024

.KEY MESSAGES...

- Another round of stronger storms are possible this evening for
  areas south of I-72. Discrete cells with the threat of large
  hail and isolated tornadoes are initially forecast before
  becoming a line of thunderstorms, with hail and damaging winds
  as the hazards.

- Localized heavy rain and flooding for areas near and south of
  I-70 as storms, bringing high precipitation amounts, pass
  through this evening.

- The weather calms down after tonight, providing us a benign week
  of weather. The next chance (30-40%) of showers and
  thunderstorms arrives Friday night into Saturday.

&&

.UPDATE...
Issued at 859 PM CDT Sun May 26 2024

A QLCS/linear thunderstorm system continues eastward along/south
of I-70 this evening, generating reports of wind damage and large
hail, but so far no confirmed tornadoes this far north. However,
a severe thunderstorm watch continues north of I-70 and a tornado
watch south of I-70. This feature should exit southeast IL into
Indiana by 10 PM. The cold front associated with this system
appears to be roughly along the Illinois River as of 830 PM,
however subsidence and increasing CIN behind the QLCS should
eliminate the severe weather threat. Overnight, the front will
continue to traverse the central IL forecast area, exiting the
area by around sunrise. Overnight, a few more showers and
thunderstorms could be triggered by the front, while winds will
switch to northwesterly and trigger some cooler temperatures with
lows in the mid 50s to lower 60s south of I-70. Updates have been
sent for trends in precipitation coverage this evening, and a
couple degrees off of lows for tonight.

37

&&

.DISCUSSION...
Issued at 233 PM CDT Sun May 26 2024

The next round of storms is possible this evening, mainly near and
south of I-72. There is some uncertainty whether this round will
make far enough north to be in the CWA or not but the newest HRRR
and ARW show it just south of I-72. These are likely to be supercell
structured with a large hail and tornado risk early in the event
(21z-00z). Then will merge into a more linear form as it exits
southeastern Illinois, posing more of a hail and damaging wind risk.
The HRRR 12z soundings show STP of 1, SHIP of 2.1, midlevel lapse
rates of ~8 C/km, and PWATs of 1.5-1.9 inches for this evening. We
kept the Flood Watch for south of I-70 because of the higher PWATs,
and the potential for training cells.

After this evening, the weather will clear out. Memorial Day will be
nice and dry with highs in the low to mid 70s. There could be some
breezy winds at times, particularly late in the day. From the 12z
HREF, there is a 50-60% chance of wind gusts greater than 30 mph
in the late afternoon into the evening hours, then calming down by
the overnight hours.

Temperatures through the extended forecast will gradually warm up by
next weekend. Low to mid 70s for highs through Thursday, then
reaching the upper 70s to low 80s. The next significant chance for
precipitation comes Friday night into Saturday, with 30-40% chance
of showers and thunderstorms.

Copple

&&

.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 714 PM CDT Sun May 26 2024

A few thunderstorms will be near KDEC and KCMI until 02Z, then all
thunderstorm activity is expected to shift well south of the
central IL terminals as a cold front moves through this evening.
An area of BKN cigs over the upper Midwest will move southward
into the area behind the cold front, expected to reach KBMI, KCMI,
and KDEC northeastward by around 12Z, and linger through the
morning hours. Expect northwesterly winds overnight, although the
first few hours will see some lingering SW winds from I-55
eastward. Winds will be 8-12 kts with gusts 15-20 kts.

37

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 1 AM CDT Monday for ILZ066>068-071>073.

&&

$$