Severe Thunderstorm Warning 96, NWS Lincoln, IL

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1251 PM CDT Fri May 24 2024

.KEY MESSAGES...

- A couple rounds of showers and storms are possible today
  including a decaying line of storms this morning and
  redevelopment of strong to severe storms this afternoon and
  evening ahead of a cold front.

- Showers and thunderstorms are expected (90 percent chance)
  Sunday, some of which (15-30 percent) could be severe with all
  hazards in play.

&&

.UPDATE...
Issued at 1013 AM CDT Fri May 24 2024

There is a line of thunderstorms moving east across north-central
Illinois currently and should continue to weaken. Most of the
line is stay sub- severe. There is still some redevelopment
possible behind this line as the actual cold front starts to make
its way across central and southeastern Illinois this afternoon.
The main threats we are concerned about today continues to be
damaging wind but large hail is a close second.

Copple

&&

.DISCUSSION...
Issued at 236 AM CDT Fri May 24 2024

Early this morning, an occluded area of low pressure is centered
over South Dakota while a cold front is in place across potions of
Nebraska and Kansas. An MCS is ongoing along the cold front and
is expected to track east across Iowa early this morning before
shifting into Illinois mid to late this morning. Guidance is mixed
on how well this line will stay together, but there is at least a
chance for showers and storms to move across central Illinois mid
to late this morning in a decaying state. Depending on how
quickly we clear out from any morning convection, some models
indicate that moderately strong instability will redevelop this
afternoon as dew points near 70 degrees advect across central
Illinois contributing to MLCAPE values of around 2000 J/kg.
Forecast soundings show steep low/mid level lapse rates with no
appreciable capping in place. Storms should be able to redevelop
this afternoon on remnant outflow boundaries, or this evening as
the synoptic cold front begins to move across the area. In
general, deep layer shear is a bit marginal today, around 25-30
kt, but does become more favorable with values around 30-35 kt as
the cold front approaches this evening.

High pressure will build across central Illinois behind the
departing cold front Saturday. At least a brief respite from the
humidity is expected as dew points mix into the 40s Saturday
afternoon under sunny skies.

Sunday, low pressure is progged to lift from near Kansas City
early in the morning to the western Great Lakes late in the
evening. A broad warm sector will be in place across much of the
Midwest. Central Illinois is expected to see temps in the upper
70s to lower 80s while dew points will be unseasonably high near
70 degrees. This combination of heat and humidity will contribute
to strong instability Sunday afternoon with MLCAPE values around
3000 J/kg. Despite the somewhat loosely organized surface low, a
negatively tilted shortwave trough and coupled upper jet will
result in strong forcing for ascent across central Illinois
Sunday. In addition, deep layer shear will be strong, 40 to 50
kts. Overall, kinematics and thermodynamics appear very favorable
for severe weather somewhere in the region. The main question mark
revolves around the evolution of early day convection which will
be working across the mid Mississippi Valley Sunday morning on a
veering LLJ initially focused over the mid Missouri Valley
Saturday night. Outflow from these storms and convective debris
adds some uncertainty in the details, but the day bears close
watching for severe weather both along the warm front earlier in
the day, and along the trailing cold front later in the day.
Forecast soundings (NAM/SREF) Sunday show long, cyclonically
curved hodographs along with very steep (>8.5-9.0 C/km) mid level
lapse rates supportive of supercells and large hail. 0-1 km bulk
shear of 15-25 kt and high SRH (>200 m2/s2) are supportive of
supercell tornadoes. Storms should become linear with time with
wind then becoming the primary hazard.

Low pressure will lift to the Canadian Maritimes early next week
while high pressure builds across the Great Plains. NW flow will
prevail across central Illinois. Cold advection will drive steep
low/mid level lapse rates and couldn't rule out some scattered
showers/isolated storms, diurnally favored, in response to low
amplitude shortwaves digging across the region in the NW flow.
Temperatures will run a bit cooler through the first half of next
week with highs only in the lower to mid 70s and overnight lows in
the lower 50s.

Deubelbeiss

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1245 PM CDT Fri May 24 2024

Scattered showers and thunderstorms will affect the central IL
airports through early evening with MVFR conditions at times with
heavier showers. Breezy south winds 12-18 kts with gusts 20-28
kts will occur (stronger gusts possible with thunderstorms),
except an outflow boundary from this mornings MCS giving north to
NE wind direction early this afternoon. A cold front will push
eastward over central IL early overnight with winds shifting NW to
north and averaging around 10 kts. Showers will end after cold
frontal passage and clouds to scatter out during overnight from
west to east with fair skies on Saturday morning as weak high
pressure settles into IL.

07

&&

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

&&

Hazardous Weather Outlook
National Weather Service Lincoln IL
1114 AM CDT Fri May 24 2024

ILZ027>031-036>038-040>057-061>063-066>068-071>073-251615-
Knox-Stark-Peoria-Marshall-Woodford-Fulton-Tazewell-McLean-Schuyler-
Mason-Logan-De Witt-Piatt-Champaign-Vermilion-Cass-Menard-Scott-
Morgan-Sangamon-Christian-Macon-Moultrie-Douglas-Coles-Edgar-Shelby-
Cumberland-Clark-Effingham-Jasper-Crawford-Clay-Richland-Lawrence-
1114 AM CDT Fri May 24 2024

This Hazardous Weather Outlook is for central Illinois, east
central Illinois, southeast Illinois and west central Illinois.

.DAY ONE...This afternoon and tonight.

Some of the storms late this morning north of a Lewistown to
Bloomington line could be severe with damaging wind gusts and small
hail.

Strong to severe storms are possible again areawide this
afternoon and evening and will be capable of damaging wind gusts,
large hail, and an isolated tornado.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

There is an enhanced risk (level 3 of 5) for severe thunderstorms
Sunday across central Illinois. All hazards are possible including
damaging wind gusts, large hail, tornadoes, and flooding.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed 11am to 11pm.

Expected storm motion is toward the east around 40 mph.

Copple

Preliminary Local Storm Report
National Weather Service Lincoln IL
935 AM CDT Fri May 24 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0918 AM     Tstm Wnd Dmg     4 NNW Toulon            41.15N 89.89W
05/24/2024                   Stark              IL   Emergency Mngr

            Power outages from powerlines blown over
            near Henry and Stark county border.

&&