922
FXUS63 KILX 201727
AFDILX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE LINCOLN IL
1227 PM CDT TUE MAY 20 2025
KEY MESSAGES
- WIDESPREAD SHOWERS AND THUNDERSTORMS WILL DIMINISH EARLY THIS
MORNING OVER CENTRAL AND SOUTHEAST IL, WITH MANY AREAS SEEING 1
TO 1.5 INCH OF TOTAL RAINFALL BY 8 AM WITH LOCALLY 2-3 INCH
AMOUNTS POSSIBLE. SOME OF THE STORMS COULD BE STRONG TO SEVERE
IN RICHLAND AND LAWRENCE COUNTIES BEFORE DAWN.
- ANOTHER ROUND OF STRONG TO SEVERE THUNDERSTORMS IS POSSIBLE THIS
AFTERNOON AND EARLY EVENING UNTIL SUNSET, WITH A SLIGHT RISK
(LEVEL 2 OF 5) OVER NEARLY THE ENTIRE CWA EXCEPT FAR NORTHWEST
PORTIONS OF KNOX AND STARK COUNTIES WHERE THERE IS A MARGINAL
RISK (LEVEL 1 OF 5).
- BELOW NORMAL TEMPERATURES ARE LIKELY FROM WEDNESDAY THROUGH THE
HOLIDAY WEEKEND. WEDNESDAY AND THURSDAY WILL BE THE COOLEST DAY,
WITH HIGHS IN THE LOWER 60S OVER MUCH OF CENTRAL IL, WITH LOWS
IN THE LOW TO MID 40S WEDNESDAY NIGHT.
UPDATE
ISSUED AT 934 AM CDT TUE MAY 20 2025
*** MCV TO BRING ALL HAZARDS SEVERE THREAT THIS AFTERNOON ***
BOTTOM LINE UP FRONT: THIS EVENT APPEARS CAPABLE OF ALL SEVERE
HAZARDS, BUT SIG. HAIL/WIND SEEM UNLIKELY. ALL IN ALL, THE LATEST
SPC CONVECTIVE OUTLOOK (SLIGHT RISK, LEVEL 2 OF 5, WITH A 5%
TORNADO/15% HAIL/15% WIND THREAT) SEEMS APPROPRIATE.
A COMPLEX PATTERN IS EVIDENT ACROSS THE MIDWEST THIS MORNING, WITH
A SFC LOW ANALYZED OVER SW IA AND A STATIONARY/WARM FRONT DRAPED
EAST ACROSS IA AND THEN ARCING TO THE SE, JUST SOUTH OF THE I-74
CORRIDOR AS OF 14Z/9AM. A MESOSCALE CONVECTIVE VORTEX (MCV) WAS
EVIDENT IN RADAR/SATELLITE, LOCATED ABOUT 50 MILES ENE OF KANSAS
CITY, MO, AND TRACKING ENE TOWARDS THE ILX CWA. THIS MCV WILL BE A
KEY FACTOR IN THE LOCAL SVR STORM POTENTIAL TODAY. AHEAD OF THE
MCV, PATCHES OF CLEARING ARE EVIDENT. ADDITIONALLY, SFC TEMPS
ACROSS ILX IN THE WARM SECTOR ARE ALREADY NEAR 70F.
AS THE UPPER LOW APPROACHES, 500MB HEIGHT FALLS COMBINED WITH SOME
ADDITIONAL SFC HEATING BENEATH THE PARTLY CLOUDY SKIES SHOULD
CREATE MODERATE INSTABILITY (1000-2000 J/KG OF CAPE). FCST
SOUNDINGS SHOW STEEP MID-LEVEL LAPSE RATES, BUT A RELATIVELY
SHALLOW UPDRAFT LAYER WITH EQUILIBRIUM LEVELS (ELS) BETWEEN
300-400MB (AROUND 25KFT IN THIS CASE). THERE IS A WIDE CAPE
PROFILE THROUGH THE HAIL GROWTH ZONE (THE -10 TO -30 DEGC LAYER),
RESULTING IN "HAIL CAPE" VALUES OF AROUND 600 J/KG (>500 J/KG
CONSIDERED SUPPORTIVE OF SEVERE HAIL). HOWEVER, THE WARM CLOUD
LAYER, WHICH IS THE DEPTH BETWEEN THE CLOUD BASE/LCL AND THE
FREEZING LEVEL, IS STILL FAIRLY DEEP, AROUND 7-8 KFT, WHICH WOULD
SUGGEST SOME IMPACTS OF MELTING ON THE HAIL AS IT FELL. DESPITE
THE STEEP LAPSE RATES AND SUPPORTIVE HAIL CAPE VALUES, THE
THINKING IS THAT THE SHALLOW ELS AND WARM CLOUD LAYER WILL TEMPER
THE POTENTIAL HAIL SIZE SOMEWHAT. SOME SEVERE HAIL IS POSSIBLE,
BUT SIGNIFICANT SEVERE HAIL (>2") SEEMS UNLIKELY.
SFC WIND FIELDS FROM THE CAMS DEPICT S OR SSW WINDS ACROSS THE
WARM SECTOR THROUGH THE AFTERNOON, LIMITING THE LOW-LEVEL
HODOGRAPH CURVATURE. THE CONCERN, HOWEVER, IS THAT THE INFLUENCE
OF THE MCV IS NOT BEING PROPERLY MODELED. SFC OBS FROM NORTH-
CENTRAL AND NE MO, IMMEDIATELY AHEAD OF THE MCV, ARE OUT OF THE
SOUTHEAST. SUCH A WIND DIRECTION WOULD ENHANCE THE LOW-LEVEL
HELICITY AND THUS ENHANCE THE TORNADO THREAT, AT LEAST IN A NARROW
CORRIDOR NEAR/AHEAD OF THE MCV. MODELS DO SHOW STRONG 0-3 KM CAPE
(>100 J/KG) AND LOW LCLS (500- 750M), BOTH OF WHICH ARE
SUPPORTIVE OF TOR POTENTIAL.
WHILE LOW-LEVEL LAPSE RATES ARE STEEP, THE PBL IS ALSO QUITE MOIST
(HENCE THE LOW LCLS). THIS MEANS THAT, UNLIKE LAST FRIDAY,
CONDITIONS ARE NOT QUITE AS FAVORABLE FOR NEGATIVELY BUOYANT
DOWNDRAFT GUSTS. FCST DCAPE VALUES ARE AROUND 800-900 J/KG, ENOUGH
FOR SOME LOW-END SEVERE GUSTS, WHICH IS REFLECTING IN THE HRRR
WIND GUST OUTPUT.
TIMING TOOLS SUGGEST THE MCV REACHES THE WESTERN FRINGES OF THE
ILX CWA AROUND 18Z, THOUGH CONVECTION COULD ALREADY BE FIRING OUT
AHEAD OF IT. ACTIVITY WILL THEN PROGRESS EAST THROUGH THE
AFTERNOON, EVENTUALLY EXITING THE ILX CWA BY ABOUT 8PM.
ERWIN
DISCUSSION
ISSUED AT 400 AM CDT TUE MAY 20 2025
A STRONG MCS WAS OVER CENTRAL/EASTERN IL AND INTO WESTERN INDIANA
EARLY THIS MORNING WITH WIDESPREAD SHOWERS AND SCATTERED
THUNDERSTORMS, THOUGH DIMINISHING SW OF A CANTON TO LINCOLN TO
SHELBYVILLE LINE AT 4 AM. THUNDERSTORMS WERE FOCUSED OVER COUNTIES
ALONG THE INDIANA BORDER. A TORNADO WATCH REMAINS IN EFFECT UNTIL
8 AM FOR RICHLAND AND LAWRENCE COUNTIES, THOUGH SEVERE THREAT MAY
PASS EAST OF THE WABASH RIVER BY SUNRISE.
THE 09Z/4 AM SURFACE MAP SHOWS 998 MB LOW PRESSURE OVER FAR
SOUTHEAST NEBRASKA WITH A WARM FRONT EXTENDING ESE THROUGH
NORTHERN MO INTO FAR WEST CENTRAL IL NEAR QUINCY AND EXTENDING SE
THROUGH LITCHFIELD AND FLORA. LOW PRESSURE TO TRACK INTO CENTRAL
IOWA BY 18Z/1 PM AS WARM FRONT LIFTS SLOWLY NE TOWARD I-74. LOW
PRESSURE SYSTEM STARTS OCCLUDING LATE THIS AFTERNOON AND EVENING
AS IT MOVES INTO NORTHERN IL AND CENTRAL IN BY LATE EVENING,
PUSHING COLD FRONT EAST THRU CENTRAL IL LATE AFTERNOON/EARLY
EVENING. THIS WILL LIKELY REDEVELOP SCATTERED CONVECTION IN
UNSTABLE AIR MASS DURING EARLY TO MID AFTERNOON AND PUSH EAST
INTO INDIANA DURING EARLY/MID EVENING.
PER LATEST SPC DAY1 OUTLOOK... WITHIN THE LEFT EXIT REGION OF THE
AFOREMENTIONED MID LEVEL JET, A DRY SLOT AND ATTENDANT CORRIDOR
OF STEEP LAPSE RATES WILL LIKELY EVOLVE ACROSS PORTIONS OF MO TO
IL/IN FROM MIDDAY INTO THIS AFTERNOON. TO THE NORTH OF THIS, A
CLUSTER OF SUSTAINED STORM DEVELOPMENT IS INITIALLY ANTICIPATED
TOWARDS MID AFTERNOON, CENTERED ON CENTRAL IL AHEAD OF THE SURFACE
LOW. ADDITIONAL STORMS SHOULD DEVELOP FARTHER SOUTH IN TIME
TOWARDS THE LOWER OHIO VALLEY. A MIX OF SUPERCELLS AND MULTICELL
CLUSTERING IS ANTICIPATED, WITH ISOLATED TO SCATTERED COVERAGE OF
SEVERE AND ALL HAZARDS POSSIBLE. SPC DAY1 HAS SLIGHT RISK OVER
MUCH OF CWA (EXCEPT MARGINAL RISK OVER NW PARTS OF KNOX AND STARK
COUNTIES) FOR THIS AFTERNOON AND EARLY EVENING. THERE IS A 5% RISK
OF TORNADOES AND 15% RISK OF LARGE HAIL IN THE SLIGHT RISK AREA.
THERE IS A 15% RISK OF DAMAGING WINDS EAST OF THE IL RIVER.
HIGHS TODAY WILL BE TRICKY DEPENDING ON HOW FAR WARM FRONT GETS
AND IF WE GET ANY BREAKS IN THE LOW CLOUDS. CURRENTLY WE HAVE
HIGHS IN THE LOWER 70S FROM PEORIA AND BLOOMINGTON NORTH TO THE
UPPER 70S TO AROUND 80F FROM SPRINGFIELD TO TERRE HAUTE SOUTH.
HAVE RATHER STRONG ESE TO SE WINDS GUSTING 25-35 MPH EARLY TO MID
MORNING AND TURNING SW TO WEST AFTER COLD FRONTAL PASSAGE LATE
THIS AFTERNOON OR EVENING. A SECONDARY COLD FRONT/TROF PUSHES SE
THRU CWA OVERNIGHT WITH BREEZY WEST TO NW WINDS GUSTING 25-30 MPH
ON WED AND BRINGING IN MUCH COOLER AIR. HIGHS WED IN THE LOWER 60S
OVER MUCH OF CENTRAL IL AND A FEW UPPER 50S NORTH OF I-74, WITH
MID TO UPPER 60S IN SOUTHEAST IL. SURFACE LOW MOVES INTO THE UPPER
OHIO RIVER VALLEY BY MIDDAY WED WHILE A TROF HANGS BACK ACROSS THE
SOUTHERN GREAT LAKES AND NORTHERN IL, KEEPING MORE LOW CLOUDS
AROUND ALONG WITH A CHANCE OF SHOWERS/DRIZZLE, ESPECIALLY FROM
I-74 NORTH.
A WEAK SYSTEM PUSHES EASTWARD ACROSS THE OZARKS AND INTO THE MID
MS RIVER VALLEY WED NIGHT WITH ITS SHOWERS PASSING SOUTH OF CWA.
THOUGH LINGERING TROF TO OUR NORTHEAST WILL KEEP SMALL CHANCES OF
SHOWERS AROUND INTO THU ESPECIALLY NORTHEAST/EASTERN CWA. HIGHS
THU IN THE LOWER 60S WITH BREEZY NW WINDS (THOUGH NOT QUITE AS
STRONG AS WED). LOWS IN THE MID TO UPPER 40S WED NIGHT IN CENTRAL
IL AND AROUND 50F SOUTHEAST OF I-70. COOLER LOWS IN THE LOW TO MID
40S THU NIGHT.
FORECAST MODELS DEEPEN MID/UPPER LEVEL TROF OVER THE EASTERN
STATES LATE THIS WEEK WITH IL IN A NW UPPER LEVEL FLOW AND KEEPING
TEMPS ON THE COOLER SIDE, THOUGH SOME SLIGHT MODIFICATION LATE
THIS WEEK INTO MEMORIAL DAY WEEKEND. CANADIAN HIGH PRESSURE NOSING
DOWN INTO IL FROM HUDSON BAY BY FRIDAY TO BRING DRIER WX FRIDAY.
STILL A SPECTRUM OF MODEL SOLUTIONS FOR WX SYSTEMS EJECTING OUT OF
THE CENTRAL PLAINS DURING THE MEMORIAL DAY WEEKEND. CONSENSUS HAS
20-30% CHANCE OF SHOWERS SW OF I-74 ON SATURDAY THEN 30-50% CHANCE
OF SHOWERS SAT NIGHT THROUGH MONDAY. A REINFORCING SHORT WAVE TROF
DIGGING INTO THE WESTERN GREAT LAKES AND IL ON MONDAY/MEMORIAL DAY
INTO TUE TO KEEP TEMPS BELOW NORMAL ALONG WITH CHANCES OF SHOWERS
AND MOSTLY CLOUDY SKIES/MORE CLOUD COVER.
07
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1227 PM CDT TUE MAY 20 2025
A WARM FRONT IS NEAR THE I-74 CORRIDOR, WITH IFR CEILINGS NORTH OF
THE FRONT AND MVFR/VFR CEILINGS TO THE SOUTH. A SFC LOW WILL TRACK
ACROSS THE AREA THIS AFTERNOON RESULTING IN SCATTERED
SHOWERS/STORMS SHIFTING FROM WEST TO EAST. THESE SHOULD DEPART TO
THE EAST OF KCMI BY 23Z. SCATTERED LIGHT SHOWERS COULD CONTINUE
INTO THE EVENING, BUT THE THREAT OF THUNDER SHOULD END AFTER 23Z,
OR 00Z AT THE LATEST. OVERNIGHT ANOTHER PUSH OF MVFR, OR PERHAPS
IFR, CEILINGS ARRIVES FROM THE NORTH. WINDS WILL HAVE A SOUTHERLY
COMPONENT THIS AFTERNOON, THEN SHIFT TO WESTERLY TONIGHT AND
BECOME BREEZY INTO THE DAYTIME HOURS ON WEDNESDAY.
ERWIN
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
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