246
FXUS63 KILX 200559
AFDILX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE LINCOLN IL
1259 AM CDT TUE MAY 20 2025
KEY MESSAGES
- WIDESPREAD SHOWERS AND STORMS ARE EXPECTED TONIGHT (GREATER THAN
90% CHANCE). SOME OF THE STORMS COULD BE STRONG TO SEVERE,
PRIMARILY IN AREAS TO THE SOUTH AND WEST OF LINCOLN LATE THIS
EVENING (LEVEL 2 OF 5 RISK).
- HEAVY RAINFALL IS ALSO LIKELY OVERNIGHT. THERE IS A 70% CHANCE
OF 1" OF RAINFALL, WHILE LOCALIZED AMOUNTS COULD EXCEED 3" (10%
CHANCE). THERE IS A SLIGHT RISK (LEVEL 2 OF 4) OF FLASH
FLOODING.
- ANOTHER ROUND OF SEVERE STORMS IS POSSIBLE TUESDAY AFTERNOON,
WITH THE BEST CHANCE BEING EAST OF I-55 AND SOUTH OF I-74
(LEVEL 2 OF 5 RISK).
- BELOW NORMAL TEMPERATURES ARE LIKELY FROM WEDNESDAY THROUGH THE
WEEKEND. WEDNESDAY WILL BE THE COOLEST DAY, WITH HIGHS ONLY IN
THE UPPER 50S AND LOW 60S.
UPDATE
ISSUED AT 753 PM CDT MON MAY 19 2025
LATEST SURFACE MAP SHOWS THE WARM FRONT REMAINING DRAPED ACROSS
SOUTHERN ILLINOIS, BUT NUDGING NORTH PAST THE I-64 CORRIDOR.
MESOANALYSIS INDICATES A MLCAPE GRADIENT ALONG THIS BOUNDARY, WITH
VALUES OVER 1500 J/KG SOUTH OF IT. STORM ACTIVITY HAS LARGELY
BEEN LIFTING NORTHEAST ACROSS MISSOURI AND IOWA THUS FAR, THOUGH
NOW APPROACHING THE WESTERN BULGE OF ILLINOIS, AND THE FRONT
ITSELF IS BEGINNING TO LIGHT UP WITH SOME CONVECTION AS WELL. THE
MLCAPE GRADIENT DOESN'T MAKE A TREMENDOUS AMOUNT OF NORTHWARD
PROGRESS, WITH 500 J/KG GETTING CLOSE TO SPRINGFIELD BY ABOUT
MIDNIGHT.
POP'S HAVE BEEN ADJUSTED TO REFINE THE PRECIPITATION TIMING, WITH
THE MAIN FOCUS IN THE PERIOD BETWEEN MIDNIGHT AND SUNRISE.
INCOMING MOISTURE SURGE WILL BRING PRECIPITABLE WATER VALUES UP TO
ABOUT 1.8 INCHES BY MIDNIGHT PER THE LATEST RAP MODEL, WITH A
WIDESPREAD 1 TO 1.5 INCHES OF RAIN EXPECTED DURING THIS TIME
FRAME.
GEELHART
DISCUSSION
ISSUED AT 140 PM CDT MON MAY 19 2025
A STACKED LOW PRESSURE SYSTEM IS POSITIONED OVER WESTERN SD AS OF
1830Z/130PM. A WEAK WARM FRONT ASSOCIATED WITH THIS SYSTEM
REMAINED DRAPED FROM NORTH OF LINCOLN, NE TOWARDS ST. LOUIS, MO,
LARGELY UNCHANGED FROM THIS MORNING (AT LEAST IN RELATION TO THE
ILX CWA). CLOSER TO HOME, A SWATH OF LIGHT RAIN AND EMBEDDED
T-STORMS WAS LOCATED NEAR THE IL RIVER VALLEY, PUSHING EAST IN
TIME. THESE STORMS SHOULD GRADUALLY SHIFT INTO A LESS UNSTABLE
ENVIRONMENT IN TIME, AND THAT MATCHES THE DECREASING TREND THAT
WE'VE SEEN IN THE LIGHTNING ACTIVITY WITH THESE CELLS. A 20-40%
CHANCE OF SHOWERS/STORMS WILL PERSIST THROUGH THE AFTERNOON.
INTO TONIGHT, THE WARM FRONT WILL CONTINUE TO BE DRAPED IN A WNW-
TO-ESE ORIENTATION EITHER NEAR OR JUST SOUTH OF THE SOUTHERN
FRINGES OF THE ILX CWA. DEEP LAYER SHEAR VECTORS ARE ORIENTED
ACROSS THE BOUNDARY, LIMITING THE RESIDENCE TIME OF ANY INDIVIDUAL
CELLS TO BECOME SFC-BASED. ENS MEAN PWAT VALUES ARE STILL AROUND
1.5", WHICH IS ABOVE THE 90TH PERCENTILE OF THE ILX SOUNDING
CLIMATOLOGY FOR MID- MAY. WITH FLOW ORIENTED TOWARDS AND
PERPENDICULAR TO THIS BOUNDARY, IT'S NO SURPRISE THAT MODEL SHOW
STRONG ISENTROPIC UPGLIDE NORTH OF THE SFC WARM FRONT SUPPORTING
WIDESPREAD, PERSISTENT PRECIP. MODELS SHOW RICH 850MB MOISTURE
ADVECTING ACROSS THE BOUNDARY, WITH 850MB TD IN THE 14-16 DEGC
RANGE, WHICH IS NEAR THE MAX OF THE ILX SOUNDING CLIMATOLOGY. ALL
OF THIS COLLECTING POINTS TOWARDS WIDESPREAD, APPRECIABLE RAINFALL
OVERNIGHT. CAMS HAVE GENERALLY SHOWN A BROAD 1-2" OF RAIN WITH
LOCALLY HIGHER AMOUNTS, WITH MAX AMOUNTS AS HIGH AS 4-6" (THOUGH
TO BE CLEAR THE PROBS OF HITTING THESE KINDS OF AMOUNTS IS LOW,
LESS THAN 5-10%, AT ANY ONE LOCATION). SINCE WE AVOIDING MUCH IN
THE WAY OF APPRECIABLE RAINFALL EARLY MON AM, I EXPECT WE'LL BE
ABLE TO HANDLE 1-2" RAINFALL AMOUNTS WITHOUT MUCH IN THE WAY OF
FLOODING ISSUES, BUT CAN'T RULE OUT SOME ISSUES IF WE START TO
CREEP UP TOWARDS HIGHER TOTALS. WPC MAINTAINED A SLIGHT RISK
(LEVEL 2 OF 4) OF EXCESSIVE RAINFALL/FLASH FLOODING.
I'M NOT PARTICULARLY IMPRESSED WITH THE SEVERE STORM THREAT THIS
EVENING. AS NOTED ABOVE, THE DEEP LAYER SHEAR IS ORIENTED
PERPENDICULAR TO THE WARM FRONT, SO EVEN IF THE WARM FRONT IS
DRAPED NEAR OUR SOUTHERN CWA, CELLS WILL BE QUICK TO MOVE NORTH OF
THE BOUNDARY. THE BEST CHANCE FOR SEVERE HAZARDS SEEMS TO BE AT
THE ONSET OF PRECIP IN OUR AREA, WHEN CAMS DEPICT UPSCALE GROWTH
OF STORMS ACROSS MO ROLLING IN FROM THE WEST. THIS COMPLEX SHOULD
WEAKEN IN TIME BUT COULD PERHAPS POSE A THREAT OF WIND IN AREAS
TO THE SOUTH/WEST OF LINCOLN BEFORE IT DOES. THIS WOULD BE BETWEEN
ROUGHLY 9PM-11PM. INTO THE OVERNIGHT, MUCAPE VALUES DON'T APPEAR
OVERLY IMPRESSIVE (500-1500 J/KG), SO EVEN THE ELEVATED HAIL
THREAT APPEARS SOMEWHAT LIMITED.
FOR TUES, THE FOCUS SHIFTS BACK TO SEVERE STORM POTENTIAL AS THE
SFC LOW APPROACHES AND FINALLY LIFTS THE WARM FRONT NORTHWARD
ACROSS THE ILX CWA. THE PRIMARY QUESTION CONTINUES TO BE 'HOW MUCH
DOES THE ATMOSPHERE RECOVER?' AFTER THE WIDESPREAD PRECIP MON
NIGHT INTO TUES AM. MODELS CONTINUE TO SHOW SOME DESTABILIZATION
OCCURRING, WITH MODERATE INSTABILITY (1000-1500 J/KG) AND DEEP
LAYER SHEAR (40 KNOTS). WITH THE PRESENCE OF THE WARM FRONT AND A
POTENTIAL TRIPLE POINT, THERE WOULD BE A NON-ZERO TORNADO THREAT
ACROSS THE ILX CWA TUES PM. HOWEVER, MODELS FOCUS THE RICHEST
MOISTURE ACROSS OUR SE COUNTIES (THIS IS EVIDENT IN BOTH SFC AND
850MB MOISTURE FIELDS). IN THESE AREAS, INSTABILITY WOULD BE
HIGHER (OVER 2000 J/KG) BUT SFC WINDS ARE LESS LIKELY TO BE BACKED
GIVEN THE SEPARATION FROM THE SFC LOW. FORECAST HODOGRAPHS
SUPPORT THIS NOTION, SHOWING UNIDIRECTIONAL WIND PROFILES IN THE
SE CWA WITH LONG, STRAIGHT HODOGRAPHS FAVORING A HAIL THREAT AND
POTENTIAL FOR SPLITTING STORMS. WILL NOTE THAT THE 12Z GUIDANCE
HAD A NW-WARD SHIFT IN THE SFC LOW LOCATION, WHICH COULD
NECESSITATE THE RISK AREA BEING ENLARGED FURTHER TO THE WEST AS
WELL, IF THESE TRENDS HOLD IN FUTURE MODEL CYCLES.
MUCH OF THE FORECAST FOR THE REST OF THE PERIOD REMAINS ON TRACK.
UPPER LEVEL TROUGHING WILL REMAIN IN PLACE OVER THE NORTHEASTERN
US FROM MID-WEEK INTO THE WEEKEND. LOCALLY, IT APPEARS WE'LL HAVE
A PROLONGED STRETCH OF SEASONABLY COOL TEMPERATURES, THE COLDEST
OF WHICH WILL BE ON WED WITH HIGHS NEAR 60F. WED WILL ALSO FEATURE
BREEZY NW WINDS AND A 20-30% CHANCE OF LIGHT SHOWERS, WITH THE
HIGHEST PROBS BEING NORTH OF I-74. THE GEFS ENS KEEPS BELOW NORMAL
TEMPS IN PLACE FOR THE MID-MS AND OHIO VALLEYS WELL INTO THE
FOLLOWING WEEK. OUR HIGHS DO WARM SLIGHTLY IN THE UPPER 60S/LOW
70S FOR THE END OF THE WORK WEEK, BUT SEEM UNLIKELY TO WARM MUCH
BEYOND THAT FOR AWHILE. GUIDANCE KEEPS LOWS IN THE MID 40S, SO
FROST IS NOT EXPECTED TO BE A CONCERN DURING THIS COOL STRETCH OF
WEATHER. MOSTLY DRY CONDITIONS ARE FAVORED LATE WEEK, ALTHOUGH A
STRAY SHOWER CAN'T BE RULED OUT THURS (20% CHANCE). INTO THE
WEEKEND, GUIDANCE DEPICTS ANOTHER WAVE EMERGING ONTO THE PLAINS.
DEPENDING ON WHERE THE WARM FRONT SETS UP, THIS COULD REINTRODUCE
PRECIP TO THE ILX CWA, BUT THERE IS STILL A BROAD SPREAD IN THE
TIMING/LOCATION OF THIS WAVE.
ERWIN
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1255 AM CDT TUE MAY 20 2025
A STRONG MCS SYSTEM HAS SPREAD SHOWERS AND SCATTERED THUNDERSTORMS
INTO PIA, SPI AND DEC AIRPORTS AND WILL OVERSPREAD BMI AND CMI IN
NEXT HOUR OR SO. VFR CONDITIONS TO DETERIORATE TO IFR TO MVFR WITH
PERIODIC THUNDERSTORM BRINGING HEAVY RAINS AND VSBYS DOWN TO 1-2
MILES. LOOKING AT AROUND A 5 HOUR PERIODS OF WIDESPREAD SHOWERS
AND SCATTERED THUNDERSTORMS OVERNIGHT AND DIMINISHING TO ISOLATED
SHOWERS FROM 10-14Z FROM SW TO NE. EAST WINDS AT 15-20 KTS AND
GUSTS 25-30 KTS TO VEER SOUTH TO SE DURING OVERNIGHT AS WARM FRONT
IN SOUTHERN IL LIFTS NORTHWARD INTO CENTRAL IL. WINDS TO REMAIN
GUSTY INTO TUESDAY. AS LOW PRESSURE AND COLD FRONT MOVES EASTWARD
INTO CENTRAL IL DURING TUE AFTERNOON, WILL SEE SCATTERED
CONVECTION DEVELOP FROM 17-19Z AND PUSH EAST OF CMI BY 00Z WED.
BEST CHANCES OF CONVECTION TO BE EASTERN AIRPORTS AND MVFR
CONDITIONS POSSIBLE. WINDS TO SHIFT SW TO WEST BEHIND THE COLD
FRONT.
07
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
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