533
FXUS63 KILX 251359
AFDILX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LINCOLN IL
859 AM CDT FRI APR 25 2025
KEY MESSAGES
- SHOWERS AND A FEW THUNDERSTORMS WILL TRACK ACROSS CENTRAL
ILLINOIS TODAY...WITH A LOW RISK (5-15% CHANCE) FOR EXCESSIVE
RAINFALL EAST OF THE I-55 CORRIDOR.
- THE NEXT SIGNIFICANT CHANCE FOR THUNDERSTORMS WILL ARRIVE EARLY
NEXT WEEK AS A COLD FRONT APPROACHES FROM THE WEST. THERE IS A
15% CHANCE FOR SEVERE WEATHER NORTHWEST OF A LITCHFIELD TO
HOOPESTON LINE MONDAY NIGHT...AND EVERYWHERE EAST OF THE
ILLINOIS RIVER DURING THE DAY TUESDAY.
UPDATE
ISSUED AT 859 AM CDT FRI APR 25 2025
13Z/8AM SURFACE ANALYSIS SHOWS A SLOW-MOVING COLD FRONT EXTENDING
FROM SOUTHERN MICHIGAN SOUTHWESTWARD TO THE TEXAS PANHANDLE.
WHILE MUCH OF CENTRAL ILLINOIS IS IN THE WARM SECTOR OF THE SYSTEM
WITH TEMPERATURES WELL INTO THE 60S, LOCATIONS ALONG/NORTH OF A
MACOMB TO PONTIAC LINE REMAIN NORTH OF THE BOUNDARY WHERE WINDS
ARE NE AND TEMPERATURES ARE HOVERING IN THE MIDDLE 50S. THE FRONT
WILL ONLY SLUGGISHLY EDGE EASTWARD TODAY, SO THINK THE FAR N/NW
KILX CWA WILL STAY ON THE COOL SIDE. AS SUCH, HAVE LOWERED HIGHS
INTO THE UPPER 60S FOR KNOX, STARK, AND MARSHALL COUNTIES. FURTHER
SOUTH, AFTERNOON HIGHS IN THE MIDDLE 70S ARE STILL RIGHT ON
TRACK. 1345Z/845AM RADAR IMAGERY CONTINUES TO SHOW THE MOST
CONCENTRATED AREA OF SHOWERS WITH A FEW EMBEDDED THUNDERSTORMS
FOCUSED ALONG/EAST OF I-57 WHERE POPS HAVE BEEN INCREASED TO
80-100%. FURTHER WEST, THE PRECIP IS MUCH MORE SCATTERED IN
NATURE...AND THINK IT WILL STAY THAT WAY FOR THE BALANCE OF THE
DAY. BASED ON LATEST HRRR/RAP, HAVE FOCUSED HIGHEST POPS ACROSS
THE EAST THROUGH THE BALANCE OF THE DAY, WITH ONLY 40-50 POPS
ALONG/WEST OF I-55. WILL NEED TO KEEP AN EYE ON THE SHOWERS/STORMS
EAST OF I-55...AS RAINFALL RATES INCREASING TO UP TO 1-INCH PER
HOUR THIS AFTERNOON MAY POSE AN ISOLATED FLASH FLOODING RISK. THE
COLD FRONT WILL SLOWLY ADVANCE EASTWARD LATER TODAY, KEEPING THE
SHOWER CHANCES ALIVE THROUGH THE EVENING BEFORE FINALLY DEPARTING
INTO INDIANA BY AROUND MIDNIGHT.
BARNES
DISCUSSION
ISSUED AT 153 AM CDT FRI APR 25 2025
MID LEVEL WATER VAPOR SATELLITE SHOWS CLUSTERS OF THUNDERSTORMS
DRIFTING ACROSS THE GREAT PLAINS EARLY THIS MORNING. AHEAD OF A WEAK
MID LEVEL DISTURBANCE, FLOW ACROSS THE PRAIRIE STATE IS TRANSPORTING
MOISTURE NORTHEASTWARD WITH UP TO AROUND 500 J/KG MUCAPE FUELING A
COUPLE ISOLATED SHOWERS AND STORMS.
***** SHOWERS AND STORMS TODAY *****
AS THE MID LEVEL SHORTWAVE LIFTS OVER THE REGION LATER TODAY, A WEAK
SURFACE LOW WILL MEANDER EAST ACROSS CENTRAL IL, SPARKING A FEW
ADDITIONAL SHOWERS AND STORMS WHICH WILL END NORTHWEST TO SOUTHEAST
THIS EVENING. AN AREA OF 60+ DEGF DEWPOINTS, LIMITED IN NORTHWARD
EXTENT BY A LAKE BREEZE WHICH PUSHED SOUTH OFF OF LAKE MICHIGAN LAST
EVENING, IS EXPECTED TO EXPAND NORTHWARD TO ROUGHLY THE I-74
CORRIDOR WITH AND AHEAD OF THAT SURFACE LOW BY EARLY AFTERNOON. THIS
SEASONABLY RICH LOW LEVEL MOISTURE WILL SUPPORT ANYWHERE FROM 500-
1500 J/KG OF SBCAPE WHICH IN FORECAST SOUNDINGS LOOKS PRETTY TALL
AND NARROW (LOW NCAPE VALUES) DUE TO POOR MID LEVEL LAPSE RATES
(HREF MEAN IS 6-6.5 C/KM). AS A RESULT, DEEP WARM CLOUD PROCESSES
WILL BE CONDUCIVE TO MODERATE-HEAVY PRECIP WITH STORMS, WHICH WILL
ALSO BE MOVING SLOWLY. THE HREF LPMM SUGGESTS SOME HIGHLY LOCALIZED
POCKETS OF 2+ INCHES OF RAIN MAY OCCUR BENEATH THE HEAVIEST SHOWERS
AND STORMS, WHICH COULD LEAD TO BRIEF NUISANCE FLOODING. THAT BEING
SAID, NOT EVERYONE WILL GET IN ON THESE SHOWERS; A BLEND OF NBM AND
HREF SUGGESTS 12 HOUR POPS FROM 7AM-7PM WILL RANGE FROM 40-50% WEST
OF I-55 TO 50-70% FURTHER EAST. AS THE SURFACE LOW PULLS AWAY
TOWARDS THE EAST THIS EVENING, ITS TRAILING COLD FRONT, BOLSTERED
EAST OF I-57 BY ANOTHER LAKE MICHIGAN LAKE BREEZE, WILL SHIFT
SOUTHWARD ACROSS THE ILX CWA. NORTHERLY WINDS IN ITS WAKE WILL GUST
20-25 MPH, MAKING FOR A CHILLY EVENING AS TEMPERATURES FALL INTO THE
50S.
***** COOLER SATURDAY AND SUNDAY *****
WINDS SHOULD STAY UP ENOUGH TO KEEP TEMPERATURES FROM HITTING ROCK
BOTTOM TONIGHT INTO TOMORROW MORNING, BUT THE CONTINUED COOL
ADVECTION WILL HOLD HIGHS A BIT COOLER TOMORROW AS WELL. FORECAST
HIGHS ARE GENERALLY IN THE MID 60S, WHICH, THOUGH COOLER THAN WHAT
WE'VE GROWN ACCUSTOMED TO THIS PAST WEEK, ARE ONLY 1-3 DEGREES BELOW
SEASONABLE NORMALS. IN ADDITION, 00Z HREF GUIDANCE SUGGESTS IT'LL BE
A MOSTLY SUNNY DAY WITH WINDS EASING IN THE EVENING AS SURFACE HIGH
PRESSURE SETTLES IN FROM THE NORTH. WITH THE LACK OF CLOUD COVER AND
LIGHT WINDS, SUNDAY MORNING WILL BE COOLER WITH NBM GIVING A 30-50%
CHANCE FOR LOWS BELOW 40 ALONG THE I-74 CORRIDOR; THIS WILL BEAR
WATCHING FOR FROST POTENTIAL, THOUGH WHEN WE HAVE FROST 2M TEMPS
USUALLY ARE IN THE MID 30S AND CONFIDENCE IS LOWER (10-25%) IN THAT
HAPPENING AT THIS TIME. LOW LEVEL FLOW VEERS TO SOUTHEASTERLY ON
SUNDAY BEHIND THE DEPARTING SURFACE HIGH, AND 1000-500MB THICKNESS
INCREASES AHEAD OF A DEEPENING TROUGH IN THE GREAT BASIN, SPELLING
THE BEGINNING OF A WARMING TREND FOR US. HIGHS WILL KISS 70 AGAIN IN
MANY PLACES ACROSS CENTRAL IL, ESPECIALLY WEST OF THE I-55 CORRIDOR.
***** BREEZY AND WARM MONDAY *****
THE APPROACH OF A DEVELOPING LEE CYCLONE WILL TIGHTEN THE SURFACE
PRESSURE GRADIENT ACROSS THE AREA ON MONDAY AS HIGH PRESSURE SLOWLY
SHIFTS EAST. SOUTHERLY WINDS WILL THUS INCREASE WITH GUSTS OVER 30
MPH COMMON DURING THE AFTERNOON AND EVENING - HIGHEST ACROSS OUR
WEST. A 50-60 KT LLJ INTENSIFIES OVER THE NORTHWEST PORTION OF THE
CWA MONDAY EVENING, THOUGH FORECAST SOUNDINGS SUGGEST A CAPPING
INVERSION WILL SHIELD THE SURFACE FROM THE STRONGEST WINDS ALOFT.
NONETHELESS, IF MIXING IS AS DEEP AS THE GFS SUGGESTS (A FUNCTION
OF CLOUD COVER), BUFKIT MIXING TECHNIQUES WOULD SUGGEST SOME
SPORADIC GUSTS OF 40-45 MPH MAY OCCUR. TEMPERATURES IN THIS STRONG
WARM AIR ADVECTION (WAA) REGIME WILL SOAR INTO THE 80S AREA-WIDE,
AND WITH ENOUGH SUNSHINE WE MAY SURPASS 85 DEGF IN MANY SPOTS
(NBM CHANCES ARE 30-50%, HIGHEST SOUTHWEST).
***** SEVERE WEATHER RISK LATE MONDAY INTO TUESDAY *****
THE BIGGEST CONCERN DURING THE FORECAST PERIOD AT THIS POINT IS
SEVERE WEATHER MONDAY AND TUESDAY. IT REMAINS A CONDITIONAL THREAT,
AND SINCE THE SYSTEM RESPONSIBLE FOR OUR POTENTIAL STORMS IS
CURRENTLY OFF THE CALIFORNIA COAST THE GLOBAL MODELS ARE
UNDERSTANDABLY IN SOME DISAGREEMENT ON SPECIFICS; OF COURSE, THEY
ALSO LACK THE RESOLUTION TO CAPTURE UPSTREAM CONVECTION WHICH WILL
INEVITABLY HAVE IMPLICATIONS FOR OUR LOCAL STORM RISK. SPC MAINTAINS
A BROAD 15% RISK ACROSS AREAS WEST OF A ROUGHLY LITCHFIELD TO
HOOPESTON LINE FOR MONDAY-MONDAY NIGHT, AND AREAS EAST OF THE IL
RIVER TUESDAY (WHICH SEEMS PRUDENT TAKING ALL OF THE EXTENDED GLOBAL
GUIDANCE TOGETHER), THOUGH ULTIMATELY WHO SEES SEVERE STORMS ON
WHICH DAY WILL BE A FUNCTION OF THE COLD FRONT POSITION AND UPSTREAM
CONVECTION WHICH OF COURSE ARE NOT GOING TO BE CLEAR THAT FAR OUT.
THE PAST SEVERAL ITERATIONS OF THE DETERMINISTIC GFS AND ECMWF
SUGGEST THE COLD FRONT WILL BE POSITIONED THROUGH THE GREAT PLAINS
AND UPPER MIDWEST - WELL UPSTREAM - ON MONDAY, WITH ABUNDANT
INSTABILITY AHEAD OF IT. LREF MEAN MUCAPE RUNS FROM 1800 TO 2500
J/KG ACROSS OUR CWA (WITH EVEN HIGHER VALUES TO OUR WEST), THOUGH
FORECAST SOUNDINGS SUGGEST THIS WILL BE ROOTED NEAR 700MB AND ATOP A
ROBUST CAP. FRONTAL FORCING AND COOLING TEMPS ALOFT SHOULD ERODE THE
CAP UPSTREAM, THOUGH THAT WOULD BE A MORE DIFFICULT FEAT FOR US TO
ACHIEVE THIS FAR EAST. CONSEQUENTLY, WE SHOULD STAY DRY DURING THE
DAYLIT HOURS MONDAY. EVENTUALLY, UPSTREAM STORMS WILL MAKE THEIR WAY
TOWARDS US FROM THE WEST/NORTHWEST, AND IF THEIR OUTFLOW IS STRONG
ENOUGH TO OVERCOME OUR CIN THEY MAY CONTINUE THROUGH A PORTION OF
OUR AREA MONDAY NIGHT (PARTICULARLY IF THE MORE PROGRESSIVE MODEL
SOLUTIONS MATERIALIZE). EVENTUALLY, THE LOWER SHEAR ENVIRONMENT
SHOULD CAUSE THE STORMS TO SLOW DOWN AND FALL APART, THOUGH THEY MAY
END WITH SOME HEAVY RAIN GIVEN NEAR RECORD PWATS BETWEEN 1.3 AND 1.5
INCHES.
AT SOME POINT TUESDAY, STORMS WILL REFIRE ALONG THE COLD FRONT,
THOUGH THE UPPER LOW AND MORE FAVORABLE KINEMATICS FOR SEVERE
WEATHER WILL BE WELL DISPLACED TO THE NORTH BY THAT TIME. IN
ADDITION, LOW LEVEL SHEAR VECTORS WILL BE ORIENTED MORE PARALLEL TO
THE COLD FRONT ON TUESDAY, FAVORING A LINEAR STORM MODE AND A LOWER
TORNADO THREAT COMPARED TO MONDAY EVENING-NIGHT. WHEN AND WHERE
MONDAY NIGHT'S STORMS FALL APART, AS WELL AS THE TIMING OF THE COLD
FRONT, WILL BE KEY IN PRECISELY WHERE TUESDAY'S WAVE OF STORMS FIRE;
HOWEVER, THE RISK SEEMS HIGHEST ACROSS OUR SOUTHEAST COUNTIES.
***** REST OF THE WEEK *****
SINCE THE COLD FRONT WILL BE GROWING INCREASINGLY DISPLACED FROM ITS
FORCING AS IT SHIFTS SOUTHWARD LATE TUESDAY INTO WEDNESDAY, IT'LL
SLOW DOWN AND EVENTUALLY STALL SOMEWHERE ACROSS THE OHIO/TENNESSEE
VALLEY REGION. CONSEQUENTLY, WE CAN'T QUITE GUARANTEE A DRY
PERIOD THROUGH THE END OF THE WORK WEEK AT THIS POINT THOUGH WE
DON'T EXPECT A WASH OUT AS THE PROLONGED PERIOD OF CONTINUED POPS
MIGHT IMPLY. IF AND WHEN IT BECOMES CLEAR THAT THAT BOUNDARY WILL
CLEAR THE AREA, POPLESS PERIODS OF THE FORECAST WILL REFLECT IT.
HIGHS THE SECOND HALF OF THE WORK WEEK ARE CURRENTLY FORECAST TO
RUN NEAR CLIMATOLOGICAL NORMAL FOR THE CLOSE OF APRIL/BEGINNING OF
MAY - AROUND 70 DEGREES - THOUGH THESE WILL ALSO BE A FUNCTION OF
THE FRONT'S POSITION. WE'LL CONTINUE TO MONITOR.
BUMGARDNER
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 543 AM CDT FRI APR 25 2025
PREDOMINANTLY VFR CONDITIONS WILL BE INTERRUPTED BY ISOLATED
SHOWERS AND POSSIBLY A THUNDERSTORM THROUGHOUT THE DAY TODAY.
DUE TO WEAK WIND SHEAR, THESE STORMS WILL BE PULSEY (QUICK TO
DEVELOP AND SUBSEQUENTLY DISSIPATE) AND HENCE A CHALLENGE TO
PREDICT IN THE TAFS. PROB30 GROUPS WERE ADDED DURING THE PERIODS
OF HIGHEST THUNDER CHANCES AT EACH SITE.
THIS EVENING, NORTHERLY WINDS INCREASE AND BORDERLINE MVFR/VFR
CEILINGS WILL ARRIVE WITH A COLD FRONT. HREF PROBABILITIES FOR SUB
3,000 FT CEILINGS DROP DRASTICALLY AFTER AROUND 15Z/10AM CDT
SATURDAY AS CLOUDS SCATTER WITH HIGH PRESSURE BUILDING INTO THE
REGION FROM THE NORTH.
BUMGARDNER
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
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