913
FXUS63 KILX 211846
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
146 PM CDT MON APR 21 2025
KEY MESSAGES
- ABOVE NORMAL TEMPERATURES RETURN TO THE FORECAST TUESDAY THROUGH
THE REMAINDER OF THE WEEK. TEMPS WILL PEAK WEDNESDAY AND
THURSDAY WITH HIGHS AROUND 80 DEGREES.
- THERE IS A 30-40 PERCENT CHANCE FOR SHOWERS AND STORMS MAINLY
ALONG AND NORTH OF A RUSHVILLE TO BLOOMINGTON LINE TUESDAY
AFTERNOON AND EVENING. THE NEXT MORE WIDESPREAD CHANCE FOR
SHOWERS AND STORMS IS LATER THURSDAY THROUGH FRIDAY.
DISCUSSION
ISSUED AT 142 PM CDT MON APR 21 2025
THIS AFTERNOON, HIGH PRESSURE IS CENTERED OVER THE MID MISSISSIPPI
VALLEY WITH RIDGING EXTENDING NORTH ACROSS ILLINOIS INTO THE UPPER
MIDWEST. LOW PRESSURE IS OVER THE NORTHERN PLAINS AND WILL LIFT
INTO THE CANADIAN PRAIRIES TUESDAY WHILE A COLD FRONT PUSHES INTO
IOWA AND NORTHERN ILLINOIS AND STALLS. SOUTH TO SOUTHWEST WINDS
WILL SET UP ACROSS CENTRAL ILLINOIS TUESDAY IN BETWEEN THESE
FEATURES AND HELP PUSH TEMPS BACK UP WELL INTO THE 70S TUESDAY
AFTERNOON. DEW POINTS POOLING IN THE UPPER 50S ALONG THE
APPROACHING FRONTAL BOUNDARY WILL CONTRIBUTE TO MODERATE
INSTABILITY WITH MLCAPE VALUES AROUND 1000 J/KG NEAR THE FRONTAL
TROUGH LATE TUESDAY AFTERNOON. DEEP LAYER SHEAR WILL BE 30-40KT
AROUND THIS TIME, AND THESE PARAMETERS SUPPORT A SEVERE WEATHER
THREAT OVER PORTIONS OF, OR AT LEAST VERY CLOSE TO, THE ILX
FORECAST AREA. THERE REMAINS SOME UNCERTAINTY ON THE PLACEMENT OF
THE FRONTAL BOUNDARY WITH THE NAM/NAM NEST/ARW ALL SLIGHTLY MORE
PROGRESSIVE IN BRINGING THE FRONTAL BOUNDARY FURTHER SOUTHEAST TO
NEAR A RUSHVILLE TO BLOOMINGTON LINE.
WEDNESDAY AND THURSDAY, SURFACE FRONT IS PROGGED TO LIFT BACK
NORTH INTO WISCONSIN WHILE SOUTHERLY FLOW WITH AN OPEN GULF
TRANSPORTS EVEN WARMER AND MORE HUMID CONDITIONS INTO THE
MIDWEST. TEMPS WEDNESDAY AND THURSDAY ARE EXPECTED TO TOP OUT
AROUND THE 80 DEGREE MARK BOTH DAYS WHILE DEWPOINTS CLIMB INTO THE
MID 50S AREAWIDE WEDNESDAY AND UPPER 50S/LOWER 60S THURSDAY. A
SHORTWAVE TROUGH LIFTING FROM THE GREAT PLAINS WILL BRING THE NEXT
CHANCE FOR SHOWERS AND STORMS TO CENTRAL ILLINOIS STARTING
THURSDAY AFTERNOON AND EVENING. DESPITE THE HEAT AND HUMIDITY
RETURNING, MODEST MID LEVEL LAPSE RATES AROUND 6.0-6.5 C/KM WILL
ONLY ALLOW FOR WEAK INSTABILITY TO DEVELOP THURSDAY AFTERNOON AS
THE UPPER LEVEL DISTURBANCE APPROACHES. MLCAPE VALUES ARE EXPECTED
TO REMAIN BELOW 600 J/KG. IN ADDITION, DEEP LAYER SHEAR WILL BE
MARGINAL, ONLY AROUND 20-25KT. THIS WILL HELP TO KEEP A SEVERE
WEATHER RISK LOW THURSDAY AFTERNOON AND EVENING.
ANOTHER SHORTWAVE TROUGH WILL DIG ACROSS THE MIDWEST FRIDAY
BRINGING ANOTHER ROUND OF SHOWERS AND STORMS TO CENTRAL
ILLINOIS. THIS SYSTEM WILL PUSH A COLD FRONT ACROSS CENTRAL
ILLINOIS AND ACROSS THE OHIO VALLEY WELL TO OUR SOUTH BY SATURDAY.
THIS WILL SET THE STAGE FOR DRY AND SLIGHTLY COOLER WEATHER
SATURDAY UNDER THE INFLUENCE OF HIGH PRESSURE CENTERED OVER THE
GREAT LAKES AND ONTARIO. AS THE RIDGE AXIS SHIFTS EAST LATE SUNDAY
INTO MONDAY, SOUTHERLY FLOW WILL RETURN TO CENTRAL ILLINOIS WITH
WARM AIR ADVECTION AHEAD OF THE ADVANCING WARM FRONT BRINGING YET
ANOTHER CHANCE FOR SHOWERS AND STORMS LATE THIS WEEKEND INTO EARLY
NEXT WEEK.
DEUBELBEISS
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1214 PM CDT MON APR 21 2025
MVFR CEILINGS CONTINUE TO RISE TOWARDS THE VFR THRESHOLD AS
DIURNAL MIXING DEEPENS. AS THE SURFACE LOW LIFTS FURTHER OFF
TOWARDS THE NORTHEAST THROUGH THE AFTERNOON, THESE CLOUDS WILL
EVENTUALLY BREAK UP AND SHIFT OUT OF THE AREA. WINDS WILL ALSO
GRADUALLY ABATE WITH THE WEAKENING PRESSURE GRADIENT THIS
AFTERNOON. LATE THIS EVENING INTO THE OVERNIGHT PERIOD, THOSE
WINDS BECOME LIGHT AND FICKLE, BUT TOWARDS SUNRISE/11Z THEY
SHOULD BECOME PREDOMINANTLY SOUTHERLY, INCREASING AND VEERING
SLIGHTLY TO SOUTH-SOUTHWESTERLY TOWARDS THE END OF THE FORECAST
PERIOD WHEN GUSTS OVER 20 KT ARE EXPECTED ONCE AGAIN.
BUMGARDNER
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
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