621
FXUS63 KLOT 232015
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
ISSUED BY NATIONAL WEATHER SERVICE LINCOLN IL
315 PM CDT WED APR 23 2025
KEY MESSAGES
- SHARP TEMPERATURE CONTRAST ACROSS THE REGION ON THURSDAY AS A
LAKE-ENHANCED FRONT PUSHES INTO THE REGION.
- SHOWER AND STORM CHANCES INCREASE THURSDAY NIGHT INTO FRIDAY
WITH THE NEXT WEATHER MAKER, ALTHOUGH THE SEVERE RISK APPEARS
LOW.
- THE STRETCH OF WARM WEATHER WILL CONTINUE (AWAY FROM THE LAKE),
PAUSING BRIEFLY ON SATURDAY BEFORE TEMPERATURES TURN EVEN
WARMER EARLY NEXT WEEK.
- STRONGER STORM SYSTEM SET TO ARRIVE EARLY NEXT WEEK, WITH SOME
THREAT FOR STRONG TO SEVERE STORMS IN THE REGION.
DISCUSSION
ISSUED AT 315 PM CDT WED APR 23 2025
THROUGH THURSDAY:
IN THE WAKE OF THIS MORNING'S CONVECTION, QUITE A CONTRAST HAS
SET UP ACROSS THE REGION, WITH TEMPERATURES IN THE MID AND UPPER
70S SOUTH OF I-80 WHERE INSOLATION HAS BEEN THE MOST
SIGNIFICANT. FARTHER TO THE NORTH, THE AIRMASS IS ONLY JUST NOW
STARTING TO RECOVER, WITH WINDS TURNING OUT OF THE SOUTH AND
SOUTHWEST AND AIR TEMPERATURES MEANDERING TOWARDS 70. LATEST
GUIDANCE SUGGESTS THAT CONVECTIVE INHIBITION--AT LEAST TO
SURFACE-BASED PARCELS--WILL REMAIN IN PLACE ACROSS MOST OF THE
REGION, EXCEPT PERHAPS WELL NORTH OF I-88 LATE THIS AFTERNOON.
IN THIS AREA AND TOWARDS THE WISCONSIN STATE LINE, CAN'T RULE
OUT A FEW SHOWERS OR STORMS DEVELOPING INTO THE EARLY EVENING,
AND HAVE MAINTAINED SOME SLIGHT CHANCES TO ACCOUNT FOR THIS.
TO THE SOUTH OF I-88, SOME ENHANCED VERTICAL GROWTH WITHIN A
CLOUD DECK WITH BASES NEAR 12 KFT SUGGEST A FEW HIGH-BASED
SPRINKLES/SHOWERS MAY ALSO DEVELOP THROUGH THE AFTERNOON AS THIS
ACTIVITY SHIFTS EASTWARD TOWARDS THE LAKE.
OTHERWISE, THE FOCUS FOR ANY ADDITIONAL SHOWERS AND STORMS
TONIGHT SHOULD CONTINUE TO INCREMENTALLY SHIFT FARTHER TO THE
WEST AND NORTH OF THE REGION AS THE MAIN RESERVOIR OF ELEVATED
INSTABILITY PIVOTS NORTHWESTWARD. BROAD/WEAK ISENTROPIC ASCENT
TONIGHT MAY PROVIDE ENOUGH IMPETUS FOR RENEWED ELEVATED
CONVECTIVE DEVELOPMENT, BUT AGAIN WITH THE MUCAPE AXIS MIGRATING
OUT OF THE REGION, HAVE PUSHED MENTIONABLE POPS OUT OF THE
FORECAST AREA.
THE MAIN STORY ON THURSDAY WILL BE A SHARP TEMPERATURE CONTRAST
ACROSS THE REGION AS A NOTABLE COLD FRONT DROPS DOWN THE LAKE.
WHILE THERE'S BEEN SOME SIGNIFICANT DISPARITY IN THE HANDLING OF
THE TIMING OF THIS FEATURE ACROSS THE GUIDANCE SUITE, GIVEN THE
FRONT'S SHALLOW NATURE AND LAKE TEMPERATURES STILL IN THE UPPER
40S/NEAR 50 DEGREES, SEEMS PRUDENT TO CONTINUE TO FOLLOW THE
FASTER GUIDANCE (WRFARW, ECMWF). LATEST HRRR HAS SPED UP
MARKEDLY AS WELL, WHICH LENDS SOME CONFIDENCE TO THIS.
TEMPERATURES WILL FALL SHARPLY WITH THE FRONT'S ARRIVAL NEAR THE
LAKE, AND WILL LIKELY REMAIN IN THE MID/UPPER 50S, WHILE INLAND
LOCALES SOUTH OF I-80 WILL ROCKET INTO THE UPPER 70S AND LOWER
80S. CAN'T ENTIRELY RULE OUT SOME MARINE FOG WITH THE FRONT TOO,
WHICH MIGHT BLEED INLAND, PARTICULARLY THURSDAY EVENING. AT
THIS TIME, CONFIDENCE IN FOG WAS A BIT TOO LOW TO INTRODUCE INTO
THE FORECAST, BUT IS SOMETHING WE'LL KEEP A CLOSE EYE ON.
THURSDAY NIGHT THROUGH WEDNESDAY:
OUR NEXT WEATHER MAKER WILL ARRIVE THURSDAY NIGHT INTO FRIDAY AS
A FAIRLY LOW AMPLITUDE MID-LEVEL WAVE PUSHES OVERHEAD. WHILE
SOME INITIAL WARM ADVECTION-DRIVEN SHOWERS AND STORMS WILL BE
POSSIBLE THURSDAY EVENING ACROSS OUR WEST, THE MAIN PUSH OF
DEEP LAYER MOISTURE AND ASCENT WON'T ARRIVE UNTIL LATE THURSDAY
EVENING AND OVERNIGHT. THE SEVERE WEATHER THREAT WILL BE LOW
DURING THIS PERIOD WITH LIMITED DEEP LAYER SHEAR, ALTHOUGH CAN'T
RULE OUT SOME SMALL HAIL. ADDITIONAL SHOWERS WILL LIKELY DEVELOP
THROUGH FRIDAY MORNING AS A REINFORCING COLD FRONT SHIFTS
SOUTHWARD ACROSS THE REGION. AS THIS OCCURS, THE MAIN
THUNDERSTORM THREAT AREA WILL COMMENSURATELY PUSH SOUTH OF I-80
DURING THE AFTERNOON. ALTOGETHER, THE SEVERE WEATHER THREAT ON
FRIDAY LOOKS LOW GIVEN A DEARTH OF INSTABILITY AND SHEAR.
COULDN'T RULE OUT A FEW FUNNEL CLOUDS MATERIALIZING IN THIS
SETUP WITH INCREASING NEAR-SURFACE VORTICITY ALONG THE FRONT,
PWATS RAPIDLY PUSHING THROUGH 1.5 INCHES, AND LIMITED BULK
SHEAR.
HIGH PRESSURE BUILDS INTO THE REGION OVER THE WEEKEND WITH
COOLER BUT TRANQUIL CONDITIONS. LOOKS LIKE SATURDAY NIGHT WILL
BE A COOL/CRISP ONE, WITH LOWS POTENTIALLY MEANDERING INTO THE
MID 30S IN OUR TYPICAL SHELTERED/COOL SPOTS.
HIGH PRESSURE MOVES EAST OF THE REGION EARLY NEXT WEEK, WITH
RETURN FLOW COMMENCING. THIS WILL PUMP MOISTURE AND INSTABILITY
RAPIDLY NORTHWARD ACROSS THE REGION AS A ROBUST WAVE EMBEDDED
WITHIN BROAD UPPER TROUGHING SLICES THROUGH THE UPPER MIDWEST
DURING THE MONDAY AFTERNOON - TUESDAY TIMEFRAME. INCREASING WIND
FIELDS NEAR THE SURFACE AND ALOFT SPELL SOME POTENTIAL FOR
STRONG TO SEVERE STORMS IN THE VICINITY DURING THIS PERIOD AS
WELL, SO SOMETHING TO KEEP AN EYE ON.
LOOKS LIKE WE'LL GET A BRIEF BREAK IN THE ACTION TOWARDS THE
MIDDLE OF THE WEEK AS SURFACE HIGH PRESSURE RETURNS, BUT A
FAIRLY ACTIVE WEATHER PATTERN LOOKS TO RE-COMMENCE SHORTLY
THEREAFTER INTO THE END OF THE WEEK AND NEXT WEEKEND.
CARLAW
AVIATION /18Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 1235 PM CDT WED APR 23 2025
THE MAIN AVIATION WEATHER MESSAGES ARE:
- GENERALLY S/SW WINDS DEVELOPING THIS AFTERNOON. SOME POTENTIAL
FOR WINDS TO FLIP SE/E AT THE CHICAGO-AREA TERMINALS THIS
EVENING, BUT CHANCES TOO LOW FOR A MENTION.
- MAIN THREAT FOR SHRA/TS SHIFTING NORTH OF THE CHICAGO-AREA
SITES THIS AFTERNOON AND EVENING.
- SMALL POTENTIAL FOR TS INVOF RFD THIS AFTERNOON, BUT CHANCES
ARE TOO LOW/BRIEF FOR A FORMAL VCTS MENTION AT THIS TIME.
- EVENTUAL NORTH/NORTHEAST WIND SHIFT WITH A COLD FRONT THURSDAY
MORNING/AFTERNOON. TIMING REMAINS A BIT UNCERTAIN.
LINGERING MORNING CONVECTION HAS LARGELY DIMINISHED AND SHIFTED
EAST OF THE TERMINALS. WHILE THERE REMAINS ABOUT A 10-20% CHANCE
FOR AN ADDITIONAL SHOWER OR STORM THIS AFTERNOON, CHANCES ARE
TOO LOW FOR A PRECIP MENTION AT THE CHICAGO-AREA SITES. AT RFD,
HAVE PREVAILED VCSH WHERE ADDITIONAL SPOTTY ACTIVITY WILL LIKELY
MATERIALIZE OUT OF A MID-LEVEL CLOUD DECK THROUGH THE AFTERNOON.
WILL NEED TO KEEP AN EYE ON TRENDS, AS THE TS POTENTIAL IS NOT
ZERO, BUT CURRENTLY IS TOO LOW TO JUSTIFY A FORMAL VCTS MENTION.
WIND TRENDS ARE ALSO A BIT UNCERTAIN THIS EVENING, WITH SOME
GUIDANCE INDICATING WINDS WILL FOLD OVER OUT OF THE EAST OR
SOUTHEAST WITH VERY WEAK FLOW IN PLACE ACROSS THE REGION. FOR
NOW, HAVE CONTINUED WITH A MENTION OF JUST LIGHT SW WINDS, BUT
WILL CLOSELY MONITOR OBSERVATIONS AND MODEL TRENDS. REGARDLESS,
WINDS WILL BECOME LIGHT THIS EVENING AND OVERNIGHT, OUTSIDE OF
ANY CONVECTIVE OUTFLOW THAT GETS KICKED SOUTHWARD OUT OF
AFTERNOON CONVECTION ACROSS WISCONSIN.
A COLD FRONT WILL PRESS SOUTH THROUGH THE REGION THURSDAY
MORNING AND AFTERNOON. TIMING THIS WIND SHIFT REMAINS UNCERTAIN,
BUT THE INHERITED MID-LATE MORNING TIMING STILL SEEMED
APPROPRIATE AND MADE MINIMAL CHANGES THERE. AT THIS TIME, IT
APPEARS THE THREAT FOR LOW CLOUDS WITH THIS FRONT REMAIN PRETTY
MINIMAL, WITH VFR CONDITIONS EXPECTED TO PREVAIL.
CARLAW
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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