195
FXUS63 KLOT 232343
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
643 PM CDT MON JUN 23 2025
KEY MESSAGES
- HEAT INDICES WILL STILL BE IN THE UPPER 90S TO NEAR 100
THROUGH MUCH OF THE WEEK. THE CURRENT HEAT ADVISORY WAS
EXTENDED INTO TUESDAY FOR SELECT COUNTIES SOUTH OF INTERSTATE
80.
- PERIODIC SHOWER AND STORM CHANCES EXIST THROUGH THIS WEEK.
SOME MAY BE SEVERE WITH DAMAGING WINDS AND FLASH FLOODING.
DISCUSSION
ISSUED AT 252 PM CDT MON JUN 23 2025
THROUGH TUESDAY:
RECENT WATER VAPOR SATELLITE IMAGERY IS SHOWING A NARROW CORRIDOR OF
HIGHER MOISTURE FROM LINCOLN, NE THROUGH MARQUETTE MICHIGAN.
SWITCHING OVER TO VISIBLE OR IR IMAGERY, TALLER STORMS ARE
FIRING ALONG A COLD FRONT FROM NORTHERN IOWA TO CENTRAL
WISCONSIN. RECENT MESOANALYSIS SHOWS A STRONG SURFACE
TEMPERATURE AND ML CAPE GRADIENT CO-LOCATED WITH THIS BOUNDARY.
HIGH-RES MODELS ARE SUGGESTING THAT THIS FRONT WILL GRADUALLY
SLINK ITS WAY THROUGH IOWA AND WISCONSIN AND EVENTUALLY MOVE
INTO OUR NORTH AND NORTHWEST CWA SOMETIME TUESDAY MORNING.
BUT BY THE TIME IT GETS TO THE FORECAST AREA, MODELS ARE
SUGGESTING IT STALLS OUT IN ITS MOVEMENT. THE HIGHEST CHANCE FOR
STORMS AHEAD OF THE FRONT WOULD BE NORTH AND WEST OF THE FOX
VALLEY, THOUGH MUCH OF THE AREA WILL REMAIN DRY. ONE THING THAT
WILL BE CLOSELY MONITORED THROUGH THE NIGHT IS ANY OUTFLOW THAT
DEVELOPS FROM THE STORMS TO THE NORTHWEST THAT COMES DOWN ACROSS
OUR AREA. THIS OUTFLOW COULD TRIGGER NEW STORMS THAT COULD
DEVELOP OVER THE AREA TONIGHT, BUT THERE IS LOWER CONFIDENCE IN
THE EXACT TIMING AND LOCATION THAT THEY DEVELOP.
TEMPERATURES REMAIN IN THE MID 90S AREA WIDE AND THE DEW POINTS
HAVN'T MIXED OUT MUCH TODAY AND REMAIN IN THE LOWER 70S
RESULTING IN HEAT INDEX VALUES IN THE LOW 100S. FOR A THIRD
STRAIGHT DAY, HOT AND HUMID CONDITIONS SURROUND THE FORECAST
AREA. AND TEMPERATURES ARE ONLY GOING TO DIMINISH TONIGHT
GRADUALLY. AND COULD STILL BE ABOVE 80 JUST BEFORE MIDNIGHT.
TEMPERATURES WILL ONCE AGAIN BE WARM TOMORROW. LUCKILY, THE
PREVIOUSLY MENTIONED FRONT SHOULD SLOWLY DROP SOUTH THROUGH THE
DAY WHICH SHOULD HELP MITIGATE EXTREME TEMPERATURES FOR AREAS
NORTH OF INTERSTATE 80 TOMORROW. HOWEVER, FOR LIVINGSTON,
KANKAKEE, FORD, IROQUOIS COUNTIES IN ILLINOIS AND BENTON, NEWTON
AND JASPER IN INDIANA, THE COMBINATION OF WARM TEMPERATURES AND
HIGH SURFACE DEW POINTS OUT AHEAD OF THE FRONT AND HAVE A
CHANCE FOR HEAT INDICES ABOVE 100 ONCE AGAIN FOR A FOURTH
STRAIGHT. GIVEN THAT HEAT IMPACTS COMPOUND OVER TIME, THE HEAT
ADVISORY FOR THOSE COUNTIES WAS EXTENDED THROUGH TOMORROW
AFTERNOON DURING THE PEAK HEATING.
AS THAT FRONT MOVES SOUTH TOMORROW, THERE WILL BE A RENEWED
EFFORT FOR SHOWERS AND STORMS ACROSS THE AREA. FORCING ALONG THE
GRADIENT STILL LOOKS FAIRLY MARGINAL, AS DOES THE SHEAR.
COVERAGE IS LOOKING WIDELY SCATTERED ALONG AND AHEAD OF THE
FRONT AS IT MOVES SOUTH. THE FORECAST AREA REMAINS IN A LEVEL 1
OUT OF 5 THREAT FOR SEVERE WEATHER FROM THE STORM PREDICTION
CENTER, WITH THE MAIN SEVERE THREAT BEING FROM DAMAGING WIND.
HOWEVER, PRECIPITABLE WATER LEVELS WILL REMAIN HIGH. RECENT CAMS
ARE SHOWING NEAR IF NOT RECORD P-WATS FOR THIS TIME OF YEAR
COMPARED TO HISTORICAL KDVN SOUNDINGS. WITH THIS TYPE OF SET-UP,
IT WOULD NOT BE SURPRISING IF MOST OF THE STORMS HAD A NICE
STEADY RAIN RATE THAT THE SOIL CAN HANDLE. BUT WITH P-WATS AS
HIGH AS THESE, ISOLATED DOWNPOURS WITH RAIN RATES OF 1-3 INCHES
PER HOUR ARE POSSIBLE. THAT'S NOT TO SAY THAT THEY WILL BE
RAINING FOR THE FULL HOUR AT THAT RATE, BUT ENOUGH TO KEEP THE
CONCERN FOR LOCALIZED FLOODING IN THE FORECAST.
DK
AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 643 PM CDT MON JUN 23 2025
MAIN CONCERNS:
- POSSIBLE OUTFLOW WIND SHIFT TO NORTH THIS EVENING (TS POSSIBLE
AT RFD)
- PROBABLE LAKE BREEZE WIND SHIFT TO NORTHEAST AT ORD, MDW, GYY
ON TUESDAY AFTERNOON
- SCATTERED TS TUESDAY AFTERNOON AND EARLY EVENING MAY PRODUCE
HEAVY RAIN WITH LOW VSBY AND GUSTY, VARIABLE WINDS
THIS EVENING, WE'RE TRACKING STORMS FROM NORTHEAST IA INTO
SOUTHERN WI FOR OUTFLOW BOUNDARIES THAT MAY BRING THE WIND SHIFT
INDICATED IN PROB30S IN THE TAFS (EXCEPT GYY). IT'S UNCLEAR IF
AN INITIAL OUTFLOW PUSHING SOUTHEAST FROM THE WESTERN MILWAUKEE
SUBURBS WILL MAKE IT TO THE TERMINALS. STILL CAN'T RULE OUT
LIGHTNING NEAR RFD AND -SHRA AT THE CHICAGO AREA TERMINALS
BEHIND OUTFLOW WIND SHIFT, IF IT OCCURS.
ON TUESDAY, CONDITIONS APPEAR MORE FAVORABLE FOR AT LEAST WIDELY
SCATTERED CONVECTION TO DEVELOP OVER THE AREA DURING THE AFTERNOON.
MAINTAINED PROB30 MENTION IN THE TAFS WITH THIS ISSUANCE, GIVEN
CONSIDERABLE VARIANCE IN TIMING AND SHRA/TSRA COVERAGE. IT ALSO
APPEARS LIKELY THAT A LAKE BREEZE SHOULD PUSH ACROSS THE NEAR
LAKE TERMINALS, UNLESS THE BOUNDARY PUSH IS DISRUPTED BY
VARIABLE OUTFLOW WINDS FROM TS NEARBY PRIOR TO THE WIND SHIFT.
CASTRO
CLIMATE
ISSUED AT 643 PM CDT MON JUN 23 2025
TEMPERATURES WILL CONTINUE TO THREATEN RECORD WARM LOWS FOR
CHICAGO AND ROCKFORD. HERE ARE THE CURRENT RECORDS FOR TODAY:
CHICAGO WARM LOW
MONDAY 6/23 79 (1923)
ROCKFORD WARM LOW
MONDAY 6/23 74 (1908)
NWS CHICAGO
LOT WATCHES/WARNINGS/ADVISORIES
IL...HEAT ADVISORY UNTIL MIDNIGHT CDT TONIGHT FOR ILZ003-ILZ004-
ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-
ILZ020-ILZ021-ILZ106-ILZ107-ILZ108.
EXTREME HEAT WARNING UNTIL MIDNIGHT CDT TONIGHT FOR ILZ103-
ILZ104-ILZ105.
HEAT ADVISORY UNTIL 7 PM CDT TUESDAY FOR ILZ023-ILZ032-ILZ033-
ILZ039.
IN...HEAT ADVISORY UNTIL MIDNIGHT CDT TONIGHT FOR INZ001-INZ002.
HEAT ADVISORY UNTIL 7 PM CDT /8 PM EDT/ TUESDAY FOR INZ010-
INZ011-INZ019.
LM...SMALL CRAFT ADVISORY UNTIL 10 PM CDT THIS EVENING FOR THE IL
AND IN NEARSHORE WATERS.
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