297
FXUS63 KLOT 260537
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1237 AM CDT THU JUN 26 2025
KEY MESSAGES
- ISOLATED TO WIDELY SCATTERED SHOWERS AND STORMS ARE POSSIBLE THIS
AFTERNOON AND EVENING. THE STRONGEST STORMS WILL BE CAPABLE
OF STRONG TO LOCALLY DAMAGING WIND GUSTS.
- HOT AND HUMID CONDITIONS WILL CONTINUE THROUGH THE WEEKEND
WITH PEAK HEAT INDICES IN THE MID 90S TO NEAR 100 MUCH OF THE
WEEK.
- PERIODIC SHOWER AND STORM CHANCES EXIST THROUGH EARLY NEXT
WEEK WITH MANY DRY HOURS IN BETWEEN ROUNDS.
- A BIT OF RELIEF EARLY TO MIDDLE OF NEXT WEEK WITH DRY
CONDITIONS AND SEASONAL TEMPERATURES
DISCUSSION
ISSUED AT 211 PM CDT WED JUN 25 2025
THROUGH THURSDAY NIGHT:
RECENT MESOANALYSIS IS SUGGESTING THE QUASI-STATIONARY BOUNDARY
HAS DRIFTED NORTHWARD EVER SO SLIGHTLY TOWARD SOUTHERN
WISCONSIN. AS SUCH, THE THICKER CLOUD COVER HAS MOVED NORTHWARD
AS WELL ALLOWING FOR MORE NUMEROUS SHALLOW CUMULUS CLOUDS TO
DEVELOP ACROSS THE FORECAST AREA. HOWEVER, WITH A GRADIENT FROM
1500 TO 2500 J/KG IN CENTRAL ILLINOIS OF MLCAPE, SHOWERS AND
THUNDERSTORMS ARE SLOWLY GAINING IN COVERAGE FOR AREAS SOUTH OF
INTERSTATE 80. THE LACK OF DEEP LAYER SHEAR WILL LIMIT STRONG
ORGANIZATION, BUT HAVING A STORM PRODUCE A "SPLAT" OF LOCALLY
STRONGER WIND 50 TO 60 MPH IS NOT OUT OF THE QUESTION. WITH
AROUND 20 TO 25 KNOTS OF LOW LEVEL SHEAR, A BRIEF SUPERCELL OR
POSSIBLE FUNNEL CLOUD IS POSSIBLE. LASTLY, ANYONE WHO HAS
STEPPED OUT SIDE RECENTLY HAS KNOWN HOW HUMID IT HAS BEEN DEW
POINTS AROUND THE REGION REMAIN IN THE LOW 70S THIS AFTERNOON.
PRECIPITABLE WATER AMOUNTS ARE WELL ABOVE 1.5 INCHES. AS SHOWERS
AND STORMS DEVELOP, HIGH RATES WILL BE POSSIBLE. MOST CELLS
SHOULD BE TRANSIENT ENOUGH, IT SHOULD LIMIT FLOODING CONCERNS.
SHOULD CELLS FORM ALONG AN AXIS AND START TRAINING OVER THE SAME
AREA, THEN LOCALIZED FLOODING CONCERN ARE POSSIBLE.
WITH STORM MOTIONS TO THE EAST NORTHEAST UP TO 30 MPH, COVERAGE
FOR SHOWERS AND STORMS SHOULD EXPAND NORTHWARD INTO THE CHICAGO
METRO LATE THIS AFTERNOON AND INTO THIS EVENING. HOWEVER, AS
INSTABILITY IS LOST AFTER SUNSET, THE THREAT FOR THUNDER SHOULD
TREND DOWN AS WELL, THOUGH LINGERING SHOWERS COULD REMAIN INTO
THE EARLY MORNING.
THURSDAY'S SHOWER/STORM POTENTIAL LOOKS FAIRLY SIMILAR TO TODAY
WITH ISOLATED TO WIDELY SCATTERED SHOWERS AND STORMS POSSIBLE,
FOCUSED ALONG ANY SUBTLE SURFACE CONVERGENCE AXES/BOUNDARIES,
MAINLY TO THE SOUTHEAST FORECAST AREA IN THE MORNING. OFFSHORE
WINDS WILL ALLOW TEMPERATURES TO BE WARMER CLOSER TO THE
LAKESHORE WITH HIGHS IN THE UPPER 80S TO LOWER 90S MAKING FOR
ANOTHER HOT AND HUMID SUMMER DAY. A SUBTLE MID-LEVEL WAVE WILL
IS PROJECTED TO PASS FROM SOUTHEASTERN MINNESOTA THROUGH CENTRAL
WISCONSIN ON THURSDAY. A SURFACE LOW WILL LIKELY BE INDUCED AND
TRACK EASTWARD TOWARD LAKE MICHIGAN WITH A COLD FRONT TRAILING
IN ITS WAKE. SHOWERS AND STORMS ARE EXPECTED TO DEVELOP ALONG
AND AHEAD OF THE FRONT TO OUR NORTHWEST AND POTENTIALLY REACH
THE NORTHERN PART OF THE FORECAST AREA THURSDAY EVENING. BETTER
COVERAGE FOR STORMS WILL LIKELY BE NORTHWEST OF THE FORECAST
AREA IN THE AFTERNOON AND EVENING. STORMS ARE PROJECTED TO MOVE
INTO THE FORECAST AREA, BUT A POINT OF UNCERTAINTY WILL BE HOW
MUCH THE STORM COVERAGE REMAINS AFTER SUNSET AS THE FRONTAL
BOUNDARY HANGS UP FROM WEST TO EAST ACROSS NORTHERN ILLINOIS
THROUGH THE OVERNIGHT HOURS.
DK
FRIDAY THROUGH WEDNESDAY:
THE ANOMALOUS EASTERN CONUS UPPER RIDGE WILL SLOWLY BEGIN TO BREAK
DOWN LATE THIS WEEK, AND EVEN MORE SO EARLY NEXT WEEK. AS THIS
OCCURS, THE MID LEVEL FLOW WILL BECOME MORE ZONAL, WHICH WOULD THEN
KEEP THE LOCAL AREA IN THE ZONE FOR WAVES OF SHOWERS AND
THUNDERSTORMS FROM TIME TO TIME.
SURFACE LOW PRESSURE WILL SPREAD SHIFT EAST INTO MICHIGAN AND IT
WILL DRAG A TRAILING COLD FRONT ACROSS THE SOUTHERN GREAT LAKES ON
FRIDAY. THE STRONGER FORCING WILL BE AHEAD OF THE FRONT, WHICH MAY
OR MAY NOT HAVE CLEARED THE AREA DURING PEAK HEATING FRIDAY
AFTERNOON, BUT WITH THE WEAK/SUBTLE SHORTWAVE FORCING COUPLED WITH A
MOIST AIRMASS (DEWPOINTS IN THE 70S) RESULTING IN SOME TALL AND
NARROW CAPE PROFILES, A FEW SCATTERED THUNDERSTORMS WOULD BE FAVORED
DURING THE AFTERNOON AND EARLY EVENING HOURS. FLOW OFF THE LAKE
BEHIND THE DEPARTING LOW ALSO PROVIDE A FOCUS AREA FOR STORMS AS
WELL.
THE FRONT WILL THEN BE PARKED OVER THE AREA FRIDAY NIGHT, AND WITH
NO APPRECIABLE AIRMASS CHANGE, AND MID LEVEL FLOW PARALLEL TO THE
FRONT, THAT HEAVY RAINFALL PRODUCING STORMS COULD BE AROUND THE
REGION. ALL INDICATIONS ARE THAT THE LINGERING FRONT WOULD GET
SHOVED A BIT FARTHER SOUTH ON SATURDAY (SOUTH OF A ROCKFORD TO
VALPARAISO LINE. FORCING LOOKS FAIRLY BENIGN, BUT SCATTERED SHOWERS
AND STORMS ALONG LAKE BOUNDARY AND THE FRONT WOULD BE FAVORED, AND
OUR FORECAST HAS THE HIGHEST CHANCES SOUTH OF I-80. WITH WEAKER
FORCING THOUGH WE WOULD EXPECT LOWER COVERAGE THAN ON FRIDAY. INLAND
TEMPERATURES REMAIN SEASONALLY WARM, BUT SATURDAY WILL FEATURE MORE
PRONOUNCED COOLING NEAR THE LAKE.
LOWER 90S ARE EXPECTED ON SUNDAY AS SOME WARMER AIR FEEDS IN AHEAD
OF AN APPROACHING WAVE. HEAT INDICES ON SUNDAY COULD EXCEED 100
DEGREES AROUND A MAJORITY OF NORTHEAST ILLINOIS AND NORTHWEST
INDIANA.
EARLY NEXT WEEK, AN UPPER TROUGH WILL DEEPEN AS IT SWINGS FROM THE
NORTHERN PLAINS INTO THE MIDWEST. THE SURFACE RESPONSE WILL BE A
POTENT BAROCLINIC ZONE THAT WILL MOVE ACROSS THE GREAT LAKES REGION
EARLY NEXT WEEK BRINGING ADDITIONAL RAIN AND THUNDER CHANCES. THAT
LOOKS TO TAKE PLACE SOMETIME BETWEEN LATE SUNDAY AND MIDDAY MONDAY.
A QUIETER AND RELATIVELY COOLER SYNOPTIC PATTERN THEN LOOKS TO
INTERVENE FOR AT LEAST A COUPLE OF DAYS DURING THE MIDDLE OF NEXT
WEEK. THESE DAYS WILL FEATURE MORE SEASONAL HIGHS IN THE MID 80S,
DRY WEATHER, AND MORE COMFORTABLE CONDITIONS AS DEWPOINTS FALL INTO
THE 60S.
KMD
AVIATION /06Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 1236 AM CDT THU JUN 26 2025
KEY MESSAGES FOR THE 06Z TAF PERIOD INCLUDE:
* A PERIOD OF SHOWERS AND THUNDERSTORMS POSSIBLE THURSDAY
EVENING, CAPABLE OF PRODUCING GUSTY WINDS AND MVFR VSBYS.
ISOLATED SHOWERS AND THUNDERSTORMS AROUND THE REGION TONIGHT
SHOULD REMAIN OUTSIDE OF THE VCY OF THE TAF SITES THROUGH THE
FIRST HALF OF THURSDAY. LATE THURSDAY AFTERNOON INTO EARLY
EVENING, A COUPLE OF ISOLATED SHOWERS AND MAYBE A THUNDERSTORM
LOOK TO POP UP AROUND THE REGION BEFORE A MUCH BETTER CHANCE
ARRIVES MID-EVENING. THIS EXPECTED LINE OF SHOWERS AND POSSIBLY
EMBEDDED THUNDERSTORMS SHOULD LAST ON THE ORDER OF A COUPLE TO A
FEW HOURS AT ANY GIVEN SITE, AND COULD FEATURE GUSTY WINDS OUT
OF VARIABLE DIRECTIONS AND A PERIOD OF REDUCED VSBYS. THE RAIN
WILL MOVE AWAY OVERNIGHT AND WE SHOULD BEGIN FRIDAY RAIN-FREE.
EXPECT WINDS OUT OF A SW DIRECTION THROUGHOUT THE PERIOD, BELOW
10 KT TONIGHT THEN GUSTING TO AROUND 20 KT DURING THE DAY ON
THURSDAY. WITH THE EXCEPTION OF HIGHER GUSTS AROUND STORMS,
WINDS SHOULD THEN SUBSIDE TO NEAR OR BELOW 10 KT FOR THURSDAY
NIGHT.
DOOM
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY UNTIL 4 AM CDT EARLY THIS MORNING FOR THE
IL NEARSHORE WATERS.
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