974
FXUS63 KLOT 050557
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1257 AM CDT FRI JUN 5 2026
KEY MESSAGES
- TRENDING WARMER AND MORE HUMID WITH PERIODS OF SHOWERS AND
THUNDERSTORMS STARTING EARLY FRIDAY AND CONTINUING INTO NEXT
WEEK.
- LOW (LEVEL 1 OUT OF 5) SEVERE WEATHER THREAT FRIDAY PM ALONG
WITH A THREAT FOR LOCALLY HEAVY RAINFALL.
DISCUSSION
ISSUED AT 217 PM CDT THU JUN 4 2026
FOR FRIDAY AND SATURDAY THE MAIN FORECAST QUESTION IS SHOWER AND
THUNDERSTORM TRENDS, WITH GREATER EMPHASIS ON THE SHOWERS GIVEN THE
OVERALL MARGINAL LAPSE RATES AND LACK OF STRONG FORCING FOR
CONVECTION. CAM GUIDANCE NORMALLY WOULDN'T BE RELIED ON TOO
CLOSELY, BUT SEVERAL MODELS SHOW SIMILAR TRENDS AND ALIGN WITH THE
OVERALL CONCEPT OF HOW THINGS APPEAR LIKELY TO EVOLVE, SO ELECTED TO
FOLLOW A BLEND OF THOSE THAT APPEARED TO REFLECT THIS THINKING.
A CLUSTER OF SHOWERS WITH SOME EMBEDDED THUNDERSTORMS IS EXPECTED TO
MAKE ITS WAY INTO THE AREA FROM IOWA EARLY FRIDAY AHEAD OF A DIFFUSE
COLD FRONT AND WEAK SHORTWAVE ALOFT. THIS ACTIVITY SHOULD
OVERSPREAD THE AREA THROUGH THE MORNING INTO EARLY AFTERNOON AT
WHICH POINT SLIGHT RIDGING ALOFT AND MOVEMENT AWAY FROM THE
SUPPORTING SURFACE BOUNDARY MAY ALLOW FOR A DECREASE IN COVERAGE FOR
LATER IN THE AFTERNOON AND EVENING. THE EXCEPTION MAY BE IN THE
SOUTHERN HALF OF OUR FORECAST AREA WHERE AN OUTFLOW BOUNDARY FROM
THE EARLIER ACTIVITY COULD PROVIDE THE FOCUS FOR ADDITIONAL
DEVELOPMENT.
MOST LOCATIONS ON FRIDAY AND FRIDAY NIGHT DO NOT APPEAR POISED FOR A
COMPLETE WASHOUT, BUT GIVEN AN AXIS OF PWATS EXCEEDING 1.75" AND THE
EXPECTED SLOW MOTION OF THIS CLUSTER, SOME AREAS COULD SEE SOME
HEAVY RAINFALL. SPC ALSO HAS US IN A DAY TWO MARGINAL RISK BUT THIS
WOULD NOT APPEAR TO POSE A WIDESPREAD THREAT GIVEN THE
AFOREMENTIONED MARGINAL SUPPORT FOR CONVECTION OVERALL.
LATER FRIDAY NIGHT INTO SATURDAY THE MODEL GUIDANCE BEGINS TO
DIVERGE, BUT THE GENERAL IDEA STILL APPEARS TO KEEP THE BEST FOCUS
FOR CONTINUED SHOWERS IN SOUTHERN AND WESTERN PORTIONS OF THE
FORECAST AREA. THE EXCEPTION COULD BE ALONG A DEVELOPING LAKE
BREEZE THAT MIGHT BE ABLE TO TAP INTO THE MOIST AIRMASS AND SUPPORT
AN ADDITIONAL AREA OF SHOWERS SATURDAY AFTERNOON.
FOR SUNDAY INTO THE FIRST PART OF NEXT WEEK, MODEL GUIDANCE IS
SHOWING A NARROW MID TO UPPER LEVEL RIDGE BUILDING OVERHEAD, WITH A
STATIONARY FRONT AT THE SURFACE EXTENDING EAST FROM THE PLAINS INTO
THE OHIO VALLEY. THIS BOUNDARY, WHEREVER IT HAPPENS TO PARK, WOULD
APPEAR TO BE THE BEST FOCUS FOR ADDITIONAL SHOWER AND THUNDERSTORM
ACTIVITY, ESPECIALLY WITH SUPPORT FROM AFTERNOON HEATING AND
DEWPOINTS IN THE 60S TO OCCASIONALLY LOWER 70S.
LENNING
AVIATION /06Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 1257 AM CDT FRI JUN 5 2026
MAIN CONCERNS:
- POTENTIAL FOR OCCASIONAL SHRA/TS WITH ASSOCIATED VSBY
REDUCTIONS TODAY AND AGAIN LATE THIS EVENING-OVERNIGHT
- LOWER CIG TRENDS THIS MORNING THROUGH THIS AFTERNOON
- CHANCE FOR A NORTH-NORTHEASTERLY WIND SHIFT ASSOCIATED WITH
THE SHRA/TS THREAT LATE THIS EVENING-OVERNIGHT
THE LONG STRETCH OF MAINLY QUIET FLYING WEATHER WILL COME TO AN
END OVER THE NEXT 24+ HOURS. INITIAL SHOWERS AND POSSIBLE EMBEDDED
TS IN THE PRE-DAWN THROUGH MID MORNING SHOULD GENERALLY FAVOR
NORTHWEST IL/RFD AREA (PROB30 FOR TS THERE), THOUGH SPOTTY VFR
SHOWERS COULD DEVELOP OVER THE CHICAGO METRO. THE OVERALL BEST
CHANCE FOR ON STATION TS IMPACTS WILL BE FROM MID MORNING
THROUGH EARLY TO MID AFTERNOON, EARLIEST AT RFD, AND LATEST AT
GYY. MAINTAINED TEMPO TS MENTION WITH SIMILAR TIMING TO
PREVIOUS ISSUANCES. AFTER THE AFTERNOON ACTIVITY SHIFTS EAST,
OUR NEXT PERIOD OF INTEREST IS LATE THIS EVENING AND OVERNIGHT.
THERE'S SOME SIGNAL FOR SHOWERS AND STORMS TO DEVELOP NORTH OF
THE TERMINALS (POSSIBLY OVER WI) AND SAG SOUTH, ACCOMPANIED BY
AN OUTFLOW DRIVEN WIND SHIFT TO NORTH OR NORTHEAST. INTRODUCED
PROB30S AT ORD, MDW, AND GYY FOR THIS WINDOW.
SOUTH-SOUTHWEST WINDS EARLY THIS MORNING WILL BECOME GUSTY OUT
OF THE SOUTHWEST AFTER DAYBREAK, WITH SOME POTENTIAL FOR
OCCASIONAL GUSTS AS HIGH AS 25-30 KT IN THE EARLY TO MID
AFTERNOON. LOWEST CIGS (LOWER MVFR TO TEMPORARY IFR) DURING
DAYLIGHT HOURS TODAY SHOULD FOCUS INTO RFD AREA, THOUGH 2-3KFT
AGL CIGS APPEAR PROBABLE AT TIMES AT THE CHICAGO METRO
TERMINALS.
CASTRO
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 7 PM CDT THIS
EVENING FOR THE IL AND IN NEARSHORE WATERS.
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