818
FXUS63 KLOT 071934
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
234 PM CDT SUN JUN 7 2026
KEY MESSAGES
- SHOWERS AND STORMS ARE EXPECTED THIS AFTERNOON/EVENING WITH
THE HIGHEST COVERAGE SOUTHWEST OF THE CHICAGO METRO, SOME
CAPABLE OF TORRENTIAL DOWNPOURS AND GUSTY WINDS.
- AN ADDITIONAL ROUND OF SHOWERS AND STORMS ARE EXPECTED AREAWIDE
TOMORROW.
- HEAT AND HUMIDITY INCREASE MID-WEEK WITH HEAT INDICES IN THE
MID TO UPPER 90S.
- LOW CHANCES FOR SHOWERS AND STORMS TUESDAY AND WEDNESDAY, BUT
THERE IS A CHANCE THAT THURSDAY COULD BE THE NEXT THREAT FOR
SEVERE WEATHER.
DISCUSSION
ISSUED AT 233 PM CDT SUN JUN 7 2026
SPC MESOANALYSIS DEPICTS A STOUT THETA-E GRADIENT ALONG A
SURFACE STATIONARY FRONT FROM NORTHWEST ILLINOIS THROUGH GARY,
INDIANA. LUCKILY FOR THE CHICAGO METRO, MOST OF THE ACTIVITY
THIS AFTERNOON AND EVENING SHOULD BE ALONG AND SOUTHWEST OF THIS
BOUNDARY. STORM MOTIONS ARE INCREDIBLY SLOW (TO THE NORTH-
NORTHEAST AT 10 TO 15 MPH). WHILE WET MICROBURSTS PRODUCING
LOCALLY GUSTY WINDS ARE POSSIBLE, THE MAIN HAZARD THIS AFTERNOON
IS BECOMING A HYDRO CONCERN. INSTANTANEOUS RAIN RATES ON MRMS
FOR STORMS CLOSER TO THE MISSISSIPPI RIVER (WHERE THE BETTER
FORCING IS LOCATED) HAVE HAD ISOLATED STORMS PRODUCING OVER 2
INCH PER HOUR RATES! FOR NOW, THE HIGHER RAIN TOTALS HAVE
REMAINED WEST OF THE AREA, BUT THE THREAT FOR LOCALIZED
TORRENTIAL DOWNPOURS THIS AFTERNOON AND EVENING KEEPS THE THREAT
FOR FLASH FLOODING PREVALENT.
AN UPPER LEVEL TROUGH OVER THE CENTRAL PLAINS IS EXPECTED TO
SLOWLY MOVE EAST THROUGH THE OVERNIGHT AND OVER NORTHERN
ILLINOIS ON MONDAY. THIS SHOULD EVENTUALLY KICK THE
AFOREMENTIONED STATIONARY FRONT NORTHEASTWARD AND PRODUCE
WIDESPREAD SHOWERS AND STORMS ACROSS THE FORECAST AREA TOMORROW.
WITH THE WAVE BEING MORE PROGRESSIVE IN NATURE, THE THREAT FOR
FLOODING CONCERNS IS SOMEWHAT LOWER THAN THIS AFTERNOON. BUT
GIVEN THE AMOUNT OF MOISTURE AVAILABLE AND HOW EFFICIENT THE
RAIN SHOULD BE PRODUCED, FLOODING CONCERNS REMAIN ELEVATED
TOMORROW. ADDITIONALLY, THERE WILL REMAIN A THREAT FOR WET
MICROBURSTS PRODUCING LOCALIZED GUSTY WINDS. WITH HIGH CAPE,
WEAK SHEAR, AND AMPLE AMBIENT VORTICITY, A FUNNEL CLOUD OR TWO
CANNOT BE COMPLETELY RULED OUT, PARTICULARLY IN THE AFTERNOON
WHEN THE TROUGH AXIS IS OVERHEAD.
WEAK RIDGING WILL GROW ON TUESDAY FROM THE WEST. LINGERING
SHOWERS AND SOME ISOLATED STORMS ARE POSSIBLE IN THE MORNING,
MAINLY EAST OF I-55. WHILE SOME AFTERNOON SUMMERTIME POP-UP
SHOWERS ARE POSSIBLE, WITH WEAK FORCING, THE FORECAST FOR
TUESDAY AND WEDNESDAY IS TRENDING DRIER. MORE IMPACTFULLY, THIS
RIDGE WILL DRIVE FLOW BACK TO SOUTHWESTERLY AND ADVECT IN A
MUCH WARMER, AND MUGGY, AIRMASS. 850 MB TEMPERATURES ARE
EXPECTED TO INCREASE TO AND POTENTIALLY IN EXCESS OF 20C.
SURFACE TEMPERATURES ARE EXPECTED TO CLIMB ABOVE NORMAL INTO THE
MID TO UPPER 80S AND EVEN THE LOW 90S. WITH FORECASTED DEW
POINTS IN THE 70S, HEAT INDICES ARE EXPECTED TO CLIMB INTO THE
MID TO UPPER 90S EACH DAY.
THAT RIDGE AXIS IS EXPECTED TO SLIDE EASTWARD OVER THE AREA ON
WENDESDAY AS THE NEXT LONG WAVE TROUGH SETS UP OVER THE NORTHERN
PLAINS. AN UPPER LEVEL LOW IS EXPECTED TO DEEPEN WEDNESDAY NIGHT
OVER MANITOBA WITH A STRENGTHENING 100 KNOT UPPER LEVEL JET
EMBEDDED IN THE TROUGH. A REFLECTED SURFACE LOW OVER SOUTHERN
CANADA IS EXPECTED TO DEVELOP WITH A COLD FRONT DRAPED SOUTHWARD
DOWN THE PLAINS. THERE IS A LOT OF MODEL UNCERTAINTY ON STORM
DEVELOPMENT ALONG THE FRONT ON WEDNESDAY. THERE IS A NON-ZERO
CHANCE THAT A MCS DEVELOPS AND ARRIVES IN NORTHWEST ILLINOIS
OVERNIGHT, IT WOULD ARRIVE IN A LESS THAN FAVORABLE TIME OF
DAY. MODELS ARE SHOWING A LITTLE BETTER CONSISTENCY WITH SHOWERS
AND STORMS DEVELOPING WITH THE BETTER FORCING WITH THE FRONT ON
THURSDAY. WITH STRONG LOW LEVEL FLOW, A STOUT UPPER LEVEL JET
FOR SYNOPTIC FORCING, AND MUCAPE VALUES 2000-3000 J/KG, AN
EASTWARD PROPAGATING SQUALL LINE MAY DEVELOP WITH STRONG TO
POSSIBLY EVEN SEVERE STORMS THURSDAY. LASTLY, THERE IS ALSO A
LITTLE UNCERTAINTY ON TEMPERATURES FOR THURSDAY DUE TO THE
FRONT. IT COULD SET UP AS ANOTHER HOT AND HUMID DAY AT FIRST,
BUT THE TIMING OF THE FRONT MAY IMPACT MAX TEMPS.
QUASI-ZONAL FLOW ALOFT IS EXPECTED TO DEVELOP BEHIND THE FRONTAL
PASSAGE ON THURSDAY. TEMPERATURES SHOULD BECOME SLIGHTLY MORE
MUTED AT THE END OF THE WEEK. ANOTHER UPPER LEVEL WAVE MAY PASS
OVER ON SATURDAY PROVIDING ANOTHER CHANCE FOR SHOWERS AND STORMS
OVER THE WEEKEND, BUT LOW CONFIDENCE IN TIMING AND STRENGTH AT
THIS DISTANCE.
DK
AVIATION /18Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 127 PM CDT SUN JUN 7 2026
KEY MESSAGES:
- PERIODIC SHOWER AND THUNDERSTORM CHANCES EXIST THROUGH MOST OF
THE TAF PERIOD.
- MVFR CEILINGS ARE POSSIBLE TONIGHT INTO TOMORROW MORNING.
A WARM AND HUMID AIR MASS WILL PROMOTE SHOWER AND STORM CHANCES
THROUGH MUCH OF THE CURRENT TAF PERIOD AS AN UPPER-LEVEL
DISTURBANCE PIVOTS THROUGH THE REGION.
FOR THIS AFTERNOON, THUNDERSTORMS ARE LIKELY IN THE 19Z TO 21Z
OR SO TIME WINDOW AT RFD, WHERE TORRENTIAL RAINFALL WILL ALSO
LIKELY REDUCE VISIBILITIES TO IFR LEVELS OR LOWER FOR A BRIEF
PERIOD OF TIME. CONFIDENCE IN THUNDERSTORMS OCCURRING AT OR IN
CLOSE PROXIMITY TO THE CHICAGO METRO TERMINALS THROUGH THIS
EVENING IS LOWER COMPARED TO RFD, BUT DID INTRODUCE SOME
TARGETED PROB30 GROUPS FOR SHRA (TSRA FOR DPA) DURING THE TIME
FRAME WHEN AT LEAST ISOLATED SHOWER ACTIVITY IS MOST LIKELY TO
PERCOLATE CLOSE BY. BROAD ISENTROPIC ASCENT WITHIN THIS MOIST
AND UNSTABLE AIR MASS MAY THEN PERMIT SOME NUISANCE SHOWER
ACTIVITY TO PERSIST IN THE AREA THROUGH MUCH OF TONIGHT. THERE
MAY BE A PERIOD OF TIME TONIGHT WHERE SHOWER COVERAGE COULD GROW
LARGE ENOUGH TO WARRANT SOMETHING MORE THAN JUST A VCSH MENTION
IN THE TAFS, BUT CONFIDENCE IN WHETHER THIS WILL OCCUR AND
WHERE/WHEN IS LOW.
THE EARLY-MID MORNING TOMORROW APPEARS TO BE THE MOST LIKELY
TIME FRAME FOR LITTLE TO NO SHOWER/STORM COVERAGE ACROSS
NORTHERN ILLINOIS AND NORTHWEST INDIANA DURING THE CURRENT TAF
PERIOD. BY THE LATE MORNING OR EARLY AFTERNOON, ANOTHER WAVE OF
SCATTERED SHOWERS AND STORMS WILL DEVELOP, AND THE EXPECTATION
IS FOR THIS CONVECTION TO PERSIST THROUGH THE AFTERNOON. GUSTY
OUTFLOW WINDS ASSOCIATED WITH THE MOST ROBUST THUNDERSTORMS
TOMORROW (AND REALLY, TODAY AS WELL) MAY LEAD TO ERRATIC WIND
SHIFTS, WHILE TORRENTIAL RAINFALL WILL ALSO CAUSE SHARP
VISIBILITY REDUCTIONS.
OTHERWISE, EASTERLY WINDS TODAY WILL TREND MORE SOUTHEASTERLY
TONIGHT INTO TOMORROW MORNING, THEN MORE SOUTHERLY TOMORROW
AFTERNOON. AT LEAST PATCHY MVFR CEILINGS MAY ALSO MOVE INTO THE
AREA LATE TONIGHT OR EARLY TOMORROW MORNING. RFD STANDS THE
HIGHEST CHANCE OF SEEING PREVAILING MVFR (OR LOWER) CEILINGS,
THOUGH SOME CHANCE FOR THEM EXISTS AT THE CHICAGO METRO
TERMINALS AS WELL.
OGOREK
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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