644
FXUS63 KLOT 011732
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1232 PM CDT WED JUL 1 2026
KEY MESSAGES
- HEAT WAVE EXPECTED TO CONTINUE THROUGH AT LEAST THURSDAY,
POTENTIALLY EXTENDING INTO FRIDAY DEPENDING COVERAGE OF STORMS
AND CLOUDINESS.
- WHILE NOT A COMPLETE WASH OUT, THUNDERSTORM CHANCES INCREASE
THURSDAY NIGHT, WITH AT LEAST A COUPLE OF WAVES OF SHOWERS
AND THUNDERSTORMS EXPECTED FRIDAY INTO THE 4TH OF JULY
WEEKEND. SOME STORMS MAY BE SEVERE AND PRODUCE HEAVY RAINFALL.
DISCUSSION
ISSUED AT 147 AM CDT WED JUL 1 2026
STRONG MID-UPPER LEVEL RIDGE OF HIGH PRESSURE WILL CHANGE VERY
LITTLE THROUGH THURSDAY PROVIDING FOR A CONTINUATION OF OUR HOT
AND HUMID CONDITIONS. BY LATER THURSDAY THIS RIDGE WILL BEGIN TO
SLOWLY WEAKEN AND SHIFT EASTWARD. THIS WILL ALLOW FOR THE
ACTIVE RING OF FIRE PATTERN THAT HAS BEEN PROVIDING FOR WAVES OF
SEVERE THUNDERSTORMS FROM THE CENTRAL PLAINS INTO THE UPPER
GREAT LAKES TO GRADUALLY SHIFT SOUTHWARD IN OUR AREA BY WEEK'S
END AND THROUGH THE HOLIDAY WEEKEND.
NO CHANGES PLANNED OR NEEDED FOR THE CURRENT EXTREME HEAT
WARNING. TODAY WILL BE ANOTHER HOT AND HUMID DAY WITH CONDITIONS
PRETTY SIMILAR TO TUESDAY EXPECTED. THE NAM, WHICH HAS BEEN ON
THE UPPER END OF THE GUIDANCE SPECTRUM WITH DEWPOINTS, HAS
GENERALLY BEEN VERIFYING BEST. FOR THIS REASON, LEANED PRETTY
HEAVILY ON THE NAM WHICH HAS TDS IN THE MID TO LOCALLY UPPER 70S
THIS AFTERNOON, GENERALLY 2-4F LOWER THAN TUESDAY. FORECAST
SOUNDINGS DEPICT A CONTINUED STRONG SUBSIDENCE INVERSION
LIMITING THE DEPTH OF MIXING, SO IT IS POSSIBLE THAT DEWPOINTS
END UP A BIT HIGHER, BUT WITH ALL GUIDANCE GENERALLY DEPICTS
LOWER TDS TODAY VS TUESDAY. TEMPERATURE SHOULD AGAIN CLIMB INTO
THE LOWER TO MIDDLE 90S, HOTTEST IN THE CHICAGO URBAN HEAT
ISLAND. HEAT INDICES SHOULD ONCE AGAIN CLIMB INTO THE 100 TO
LOCALLY 110 DEGREE RANGE THIS AFTERNOON.
CONVECTION AND ESPECIALLY CONVECTIVE OUTFLOW IS LIKELY TO GET
NEARER TO OR EVEN INTO OUR NORTHERN CWA LATE TONIGHT INTO EARLY
THURSDAY MORNING. GUIDANCE GENERALLY SUGGESTS THAT CAPPING
SHOULD BE SUFFICIENT TO KEEP MOST OF THE EFFECTS OF THIS
CONVECTION NORTH OF OUR AREA THURSDAY ALLOWING FOR ANOTHER HOT
AND HUMID AFTERNOON THURSDAY.
BY THURSDAY NIGHT, IT APPEARS THAT THE RIDGE SHOULD HAVE
WEAKENED/SHIFTED SUFFICIENTLY EAST TO AT LEAST OPEN THE DOOR TO
THE POTENTIAL FOR MCS ACTIVITY TO MEANDER INTO OUR CWA. TIMING
OF THE VERY LOW AMPLITUDE SYNOPTIC DISTURBANCES THAT
ULTIMATELY SERVE AS THE IMPETUS FOR MCS DEVELOPMENT IS OFTEN
DIFFICULT TO IMPOSSIBLE AT THIS DISTANCE. DEPENDING ON WHERE/IF
AN MCS TRACKS ACROSS THE GENERAL REGION THURSDAY NIGHT/FRIDAY
TIME FRAME WILL PLAY A PIVOTAL ROLE IN TEMPERATURES FOR FRIDAY.
IF (AND WHERE) CONVECTION AND/OR LINGERING EFFECTS FROM
CONVECTION (CLOUD COVER, COLD POOL, ETC) AREN'T A SIGNIFICANT
FACTOR, THEN FRIDAY HAS THE POTENTIAL TO BE A 5TH DAY WITH HEAT
INDICES ABOVE 100 DEGREES. CERTAINLY PLAUSIBLE THAT HEAT
HEADLINES MAY NEED TO BE EXTENDED INTO FRIDAY FOR SOME PORTIONS
OF THE AREA, BUT CONFIDENCE IS FAR TOO LOW TO MAKE ANY SUCH
CHANGE ON THIS SHIFT.
OVER THE UPCOMING HOLIDAY WEEKEND, CERTAINLY PLAUSIBLE THAT
THERE COULD BE ONE OR TWO ADDITIONAL ROUNDS OF SHOWERS AND
THUNDERSTORMS. THE WEEKEND MOST CERTAINLY DOES NOT LOOK LIKE IT
WILL BE A WASH OUT, BUT ONE OR TWO CONVECTIVELY ENHANCED
SHORTWAVES COULD LEAD TO CONVECTION IN THE AREA PRETTY MUCH AT
ANY POINT IN TIME OVER THE WEEKEND. AS THE UPPER RIDGE WEAKENS,
A SUBSEQUENT RELAXING OF THE GEOPOTENTIAL HEIGHT GRADIENT ON ITS
NORTHERN FLANK IS LIKELY TO RESULT IN A WEAKENING OF THE MID
AND UPPER LEVEL FLOW. THIS SHOULD LESSEN THE THREAT OF
SIGNIFICANT SEVERE WEATHER THIS WEEKEND, THOUGH A STRONGER MCV
COULD CERTAINLY LEAD TO A MORE LOCALIZED GREATER SEVERE THREAT
THIS WEEKEND. A VERY MOIST AIR MASS WILL REMAIN IN THE AREA,
SETTING THE STAGE FOR VERY HEAVY RAINFALL PRODUCTION WITH
STRONGER STORMS. GIVEN THE LOW CONFIDENCE IN TIMING/TRACK OF
MCVS THIS WEEKEND, MADE NO CHANGES TO THE NBM POPS WHICH AT
FIRST GLANCE APPEAR VERY HIGH, BUT IMPORTANT TO NOTE THEY JUST
REFLECT THE CHANCE OF A HUNDREDTH OF AN INCH OF RAIN IN A 12
HOUR PERIOD.
- IZZI
AVIATION /18Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 1232 PM CDT WED JUL 1 2026
MAIN CONCERN:
- POTENTIAL FOR WEAKENING SHRA/TS NEARBY TO DRIVE AN OUTFLOW
ASSOCIATED WIND SHIFT ACROSS THE AREA EARLY THURSDAY MORNING
VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD, WITH THE SMALL
POSSIBLE EXCEPTION OF ANY PRECIP RELATED VSBY EFFECTS.
SOUTHWESTERLY WIND GUSTS ARE EXPECTED TO INCREASE INTO THE
25-30 KT RANGE (AT LEAST OCCASIONALLY) LATE THIS AFTERNOON INTO
EARLY THIS EVENING, THEN LIKELY EASE WITH OR JUST AFTER SUNSET.
THERE MAY BE SPORADIC GUSTS NEAR 20 KT, ESPECIALLY AT ORD AND
MDW.
THE AREA TO WATCH LATE TONIGHT IS FROM FAR NE IOWA ACROSS TO
CENTRAL AND SOUTHERN WISCONSIN. EXACT COVERAGE OF TS IN THAT
AREA WILL LIKELY CONTRIBUTE TO POTENTIAL FOR AN OUTFLOW BOUNDARY
TO PUSH ACROSS THE AREA AND RESULT IN A TEMPORARY WIND SHIFT (NW
TO NE TO SE BEFORE RETURNING TO SW). ALSO CAN'T RULE OUT SHRA
AND A FEW ISOLATED TS MAKING IT INTO NORTHERN IL (~20% CHANCE).
DUE TO UNCERTAINTY, CONFIDENCE WAS NOT HIGH ENOUGH FOR ANY
FORMAL MENTION OF A WIND SHIFT AND PRECIP IN THE TAFS. THE NEXT
DECENT CHANCE FOR TS AT THE TAF SITES IS LOOKING TO BE THURSDAY
EVENING, BEYOND THE CURRENT ORD/MDW 30-HOUR TAF PERIOD.
CASTRO
CLIMATE
ISSUED AT 1246 AM CDT WED JUL 1 2026
.DAILY RECORDS FOR THE UPCOMING WEEK........
CHICAGO (KORD)
RECORD HIGH RECORD WARM MINIMUM
JULY 1 103 (1956) 78 (1931)
JULY 2 99 (1970) 79 (1911)
JULY 3 102 (1949) 78 (1911)
JULY 4 102 (2012) 80 (1921)
ROCKFORD (KRFD)
RECORD HIGH RECORD WARM MINIMUM
JULY 1 101 (1931) 76 (1970)
JULY 2 99 (1910) 74 (1970)
JULY 3 99 (1925) 75 (2012)
JULY 4 102 (2012) 77 (1977)
NWS CHICAGO
LOT WATCHES/WARNINGS/ADVISORIES
IL...EXTREME HEAT WARNING UNTIL MIDNIGHT CDT THURSDAY NIGHT FOR
ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-
ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-
ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.
IN...EXTREME HEAT WARNING UNTIL MIDNIGHT CDT /1 AM EDT/ THURSDAY
NIGHT FOR INZ001-INZ002-INZ010-INZ011-INZ019.
LM...NONE.
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