815
FXUS63 KIWX 030603
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
203 AM EDT FRI JUL 3 2026
KEY MESSAGES
- THE EXTREME HEAT WARNING REMAINS IN EFFECT AREA-WIDE THROUGH
THIS EVENING. HIGHS IN THE LOW TO MID 90S AND HEAT INDICES
BETWEEN 100 TO 110 DEGREES ARE EXPECTED THIS AFTERNOON.
- THE EXTREME HEAT WARNING CONTINUES THROUGH FRIDAY EVENING
MAINLY ALONG AND SOUTH OF US 24. A HEAT ADVISORY HAS BEEN
ISSUED FOR FRIDAY FOR THE REST OF THE FORECAST AREA. PEAK HEAT
INDICES FRIDAY AFTERNOON ARE EXPECTED TO BE BETWEEN 100 TO
105 DEGREES, HIGHEST IN THE WARNING AREA.
- THERE IS A SLIGHT RISK (LEVEL 2 OF 5) FOR SEVERE WEATHER ON FRIDAY.
SCATTERED STORMS ARE MOST LIKELY AFTER 3 PM EDT WITH DAMAGING WIND
GUSTS, HEAVY RAIN, AND LIGHTNING AS THE MAIN THREATS.
- HOT AND HUMID FOR THE 4TH OF JULY WITH UP TO 70% CHANCES FOR
SHOWERS AND STORMS. THERE IS A MARGINAL RISK (LEVEL 1 OF 5)
FOR SEVERE WEATHER. ISOLATED STORMS ARE MOST LIKELY BETWEEN
2-11 PM EDT WITH DAMAGING WIND GUSTS, HEAVY RAIN, AND
LIGHTNING AS THE MAIN THREATS.
DISCUSSION
ISSUED AT 210 PM EDT THU JUL 2 2026
ONE MORE DAY OF DRY CONDITIONS TODAY BEFORE THE EXPANSIVE UPPER
LEVEL RIDGES BEGINS TO BREAK DOWN AND FLATTEN OUT, ALLOWING FOR
RAIN/STORM CHANCES TO RETURN FRIDAY AND INTO THE HOLIDAY WEEKEND.
HIGH HEAT AND HUMID CONTINUES TODAY WITH THE EXTREME HEAT WARNING IN
EFFECT AREA-WIDE. TEMPERATURES ARE CURRENTLY IN THE MID TO UPPER 80S
WITH DEWPOINTS IN THE MID 70S. EXPECT PEAK HEAT INDICES TO 110
DEGREES THIS AFTERNOON AS TEMPERATURES ONCE AGAIN CLIMB INTO THE LOW
TO MID 90S FOR HIGHS AMIDST MOSTLY SUNNY SKIES.
AN MCS IS EXPECTED TO DEVELOP LATER TONIGHT IN WI/IL/IA AND DIVE
SOUTHEAST AS THE RIDGE WEAKENS. THIS COMPLEX OF STORMS IS EXPECTED
TO WEAKEN BUT MAY SURVIVE LONG ENOUGH TO YIELD SOME SPS WORTHY
STORMS IN OUR FAR NORTHWEST (ESPECIALLY LA PORTE AND BERRIEN
COUNTIES) OVERNIGHT. CONFIDENCE IS LOW AS THIS SYSTEM WOULD ARRIVE
AT A DIURNALLY UNFAVORABLE TIME AND THE ENVIRONMENT IS EXPECTED TO
BE CAPPED OVERNIGHT, BUT AN ISOLATED THREAT FOR STRONG WINDS IS
STILL POSSIBLE.
FRIDAY FEATURES BOTH HEAT AND CONVECTION, WITH HIGHER CONFIDENCE NOW
IN BOTH THREATS. IT APPEARS AS IF THE CONVECTION, AS OF NOW, MAY NOT
IMPACT PEAK DIURNAL HEATING (ESPECIALLY IN OUR EASTERN HALF OF THE
AREA). GIVEN THAT HIGH TEMPERATURES SHOULD STILL MAKE IT TO THE
UPPER 80S TO MID 90S (HIGHEST IN NORTHWEST OHIO), HEAT HEADLINES
HAVE BEEN ISSUED FOR FRIDAY. THE EXTREME HEAT WARNING WAS EXTENDED
UNTIL SUNSET FRIDAY ALONG AND SOUTH OF US 24, WHILE A HEAT ADVISORY
WAS ISSUED FOR THE REST OF THE FORECAST AREA. PEAK HEAT INDICES
FRIDAY AFTERNOON ARE EXPECTED TO BE BETWEEN 100 TO 105 DEGREES,
HIGHEST IN THE WARNING AREA. HEATRISK IS STILL SHOWING MAJOR TO
EXTREME FOR FRIDAY WITH OUR LONG DURATION HEATWAVE CONTINUING. HIGH
HEAT AND HUMIDITY IS EXPECTED TO FUEL SCATTERED RAIN/STORMS.
CONVECTIVE INITIATION IS EXPECTED TO OCCUR BETWEEN 19Z-22Z FRIDAY
ALONG A REMNANT OUTFLOW BOUNDARY LEFTOVER FROM MORNING CONVECTION.
THERE IS A SLIGHT RISK (LEVEL 2 OF 5) FOR SEVERE WEATHER ON FRIDAY,
WITH DAMAGING WIND GUSTS AS THE MAIN THREAT. MULTICELL CLUSTERS OF
STORMS MAY ALSO BE AIDED BY AN MCV MOVING THROUGH THE GREAT LAKES.
MICROBURST POTENTIAL IS FAVORABLE FRIDAY AFTERNOON/EVENING,
ESPECIALLY GIVEN THAT THE HIGH HEAT AND HUMIDITY COULD YIELD
EXPLOSIVE SBCAPE VALUES OF UP TO 4000 J/KG. OTHER FAVORABLE
PARAMETERS INCLUDE LOW LEVEL LAPSE RATES IN EXCESS OF 8 C/KM AND
PWATS AROUND 1.5". FORECAST SOUNDINGS DEPICT INVERTED V PROFILES
WITH DCAPE ABOVE 1000 J/KG, WHICH ALSO INDICATES ELEVATED POTENTIAL
FOR MICROBURSTS. IN ADDITION TO THE DAMAGING WIND THREAT TOMORROW,
HEAVY RAINFALL AND LIGHTNING WILL BE HAZARDS AS WELL.
JULY 4TH WILL NOT BE A COMPLETE WASHOUT, HOWEVER, THERE IS STILL A
MARGINAL RISK (LEVEL 1 OF 5) FOR SEVERE WEATHER. SATURDAY MARKS THE
BEGINNING OF OUR SLIGHT COOL DOWN, WITH HIGHS IN THE MID 80S TO NEAR
90 DEGREES. HUMID CONDITIONS STICK AROUND FOR THE HOLIDAY THOUGH
WITH DEWPOINTS IN THE LOW TO MID 70S. WITH A STATIONARY FRONT IN THE
VICINITY, CONTINUED HEAT AND HUMIDITY WILL AID IN THUNDERSTORM
DEVELOPMENT BY THE AFTERNOON AND EVENING HOURS SATURDAY. ISOLATED
DAMAGING WIND GUSTS WOULD BE THE MAIN THREAT AGAIN IN ANY STRONG
TO SEVERE STORMS; EVEN IF STORMS STAY SUB-SEVERE, HEAVY RAIN AND
LIGHTNING WILL STILL BE HAZARDS.
A TROUGH EJECTING OUT OF THE WESTERN US COULD BRING ADDITIONAL
CHANCES FOR SHOWERS AND STORMS ON SUNDAY. WHILE IT MAY BE SLIGHTLY
'COOLER' INTO EARLY NEXT WEEK WITH HIGHS IN THE 80S, THE LONG TERM
PATTERN CONTINUES TO FAVOR ABOVE NORMAL TEMPERATURES THROUGH MID
JULY. PERIODIC CHANCES FOR RAIN/STORMS NEXT WEEK AS ZONAL FLOW ALOFT
CONTINUES.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 155 AM EDT FRI JUL 3 2026
CONVECTIVE POTENTIAL WILL CONTINUE TO BE THE PRIMARY AVIATION
WEATHER CONCERN. A CLUSTER OF SHOWERS AND THUNDERSTORMS ACROSS
NORTHEAST ILLINOIS INTO SOUTHWEST LOWER MICHIGAN HAS KICKED AN
OUTFLOW BOUNDARY SOUTHWARD THAT HAS JUST PASSED THROUGH KSBN
VICINITY. SHOWERS AND A FEW STORMS HAVE ATTEMPTED TO DEVELOP
ALONG THIS OUTFLOW BOUNDARY, BUT DEVELOPMENT OF SOME WEAK MLCIN
OVERNIGHT MAY TEND TO LIMIT COVERAGE AND RESULT IN SOME
DIMINISHMENT OF UPSTREAM CONVECTION AS IT PUSHES EAST. WITH
CONTINUED LOW CONFIDENCE IN NEAR TERM, HAVE INDICATED A PROB30
THUNDER MENTION AT KSBN WITH A POTENTIAL OUTFLOW BOUNDARY COULD
BE A FOCAL POINT, AND THE POSSIBILITY THAT CONVECTIVE COMPLEX
ACROSS NORTHEAST ILLINOIS SURVIVES EASTWARD. A MORE ORGANIZED
ROUND OF CONVECTION IS STILL EXPECTED LATE THIS AFTERNOON INTO
THIS EVENING AS ANOTHER CONVECTIVELY ENHANCED SHORT WAVE FROM
THE PLAINS ROUNDS THE FLATTENING UPPER RIDGE AND INTERACTS WITH
AN UNSTABLE AIRMASS. SOME UNCERTAINTIES PERSIST REGARDING WHERE
LEFTOVER OUTFLOW BOUNDARIES FROM THIS MORNING'S CONVECTION WILL
BE LOCATED AND ALSO TIMING THE CONVECTIVELY ENHANCED SHORT WAVE.
COULD SEE ISOLATED-SCATTERED STORMS DEVELOP TOWARD 19-20Z ALONG
REMNANT OUTFLOW BOUNDARY THAT MAY BEGIN TO SLOWLY RETREAT
NORTHWARD ACROSS FAR NORTHERN INDIANA. BETTER CHANCE OF STORMS
STILL LOOKS TO BE IN THE 22Z-03Z TIMEFRAME AS THE SHORT WAVE
APPROACHES. GIVEN THE UNCERTAINTIES MENTIONED, WILL LIMIT
AFTERNOON/EVENING CONVECTION AT TERMINALS TO A PROB30 FOR NOW.
OUTSIDE OF ANY HEAVIER SHOWERS AND STORMS, VFR CONDITIONS SHOULD
HOLD THROUGH THIS PERIOD.
IWX WATCHES/WARNINGS/ADVISORIES
IN...HEAT ADVISORY UNTIL 8 PM EDT /7 PM CDT/ THIS EVENING FOR
INZ005>008-012>015-020-103-104-116-203-204-216.
EXTREME HEAT WARNING UNTIL 8 PM EDT THIS EVENING FOR INZ009-
017-018-022>027-032>034.
OH...EXTREME HEAT WARNING UNTIL 8 PM EDT THIS EVENING FOR OHZ001-
002-004-005-015-016-024-025.
MI...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR MIZ078>081-177-
277.
MARINE...NONE.
DISCUSSION...JOHNSON
AVIATION...MARSILI
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