535
FXUS63 KIWX 240528
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
128 AM EDT TUE JUN 24 2025
KEY MESSAGES
- AN EXTREME HEAT WARNING REMAINS IN EFFECT THROUGH TUESDAY
EVENING. PEAK HEAT INDICES OF 100 TO 105 DEGREES ARE EXPECTED
TODAY.
- CUMULATIVE EFFECTS OF LONG-DURATION HEAT WILL LIKELY CAUSE
SIGNIFICANT IMPACTS AT LEAST THROUGH MIDWEEK.
- DAILY CHANCES FOR SHOWERS AND STORMS, THOUGH THE BEST CHANCE
WILL BE WEDNESDAY AFTERNOON AND EVENING. THERE IS A MARGINAL
RISK FOR ISOLATED STRONG TO SEVERE STORMS TUESDAY AFTERNOON
AND EVENING, AND THEN AGAIN ON WEDNESDAY. DAMAGING WIND WILL
BE THE PRIMARY HAZARD.
DISCUSSION
ISSUED AT 241 PM EDT MON JUN 23 2025
AN AREA OF SURFACE HIGH PRESSURE AND AN EXPANSIVE UPPER LEVEL
RIDGE WILL CONTINUE BRING HIGH HEAT AND OPPRESSIVE HUMIDITY TO
THE AREA THIS WEEK. THE EXCESSIVE HEAT WARNING REMAINS IN EFFECT
THROUGH 8 PM ET TUESDAY. AMPLE WAA AND MOISTURE TRANSPORT FROM
THE GULF WILL YIELD HIGHS IN THE LOW TO MID 90S AND DEWPOINTS IN
THE MID 70S OVER THE NEXT SEVERAL DAYS. NEAR RECORD OVERNIGHT
LOWS IN THE MID 70S WILL OFFER LITTLE TO NO RELIEF FROM THE
HEAT, SO CUMULATIVE HEAT IMPACTS ARE LIKELY. PEAK HEAT INDICES
LATER TODAY AND TUESDAY AFTERNOON WILL BE BETWEEN 100 TO 105
DEGREES AREA-WIDE. THE NWS HEAT RISK SHOWS MAJOR TO EXTREME
(LEVELS 3 AND 4 OUT OF 4) HEAT IMPACTS WILL BE POSSIBLE FOR THE
REST OF TODAY THROUGH TUESDAY. STAY HYDRATED, TAKE BREAKS IF YOU
MUST BE OUTSIDE, AND CHECK IN ON THOSE WHO COULD BE ESPECIALLY
VULNERABLE TO THE HIGH HEAT AND HUMIDITY. ADDITIONAL HEAT
HEADLINES MAY BE NEEDED BEYOND TUESDAY GIVEN THAT HIGH
TEMPERATURES ARE STILL FORECAST TO BE IN THE UPPER 80S MID TO
LATE IN THE WEEK WITH HEAT INDICES PEAKING BETWEEN 95 TO 100
DEGREES, ESPECIALLY ALONG AND SOUTH OF US 30.
AS THE RIDGE FLATTENS OUT BY MIDWEEK AND CHANCES FOR RAIN/STORMS
RETURN, WE MAY GET SOME REPRIEVE FROM THE DANGEROUS HEAT. CONFIDENCE
IS LOW TO MEDIUM FOR THE HEAT CONTINUING PAST MIDWEEK, AS THE
TEMPERATURE FORECAST WILL BE HIGHLY DEPENDENT ON IF WE GET ANY
STORMS OR REMNANT OUTFLOW BOUNDARIES OVER THE AREA. DAILY DIURNAL
CHANCES FOR RAIN/STORMS EXIST THIS WEEK STARTING TUESDAY, HOWEVER,
THIS IS A TOUGH FORECAST PATTERN FOR MODELS TO RESOLVE. MODEL
GUIDANCE TYPICALLY STRUGGLES WITH A PATTERN LIKE THIS AS IT IS TOUGH
TO KNOW WHAT WILL OCCUR A FEW DAYS OUT WHEN THERE IS CONSIDERABLE
UNCERTAINTY AS TO IF AND WHEN STORMS DEVELOP. IF STORMS DO MANAGE TO
DEVELOP IN OUR AREA ON ANY GIVEN DAY, THIS COULD MEAN TEMPERATURES
END UP COOLER THAN ORIGINALLY FORECAST (ESPECIALLY IF ANY
OUTFLOW BOUNDARIES MOVE THROUGH). A COLD FRONT OVER THE MIDWEST
AND CENTRAL PLAINS WILL STALL OFF TO OUR WEST OVER THE NEXT
24-36 HOURS, FINALLY REACHING OUR FORECAST AREA BY WEDNESDAY. IT
IS POSSIBLE SOME REMNANT OUTFLOW BOUNDARIES ASSOCIATED WITH
THIS FRONT DRIFT EAST INTO OUR AREA ON TUESDAY, WHICH IS WHY WE
HAVE CHANCES FOR AFTERNOON/EVENING POP-UP SCATTERED SHOWERS AND
STORMS. WITH OUR AREA ON THE NORTHERN PERIPHERY OF THE RIDGE, IT
IS ALSO POSSIBLE WE GET SOME RAIN/STORMS IN OUR AREA MID TO
LATE IN THE WEEK AS THE RIDGE STARTS TO BREAK DOWN AND STORM
COMPLEXES RIDE THE FRINGES OF THE RIDGE. BEST CHANCES FOR
RAIN/STORMS THIS WEEK WILL LIKELY BE WEDNESDAY AFTERNOON/EVENING
AS THIS COLD FRONT MOVES THROUGH. THE PERSISTENT HIGH HEAT AND
HUMIDITY WILL MAKE FOR A VERY UNSTABLE AIRMASS. DEWPOINTS IN THE
LOW TO MID 70S EACH DAY AND TEMPERATURES IN THE LOW TO MID 90S
WILL CREATE ANYWHERE FROM 2500 TO 4000 J/KG OF SBCAPE ON TUESDAY
AND WEDNESDAY. WITH HOW MOIST AND UNSTABLE THE ATMOSPHERE
OVERHEAD IS, IT IS NOT UNREASONABLE TO THINK THAT STORMS COULD
DEVELOP AND BECOME STRONG TO SEVERE. THE STORM PREDICTION CENTER
CURRENTLY HAS US IN A MARGINAL RISK (LEVEL 1 OF 5) FOR SEVERE
WEATHER ON TUESDAY AND WEDNESDAY. THE MAIN HAZARD AT THIS TIME
WOULD BE DAMAGING WINDS.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 121 AM EDT TUE JUN 24 2025
AN OUTFLOW BOUNDARY FROM A DECAYING LINE OF SHOWERS AND
THUNDERSTORMS IS APPROACHING KORD, TRACKING SOUTHEAST. THIS
FEATURE APPEARS TO BE WEAKENING. THIS IN-HOUSE TIME OF ARRIVAL
TOOL SUGGESTED AN ARRIVAL TIME TO KSBN NEAR 09Z; THUS FORWARD
PROGRESS IS SLOW. SEEING THE DECAYING TREND ON RADAR RETURNS, I
WILL OMIT AN OUTFLOW WINDSHIFT TO THE NORTHWEST BUT WILL
CONTINUE TO MONITOR.
A SOMEWHAT MURKY TAF PERIOD AHEAD WITH SCATTERED THUNDERSTORMS
ANTICIPATED THIS AFTERNOON. I DID ADJUST THE TIMING A TOUCH
BASED ON THE LATEST MODEL TRENDS. LATE IN THE PERIOD,
ADDITIONAL SHOWERS AND STORMS APPROACH KSBN (LOW CONFIDENCE)
WHILE THIS ACTIVITY PERHAPS ARRIVES AT KFWA JUST OUTSIDE THIS
TAF PERIOD.
IWX WATCHES/WARNINGS/ADVISORIES
IN...EXTREME HEAT WARNING UNTIL 8 PM EDT /7 PM CDT/ THIS EVENING
FOR INZ005>009-012>015-017-018-020-022>027-032>034-103-
104-116-203-204-216.
OH...EXTREME HEAT WARNING UNTIL 8 PM EDT THIS EVENING FOR OHZ001-
002-004-005-015-016-024-025.
MI...EXTREME HEAT WARNING UNTIL 8 PM EDT THIS EVENING FOR
MIZ078>081-177-277.
MARINE...NONE.
DISCUSSION...JOHNSON
AVIATION...BROWN
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