608
FXUS63 KIND 211743
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
143 PM EDT SAT JUN 21 2025
KEY MESSAGES
- HEAT ADVISORY IN EFFECT TODAY THROUGH TUESDAY
- HOTTEST CONDITIONS OF THE SEASON THUS FAR THIS WEEKEND INTO NEXT
WEEK, WITH HEAT INDEX VALUES PEAKING FROM 100-105 DEGREES FOR
SEVERAL CONSECUTIVE DAYS
- SLIGHT WEAKENING OF THE RIDGE MID TO LATE NEXT WEEK MAY ALLOW
THUNDERSTORM ACTIVITY TO DROP INTO THE REGION, OFFERING SOME
PROSPECT OF RELIEF FROM THE HOTTEST TEMPERATURES
FORECAST UPDATE
ISSUED AT 1029 AM EDT SAT JUN 21 2025
TODAY MARKS THE FIRST DAY IN WHAT MAY BE AN EXTENDED STREAK OF HIGHS
AT OR ABOVE 90 DEGREES. SATELLITE IMAGERY SHOWS CLEAR SKIES OVER THE
MAJORITY OF THE REGION AS RIDGING BUILDS OVERHEAD AND SURFACE HIGH
PRESSURE REMAINS THE DOMINANT WEATHER INFLUENCE LOCALLY. AS OF 10
AM, MOST LOCATIONS ARE ALREADY IN THE LOWER 80S... A FEW DEGREES
WARMER THAN GUIDANCE SHOWS FOR THIS HOUR. MAY HAVE TO RAISE HIGH
TEMPERATURES BY A FEW DEGREES AS SOME SPOTS WILL MAKE RUN FOR THE
MID 90S BY THIS EVENING. EXPECT SOUTHERLY WINDS TO INCREASE LATER
THIS AFTERNOON WITH GUSTS UPWARDS OF 20-25 MPH AS DEEP MIXING AND
STEEP LOW LEVEL LAPSE RATES ALLOW FOR STRONGER WINDS WITHIN THE LOW
LEVEL JET TO MIX DOWN TO THE SURFACE. THE CORE OF THE LOW LEVEL JET
IS TO THE WEST OVER MISSOURI AND IOWA, COINCIDING WITH STRONGER WARM
AND MOIST AIR ADVECTION. THINKING ANY LOCATION THAT COULD
OVERACHIEVE FOR HIGH TEMPERATURES WILL BE ALONG AND WEST OF THE I-65
CORRIDOR. MAX HEAT INDEX VALUES THIS AFTERNOON MAY REACH 105 DEGREES
IN THESE HOTTER LOCATIONS.
SHORT TERM (TODAY AND TONIGHT)
ISSUED AT 321 AM EDT SAT JUN 21 2025
AS IF ON SCHEDULE FOR THE FIRST FULL DAY OF ASTRONOMICAL SUMMER, THE
HOTTEST STRETCH OF THE YOUNG SEASON THUS FAR BEGINS TODAY, WITH
PLENTIFUL SUNSHINE, INCREASING HUMIDITY, AND HIGHS IN THE LOW 90S AS
UPPER LEVEL RIDGING BEGINS TO STRENGTHEN OVER THE REGION.
THE STRONG INSOLATION TODAY, COMBINED WITH A BIT OF A PRESSURE
GRADIENT IN PLACE, WILL PROMOTE DEEP BOUNDARY LAYER MIXING THIS
AFTERNOON, ON THE ORDER OF 4-7KFT, WHICH WILL ALLOW FOR GUSTY
CONDITIONS AND PROVIDE AT LEAST SLIGHT RELIEF IN THAT MANNER, WITH
WINDS GUSTING AS HIGH AS 25-30 MPH AT TIMES THIS AFTERNOON, BUT
OTHERWISE, DAY ONE OF FAIRLY STIFLING HEAT CAN BE EXPECTED, WITH
PEAK HEAT INDEX VALUES RISING INTO THE UPPER 90S TO LOW 100S ACROSS
THE AREA. HEAT ADVISORY IS ALREADY IN PLACE FOR THE PROLONGED
STRETCH OF HOT CONDITIONS, AND NO CHANGES ARE NECESSARY.
HIGH HUMIDITY WILL KEEP OVERNIGHT LOWS UP TONIGHT, WITH LOW TO MID
70S LIKELY ACROSS THE AREA, OFFERING LITTLE RELIEF FROM THE HEAT
STRESS BUILT UP DURING THE DAY.
LONG TERM (SUNDAY THROUGH FRIDAY)
ISSUED AT 321 AM EDT SAT JUN 21 2025
..PROLONGED HEAT AND HUMIDITY EXPECTED INTO LATE NEXT WEEK
HEAT AND HUMIDITY WILL REMAIN THE NAME OF THE GAME THROUGH MUCH OF
THE COMING WEEK, WITH THE UNCERTAINTY BEING HOW MUCH THE SLIGHT
WEAKENING AND RETROGRESSION OF THE UPPER RIDGE LATER IN THE WEEK MAY
ALLOW AFTERNOON CONVECTION TO DEVELOP, OR RIDGE-RIDING COMPLEXES TO
MOVE INTO THE AREA AND OFFER SOME SLIGHT RELIEF WITH TIME. IT IS
POSSIBLE THAT TRIPLE DIGIT PEAK HEAT INDEX VALUES COULD PERSIST INTO
WEDNESDAY/THURSDAY, AND MAY MERIT EXTENSION TO ALL OR PART OF THE
HEAT ADVISORY, BUT THIS WILL WAIT FOR LATER PACKAGES WHEN SOME OF
THESE DETAILS COME INTO BETTER FOCUS. CENTRAL INDIANA IS LIKELY TO
REMAIN DRY THROUGH AT LEAST MONDAY, AS A LACK OF FORCING FOR ASCENT
COMBINED WITH CAPPING (700 MB TEMPS NEAR 10-12C MUCH OF THE TIME) IS
LIKELY TO KEEP ANY INSTABILITY ALOFT FROM BEING REALIZED.
HIGHS EACH DAY THROUGH AT LEAST THURSDAY LOOK TO REACH THE LOW TO
PERHAPS MID 90S ACROSS MOST OR ALL OF CENTRAL INDIANA, WITH
OVERNIGHT LOWS NO LOWER THAN THE LOW TO MID 70S DUE TO THE HIGH
DEWPOINTS, AGAIN PROLONGING AND EXACERBATING THE CUMULATIVE HEAT
STRESS, PARTICULARLY FOR VULNERABLE POPULATIONS AND THOSE WITHOUT
ACCESS TO ADEQUATE COOLING.
WHILE RECORD TEMPERATURES ARE NOT AT RISK THROUGHOUT THIS STRETCH,
IT IS AGAIN PRUDENT TO EMPHASIZE THE CUMULATIVE NATURE OF HEAT
STRESS, WHICH IS WELL-ILLUSTRATED BY EXPERIMENTAL NWS HEATRISK INDEX
VALUES, WHICH ARE 3-4/MAJOR-EXTREME FOR MULTIPLE COMING DAYS AS A
RESULT OF BOTH THE DAYTIME HEAT AND THE HIGH HUMIDITY/WARM LOW
TEMPERATURES PREVENTING SIGNIFICANT OVERNIGHT RELIEF.
AVIATION (18Z TAF ISSUANCE)
ISSUED AT 143 PM EDT SAT JUN 21 2025
IMPACTS:
- WIND GUSTS UP TO 20-25KT FROM 200-210 DEGREES BETWEEN 15Z AND 00Z
THIS AFTERNOON/EVENING
DISCUSSION:
MAINLY VFR CONDITIONS EXPECTED THROUGH THE NEXT SEVERAL DAYS AS
RIDGING ALOFT AND HIGH PRESSURE BECOME THE DOMINANT WEATHER
INFLUENCE LOCALLY. SATELLITE IMAGERY AND OBSERVATIONS SHOW DIURNAL
CUMULUS OVER THE STATE AROUND 3000FT AGL. CLOUDS SHOULD REMAIN
SCATTERED FOR THE MOST PART, BUT WOULD NOT BE SURPRISED TO SEE A
BROKEN DECK AT TIMES. KEEPING SCT030 FOR THE TAFS FOR NOW AS
CONFIDENCE IS LOW THAT THAT CLOUD COVERAGE WILL INCREASE TO WARRANT
BKN.
THE PRIMARY IMPACT DURING THIS PERIOD WILL BE WIND GUSTS OF 20-25
KTS INTO THE EARLY EVENING AT ALL SITES. THESE GUSTS WILL SUBSIDE IN
TYPICAL DIURNAL FASHION DURING THE EVENING, WITH WINDS TOMORROW
NIGHT REMAINING SOUTHERLY (190-200 DEGREES) AT 7-11KT, AGAIN
PREVENTING ANY SIGNIFICANT FOG.
EXPECT A SIMILAR FORECAST FOR TOMORROW AS THE PATTERN LARGELY
REMAINS THE SAME. AFTERNOON WIND GUSTS TOMORROW AFTERNOON SHOULD
REMAIN BELOW 20 KTS AS THE LOW LEVEL JET WILL BE WEAKER.
IND WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY UNTIL 8 PM EDT TUESDAY FOR INZ021-028>031-035>049-
051>057-060>065-067>072.
UPDATE...CM
SHORT TERM...NIELD
LONG TERM...NIELD
AVIATION...CM
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