110
FXUS63 KIND 122251
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
651 PM EDT TUE AUG 12 2025
KEY MESSAGES
- SCATTERED STORMS WILL CONTINUE TO POSE A THREAT FOR GUSTY WINDS
AND LOCALLY HEAVY RAINFALL/MINOR FLOODING THROUGH TONIGHT.
- ADDITIONAL THUNDERSTORMS WILL BE POSSIBLE DURING THE DAY ON
WEDNESDAY.
- SLIGHTLY COOLER AND DRIER AIR FOR WEDNESDAY NIGHT INTO THURSDAY
NIGHT.
- ABOVE NORMAL TEMPERATURES RETURNS LATE WEEK. HEAT INDEX VALUES
NEAR OR EXCEED 100 LIKELY THIS WEEKEND.
SHORT TERM (THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 358 PM EDT TUE AUG 12 2025
THUNDERSTORMS ARE ONGOING AS OF 3PM OVER CENTRAL INDIANA IN AN
ENVIRONMENT CHARACTERIZED BY WEAK TO MODEST LAPSE RATES (5-6 C/KM)
WITH CAPE BETWEEN 1500-2500 J/KG. ACARS SOUNDINGS OUT OF IND SHOW
ROUGHLY 20-30 KNOTS OF SHEAR WHICH HAS ALLOWED FOR SOME UPDRAFT/COLD
POOL BALANCE. AS SUCH, STORMS HAVE BECOME LOOSELY ORGANIZED INTO
CLUSTERS AND LINE SEGMENTS PROPAGATING NORTHEASTWARD WITH OCCASIONAL
DOWNBURST SIGNATURES. A DISTINCT DRY LAYER AROUND 500MB IS NOTED IN
THE SOUNDING, SUPPORTING ROUGHLY 900 J/KG DCAPE. THIS SUGGESTS THAT
A DOWNBURST THREAT MAY CONTINUE THROUGH THE AFTERNOON HOURS.
ONGOING STORM ACTIVITY SHOULD CONTINUE TO PUSH EASTWARD WITH TIME AS
STORMS ORGANIZE ALONG A DEVELOPING COLD POOL. OCCASIONAL BOWING
SEGMENTS ARE POSSIBLE ESPECIALLY WHERE BRIEF REAR INFLOW JETS CAN
FORM. SHEAR IS WEAK ENOUGH THAT COLD POOL SHEAR BALANCE DOESN'T
SUSTAIN DUE TO STRONGER STORMS LEADING TO STRONGER COLD POOLS.
THEREFORE, STRONGER STORMS SHOULD HAVE THE TENDENCY TO SURGE
AND BECOME OUTFLOW DOMINANT.
HIGH-RES CAM GUIDANCE SHOWS RENEWED ACTIVITY OVER ILLINOIS,
ASSOCIATED WITH A COLD FRONT, TO MOVE EASTWARD AS WELL. BEST TIME OF
ARRIVAL FOR CENTRAL INDIANA WOULD BE AFTER ABOUT 00Z, WITH STORMS
PROPAGATING THROUGH INDIANA DURING THE NIGHT. GIVEN THE
ENVIRONMENT DESCRIBED ABOVE, DEVELOPMENT INTO A BROKEN LINE WITH
BOWING SEGMENTS APPEARS MOST LIKELY. DAMAGING WINDS ARE THE PRIMARY
HAZARD THROUGH TONIGHT, WITH SOME DOWNBURSTS POSSIBLE EARLY WITH
INITIAL DEVELOPMENT. THE WIND THREAT SHOULD THEN EVOLVE TO FOCUS
MORE ON BOWING SEGMENTS / REAR INFLOW JETS. STORMS SHOULD EXIT THE
AREA BY 06Z OR SO.
OUR SECONDARY THREAT IS LOCALIZED FLOODING. ACARS SOUNDINGS ALSO
SHOW A DEEP WARM CLOUD LAYER SUPPORTIVE OF EFFICIENT WARM RAIN
PROCESSES. STORMS MAY HAVE A TENDENCY TO BACK-BUILD ALONG RESIDUAL
OUTFLOW BOUNDARIES, ESPECIALLY ALONG THE SOUTHERN SIDE OF EXITING
COLD POOLS AND WHERE SHEAR IS MORE PARALLEL TO THE BOUNDARY. GIVEN
EFFICIENT RATES, ANY TRAINING OR SLOW-MOVING STORMS MAY BE ABLE TO
QUICKLY PRODUCE HEAVY RAINFALL CAPABLE OF LOCALIZED FLOODING OR
FLASH FLOODING.
AFTER STORMS DEPART OVERNIGHT, WE'LL BE LEFT WITH A GENERALLY QUIET
ATMOSPHERE WITH OCCASIONAL FOG DEVELOPMENT. FOG SHOULD BE FAIRLY
PATCHY IN NATURE BUT LOCALLY DENSE FOG CANNOT BE RULED OUT. FOG WILL
BE MOST LIKELY IN TYPICALLY FOG-PRONE LOCATIONS AND IN AREAS THAT
SAW RAINFALL TODAY.
ON WEDNESDAY, A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE AS THE
COLD FRONT ITSELF PUSHES THROUGH. ACTIVITY SHOULD BE WEAK, HOWEVER,
DUE TO POOR LAPSE RATES AND GREATER AMOUNTS OF DRY AIR IN THE MID TO
UPPER-LEVELS. BY EVENING, THE COLD FRONT SHOULD BE MOVING THROUGH
WITH LITTLE IN THE WAY OF TEMPERATURE CHANGE. THE MOST NOTICEABLE
CHANGE MAY BE LOWER DEW POINTS AND HUMIDITY LEVELS COMPARED TO
PREVIOUS DAYS.
LONG TERM (WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 358 PM EDT TUE AUG 12 2025
WITH A PROGRESSIVE MID LEVEL SHORTWAVE TROUGH, THE ASSOCIATED
FRONTAL BOUNDARY LOOKS TO PUSH JUST SOUTHEAST OF THE FORECAST AREA
BY WEDNESDAY NIGHT IN LINE WITH NAM MODEL, SO HAVE TRIMMED NBM POPS
FROM THE FAR EAST PART OF THE FORECAST AREA.
AS A DEEPENING UPPER TROUGH APPROACHES THE WEST COAST, A SEASONABLY
STRONG UPPER RIDGE CENTERED OVER THE FOUR CORNERS WILL SHIFT EAST
INTO THE PLAINS LATE WEEK AND INTO THE MS VALLEY BY SATURDAY. AS A
RESULT, HIGH TEMPERATURES WILL CLIMB TO WELL ABOVE NORMAL BY THE
WEEKEND BETWEEN 90-95F. WITH SURFACE DEWPOINTS RANGING FROM
70-75F, EXPECTATION IS FOR ANOTHER ROUND OF HEAT INDICES NEAR TO
JUST ABOVE 100F, APPROACHING ADVISORY CRITERIA.
AFTER SATURDAY THE PATTERN BECOMES GRADUALLY MORE UNSETTLED. ONCE
AGAIN CENTRAL INDIANA WILL BE ON THE TRANSITION ZONE SUNDAY/MONDAY
WITH VERY SLIGHT CHANCES OF RIDGE RIDER PRECIP EVENTS COMING FROM
THE NORTHERN PLAINS /ORIGINATING FROM MONSOON REGIONS OF THE DESERT
SW/. HAVE KEPT THE FORECAST DRY FOR NOW ON SUNDAY WITH SLIGHT CHANCE
POPS FOR MONDAY IN LINE WITH NBM GIVEN LACK OF CONFIDENCE IN TIMING
OR GREATER COVERAGE AND SOUTHWARD EXTENT TO THE RIDGE AXIS. BEYOND
MONDAY A MORE STOUT SHORTWAVE TROUGH, LIKELY CONVECTIVELY
ENHANCED/GENERATED OVER THE NORTHERN PLAINS, SHOWN BY BOTH THE GFS
AND EURO DETERMINISTIC MODELS WILL DEVELOP TOWARDS CENTRAL INDIANA.
SUBTLE INFLUENCES FROM THE EVENTUAL TRACK OF HURRICANE ERIN COULD
ENHANCE OF DIMINISH THE THREAT FOR HEAVY PRECIP WITH THIS SYSTEM BY
HELPING SLOW DOWN OR ACCELERATE THE ASSOCIATED COLD FRONT.
AVIATION (00Z TAF ISSUANCE)
ISSUED AT 650 PM EDT TUE AUG 12 2025
IMPACTS:
- SCATTERED THUNDERSTORMS REMAINING NEAR THE TAF SITES THROUGH AT
LEAST 03Z.
- THUNDERSTORMS THAT STRIKE A TAF SITE MAY PRODUCE BRIEF MVFR/IFR
CONDITIONS.
- PATCHY MVFR FOG POSSIBLE OVERNIGHT.
DISCUSSION:
SCATTERED DIURNAL CONVECTION AIDED BY A PASSING UPPER TROUGH WILL
ALLOW FOR CONTINUED STORMS AND EASTWARD PROGRESSION THROUGH 03Z-05Z.
CURRENT RADAR SHOWS SCATTERED STORMS OVER WEST CENTRAL INDIANA AND
ADDITIONAL STORMS OVER EAST CENTRAL ILLINOIS. UPDRAFTS WITH THESE
STORMS ARE RELATIVELY SHORT LIVED BUT CAPABLE OF PRODUCING VERY
HEAVY RAIN AND IFR VISIBILITY. HOWEVER WITH LIMITED SHEAR AND MANY
OUTFLOWS PRESENT FROM EARLIER CONVECTION, SUSTAINABLE LONGER TERM
ORGANIZED CONVECTION IS NOT EXPECTED. HRRR DOES ALLOW FOR SHOWERS TO
CONTINUE TO LINGER NEAR THE TAF SITES THROUGH 03Z, BUT COVERAGE IS
SHOWN TO DIMINISH AFTER THAT AS HEATING IS LOST. THUS HAVE USED A
VCTS MENTION FOR MANY OF THE LOCATIONS THROUGH 03Z.
CLEARING SKIES AND LIGHTER WINDS ARE EXPECTED OVERNIGHT. THIS ALONG
WITH EARLIER RAINFALL MAY RESULT IN SCATTERED MVFR FOG DEVELOPMENT.
FOG WILL BURN OFF ON WEDNESDAY MORNING AS HEATING RETURNS AND
CONDITIONS WILL RETURN TO VFR.
VERY ISOLATED, LOW CONFIDENCE THUNDERSTORMS WILL BE POSSIBLE ON
WEDNESDAY AFTERNOON.
IND WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...ECKHOFF
LONG TERM...CROSBIE
AVIATION...PUMA
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