457
FXUS63 KIND 111839
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
239 PM EDT THU SEP 11 2025
KEY MESSAGES
- GRADUALLY CLIMBING TEMPERATURES THROUGH THE WEEK WITH NEAR 90
DEGREE HIGHS BY SATURDAY
- DRY WEATHER OUTSIDE OF LOW RAIN CHANCES SATURDAY NIGHT WILL
LIKELY LEAD TO CONTINUED EXPANSION OF DROUGHT CONDITIONS INTO
NEXT WEEK
- DRY FUELS AND LOW RH VALUES EACH AFTERNOON MAY LEAD TO AN ELEVATED
FIRE THREAT, BUT LIGHT WINDS SHOULD LIMIT THE OVERALL THREAT
SHORT TERM (THIS EVENING THROUGH FRIDAY)
ISSUED AT 238 PM EDT THU SEP 11 2025
BROAD HIGH PRESSURE ACROSS THE OHIO VALLEY WILL PERSIST THROUGH THE
SHORT TERM, WITH WEAK FLOW SWITCHING FROM EASTERLY TO SOUTHERLY OVER
THE NEXT 24 HOURS. MODEL SOUNDINGS SHOW NEAR SATURATION AT THE TOP
OF THE BOUNDARY LAYER WEDNESDAY AFTERNOON WHICH SHOULD ALLOW FOR A
SPARSE DIURNAL CU FIELD. WEAK FLOW WILL LIMIT MIXING SOME, BUT
EXPECTED MOSTLY CLEAR SKIES AND A DRY NEAR SURFACE LAYER TO ALLOW
FOR SOME PBL MIXING AND THEREFOR A NEARLY DRY ADIABATIC NEAR SURFACE
LAYER. THIS SHOULD ALLOW FOR MIN RH VALUES TO DROP INTO THE 25 TO 35
PERCENT RANGE OVER MOST OF CENTRAL INDIANA CONTINUING SOME CONCERN
FOR ELEVATED FIRE WEATHER DANGER (COVERED MORE IN THE FIRE WEATHER
SECTION). SMOKE ALOFT FROM FIRES OUT WEST WILL CREATE SLIGHTLY HAZY
SKIES, BUT DON'T EXPECT TOO MANY IMPACTS BEYOND THAT AS THE SMOKE
WILL REMAIN WELL ALOFT.
EASTERLY FLOW DOWNSTREAM OF BROAD LOW LEVEL HIGH PRESSURE WILL
LIKELY KEEP TEMPERATURES FROM EXCEEDING GUIDANCE THIS AFTERNOON,
TYPICALLY FOUND IN THESE EARLY FALL, DRY AIRMASSES. THIS WILL SHIFT
TO SOUTHERLY TOMORROW, PUSHING TEMPERATURES SLIGHTLY HIGHER, WITH
CURRENT FORECAST HIGHS IN THE MID TO UPPER 80S.
LONG TERM (FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 238 PM EDT THU SEP 11 2025
THE PRIMARY FOCUS THROUGH THE LONG TERM PERIOD WILL BE ON THE
INCREASING HEAT AND POTENTIAL FOR EXACERBATING DROUGHT CONDITIONS.
THE UPPER LEVEL RIDGE WILL CONTINUE BUILDING INTO THE CENTRAL US
FRIDAY INTO THE WEEKEND WITH LIGHT AND CALM WINDS NEAR THE SURFACE.
DESPITE BEING WITH 84 HOURS, FORECAST CONFIDENCE REMAINS LOW FOR
PORTIONS OF THIS WEEKENDS WEATHER. THE GENERAL SYNOPTIC PATTERN
IS CONSISTENT ACROSS ENSEMBLE OUTPUT, BUT THE VARIANCE IS
ASSOCIATED WITH THE POTENTIAL FOR FOR RIDGE-RIDING DIABATIC
SHORTWAVES. THE MAIN DIFFERENCE IS ON WHERE THE BULK OF THE
850-700MB WAA WILL OCCUR FRIDAY THROUGH SATURDAY, OF WHICH WILL
HAVE A DIRECT CORRELATION ON WHERE ANY SHORTWAVE RIDGE DEVELOPS
AND IF THE SUBGEOSTROPHIC FLOW BENEATH THE PASSING WAVE OVER
EASTERN CANADA WILL PASS THROUGH THE GREAT LAKES REGION. WHILE
THERE WILL BE SOME MOISTURE RETURN INTO THE OHIO VALLEY BY
SATURDAY, INSTABILITY VALUES WILL BE FAIRLY MEAGER. THAT SAID, IN
THE CASE OF A STRENGTHENING JET ACROSS THE UPPER MIDWEST, INCREASE
SHEAR COULD CREATE A FAVORABLE ENVIRONMENT FOR THUNDERSTORM
ORGANIZATION. AT THIS POINT, CONFIDENCE IS FAIRLY HIGH IN AT LEAST
SOME THUNDERSTORMS ACROSS THE GREAT LAKES REGION, BUT CONFIDENCE
IS LOW THAT ANY REACH AS FAR SOUTH AS CENTRAL INDIANA. BENEATH THE
RIDGE, MUCH DIFFERENT CONDITIONS ARE EXPECTED, WITH WEAK
TROPOSPHERIC WINDS AND BUILDING PBL TEMPERATURES. HIGHS WILL
LIKELY BE IN THE 90S WITH AFTERNOON RH VALUES EXPECTED TO FALL
INTO THE UPPER 20S.
THE LACK OF CONFIDENCE IN SATURDAY TO EARLY SUNDAY'S FORECAST
PROVIDES CASCADING IMPACTS FOR THE REST OF THE LONG TERM, AND
THEREFOR FORECAST CONFIDENCE CONTINUES TO DECREASE SUNDAY INTO
MONDAY. GENERAL CONSENSUS IN THE OVERALL AIRMASS WILL REMAIN WARMER
THAN NORMAL, WITH THE POTENTIAL CAVEAT OF LINGERING UPPER LEVEL
CLOUD COVER. CURRENTLY LEANING TOWARDS A MORE PERSISTENT PATTERN
WITH THE UPPER LEVEL RIDGE HELPING TO PUSH THE AFOREMENTIONED LOW
PRESSURE FURTHER EAST INTO THE NORTHEASTERN STATES, BUT WILL HAVE TO
CONTINUE TO MONITOR FORECAST TRENDS.
OUTSIDE OF LOCATIONS THAT SEE ANY SPOTTY PRECIPITATION, IT'LL BE
ANOTHER DRY 7 DAYS FOR MUCH OF CENTRAL INDIANA WHICH PUTS MANY
LOCATIONS AS SEEING LITTLE TO NO RAIN FOR THE LAST 3 WEEKS. THIS
COMBINED WITH THE STRETCH OF MUCH ABOVE NORMAL WEATHER IS EXPECTED
TO LEAD TO THE EXPANSION OF DROUGHT CONDITIONS ACROSS THE STATE.
DAILY MINIMUM RH VALUES WILL AGAIN FALL TO BETWEEN 25 AND 35 PERCENT
THROUGH MUCH OF NEXT WEEK WHICH COULD CAUSE ADDITIONAL FIRE WEATHER
CONCERNS.
AVIATION (18Z TAF ISSUANCE)
ISSUED AT 1250 PM EDT THU SEP 11 2025
IMPACTS: NONE
DISCUSSION:
VFR CONDITIONS ARE EXPECTED THIS TAF PERIOD.
STRONG SURFACE HIGH PRESSURE OVER ONTARIO AND QUEBEC, SUPPORTED BY
STRONG RIDGING AND SUBSIDENCE ALOFT, WILL SAG SOUTHWEST INTO THE
OHIO VALLEY DURING THIS TAF PERIOD. THIS WILL LEAD TO MOSTLY CLEAR
SKIES AND LIGHT WINDS THROUGH THE PERIOD.
SOME PATCHY FOG NEAR 10Z-12Z WILL BE POSSIBLE, AS LIGHT WINDS AND
LOW DEW POINT DEPRESSIONS WILL BE PRESENT. HOWEVER CONFIDENCE ON
THAT REMAINS TOO LOW AT THE MOMENT TO INCLUDE A MENTION OTHER THAN
HERE.
FIRE WEATHER
ISSUED AT 238 PM EDT THU SEP 11 2025
THE LACK OF ANY SIGNIFICANT RAINFALL SINCE LATE AUGUST HAS RESULTED
IN ABNORMALLY DRY AND MINOR DROUGHT CONDITIONS TO DEVELOP ACROSS
INDIANA. WITH LITTLE TO NO RAIN IN THE FORECAST FOR THE NEXT 7 DAYS,
CONFIDENCE IS INCREASING IN AN SLIGHTLY ELEVATED FIRE WEATHER DANGER
EACH AFTERNOON AS DAILY MIN RH VALUES FALL INTO THE 25 TO 35% RANGE.
THE MAJOR FACTOR KEEPING THE FIRE WEATHER THREAT LOWER IS THE LACK
OF WIND. DESPITE DEEP MIXING, VERY WEAK LOW LEVEL FLOW SHOULD KEEP
WINDS UNDER 10 MPH THROUGH THE PERIOD. IF NO APPRECIABLE RAINFALL IS
OBSERVED THIS WEEKEND, THE FIRE WEATHER THREAT MAY CONTINUE TO
INCREASE AND PERSIST INTO MID MONTH. WILL CONTINUE TO MONITOR THE
EXTENDED FORECAST FOR INCREASING FIRE WEATHER CONCERNS.
IND WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...UPDIKE
LONG TERM...UPDIKE
AVIATION...PUMA
FIRE WEATHER...WHITE
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