261
FXUS63 KIND 201826
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
226 PM EDT MON SEP 20 2021
SHORT TERM
(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 226 PM EDT MON SEP 20 2021
THE CHANNEL OF GREATEST ISENTROPIC LIFT ASSOCIATED WITH A WEAK LLJ
IS MOVING OFF TO THE EAST,ALONG WITH AN AREA OF WIDESPREAD SHOWERS.
A WEAK SURFACE LOW OVER CENTRAL ILLINOIS HAS CONTINUED TO MOVE
NORTHWARD WITHIN THE SOUTHERLY FLOW. EAST OF THIS LOW, A REGION OF
LOCALIZED LIFT HAS HELPED INITIATE SCATTERED SHOWERS AND A FEW
EMBEDDED THUNDERSTORMS. AS THE CLOUD LAYER THINS AND BECOMES MORE
BROKEN, SURFACE BASED INSTABILITY SHOULD RISE SLIGHTLY, PEAKING
BETWEEN 1000 AND 1500 J/KG OF SBCAPE LATER THIS AFTERNOON. THIS
COULD ALLOW FOR A FEW MORE EMBEDDED THUNDERSTORMS OVER WEST CENTRAL
INDIANA LATE THIS AFTERNOON AND EVENING. WIND SHEAR REMAINS
EXTREMELY WEAK WITH THE SUBTLE LLJ OFF TO THE EAST. THIS SHOULD
INHIBIT UPDRAFT GROWTH, KEEPING ANY THUNDERSTORMS MUNDANE. PWAT
VALUES NEAR 2", AND A FAIRLY SATURATED ATMOSPHERIC PROFILE INDICATE
THE POSSIBILITY OF RAIN BEING HEAVY AT TIMES. THIS COULD LEAD TO
MINOR LOCALIZED FLOODING.
TEMPERATURES WILL CONTINUE TO RISE OVER THE NEXT FEW HOURS AS THE
CLOUD LAYER THINS OUT TO THE WEST. OVER EASTERN CENTRAL INDIANA, A
THICK CLOUD LAYER REMAINS, WHICH WILL INHIBIT SURFACE WARMING;
RESULTING IN A GRADUAL TEMPERATURE GRADIENT WITH HIGHS RANGING FROM
LOW 80S TO THE WEST AND MID 70S TO THE EAST. EXPECTATIONS ARE FOR
THERE TO BE LULL IN PRECIPITATION OVERNIGHT AS THE BOUNDARY LAYER
STABILIZES AND A NARROW CORRIDOR OF DRIER LOW LEVEL AIR MOVES IN.
CLOUD COVER SHOULD STILL REMAIN FAIRLY CONSISTENT, WITH A FEW
BREAKS.
AN AMPLIFIED TROUGH CURRENTLY OVER THE PLAINS WILL CONTINUE TO
PROGRESS EASTWARD THROUGH TONIGHT IS THE NEXT SOURCE OF
PRECIPITATION. THIS TROUGH HAS A DEEP POOL OF COLD AIR WITHIN IT,
RESULTING IS A STRONG UPPER LEVEL JET. CURRENTLY, A SURFACE LOW IS
CONTINUING TO DEEPEN OVER THE NORTHERN GREAT LAKES, FURTHER
ADVANCING THIS COLD AIR MASS INTO THE MIDWEST. THE SOUTHERLY PUSH OF
COLD AIR HAS CREATED AN INTENSE COLD FRONT, OF WHICH WILL APPROACH
INDIANA SOMETIME TOMORROW MORNING.
AS THE FRONT MOVES SOUTHWARD, INTO THE OHIO VALLEY, IT WILL BECOME
FARTHER DISPLACED FROM THE OCCLUDING LOW LEVEL CYCLONE, WEAKENING
THE FRONTOGENETICAL FORCING AND SLOWING ITS PROGRESSION. THIS HAS
CREATED SOME UNCERTAINTY ON TIMING OF PRECIPITATION TOMORROW, AS THE
FRONT WILL BE THE PRIMARY SOURCE OF LIFT. GENERAL CONSENSUS AMONG
ENSEMBLES HAS FRONT PASSING THROUGH CENTRAL INDIANA EARLY TOMORROW
AFTERNOON. FOR THIS REASON, HIGHEST POPS HAVE BEEN FORECASTED FOR
AROUND THIS TIME, WITH AN INCREASE IN CHANCES FROM WEST TO EAST
THROUGHOUT THE DAY. STRONG FORCING ALONG THE FRONT IN COMBINATION
WITH HIGHER THAN NORMAL PWAT VALUES COULD RESULT IN PROLONGED
DOWNPOURS. THIS, ALONG WITH AN ALREADY SATURATED GROUND FROM THE
PREVIOUS RAINFALL, WILL LEAD TO A SLIGHT RISK OF FLASH FLOODING.
WITH DEEP CLOUD COVER ALONG THE BOUNDARY AND WITHIN THE CYCLONIC
FLOW, TEMPERATURES WILL STRUGGLE TO INCREASE THROUGHOUT THE DAY.
CURRENT EXPECTATIONS ARE FOR HIGHS IN THE MID 70S, WITH A SLIGHT
DROP OFF FOLLOWING FRONTAL PASSAGE. WITH UNCERTAINTY AS TO TIMING OF
FRONTAL PASSAGE, HOURLY TEMPS HAVE BEEN KEPT FAIRLY DIURNAL, ALTHOUGH
THIS WILL NOT BE THE CASE FOR LOCATIONS WEST OF THE FRONT. MOST
LOCATIONS SHOULD BE WEST OF THE FRONT BY TOMORROW NIGHT WITH
WIDESPREAD LOWS IN THE MID 50S AND SCATTERED SHOWERS IN THE WRAP
AROUND MOISTURE.
LONG TERM
(WEDNESDAY THROUGH MONDAY)
ISSUED AT 226 PM EDT MON SEP 20 2021
WEDNESDAY THROUGH THURSDAY...
MODELS DISAGREEING ONCE AGAIN REGARDING THE POSITION AND STRENGTH OF
AN UPPER TROUGH OR CUT-OFF LOW EXPECTED IN THE OHIO VALLEY AND
SOUTHER GREAT LAKES ON WEDNESDAY. THE GFS IS FOLLOWING MORE OF THE
UPPER TROUGH TYPE PATTERN...WHILE THE ECMWF SHOWS THE DEEPER CUT-OFF
LOW PASSING THROUGH SOUTHERN INDIANA. DEEP MOISTURE DOES NOT APPEAR
AVAILABLE TO THE SYSTEM AS THE EARLIER COLD FRONT WILL HAVE SWEPT
THAT HIGH DEW POINT AIR EAST. NONETHELESS...SOME MID LEVEL
SATURATION APPEARS AVAILABLE WITHIN THE FORECAST SOUNDINGS WITH
PWATS NEAR 0.8 INCHES ON WEDNESDAY. THUS GIVEN THE UPPER DYNAMICS
WILL TREND TOWARD CLOUDS AND LIKELY POPS FOR SOME VERY LIGHT
RAINFALL POSSIBLE THROUGH THE DAY AND INTO THE EVENING.
THE UPPER LOW/TROUGH BEGINS TO PUSH FARTHER NORTH ON
THURSDAY...TAKING ANY CLOUDS AND LIGHT RAIN/DRIZZLE WITH IT.
MEANWHILE AT THE SURFACE...A LARGE HIGH PRESSURE SYSTEM OVER THE
PLAINS WILL BEGIN TO BUILD EASTWARD INTO THE OHIO VALLEY. THUS MAY
INCLUDE SOME SMALL POPS ON THURSDAY MORNING...BUT TREND TOWARD A DRY
FORECAST AS THE DAY PROGRESSES.
FRIDAY THROUGH MONDAY...
DRY AND COOL WEATHER IS EXPECTED TO RETURN TO THE AREA FOR MUCH OF
THIS PERIOD. THE BEST CHANCE FOR ANY PRECIP WILL BE ON FRIDAY NIGHT
AND EARLY SATURDAY.
SURFACE HIGH PRESSURE WILL BE IN PLACE ACROSS INDIANA ON FRIDAY.
ALOFT INDIANA WILL BE CAUGHT BETWEEN THE PREVIOUS UPPER LOW DEPARTING
AND AN APPROACHING SHORT WAVE DROPPING OUT OF THE NORTHERN PLAINS.
FORECAST SOUNDINGS REMAIN DRY. THUS DRY WEATHER WILL BE EXPECTED ON
FRIDAY AND EARLY FRIDAY EVENING.
THE PREVIOUSLY MENTIONED APPROACHING UPPER TROUGH IS SUGGESTED TO
DEEPEN AND PUSH TOWARD AND ACROSS CENTRAL INDIANA LATE FRIDAY NIGHT
AND INTO SATURDAY. FORECAST SOUNDINGS AT THIS TIME ARE SUGGESTING A
PERIOD OF DEEP SATURATION...ALTHOUGH...GULF MOISTURE DOES NOT APPEAR
PRESENT. WITHIN THE LOWER LEVELS...AN ACCOMPANYING WEAK COLD FRONT IS
SHOWN TO PUSH ACROSS THE STATE. THUS...CHANCES FOR RAIN ON
FRIDAY NIGHT AND EARLY SATURDAY APPEAR REASONABLE.
DRY WEATHER SHOULD RETURN FOR SUNDAY AND MONDAY AS A SURFACE HIGH
PRESSURE SYSTEM IS EXPECTED TO PUSH ACROSS THE AREA AND LITTLE IN
THE WAY OF FORCING DYNAMICS IS EXPECTED TO PASS WITHIN THE NW FLOW
ALOFT. AGAIN...WITH COOLER CANADIAN AIR IN PLACE LOOK FOR MORE
SEASONABLE TEMPERATURES NEAR EXPECTED NORMALS.
AVIATION
(18Z TAF ISSUANCE)
ISSUED AT 136 PM EDT MON SEP 20 2021
IMPACTS:
- MVFR TO IFR CONDITIONS THROUGH THIS EVENING, WITH SCATTERED
SHOWERS.
- A FEW EMBEDDED THUNDERSTORMS WILL ALSO BE POSSIBLE THIS AFTERNOON
- WINDS 160-190 DEGREES SUSTAINED FROM 10 TO 13 KTS. GUSTS UP TO 25
KTS POSSIBLE AT ALL SITES THIS AFTERNOON.
DISCUSSION: MAINLY POOR FLYING CONDITIONS OF MVFR TO IFR EXPECTED
THROUGHOUT THIS EVENING WITH MULTIPLE ROUNDS OF RAIN AND POSSIBLE
THUNDERSTORMS. A BRIEF BREAK IN RAIN LATE THIS EVENING INTO TONIGHT
SHOULD PROVIDE AN EXTENDED PERIOD OF VFR. TOMORROW MORNING, A FRONT
IS EXPECTED TO BRING A LINE OF SHOWERS AND STORMS, ONCE AGAIN
DETERIORATING CONDITIONS. RAIN COULD BE HEAVY AT TIMES TOMORROW,
LOWERING VISIBILITIES, BUT CONFIDENCE IS TOO LOW ON TIMING TO
INCLUDE AT THIS TIME. WINDS WILL GENERALLY BE OUT OF THE S TO SE
FROM 10-13 KTS, WITH GUSTS AROUND 25 KTS THIS AFTERNOON. GUSTS
SHOULD DIE DOWN OVERNIGHT, BUT WINDS ARE EXPECTED TO REMAIN
CONSISTENT AT AROUND 8-10KTS.
IND WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...UPDIKE
LONG TERM...PUMA
AVIATION...UPDIKE
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