249
FXUS63 KIND 181041
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
641 AM EDT FRI SEP 18 2020
UPDATE
THE AVIATION SECTION HAS BEEN UPDATED BELOW.
SYNOPSIS
ISSUED AT 308 AM EDT FRI SEP 18 2020
DRY WEATHER WILL CONTINUE THOUGH THE UPCOMING SEVEN DAY AS THE
REGION REMAINS UNDER THE INFLUENCE OF STRONG HIGH PRESSURE. AFTER A
TASTE OF FALL THIS WEEKEND WITH COOL DAYS AND CHILLY NIGHTS...
TEMPERATURES WILL WARM BACK TO SEASONABLE LEVELS BY NEXT WEEK.
NEAR TERM /TODAY/
ISSUED AT 308 AM EDT FRI SEP 18 2020
SKIES WERE MAINLY CLEAR EARLY THIS MORNING WITH HIGH PRESSURE
BUILDING IN FROM THE NORTH. A FEW POCKETS OF STRATOCU WERE DRIFTING
SOUTHEAST ACROSS PORTIONS OF THE FORECAST AREA. AUTUMN FEEL TO THE
AIR WITH TEMPERATURES GENERALLY IN THE 50S AS OF 07Z.
LARGE HIGH PRESSURE OVER THE UPPER MIDWEST WILL GRADUALLY EXPAND
INTO THE OHIO VALLEY THROUGH THE COURSE OF THE DAY...MAINTAINING THE
DRY CONDITIONS OF THE LAST WEEK OR TWO WHILE BRINGING THE INITIAL
AUTUMN PREVIEW OF THE YEAR AS DRIER AND MUCH COOLER AIR ADVECTS INTO
THE REGION. THERE IS A SHORT WINDOW THROUGH THE FIRST HALF OF THE
AFTERNOON WHERE A FEW CU ARE POSSIBLE WITH THE STRENGTHENING COLD
ADVECTION OVER CENTRAL INDIANA...OTHERWISE EXPECT SUNNY SKIES.
NORTH-NORTHEAST WINDS WILL BECOME GUSTY AGAIN BY MIDDAY THROUGH THE
AFTERNOON WITH A TIGHT SURFACE PRESSURE GRADIENT ACROSS THE AREA.
MODEL SOUNDINGS AND RH PROGS SHOW PROGRESSIVELY DEEPER SUBSIDENCE
SPREADING SOUTH INTO THE AREA BY LATE DAY WHICH WILL AID IN FLUSHING
OUT ANY CU THAT DEVELOPS EARLIER IN THE AFTERNOON.
TEMPS...TODAY WILL BE THE COOLEST DAY FOR THE REGION IN ABOUT 4
MONTHS WITH MOST OF THE FORECAST AREA REMAINING IN THE 60S. LOW
LEVEL THERMALS ARE SUPPORTIVE OF RUNNING NEAR THE MODEL BLEND WITH
HIGHS IN THE MID AND UPPER 60S.
SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/
ISSUED AT 308 AM EDT FRI SEP 18 2020
FORECAST CHALLENGES ARE MINIMAL THROUGH THE WEEKEND WITH THE PRIMARY
FOCUS ON TEMPERATURES AND POTENTIALLY SOME PATCHY FROST BOTH
SATURDAY AND SUNDAY MORNINGS FOR THE FIRST TIME SINCE THE SPRING.
THE AFOREMENTIONED HIGH PRESSURE WILL SERVE AS THE DOMINANT WEATHER
FEATURE ALL WEEKEND AS IT DRIFTS ACROSS THE GREAT LAKES AND NEW
ENGLAND. THE EXPANSION OF THE UPPER LEVEL TROUGH OVER MUCH OF THE
EASTERN PART OF THE COUNTRY WILL MAINTAIN A COOL AND DRY E/NE FLOW
THROUGH SATURDAY NIGHT BEFORE RETREATING AWAY TO THE NORTHEAST FOR
THE SECOND HALF OF THE WEEKEND. RISING HEIGHTS ALOFT BY SUNDAY WITH
THE APPROACH OF AN UPPER RIDGE WILL START A WARMING TREND THAT WILL
LAST THROUGH MUCH OF NEXT WEEK.
MODEL SOUNDINGS AND RH PROGS FURTHER STRENGTHEN DEEP SUBSIDENCE OVER
THE WEEKEND WITH THE EXPECTATION OF CLEAR SKIES AND A DRY AIRMASS
THROUGHOUT THE PERIOD. WINDS WILL VEER TO AN E/SE DIRECTION BY
SUNDAY AS THE CENTER OF THE HIGH MOVES INTO NEW ENGLAND. THE VERY
DRY SEPTEMBER IS SET TO CONTINUE WITH NO SIGN OF ANY SUBSTANTIAL
THREAT FOR RAIN ON THE HORIZON.
TEMPS...LOW LEVEL THERMALS MATCH UP WITH THE MODEL BLEND RELATIVELY
WELL FOR HIGHS SATURDAY AND SUNDAY. MOST OF THE FORECAST AREA WILL
AGAIN TOP OUT IN THE 60S SATURDAY WITH RECOVERY INTO THE LOW TO MID
70S SUNDAY. THE CHALLENGES EXIST WITH LOWS TONIGHT AND SATURDAY
NIGHT AS GUIDANCE CONTINUES TO COME IN COOLER WHICH MAY BE A RESULT
OF THE MODEL DATA PICKING UP ON THE DRY GROUND FEEDBACK ACROSS
CENTRAL INDIANA. EXPECT A DECENT TEMP GRADIENT BETWEEN RURAL AND
URBAN AREAS WITH THE POTENTIAL FOR UPPER 30S (AND MAYBE EVEN A FEW
MID 30S) IN SOME OF THE NORMAL COOL SPOTS TONIGHT AND SATURDAY NIGHT
FOCUSED OVER THE NORTHERN HALF OF THE FORECAST AREA. PATCHY FROST IS
CERTAINLY PLAUSIBLE BUT CURRENT THINKING IS THAT WILL BE CONFINED TO
SHELTERED AREAS IN LOCALIZED SPOTS WHERE TEMPS CAN DROP INTO THE 36-
38 RANGE...ESPECIALLY WITH HINTS THAT THE BOUNDARY LAYER MAY NOT
FULLY DECOUPLE EITHER NIGHT.
LONG TERM /MONDAY THROUGH THURSDAY/
ISSUED AT 234 AM EDT FRI SEP 18 2020
ENSEMBLES INDICATES AN UPPER RIDGE, INITIALLY OVER THE OHIO
VALLEY, IS EXPECTED TO RETROGRADE BACK INTO THE ROCKIES BY NEXT
THURSDAY AS LONG WAVE TROUGHING DEVELOPS OVER THE EAST COAST.
ENSEMBLES INDICATE LITTLE THREAT FOR PRECIPITATION DURING THIS
PERIOD, WITH THE GULF OF MEXICO MOISTURE SOURCE CUTOFF.
PRECIPITATION THREAT ASSOCIATED WITH SHORT WAVE ENERGY MOVING
THROUGH THE NORTHERN GREAT LAKES NEXT THURSDAY LOOKS TO STAY OFF
TO THE NORTHEAST OF THE LOCAL AREA AT THIS TIME.
WILL CONTINUE WITH A DRY EXTENDED.
AVIATION /DISCUSSION FOR THE 181200Z TAFS/
ISSUED AT 639 AM EDT FRI SEP 18 2020
NO SIGNIFICANT CLOUD COVER AND UNRESTRICTED VISIBILITY EXPECTED AT
THE TERMINALS TODAY.
SURFACE WINDS 020-040 DEGREES AT 7-10 KTS THIS MORNING. OCCASIONAL
TO FREQUENT SURFACE GUSTS AROUND 18 KTS BY MIDDAY AND ON INTO THE
AFTERNOON HOURS.
IND WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...RYAN
NEAR TERM...RYAN
SHORT TERM...RYAN
LONG TERM....JAS
AVIATION...JAS
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