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  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab IN Page Main Text Page