519
FXUS61 KPHI 182032
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
432 PM EDT THU JUL 18 2019
SYNOPSIS
A WEAK WAVE OF LOW PRESSURE WILL DRIFT OUT TO SEA BY FRIDAY MORNING.
A STRONG RIDGE OF HIGH PRESSURE WILL BUILD OVER THE REGION FROM
FRIDAY THROUGH THE WEEKEND. AN EXTENDED PERIOD OF EXCESSIVE HEAT IS
EXPECTED. A STRONG AND SLOW MOVING COLD FRONT WILL APPROACH BY
MONDAY. THIS FRONT WILL LIKELY MOVE OFFSHORE BY TUESDAY. HIGH
PRESSURE WITH DRY AND MUCH COOLER WEATHER SHOULD BUILD IN FROM THE
WEST BY THE MIDDLE OF NEXT WEEK.
NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
SHOWERS AND TSTMS CONTINUE TO DEVELOP ACROSS MUCH OF THE AREA AS
WEAK LOW PRESSURE PASSES THE AREA. THE WARM AND HUMID AIR MASS IN
PLACE AND WEAK DYNAMICS ARE SUFFICIENT FOR THE STORM FORMATION. THE
TSTMS ARE PRODUCING EXCESSIVE RAINFALL IN SOME AREAS, SO FFWS HAVE
BEEN ISSUES FOR SOME AREAS. THE THREAT FOR SEVERE WEATHER LOOKS LOW,
BUT STILL BE PREPARED FOR THE POSSIBILITY OF HAZARDOUS WEATHER SINCE
A STRONG WIND GUST OR TWO FROM TSTMS CAN'T BE RULED OUT.
THESE SHOWERS AND TSTMS ACROSS THE REGION WILL END FROM NW TO SE
THIS EVENING AND EARLY TONIGHT. IT WILL REMAIN WARM AND HUMID
OVERNIGHT. LOW CLOUDS AND FOG WILL ONCE AGAIN DEVELOP. WINDS WILL BE
LIGHT FROM THE N LATER TONIGHT.
SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/
A DRY DAY IS EXPECTED BY-IN-LARGE, HOLDING ONLY A SLIGHT CHC FOR AN
AFTERNOON SHOWER ACROSS THE SOUTHERN POCONOS. HOT AND HUMID
CONDITIONS EXPECTED AFTER THE MORNING LOW CLOUDS AND PATCHY FOG BURN
OFF. HIGHS WILL BE IN THE MID/UPPER 90S EVERYWHERE EXCEPT AT THE
SHORE AND ACROSS THE HIGHER ELEVATIONS OF THE SOUTHERN POCONOS.
HIGHS IN THOSE AREAS WILL BE MORE LIKE UPPER 80S TO LOW 90S. AN
EXCESSIVE HEAT WARNING WILL BE ISSUED FOR ALL AREAS OF THE CWA
BEGINNING FRIDAY.
LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/
OVERVIEW...
ALL INDICATIONS REMAIN ON TRACK FOR A PROLONGED, DANGEROUS, AND
POTENTIALLY DEADLY PERIOD OF EXCESSIVE HEAT FOR OUR AREA OVER THE
WEEKEND. AN EXPANSIVE RIDGE EXTENDING FROM THE SOUTH CENTRAL STATES
OUT INTO THE WESTERN ATLANTIC WILL YIELD NEAR RECORD WARMTH FOR
MULTIPLE DAYS. SATURDAY AND SUNDAY WILL BOTH SEE HEAT INDICES IN
EXCESS OF 100 DEGREES, POTENTIALLY AS HIGH AS 115 DEGREES ON
SATURDAY. HEAT RELATED ILLNESSES AND DEATH CAN OCCUR IN MINUTES ON
DAYS SUCH AS THESE IN CASES OF OVER-EXERTION OR ENTRAPMENTS IN HOT
VEHICLES. BECAUSE OF THIS, EXTREME CAUTION SHOULD BE EXERCISED OVER
THE WEEKEND WITH REGARDS TO THE HEAT.
A COLD FRONT, SIGNALING A PATTERN CHANGE, WILL SLOWLY APPROACH BY
MONDAY. DURING THE AIR MASS TRANSITION, A PERIOD OF HEAVY RAINFALL
IS POSSIBLE. BY THE MIDDLE OF NEXT WEEK, AN ENTIRELY DIFFERENT
PATTERN TAKES SHAPE OVER THE CONUS. AFTER THE FRONTAL PASSAGE MONDAY
NIGHT OR TUESDAY, A ROBUST TROUGH DIGS IN OVER THE EAST, WITH STRONG
RIDGING OVER THE MOUNTAIN WEST. THIS WILL YIELD MUCH COOLER AND
DRIER WEATHER AS WE HEAD TOWARDS THE MIDDLE OF NEXT WEEK, BRINGING
WELCOME RELIEF FROM THE HEAT.
DAILIES...
FRIDAY NIGHT... A VERY WARM NIGHT WITH LOWS IN THE MID TO UPPER 70S,
AROUND 80 IN THE URBAN CORRIDOR. SOME GUIDANCE IS INDICATING THE
POTENTIAL FOR AN MCS TO TRACK OVER NORTHERN OR CENTRAL PORTIONS OF
THE AREA AS A SHORTWAVE MOVES THROUGH. AS IS TYPICAL OF SUCH EVENTS,
AGREEMENT IN GUIDANCE IS VERY POOR, AND SEVERAL MODELS SHOW NOTHING
AT ALL. KEPT POPS LOW FOR NOW, BUT WILL CONTINUE TO MONITOR IN THE
EVENT THIS IDEA STARTS TO GAIN ANY TRACTION.
SATURDAY-SUNDAY... BLISTERING HEAT. NO SIGNIFICANT CHANGES IN TERMS
OF THE TEMPERATURE FORECASTS. SATURDAY'S HIGHS WERE NUDGED DOWN JUST
A DEGREE OR TWO, WITH SUNDAY'S INCHED UP A DEGREE OR SO. THE RESULT
IS BOTH DAYS NOW LOOK TO HAVE VERY SIMILAR HIGH TEMPERATURES, THOUGH
SATURDAY STILL HAS THE HIGHEST HEAT INDICES, UP TO 115 IN THE URBAN
CORRIDOR BUT WITH WIDESPREAD VALUES OVER 105. THESE HEAT INDEX
VALUES COME DOWN ABOUT 5 DEGREES SUNDAY BUT REMAIN IN VERY DANGEROUS
TERRITORY, AROUND 100 TO 110. IN ADDITION, ANOTHER IMPORTANT
CONSIDERATION IS THE OVERNIGHT MINIMUMS, ESPECIALLY SATURDAY NIGHT
WHEN MOST PLACES WON'T FALL BELOW THE MID 70S AND SOME URBAN AREAS
WILL NOT GO BELOW 80. THIS WILL MAKE FOR VERY LITTLE OVERNIGHT
RELIEF. WAS NOT GOING TO QUIBBLE ON HEADLINES; WENT WITH A BLANKET
EXCESSIVE HEAT WARNING FOR ALL AREAS THROUGH SUNDAY. SATURDAY LOOKS
TO STAY DRY THOUGH CANNOT COMPLETELY RULE OUT A POP-UP STORM
ESPECIALLY TO THE WEST. BY SUNDAY, SHOWERS AND THUNDERSTORMS MAY
APPROACH FROM THE WEST AS A FRONT BEGINS MOVING TOWARDS THE AREA,
THOUGH THERE ARE SOME INDICATIONS THIS MAY HOLD OFF UNTIL LATER.
GIVEN HIGH HEAT AND HUMIDITY, ANY STORMS COULD PRODUCE LOCALLY HEAVY
RAINFALL.
SUNDAY NIGHT-MONDAY NIGHT... THIS WILL BE OUR TRANSITION PERIOD. A
STRONG BUT SLOW MOVING COLD FRONT WILL BE APPROACHING FROM THE WEST.
THE AIR MASS AHEAD OF IT WILL BE VERY MOIST, WITH PWATS COMING BACK
UP TO AROUND 2.25" OR HIGHER AFTER EASING BACK A LITTLE ON SUNDAY.
AS THE FRONT CRAWLS THROUGH, IT LOOKS LIKE ONE OR MORE WAVES OF LOW
PRESSURE MAY DEVELOP ALONG IT. THERE IS DEFINITELY A RISK FOR HEAVY
RAINFALL AND FLASH FLOODING OVER THIS PERIOD ESPECIALLY IF WE DO GET
MULTIPLE ROUNDS OF CONVECTION AS NEW WAVES OF LOW PRESSURE DEVELOP.
IN ADDITION, GIVEN THE TROPICAL AIR MASS EXPECTED MONDAY, IT IS
POSSIBLE IF NOT LIKELY THAT SOME NEW HEAT HEADLINES WILL BE NEEDED,
THOUGH CLOUD COVER WILL KEEP THE HIGHS ABOUT 10 DEGREES COOLER THAN
SUNDAY. DEPENDING ON THE SPEED OF THE FRONT, COOLER AIR MAY START TO
FILTER IN BY MONDAY NIGHT.
TUESDAY-THURSDAY... WELCOME RELIEF. A MUCH COOLER, MUCH DRIER AIR
MASS SETTLES IN. A LINGERING SHOWER IS POSSIBLE TUESDAY ESPECIALLY
OVER DELMARVA AND COASTAL NJ. OTHERWISE, MOST OF THIS PERIOD SHOULD
BE DRY, THOUGH AN AFTERNOON SHOWER OR STORM IS POSSIBLE BY THURSDAY
AS AN UPPER LEVEL DISTURBANCE APPROACHES. HIGHS GENERALLY IN THE LOW
TO MID 80S WITH COMFORTABLE DEW POINTS, SO THIS LOOKS LIKE A REALLY
NICE STRETCH, CERTAINLY COMPARED TO THE ONGOING HEAT.
AVIATION /21Z THURSDAY THROUGH TUESDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
REST OF THE AFTERNOON...SCATTERED SHOWERS AND TSTMS WILL DIMINISH
FROM W TO E INTO THE EVENING. MVFR/IFR POSSIBLE IF ACTIVITY MOVES
DIRECTLY ACROSS TERMINAL, LIMITED CONFID. LIGHT AND VARIABLE WINDS.
TONIGHT...VFR, THEN LOW CLOUDS AND AREAS OF FOG WILL DEVELOP
OVERNIGHT. WIDESPREAD MVFR EXPECTED WITH IFR POSSIBLE. LIGHT WINDS
FRIDAY...LOW CLOUDS AND ANY FOG DIMINISH 13Z/14Z THEN VFR EXPECTED
WITH SOME SCT DAYTIME CU. MOSTLY N OR NW WINDS 5 TO 10 KNOTS.
OUTLOOK...
FRIDAY NIGHT-SATURDAY NIGHT... GENERALLY VFR. MVFR IS POSSIBLE DUE
TO VISIBILITY RESTRICTIONS IN HAZE ON SATURDAY. WEST-SOUTHWEST WIND
5 TO 10 KT.
SUNDAY... MAINLY VFR BUT MVFR POSSIBLE IN HAZE. AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS POSSIBLE ESPECIALLY NEAR AND WEST
OF PHL. WESTERLY WIND 5 TO 10 KT.
SUNDAY NIGHT-MONDAY NIGHT... WIDESPREAD SHOWERS AND THUNDERSTORMS
WITH ASSOCIATED MVFR AND IFR CONDITIONS. WESTERLY WINDS BECOMING
NORTHWESTERLY AT 5 TO 10 KT.
TUESDAY... LINGERING MVFR POSSIBLE EARLY, BUT SHOULD TREND VFR
WITH A LIGHT NORTH OR NORTHEAST WIND.
MARINE
TONIGHT...A CONTINUATION OF SUB-SCA CONDITIONS WITH
SCATTERED TSTMS THIS EVENING AND THEN SOME PATCHY FOG OVERNIGHT.
WINDS WILL BE MOSTLY SW OR W AT 5 TO 10 KNOTS. SEAS MOSTLY
AROUND 3 FT. WINDS AND SEAS HIGHER IN TSTMS.
FRIDAY...WINDS WILL BE RATHER LIGHT AND VARIABLE EARLY, THEN SWITCH
AROUND TO SW DURING THE AFTERNOON AND INCREASE TO AROUND 10 KNOTS.
SEAS WILL BE MAINLY 2 TO 3 FT.
OUTLOOK...
WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SCA CRITERIA THROUGH THE
PERIOD.
RIP CURRENTS...
LOW RISK OR DANGEROUS RIP CURRENTS WILL CONTINUE THE REST OF
TODAY.
PHI WATCHES/WARNINGS/ADVISORIES
PA...EXCESSIVE HEAT WARNING FROM NOON FRIDAY TO 10 PM EDT SUNDAY
FOR PAZ054-055-060>062-101-103-105.
EXCESSIVE HEAT WARNING UNTIL 10 PM EDT SUNDAY FOR PAZ070-071-
102-104-106.
NJ...EXCESSIVE HEAT WARNING FROM NOON FRIDAY TO 10 PM EDT SUNDAY
FOR NJZ001-007>010-012>014-016-020>027.
EXCESSIVE HEAT WARNING UNTIL 10 PM EDT SUNDAY FOR NJZ015-
017>019.
DE...EXCESSIVE HEAT WARNING FROM NOON FRIDAY TO 10 PM EDT SUNDAY
FOR DEZ002>004.
EXCESSIVE HEAT WARNING UNTIL 10 PM EDT SUNDAY FOR DEZ001.
MD...EXCESSIVE HEAT WARNING FROM NOON FRIDAY TO 10 PM EDT SUNDAY
FOR MDZ008-012-015-019-020.
MARINE...NONE.
SYNOPSIS...O'BRIEN
NEAR TERM...O'HARA
SHORT TERM...O'HARA
LONG TERM...O'BRIEN
AVIATION...O'BRIEN/O'HARA
MARINE...O'BRIEN/O'HARA
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