713
FXUS61 KPHI 310748
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
348 AM EDT SUN MAY 31 2020
SYNOPSIS
HIGH PRESSURE WILL BUILD INTO THE AREA THROUGH MONDAY BEFORE SLIDING
TO THE SOUTH AND OFFSHORE ON TUESDAY. A WEAK TROUGH MAY APPROACH THE
REGION LATE IN THE DAY ON TUESDAY. A COLD FRONT WILL DROP DOWN INTO
THE REGION WEDNESDAY AND THEN STALL OVER THE MID-ATLANTIC THROUGH
THE END OF THE WEEK.
NEAR TERM /UNTIL 6 PM THIS EVENING/
HIGH PRESSURE WILL MOVE FROM MICHIGAN THIS MORNING TOWARDS THE
UPPER OHIO VALLEY BY TONIGHT. THIS WILL KEEP FAIR WEATHER
ACROSS THE REGION TODAY. AFTER SOME SEASONABLY CHILLY MORNING
LOWS, TEMPERATURES WILL RISE INTO THE MID/UPPER 60S N/W AND LOW
70S ELSEWHERE. THESE TEMPS WILL BE ABOUT 5 DEGREE BELOW NORMAL.
WINDS WILL BE NORTH TO NORTHWEST AROUND 10 MPH WITH SOME GUSTS
NEAR 20 MPH.
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/
HIGH PRESSURE WILL CONTINUE TO MOVE SLOWLY ACROSS THE UPPER OHIO
VALLEY INTO THE MIDDLE ATLANTIC REGION. A CONTINUATION OF FAIR
WEATHER WITH MOSTLY CLEAR SKIES IS EXPECTED ACROSS OUR REGION. LOWS
TONIGHT WILL BE ABOUT 5 DEGREES COOLER THAN SAT NIGHT, SO MERCURY
READINGS WILL FALL INTO THE UPPER 30S/LOW 40S N/W AND CLOSE TO 50
FOR DELMARVA AND SRN NJ. WINDS WILL BE MOSTLY N AT 5 MPH OR
LESS.
LONG TERM /MONDAY THROUGH SATURDAY/
OVERVIEW: THE LONG TERM WILL START COOL AND DRY AS A LARGE AREA OF
HIGH PRESSURE BUILDS OVER OUR REGION BEFORE SHIFTING OFF SHORE.
HOWEVER, BY TUESDAY, WE'LL SEE A BIG SHIFT IN THE OVERALL PATTERN AS
THE MID AND UPPER LEVEL RIDGE WHICH HAS BEEN OVER THE CENTRAL U.S.
WILL START BUILDING EAST BEFORE WEAKENING AND FLATTENING. THAT WILL
LEAVE THE MID ATLANTIC WITH A MOSTLY ZONAL PATTERN UNTIL NEXT
WEEKEND, WHEN A TROUGH MAY TRY TO DIG SOUTH OVER THE NORTHEASTERN
U.S. ONCE AGAIN. AT THE SURFACE, A FRONT IS EXPECTED TO APPROACH THE
REGION MID WEEK, THEN STALL OVER THE MID ATLANTIC THROUGH THE
REMAINDER OF THE WEEK.
DETAILS:
MONDAY...MONDAY WILL BE THE MOST COMFORTABLE DAY OF THE WEEK TO BE
OUTSIDE. WE WILL STILL HAVE THE LOW HUMIDITY LIKE WHAT WE WILL SEE
TODAY, AND TEMPERATURES SHOULD BE 5 TO 10 DEGREES BELOW NORMAL, WITH
HIGHS MOSTLY IN THE LOWER 70S. SOME MODELS DO SHOW A WEAK LOW LEVEL
TROUGH IMPENDING ON THE LARGE AREA OF HIGH PRESSURE WHICH COULD LEAD
TO SHOWERS ESPECIALLY OVER NORTHERN NJ AND E CENTRAL PA. HOWEVER, I
KEPT THE FORECAST DRY AS DEWPOINTS SHOULD STILL BE IN THE 30S AND
40S, AND WE SHOULD GENERALLY SEE NORTHWESTERLY LOW AND MID LEVEL
FLOW, WHICH MEANS THERE WILL BE VERY LIMITED MOISTURE EVEN IF THE
TROUGH DOES DEVELOP.
TUESDAY...AS THE SURFACE HIGH SHIFTS OFF SHORE, LOW LEVEL
SOUTHWESTERLY RETURN FLOW DEVELOPS LEADING TO MOISTURE ADVECTION,
AND SETTING THE STAGE FOR RAIN CHANCES LATER IN THE WEEK. THE
SOUTHWESTERLY FLOW WILL ALSO HELP START A WARMING TREND, ALTHOUGH
THE MID AND UPPER LEVEL TROUGH WHICH WILL BE STUBBORNLY STICKING
AROUND FOR ONE MORE DAY, WILL KEEP TEMPERATURES NEAR NORMAL. A
SHORTWAVE TROUGH DIGGING ON THE BACK SIDE OF THE MAIN MID/UPPER
LEVEL TROUGH COULD BE ENOUGH TO RESULT IN SHOWERS, THOUGH IT REMAINS
TO BE SEEN IF THIS SHORTWAVE TROUGH WILL TRACK CLOSE ENOUGH TO OUR
REGION TO RESULT IN RAIN FOR US. THEREFORE, KEPT THE RAIN CHANCES
LIMITED TO 20 TO 40 PERCENT WITH THIS PERIOD.
WEDNESDAY...AT THIS POINT, WEDNESDAY LOOKS LIKE THE MOST
UNCOMFORTABLE DAY OF THE WEEK. THE COLD FRONT IS NOT EXPECTED TO
ARRIVE UNTIL WEDNESDAY NIGHT, KEEPING OUR REGION IN THE PRIME
LOCATION FOR MOISTURE ADVECTION (WITH DEW POINTS POSSIBLY GETTING IN
TO THE 60S) AND WARM AIR ADVECTION FOR ONE MORE DAY. IN FACT, A LOT
OF GUIDANCE HAS THE COASTAL PLAINS IN THE UPPER 80S TO NEAR 90
(SIGNIFICANT AS WE HAVE YET TO HAVE ANY 90 DEGREE DAYS AT ANY OF THE
CLIMATE SITES IN OUR AREA THIS YEAR). WE MAY NOT SEE MUCH IN THE WAY
OF RAIN DURING THE DAY ON WEDNESDAY AS WE LIKELY WON'T HAVE MUCH IN
THE WAY OF LIFT UNTIL THE FRONT GETS CLOSER TO OUR AREA.
THURSDAY THROUGH SATURDAY...THE FRONT THAT APPROACHES OUR REGION
WEDENSDAY NIGHT IS EXPECTED TO STALL AS THE MID AND UPPER LEVEL
PATTERN TRANSITIONS TO A ZONAL FLOW PATTERN. THE EXTENT AND TIMING
OF SHOWERS AND THUNDERSTORMS THROUGH THIS PERIOD WILL DEPEND ON
EXACTLY WHERE THE FRONT STALLS. FOR NOW, I HAVE STAYED CLOSE TO THE
PREVIOUS FORECAST, WITH A BROAD BRUSH OF SLIGHT CHANCE TO CHANCES OF
SHOWERS AND STORMS THROUGH OUT THE PERIOD. HOWEVER, IT IS VERY
UNLIKELY THAT THIS WILL BE A WASHOUT, AND IF THE FRONT STALLS FAR
ENOUGH SOUTH, NORTHERN PORTIONS OF OUR REGION, MAY NOT SEE MUCH RAIN
AT ALL (WITH THE EXCEPTION OF WHEN THE FRONT INITIALLY ARRIVES).
AVIATION /08Z SUNDAY THROUGH THURSDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
TODAY...VFR EXPECTED WITH A MINIMAL AMOUNT OF DIURNAL CU. THE WINDS
WILL BE MOSTLY NW AROUND 10 KNOTS WITH SOME GUSTS CLOSER TO 20 KNOTS
FROM LATE MORNING INTO THE AFTERNOON.
TONIGHT...VFR. SKC. LIGHT N TO NW WINDS, LOCALLY CALM.
OUTLOOK...
MONDAY...VFR CONDITIONS EXPECTED. NORTHWEST WINDS AROUND 5 TO 10
KNOTS WITH GUSTS TO 20 KNOTS POSSIBLE. HIGH CONFIDENCE.
MONDAY NIGHT AND TUESDAY...MOSTLY VFR CONDITIONS EXPECTED. HOWEVER,
THERE IS A CHANCE FOR BRIEF REDUCTIONS IN CEILING OR VISIBILITY WITH
SHOWERS AND THUNDERSTORMS DURING TUESDAY AND TUESDAY NIGHT. LIGHT
WINDS MONDAY NIGHT WILL BECOME SOUTHWESTERLY AROUND 5 TO 10 KNOTS.
MODERATE CONFIDENCE ON MOST ASPECTS OF THE FORECAST, BUT LOW
CONFIDENCE ON THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS.
WEDNESDAY THROUGH THURSDAY...PREDOMINANTLY VFR CONDITIONS ARE
LIKELY. HOWEVER, THERE IS A CHANCE FOR SHOWERS AND THUNDERSTORMS
THROUGH OUT THE PERIOD. WESTERLY WINDS AROUND 5 TO 10 KNOTS. LOW
CONFIDENCE, ESPECIALLY WITH THE TIMING OF SHOWERS AND
THUNDERSTORMS.
MARINE
FAIR WEATHER IS EXPECTED TODAY AND TONIGHT WITH HIGH PRESSURE ACROSS
THE WATERS. A FEW SCA GUSTS ARE POSSIBLE THIS MORNING, BUT OVERALL
CONDITIONS WILL BE SUB-SCA BOTH TODAY AND TONIGHT. WINDS WILL BE
FROM THE NORTH/NORTHWEST TODAY AND NORTH/NORTHEAST TONIGHT. SEAS ON
THE OCEAN MOSTLY 3 TO 4 FT WHILE ACROSS DEL BAY SEAS WILL BE 1-2 FT
NORTH AND 2 TO 3 FT SOUTH.
OUTLOOK...
MONDAY THROUGH THURSDAY...WINDS AND SEAS SHOULD STAY BELOW SCA
CRITERIA.
RIP CURRENTS...
A NORTHWEST WIND IS EXPECTED FOR SUNDAY WITH BREAKING WAVES
AROUND 2 FEET. AS A RESULT, THERE IS A LOW RISK FOR THE
DEVELOPMENT OF DANGEROUS RIP CURRENTS.
THE WIND IS FORECAST TO BACK TOWARD THE SOUTHWEST ON MONDAY.
BREAKING WAVES SHOULD AGAIN BE AROUND 2 FEET. THE LOW RISK IS
EXPECTED TO CONTINUE INTO MONDAY.
FIRE WEATHER
RELATIVE HUMIDITY VALUES COULD DROP TO 30 PERCENT BY THIS
AFTERNOON (ESPECIALLY ACROSS THE COASTAL PLAINS OF NJ AND DE),
AND WIND GUSTS UP TO AND IN EXCESS OF 20 MPH ARE EXPECTED TODAY.
THIS COULD LEAD TO ELEVATED FIRE WEATHER CONCERNS.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.
SYNOPSIS...JOHNSON/MEOLA
NEAR TERM...O'HARA
SHORT TERM...O'HARA
LONG TERM...JOHNSON
AVIATION...JOHNSON/O'HARA
MARINE...JOHNSON/O'HARA
FIRE WEATHER...
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