556
FXUS61 KPHI 240145
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
945 PM EDT WED SEP 23 2020
SYNOPSIS
HIGH PRESSURE REMAINS IN CONTROL OF OUR WEATHER INTO THURSDAY.
THE CENTER OF THE HIGH WILL SLOWLY SLIDE FROM THE TENNESSEE AND
OHIO RIVER VALLEYS TO THE SOUTHEAST COAST INTO THURSDAY AS THE
REMAINS OF TROPICAL CYCLONE BETA MOVE INTO THE SOUTHERN MID-
ATLANTIC FRIDAY. HEADING INTO NEXT WEEK, A SERIES OF COLD FRONTS
WILL USHER IN COOLER AIR AND WHAT LOOKS TO BE THE FIRST
APPRECIABLE PRECIPITATION IN SEVERAL WEEKS MONDAY AND TUESDAY.
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
QUIET CONDITIONS CONTINUE THIS EVENING AND OVERNIGHT ACROSS THE
MID ATLANTIC REGION. HIGH PRESSURE CONTINUES TO PUSH OFFSHORE OF
THE SOUTHEAST COAST, BUT STILL NOSE ITS WAY INTO THE MID WEST
AND MID ATLANTIC REGION. DRY WEATHER IS EXPECTED, ALTHOUGH SOME
HIGH LEVEL CLOUDS WILL MAKE THEIR WAY ACROSS THE AREA WELL
NORTHEAST OF A MID LEVEL LOW NEAR THE MID MISSISSIPPI VALLEY. THE
TREND OF WARMER OVERNIGHT LOWS WILL ALSO CONTINUE WITH TONIGHT
BEING WARMER THAN LAST NIGHT. EXPECT LOWS MAINLY IN THE 50S
TO NEAR 60 IN SOME PLACES. THERE IS A CHANCE FOR PATCHY FOG
LATER TONIGHT, MAINLY JUST RADIATION INDUCED GROUND FOG FOR MOST
PLACES, SO VISIBILITIES ARE NOT EXPECTED TO DROP SIGNIFICANTLY
FOR MOST AREAS AT THIS TIME.
SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/
FOR THURSDAY, SURFACE RIDGING OVER THE SE CONUS WEAKENS AS THE
CENTER OF HIGH PRESSURE MOVES OFF THE SE COAST INTO THE WESTERN
ATLANTIC. MEANWHILE IN THE UPPER LEVELS THE ENERGY ALOFT
ASSOCIATED WITH BETA WILL START TO GET SHEARED APART AS IT
ENTERS A JET STREAK OVER THE EAST COAST AHEAD OF AN UPPER TROUGH
CENTERED NEAR THE MIDWEST. THIS WILL ALLOW HIGH CLOUDINESS TO
LOWER AND THICKEN THROUGH THE DAY AS MOISTURE CONTINUES TO
ADVANCE NORTH IN THESE LEVELS BUT THERE STILL SHOULD BE AT LEAST
SOME SUN VISIBLE THROUGH THE CLOUDS AT LEAST THROUGH THE FIRST
PART OF THE DAY. ALSO, IT WILL REMAIN DRY IN THE LOWEST 10 TO 15
K FT DUE TO THE INFLUENCE OF RESIDUAL SURFACE RIDGING OVER THE
AREA SO EXPECT THE DAY TO REMAIN RAIN FREE. HIGHS WILL ONCE
AGAIN BE MAINLY IN THE MIDDLE TO UPPER 70S WITH DEW POINTS IN
THE 50S SO STILL NOT TOO HUMID.
NOTHING CHANGES TOO MUCH FOR THURSDAY NIGHT THOUGH WE WILL HAVE
TO WATCH AS THE NORTHERN EDGE OF DEEPER LAYER MOISTURE FROM
BETA MAKES ITS WAY CLOSER TO THE AREA. EXPECT IT TO STILL STAY
DRY THROUGH THE PERIOD FOR OUR CWA THOUGH SO WE KEEP POPS BELOW
15 PERCENT.
LONG TERM /FRIDAY THROUGH WEDNESDAY/
SEVERAL ITEMS OF INTEREST IN THE EXTENDED FORECAST. HEADING
INTO FRIDAY, THE REMNANTS OF TROPICAL CYCLONE BETA WILL MOVE TO
OUR SOUTH ACROSS PORTIONS OF VIRGINIA, BRINGING THE CHANCE FOR
SOME RAINFALL TO THE SOUTHERN HALF OF THE AREA FRIDAY AND FRIDAY
NIGHT. THE WEEKEND LOOKS QUIET AS A WEAK RIDGE OF HIGH PRESSURE
SHIFTS EASTWARD ALONG THE EASTERN SEABOARD. MEANWHILE, A SERIES
OF PROGRESSIVE SHORTWAVE TROUGHS WILL AMPLIFY A LONGER WAVE
TROUGH ACROSS THE GREAT LAKES AND INTO THE NORTHEAST. OUR FIRST
APPRECIABLE PRECIP CHANCES LOOK TO OCCUR MONDAY AND TUESDAY NEXT
WEEK AS THIS PATTERN CHANGE ENSUES.
FRIDAY'S FORECAST LOOKS A LITTLE TRICKY AS BETA REMAINS OUR
BUGABOO PER SE. LATEST MODEL GUIDANCE HAS CONTINUED TO INCH
NORTHWARD, AS NOTED IN THE PREVIOUS DISCUSSION. THE GFS BRINGS
PRECIP A LITTLE FURTHER NORTH THAN THE EC, BUT GIVEN THE TREND
AMONGST MOST OF THE GUIDANCE, THIS MAY WORK OUT. THERE IS
SIGNIFICANT DRY AIR WORKING AGAINST THIS SYSTEM, WITH DEW POINTS
IN THE UPPER 40S TO LOW 50S LATER THURSDAY AND FRIDAY. WENT
WITH A NICE BLENDED APPROACH FOR POPS WITH BEST CHANCES SOUTH OF
PHILLY-ATLANTIC CITY FOR RAIN. HIGHS IN A MIRROR OF NORMAL WITH
UPPER 70S TO NEAR 80 ACROSS NORTHERN NEW JERSEY TO THE LOW TO
MID 70S ACROSS DELMARVA, WHERE MORE PERSISTENT CLOUD COVER WILL
LIMIT DAYTIME HEATING.
QUIET WEATHER FOR THE WEEKEND WITH A WEAK RIDGE BUILDING ACROSS
THE MID-ATLANTIC AS NORTHWEST FLOW BEGINS TO SET THE STAGE FOR
A SERIES OF PROGRESSIVE SHORTWAVE PERTURBATIONS INTO EARLY NEXT
WEEK. HIGHS TRENDING IN THE UPPER 70S TO AROUND 80.
A MORE, DARE WE SAY, INTERESTING WEATHER PATTERN BEGINS TO
EVOLVE AS WE HEAD INTO NEXT WEEK WITH THE FIRST OF TWO
SHORTWAVES MOVING SOUTHEAST ACROSS THE GREAT LAKES AND INTO THE
NORTHEAST MONDAY MORNING. THIS WILL DRIVE CYCLOGENESIS AS THE
TROUGH BEGINS TO DIG AND DEVELOP A NEGATIVE TILT MONDAY. A
SURFACE LOW LOOKS TO DEVELOP ACROSS UPSTATE NEW YORK AND WORK
ITS WAY NORTHWARD INTO THE SAINT LAWRENCE RIVER VALLEY. A COLD
FRONT WILL TRAIL BEHIND THIS FEATURE, BUT TIMING HAS SLOWED IN
INTO PROGRESSION INTO OUR REGION. BEST FORCING FOR PRECIP LOOKS
TO BE MONDAY EVENING AND OVERNIGHT, BUT THERE IS SOME
DISAGREEMENT ON HOW EXPANSIVE PREFRONTAL PRECIPITATION WILL BE.
HIGHS LOOK TO RANGE FROM THE MID TO UPPER 70S ACROSS THE
FORECAST AREA.
THERE ARE INDICATIONS THAT A SECONDARY SHORTWAVE WILL FURTHER
AMPLIFY THE DEVELOPING LONG WAVE TROUGH TUESDAY INTO WEDNESDAY,
BUT CONSIDERABLE AMBIGUITY STILL EXISTS IN HOW THIS WILL EVOLVE
AND EXACTLY WHEN. THIS WILL LIKELY LEAD TO THE FORMATION OF
ANOTHER SURFACE LOW AND ATTENDANT COLD FRONT TUESDAY NIGHT INTO
WEDNESDAY. THE GFS IS A LITTLE MORE PROGRESSIVE WITH THIS
FEATURE, BRINGING PRECIP INTO THE WESTERN PORTIONS OF THE AREA
WEDNESDAY MORNING, WHEREAS THE EC HAS MOST OF THE ENERGY AND
FORCING TO OUR NORTH INTO ONTARIO AND THE NORTHEAST. CONTINUED
WITH A HIGHLY BLENDED APPROACH FOR MUCH OF NEXT WEEK GIVEN THESE
TIMING DIFFERENCES. HIGHS IN THE UPPER 70S TUESDAY, DROPPING
INTO THE 60S BEHIND THE COLD FRONT WEDNESDAY.
AVIATION /02Z THURSDAY THROUGH MONDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
THROUGH TONIGHT...VFR. WEST 5-10 KNOTS THIS EVENING BECOME LIGHT
AND VARIABLE/CALM THROUGH THE EVENING AND OVERNIGHT HOURS. HIGH
CONFIDENCE.
THERE IS A CHANCE FOR PATCHY FOG LATER TONIGHT, MAINLY JUST
RADIATION INDUCED GROUND FOG, SO VISIBILITIES ARE NOT EXPECTED
TO DROP SIGNIFICANTLY AT THIS TIME AT THE TAF SITES.
THURSDAY AND THURSDAY NIGHT...VFR. LIGHT AND VARIABLE WINDS
EARLY THURSDAY, BECOME WEST TO SOUTHWEST 5-10 KNOTS THROUGH THE
MORNING INTO THE AFTERNOON BEFORE DIMINISHING THURSDAY EVENING. HIGH
CONFIDENCE.
OUTLOOK...
FRIDAY AND SATURDAY...SUB-VFR CONDITIONS POSSIBLE AT TIMES WITH
RAIN SHOWERS AS THE REMNANTS OF BETA MOVE TO OUR SOUTH.
QUESTIONS REMAIN AS TO HOW FAR NORTH PRECIPITATION WILL REACH,
WITH BEST CHANCES SOUTH OF THE PHILLY TERMINALS. SOUTHERLY WINDS
FROM 5 TO 10 KNOTS. MODERATE CONFIDENCE.
SUNDAY AND MONDAY...VFR CONDITIONS SUNDAY AND FOR MUCH OF THE
DAY MONDAY BEFORE SHOWERS MOVE INTO THE REGION MONDAY PM.
SOUTHWESTERLY WINDS FROM 10 TO 15 KNOTS. MODERATE CONFIDENCE.
MARINE
NOW THAT ALL ADVISORIES HAVE BEEN CANCELLED, ALL MARINE ZONES
ARE EXPECTED TO REMAIN BELOW ADVISORY LEVELS THROUGH THURSDAY
NIGHT, ALTHOUGH WINDS COULD GUST AROUND 20 KNOTS AT TIMES.
OUTLOOK...
THURSDAY THROUGH MONDAY...SUB-ADVISORY WINDS/SEAS EXPECTED WITH
PREDOMINANTLY SOUTHWESTERLY FLOW FROM 10 TO 15 KNOTS. PERIODIC
CHANCES FOR SHOWERS FRIDAY AND MONDAY.
RIP CURRENTS...
AS SEAS SUBSIDE TO 2-3 FEET WITH A 10 SECOND SWELL ON THURSDAY,
WE EXPECT THE RIP- CURRENT RISK WILL LOWER TO THE MODERATE
CATEGORY.
THE RISK MAY END UP BEING LOW ON FRIDAY AS SWELLS DECREASE EVEN
FURTHER.
TIDES/COASTAL FLOODING
A FINAL SURGE FROM TROPICAL SYSTEM TEDDY ARRIVED ALONG THE
COASTS OF NEW JERSEY AND DELAWARE TODAY, RESULTING IN ONE FINAL
ROUND OF MINOR TIDAL FLOODING. TIDAL DEPARTURES WILL CONTINUE
TO DECREASE OVER THE COMING DAYS AND NO ADDITIONAL FLOODING IS
EXPECTED.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.
SYNOPSIS...DAVIS
NEAR TERM...FITZSIMMONS/ROBERTSON
SHORT TERM...FITZSIMMONS
LONG TERM...DAVIS
AVIATION...DAVIS/FITZSIMMONS/ROBERTSON
MARINE...DAVIS/FITZSIMMONS/ROBERTSON
TIDES/COASTAL FLOODING...IOVINO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page