609
FXUS61 KPHI 262029
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
329 PM EST SAT NOV 26 2022
SYNOPSIS
HIGH PRESSURE ACROSS THE AREA LATE THIS AFTERNOON WILL MOVE AWAY
TONIGHT. LOW PRESSURE WILL BE OVER THE OHIO VALLEY SUNDAY
MORNING AND IT WILL RACE NORTH OF THE AREA THROUGH SUNDAY NIGHT.
AN ATTACHED FRONT WILL CROSS THE AREA SUNDAY EVENING. MORE HIGH
PRESSURE ARRIVES FOR THE EARLY PART OF THE UPCOMING WEEK. ANOTHER
LOW AND FRONT WILL ARRIVE FOR THE MIDDLE OF THE WEEK.
NEAR TERM /THROUGH SUNDAY/
THE SURFACE HIGH AND MID/UPPER LEVEL RIDGE WILL BUILD FURTHER
EAST, PROGRESSING OFF SHORE OVERNIGHT, BUT STILL REMAINING CLOSE
TO THE REGION. CONSEQUENTLY, EXPECT DRY CONDITIONS THROUGH THE
OVERNIGHT. THAT BEING SAID, WE SHOULD SEE INCREASING CLOUDS,
STARTING LATE THIS EVENING AS THE CLOSED LOW IN THE MID AND
UPPER LEVELS, CURRENTLY CENTERED OVER NORTH TEXAS PROGRESSES
NORTHEAST CLOSER TO OUR REGION.
AS MENTIONED BY THE PREVIOUS SHIFT, WE SHOULD START TONIGHT
WITH EFFICIENT RADIATIONAL COOLING CONDITIONS, SO LOWS IN THE
30S OR AROUND 40 ARE EXPECTED. HOWEVER, AS WINDS BECOME MORE
SOUTHWESTERLY AND CEILINGS LOWER, TEMPERATURES SHOULD REMAIN
STABLE AND POSSIBLY INCREASE SLIGHTLY DURING THE LATE OVERNIGHT.
ON SUNDAY, PRECIPITATION WILL START TO MOVE IN AS THE (THEN)
VERTICALLY STACKED LOW PROGRESSES FROM THE MID MISSISSIPPI
VALLEY INTO NW NY THROUGH THE DAY. WE'LL LIKELY SEE LIGHT
PRECIPITATION MOVE IN DURING THE MORNING, BUT THE STEADIER AND
HEAVIER PRECIPITATION IS EXPECTED PRIMARILY DURING THE
AFTERNOON.
PRECIPITATION MODE SHOULD BE MOSTLY STRATIFORM RAIN THROUGH THE
EVENT. HOWEVER, THERE ARE A FEW EXCEPTIONS. FIRST, IF THE
PRECIPITATION MOVES IN BEFORE DAWN, THERE IS SOME CHANCE FOR
INITIAL WET BULB EFFECTS TO LEAD TO LIGHT SLEET, PRIMARILY IN
VALLEYS NORTH AND WEST OF THE FALL LINE. HOWEVER, THIS IS A BIG
IF, AS THE 12Z GUIDANCE HAS TRENDED LATER WITH ONSET, AND AS
MENTIONED PREVIOUSLY, WE MAY EVEN SEE RISING TEMPERATURES AFTER
MIDNIGHT. THE SECOND POSSIBLE EXCEPTION IS THE POTENTIAL FOR
SHOWERS/THUNDERSTORMS. MODEL SOUNDINGS DO SHOW SOME ELEVATED
INSTABILITY. HOWEVER, IT IS VERY ELEVATED - AT LEAST 800 MB
ACCORDING TO MODEL SOUNDINGS - SO I'M SKEPTICAL THAT WE WILL BE
ABLE TO REALIZE IT. THEREFORE, HAVE CONTINUED WITH JUST A
MENTION OF LIGHT OR MODERATE RAIN FOR NOW, BUT WILL CONTINUE TO
MONITOR TRENDS.
AS FOR THE PRECIPITATION AMOUNT AND RISK FOR HEAVY RAIN, LITTLE
CHANGE IN THE FORECAST FOR THAT. PRECIPITABLE WATER VALUES
AROUND 1.5 INCHES ARE WELL ABOVE NORMAL FOR THIS TIME OF YEAR,
SO THAT INCREASES THE RISK OF HIGHER RAIN RATES. HOWEVER, THE
THREAT FOR EXCESSIVE RAINFALL, ENOUGH TO CAUSE FLOODING ISSUES,
IS STILL LOW GIVEN HOW PROGRESSIVE THE SYSTEM IS EXPECTED TO BE.
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/
TEMPERATURES WILL BE ON THE REBOUND SUNDAY NIGHT INTO
MONDAY MORNING WITH OVERNIGHT READINGS REACHING THE UPPER 40S AND
EVEN LOW 50S FOR SOME LOCALES BEFORE TEMPERATURES THEN DROP THROUGH
THE DAY ON MONDAY. WOULDN'T ENTIRELY RULE OUT A FEW LINGERING
SCATTERED SHOWERS MAINLY FOR THE FIRST HALF OF MONDAY AS ONE LAST
SHORTWAVE TRAVERSES THE MID-ATLANTIC AND THE TRAILING SURFACE COLD
FRONT MOVES THROUGH MID-MORNING KICKING THE REMAINING MOISTURE OUT
TO SEA AND BRINGING IN A COLDER AIRMASS BEHIND IT.
AS THE LOW EXITS THE AREA, SURFACE HIGH PRESSURE WILL BUILD IN FROM
THE SOUTHWEST AND HOLD A TIGHT PRESSURE GRADIENT BETWEEN THE TWO
SYSTEMS. DRY CONDITIONS WILL ENSUE AND FLOW WILL TURN NORTHWESTERLY
SETTING UP A TYPICAL COLD AIR ADVECTION REGIME. AS A RESULT, MONDAY
WILL BE BREEZY WITH A LIKELY LOW AND MID-LEVEL CLOUD DECK NOSING
DOWN FROM THE NORTHWEST TO NEAR THE I-95 CORRIDOR. NBM EXP
PROBABILISTIC 24 HOUR WIND GUST GUIDANCE INDICATES VALUES IN THE 25-
30 MPH RANGE LIKELY. WINDS WILL GRADUALLY DIMINISH THROUGH THE DAY
AS A BUILDING SUBSIDENCE INVERSION LOWERS THE MIXING HEIGHTS AND THE
GRADIENT LESSENS. IN ADDITION, SKIES WILL CLEAR BY EVENING AS THE
COLUMN DRIES, THOUGH SOME CLOUDS MAY LINGER A BIT LONGER ACROSS THE
LEHIGH VALLEY AND POCONOS AS CAN BE EXPECTED WITH THIS CAA SETUP.
DESPITE CLEARING SKIES IN THE AFTERNOON, HIGHS IN THE UPPER 40S TO
LOW 50S MAY BE REACHED FOR MANY IN THE EARLY MORNING HOURS AS
DAYTIME COLD ADVECTION DROPS TEMPERATURES THROUGH THE DAY. AS THE
COLDER AIR BECOMES MORE FIRMLY ESTABLISHED MONDAY NIGHT, EXPECT
OVERNIGHT LOWS TO DROP INTO THE LOW 30S AND UPPER 20S FOR THE
POCONOS.
UPPER RIDGING WILL BUILD FOR THE DAY ON TUESDAY AND THE SURFACE HIGH
WILL MIGRATE TO OUR EAST. NORTHWESTERLY FLOW WILL FLIP TO SOUTHERLY
AS A RESULT. THE DAY WILL BE DRY, THOUGH UPPER LEVEL CLOUDS WILL BE
ON THE INCREASE AHEAD OF OUR NEXT APPROACHING SYSTEM FOR THE MID-
WEEK PERIOD. HIGHS WILL BE SLIGHTLY BELOW NORMAL IN THE UPPER 40S.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
WE EXPECT FAIR WEATHER FOR TUE NIGHT AT THE BEGINNING OF THE LONG
TERM. LARGE HIGH PRESSURE WILL HAVE MOVED OFFSHORE AND A SOUTHERLY
FLOW BEHIND IT WILL BE OVER THE REGION. INCREASING CLOUDS ARE
EXPECTED SINCE THE NEXT SYSTEM WILL BE STRENGTHENING OVER THE PLAINS
STATES. LOWS TUE NIGHT WILL BE IN THE MID/UPPER 30S FOR MOST AREAS.
A SHARPENING H5 TROUGH MOVING OUT OF THE ROCKIES TUE NIGHT/WED
WILL CAUSE LOW PRESSURE TO FORM OVER THE MISSISSIPPI VALLEY. THUS
LOW WILL DEEPEN AND MOVE TO THE UPPER GREAT LAKES WED MORNING.
AFTER THAT IT WILL MOVE ACROSS ONTARIO AND QUEBEC. AN ASSOCIATED
COLD FRONT WILL CROSS THE MIDDLE ATLANTIC AREA WED EVENING. A LARGE
SHIELD OF RAIN AND GUSTY WINDS WILL BE OVER THE AREA WED SO I WENT
ALONG WITH THE NBM'S CATEGORICAL POPS FOR NOW. COULD SEE 1/2 TO 3/4
INCH OF RAIN WITH THE STORM. MILD TEMPERATURES EXPECTED WED WITH
MID 50S N/W AND UPPER 50S/LOW 60S FOR DELMARVA AND SRN NJ.
AFTER THE LOW AND FRONT PULL AWAY, MORE SEASONABLE AIR ARRIVES WITH
READINGS A LITTLE BELOW NORMAL. THE PERIOD FROM THU THRU FRI NIGHT
WILL BE DRY AS HIGH PRESSURE PREVAILS. THE NICE WEATHER WILL PROBABLY
REMAIN FOR THE WEEKEND, BUT A LOW MOVING ACROSS CANADA COULD THROW
SOME MINOR SHOWER ACTIVITY FOR THE N/W AREAS ON SAT.
AVIATION /21Z SATURDAY THROUGH THURSDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS .
THROUGH TONIGHT...VFR, THOUGH INCREASING MID AND HIGH LEVEL
CLOUDS, ESPECIALLY AFTER 06Z. WINDS SHIFTING FROM NW TO SW. FOR
VALLEY LOCATIONS (INCLUDING KABE), WINDS COULD GO LIGHT AND
VARIABLE. HIGH CONFIDENCE.
SUNDAY...STARTING VFR, BUT EXPECT CEILINGS AND EVENTUALLY
VISIBILITIES TO DETERIORATE. EXPECTING THE LOWEST CONDITIONS
NEAR AND AFTER 18Z. EXPECT TO SEE WIDESPREAD MVFR, WITH IFR
CEILINGS LIKELY. VISIBILITIES COULD DROP INTO THE MVFR RANGE,
ESPECIALLY BETWEEN 15 AND 21Z WITH PERIODS OF MODERATE RAIN, BUT
CEILINGS SHOULD BE THE CONTROLLING FACTOR FOR FLIGHT CATEGORY.
WINDS ARE GOING TO BE STARTING GENERALLY OUT OF THE SW. HOWEVER,
SEVERAL HIGH RES MODELS INDICATE THAT WINDS COULD SWING AROUND
TO SE FOR A PERIOD BETWEEN 15 AND 21Z. NOT VERY CONFIDENT ON
THIS, SO HAVE STAYED CLOSE TO SW OR S FOR NOW. THE OTHER CONCERN
IS LOW LEVEL WIND SHEAR AS A LOW LEVEL 60KT SOUTHWESTERLY JET
DEVELOPS. THIS IS MOST LIKELY TO OCCUR FIRST AT KPHL, KRDG,
KILG, AND KPNE, BUT COULD AFFECT ALL TAF SITES IN THE 18 TO 21Z
TIME FRAME. MODERATE CONFIDENCE ON THE OVERALL PATTERN, BUT LOW
CONFIDENCE ON DETAILS, ESPECIALLY THE POTENTIAL FOR A PERIOD OF
SOUTHEASTERLY WINDS.
OUTLOOK...
MONDAY...PREDOMINANTLY VFR WITH SKIES CLEARING BY LATE MORNING. A
MID-LEVEL CLOUD DECK MAY PERSIST FOR KRDG AND KABE INTO THE EVENING.
SOUTHWESTERLY WINDS IN THE MORNING, VEERING TO NORTHWESTERLY IN THE
AFTERNOON, AT 10-15 KNOTS WITH GUSTS TO 20-25 KNOTS. WINDS WILL
DECREASE IN THE EVENING. MODERATE CONFIDENCE.
TUESDAY...VFR. NORTHERLY WINDS IN THE MORNING AT 5 KNOTS OR LESS
WILL BECOME SOUTHERLY IN THE AFTERNOON. HIGH CONFIDENCE.
WEDNESDAY...SUB-VFR WITH GUSTY WINDS AND RAIN EXPECTED.
THURSDAY...A RETURN TO VFR WITH GUSTY W TO NW WINDS.
MARINE
WINDS AND SEAS SHOULD STAY BELOW SCA CRITERIA THROUGH THE DAY
AND MOST OF TONIGHT. APPROACHING DAY BREAK ON SUNDAY, WE MAY SEE
WIND GUSTS NEAR 25 KT. WINDS WILL CONTINUE TO INCREASE FROM
THERE, SO GALES APPEAR LIKELY FOR A 3 TO 6 HOUR PERIOD IN THE
SUNDAY AFTERNOON OR EVENING TIME FRAME, PRIMARILY ON THE
ATLANTIC COASTAL WATERS. HOWEVER, CAN'T RULE OUT GALE GUSTS ON
THE LOWER DELAWARE BAY, BUT CONFIDENCE ISN'T AS HIGH THERE.
REGARDLESS, SHOULD HAVE AT LEAST WIDESPREAD SCA CONDITIONS
ACROSS THE BAY THROUGH THE AFTERNOON.
OUTLOOK...
SUNDAY NIGHT...EVEN AFTER THE PEAK OF THE WIND SPEEDS, SCA
CONDITIONS ARE LIKELY CONTINUE INTO THE OVERNIGHT HOURS.
MONDAY...SCA CONDITIONS LIKELY. WESTERLY WINDS AT 15-20 KNOTS WITH
GUSTS TO 30 KNOTS. SEAS 5-7 FEET.
TUESDAY...NO MARINE HEADLINES EXPECTED. WINDS AND WAVES WILL SUBSIDE
THROUGH THE DAY. NORTHWESTERLY WINDS 10-15 KNOTS WITH GUSTS TO 20
KNOTS IN THE MORNING RELAXING TO 5-10 KNOTS IN THE AFTERNOON. SEAS 3-
4 FEET IN THE MORNING DECREASING TO AROUND 2 FEET IN THE
AFTERNOON.
WEDNESDAY/THURSDAY...SCA EXPECTED. A CHANCE FOR GALE GUSTS. S/SW
WINDS ON WED. AND W/NW WINDS THU. RAIN EXPECTED WED. BUT FAIR
WEATHER FOR THU.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...GALE WATCH FROM SUNDAY AFTERNOON THROUGH SUNDAY EVENING FOR
ANZ431.
GALE WATCH FROM SUNDAY AFTERNOON THROUGH LATE SUNDAY NIGHT FOR
ANZ450>455.
SYNOPSIS...O'HARA
NEAR TERM...JOHNSON
SHORT TERM...BRUDY
LONG TERM...O'HARA
AVIATION...BRUDY/JOHNSON
MARINE...BRUDY/JOHNSON
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page