158
FXUS61 KPHI 291945
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
345 PM EDT WED MAR 29 2023
SYNOPSIS
COLD FRONT CROSSES THE REGION TONIGHT. HIGH PRESSURE BUILDS IN FOR
THURSDAY, MOVING OFFSHORE INTO FRIDAY. STRONG LOW PRESSURE MOVES UP
ACROSS THE GREAT LAKES REGION FRIDAY NIGHT INTO SATURDAY, PULLING A
STRONG COLD FRONT ACROSS OUR AREA LATER SATURDAY INTO SATURDAY NIGHT.
HIGH PRESSURE ARRIVES FOR SUNDAY, HOLDING INFLUENCE OVER THE
REGION MONDAY. WEAKENING FRONTAL BOUNDARY APPROACHES THE REGION
THEREAFTER.
NEAR TERM /THROUGH THURSDAY NIGHT/
THE REST OF THE AFTERNOON WILL REMAIN QUIET AHEAD OF A COLD FRONT
THAT WILL PUSH THROUGH LATE THIS EVENING SOMETIME BETWEEN 9PM AND
2AM. A MID LEVEL SHORTWAVE TROUGH WILL SWEEP OVERHEAD TONIGHT,
BRINGING ALONG A SURFACE COLD FRONT ACROSS THE REGION. THE FRONT IS
FORECAST TO REMAIN RATHER ROBUST AS IT PROGRESSES FROM THE GREAT
LAKES TO THE NORTHEASTERN STATES. THE SOUTHERN HALF OF THE FORECAST
AREA WILL LIKELY REMAIN DRY WITH A CHANCE FOR SOME SHOWERS ACROSS
EASTERN PA AND THE NORTHERN HALF OF NJ. PRECIPITATION TYPES SHOULD
BE MOSTLY RAIN, BUT STRONG COLD AIR ADVECTION BEHIND THE FRONT IS
EXPECTED TO ALLOW THE SWITCHOVER TO SNOW ACROSS ELEVATED TERRAIN TO
THE NORTH, LEAVING A LIGHT COATING IN SPOTS. WE WILL ALSO LIKELY MIX
DOWN SOME WIND GUSTS AROUND 30 MPH IN THE IMMEDIATE WAKE OF THE
FRONT, ESPECIALLY ACROSS EASTERN PA AND THE NORTHERN HALF OF NJ.
WINDS SHIFT FROM THE SOUTHWEST TO THE NORTHWEST BEHIND THE FRONT AS
WELL WITH SUSTAINED WIND SPEEDS AROUND 10 TO 15 MPH. TONIGHT'S LOWS
ARE EXPECTED TO RANGE FROM THE LOWER AND MIDDLE 20S IN THE POCONOS
AND IN FAR NORTHERN NEW JERSEY, TO THE MIDDLE 30S IN CENTRAL AND
SOUTHERN DELAWARE AND IN THE ADJACENT COUNTIES OF EASTERN MARYLAND.
HIGH PRESSURE BUILDS BACK IN THURSDAY, BRINGING CLEAR SKIES WITH A
COOLER AIRMASS. AFTERNOON HIGHS WILL ONLY REACH THE UPPER 30S TO LOW
40S ACROSS HIGHER ELEVATIONS WITH MID 40S TO LOW 50S ACROSS THE
COASTAL PLAIN. HIGH PRESSURE WILL BECOME CENTERED OVERHEAD THURSDAY
NIGHT, POSSIBLY ALLOWING FOR ROBUST RADIATIONAL COOLING TO ENSUE.
OVERNIGHT LOWS ARE EXPECTED IN THE MID 20S TO LOW 30S.
IN REGARDS TO FROST/FREEZE POTENTIAL ACROSS THE DELMARVA...AS IT
CURRENTLY STANDS, SOME PATCHY FROST IS VERY POSSIBLE THURSDAY NIGHT
ACROSS THE DELMARVA WHERE THE GROWING SEASON HAS BEGUN. FURTHERMORE,
IF WINDS REMAIN LIGHT AND DECOUPLE, OVERNIGHT LOWS COULD COOL BELOW
THE CURRENT FORECAST, WHICH WOULD BRING TEMPERATURES BELOW FREEZING
BY A FEW DEGREES ACROSS THE NORTH-CENTRAL DELMARVA WHERE THE GROWING
SEASON HAS BEGUN. RIGHT NOW UNCERTAINTY REMAINS TOO LOW FOR A FREEZE
WATCH, BUT A FROST ADVISORY MAY BE NEEDED.
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
SIGNIFICANT WARM-UP THROUGH SATURDAY. SHOWERS FRIDAY NIGHT AND
SATURDAY MORNING, THEN SOME SHOWERS OR A THUNDERSTORM POSSIBLE
SATURDAY AFTERNOON WITH A STRONG COLD FRONT. STRONG WINDS SATURDAY.
A MORE ZONAL FLOW ALOFT ACROSS OUR REGION FRIDAY WILL GIVE WAY TO A
POTENT CLOSED LOW FROM THE MIDWEST AND GREAT LAKES. THIS TROUGH WILL
SHIFT ACROSS THE NORTHEAST AND MID-ATLANTIC REGIONS DURING SATURDAY
AND WEAKEN SOME. IT WILL DRIVE STRONG SURFACE LOW PRESSURE ACROSS
THE GREAT LAKES TO NORTHERN NEW ENGLAND THROUGH SATURDAY, WITH A
STRONG COLD FRONT CROSSING OUR AREA SATURDAY AFTERNOON AND EVENING.
THE LOW-LEVEL WARM AIR ADVECTION CONTINUES FRIDAY WITH 925 MB
TEMPERATURES INCREASING TO +7C TO +12C. SOUTH TO SOUTHWEST WINDS
WILL ALSO INCREASE THE LOW-LEVEL MOISTURE. HIGH TEMPERATURES ARE
FORECAST TO JUMP INTO THE MID/UPPER 50S TO LOW TO MID 60S ACROSS THE
REGION (STILL COOLER THOUGH IN PARTS OF THE SOUTHERN POCONOS). AS
THE LOW-LEVEL FLOW INCREASES IN CONJUCTION WITH THE WARM AIR
ADVECTION, A WARM FRONT IS FORECAST TO BECOME BETTER ORGANIZED INTO
OUR AREA. SOME ASSOCIATED LIFT MAY RESULT IN SOME AFTERNOON SHOWERS
MAINLY NEAR AND NORTH OF I-78. THE SHOWERS WILL THEN INCREASE
EASTWARD FRIDAY NIGHT AS FORCING FOR ASCENT BECOMES ENHANCED BY A
PASSING SHORTWAVE, AN 850 MB SOUTHWESTERLY JET OF 50-70 KNOTS AND A
BURST OF LOW-LEVEL WARM AIR ADVECTION. A SOUTH TO SOUTHWEST BREEZE
WILL DEVELOP FRIDAY AND BECOME GUSTY, AND A MORE SOUTHERLY COMPONENT
WILL RESULT IN COOLER TEMPERATURES ALONG THE COAST ESPECIALLY NEW
JERSEY. MUCH MILDER FRIDAY NIGHT AS WE BECOME DEEPER INTO THE WARM
SECTOR.
AS WE GO THROUGH SATURDAY, A POTENT UPPER-LEVEL TROUGH ARRIVES AND
STRONG SURFACE LOW PRESSURE WILL TRACK TO OUR NORTHWEST AND NORTH.
ITS STRONG COLD FRONT HOWEVER WILL CROSS OUR REGION DURING THE
AFTERNOON AND EARLY EVENING. A ROBUST AND DEEP SOUTHWESTERLY WIND
FIELD WILL MOVE ACROSS OUR REGION AHEAD OF THE COLD FRONT, WITH 850
MB WINDS FORECAST TO BE 40-70 KNOTS. THE CORE OF THE LOW-LEVEL JET
HOWEVER IS FORECAST TO SHIFT OFFSHORE BY MIDDAY, AND THIS SHOULD
RESULT IN SHOWERS ENDING. THE MODEL FORECAST SOUNDINGS THEN SHOW A
GOOD AMOUNT OF DRYING TAKING PLACE IN THE AFTERNOON WHICH WOULD
RESULT IN AT LEAST PARTIAL CLEARING AHEAD OF THE COLD FRONT. THE
MORE SUNSHINE THAT IS REALIZED THE WARMER IT WILL GET AND ALSO
RESULT IN DEEPER VERTICAL MIXING. THE WARMTH WILL ALSO DETERMINE HOW
MUCH INSTABILITY CAN BE REALIZED. THE MODEL FORECAST SOUNDINGS SHOW
SOME INSTABILITY DEVELOPING IN THE AFTERNOON WHICH COULD RESULT IN
SOME THUNDERSTORMS. THE EXTENT OF THE DRY AIR ABOVE THE SURFACE
HOWEVER MAY LIMIT THE CONVECTIVE DEVELOPMENT. THE QUESTION IS HOW
MUCH FORCING ACCOMPANIES THE COLD FRONT ESPECIALLY FOR CONVECTIVE
DEVELOPMENT. GIVEN THE ROBUST WIND FIELD ALONG WITH STEEP LOW-LEVEL
LAPSE RATES, IF SOME CONVECTION WERE TO DEVELOP THEN LOCALLY
DAMAGING WINDS WOULD BE POSSIBLE.
OUTSIDE OF ANY CONVECTION, IT WILL BE A WINDY DAY AS DEEP MIXING IS
DEPICTED ON THE MODEL FORECAST SOUNDINGS. IF THE GFS SOUNDINGS ARE
CORRECT, WE MAY BE VERY CLOSE TO HIGH WIND WARNING CRITERIA (WIND
GUSTS OF 58+ MPH) FOR SOME AREAS IN THE AFTERNOON. WHILE THIS CANNOT
BE RULED OUT, THE THINKING IS THAT A WIND ADVISORY IS POSSIBLE WITH
PEAK GUSTS MOSTLY IN THE 40-50 MPH RANGE SATURDAY AFTERNOON. IN
ADDITION, THERE COULD BE A BURST OF STRONGER WINDS WITH THE COLD
FRONT AS QUICKLY INCREASING COLD AIR ADVECTION ENHANCES THE DOWNWARD
MOMENTUM TRANSFER FOR A SHORT TIME.
AHEAD OF THE COLD FRONT, THE AIR MASS IS FORECAST TO BE VERY WARM
WITH MUCH OF OUR AREA GETTING INTO THE LOW TO MID 70S. THE CURRENT
RECORD HIGH TEMPERATURES HOWEVER FOR APRIL 1ST ARE IN THE 80S FOR
ALL OF OUR CLIMATE SITES (EXCEPT LOW 70S FOR THE ATLANTIC CITY
MARINA), THEREFORE THESE WOULD BE SAFE. AS THE COLD FRONT MOVES
THROUGH, STRONG COLD AIR ADVECTION OCCURS AND THIS SHOULD KEEP THE
WINDS GUSTY SATURDAY NIGHT ALTHOUGH SOME DECREASE IS EXPECTED
OVERNIGHT. ANY SHOWERS AND/OR THUNDER ARE EXPECTED TO END DURING THE
EARLY EVENING AS MUCH DRIER AND COLDER AIR ADVECTS INTO THE
REGION.
LONG TERM /SUNDAY THROUGH WEDNESDAY/
FEATURES...THE LONG TERM PERIOD WILL LOOK TO START OUT SUNDAY WITH
SURFACE HIGH PRESSURE TO OUR NORTHWEST NEAR THE GREAT LAKES REGION.
WITH TIME, THIS HIGH WILL LOOK TO MIGRATE GENERALLY SOUTHEASTWARD
BEFORE EMERGING OFFSHORE OF THE REGION BY MONDAY. AS THE HIGH
CONTINUES TO PUSH EASTWARD OVER THE ATLANTIC MONDAY AND ONWARDS, IT
IS POSSIBLE THAT A WEAKENING FRONTAL BOUNDARY ASSOCIATED WITH LOW
PRESSURE OVER THE GREAT LAKES REGION WILL BE APPROACHING. AS THIS
FRONTAL BOUNDARY SLOWS DOWN AND POSSIBLY STALLS OVER OUR REGION
DURING THE MONDAY NIGHT TO TUESDAY TIME FRAME, SURFACE LOW PRESSURE
WILL BE DEEPENING OVER THE CENTRAL CONUS WITH FRONTOGENESIS
OCCURRING ALONG WITH IT. WITH MOST ENSEMBLES SUPPORTING THE
CENTRAL CONUS LOW TRACKING NORTHEASTWARDS TOWARDS THE GREAT
LAKES, A WARM FRONT WILL LOOK TO APPROACH THE REGION DURING THE
TUESDAY AND TUESDAY NIGHT TIME FRAME, POSSIBLY PASSING THROUGH
THE REGION COME TUESDAY NIGHT INTO WEDNESDAY.
IMPACTS...EXPECTING HIGH PRESSURE TO DOMINATE OUR REGION SUNDAY AND
MONDAY WITH MAINLY BENIGN CONDITIONS; HAVE NO POPS INCLUDED IN
FORECAST THROUGH THIS TIME FRAME. HOWEVER, IT SHOULD BE MENTIONED
THAT THERE IS SOME GUIDANCE/MODEL SUPPORT FOR SHORTWAVE ENERGY TO
LINGER SUNDAY. THE WEAKENING FRONTAL BOUNDARY APPROACHING THE REGION
MONDAY MAY LOOK TO BRING SOME RAIN TO THE REGION STARTING MONDAY
NIGHT; HAVE INCLUDED SLIGHT CHANCE POPS IN THE FORECAST FOR THIS
TIME FRAME. GUIDANCE INDICATES THIS WEAKENING BOUNDARY MAY STALL
OVER OR NEAR OUR REGION WHILE BEING FLANKED SOUTHWARDS; CANNOT RULE
OUT PRECIPITATION CONTINUING FROM THIS BOUNDARY THROUGH TUESDAY.
HENCE, SLIGHT CHANCE OF POPS CONTINUE TO BE INCLUDED. TUESDAY NIGHT
AND WEDNESDAY, CHANCE POPS ARE INTRODUCED IN ANTICIPATION OF WARM
FRONTAL BOUNDARY APPROACHING THE REGION FROM CENTRAL CONUS LOW
MOVING NORTHEASTWARDS.
TEMPERATURES WILL LIKELY BE BELOW AVERAGE SUNDAY AS COLD AND DRIER
AIR MOVES IN FROM THE NORTHWEST. MAINLY ABOVE AVERAGE TEMPERATURES
CAN BE EXPECTED THEREAFTER, ESPECIALLY FOR TUESDAY AND
WEDNESDAY.
AVIATION /20Z WEDNESDAY THROUGH MONDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
TONIGHT...MAINLY VFR. THERE IS A CHANCE OF LIGHT RAIN SHOWERS
BETWEEN ABOUT 01Z AND 05Z AROUND KRDG, KABE AND KTTN. SOUTHWEST WIND
5 TO 10 KNOTS, BECOMING NORTHWEST 10 TO 15 KNOTS WITH GUSTS OF 20 TO
25 KNOTS. A COLD FRONTAL PASSAGE AROUND 03Z TO 06Z COULD BRING A
BRIEF PERIOD OF NORTHWESTERLY WIND GUSTS NEAR THE 30 KNOT RANGE.
MEDIUM TO HIGH CONFIDENCE.
THURSDAY...VFR. NW WINDS 5-10 KTS DURING THE DAY, BECOMING CALM AT
NIGHT. HIGH CONFIDENCE.
OUTLOOK...
FRIDAY...VFR WITH INCREASING CLOUDS AND CEILINGS GRADUALLY LOWER IN
THE AFTERNOON, THEN MVFR TO IFR CONDITIONS DEVELOP AT NIGHT WITH
SHOWERS. SOUTHWEST WINDS 10-15 KNOTS WITH GUSTS TO AROUND 25 KNOTS,
DIMINISHING TO MAINLY 10 KNOTS OR LESS AT NIGHT. A PERIOD OF LOW-
LEVEL WIND SHEAR POSSIBLE AT NIGHT. MODERATE CONFIDENCE.
SATURDAY...MVFR/IFR CONDITIONS IN THE MORNING WITH SHOWERS, THEN
MAINLY VFR IN THE AFTERNOON. SOME SHOWERS OR A THUNDERSTORM POSSIBLE
IN THE AFTERNOON TO EARLY EVENING. SOUTHWEST WINDS 15-25 KNOTS WITH
GUSTS 30-40 KNOTS, WITH THE STRONGEST WINDS IN THE AFTERNOON. WINDS
THEN BECOME WEST TO NORTHWEST AT NIGHT AND DIMINISH SOME. LOW
CONFIDENCE.
SUNDAY...VFR WITH PREVAILING NW FLOW AROUND 15 KTS. HIGH CONFIDENCE.
MONDAY...VFR WITH S/SW FLOW PREVAILING AROUND 15 KTS. HIGH
CONFIDENCE.
MARINE
A EASTERLY WIND AROUND 10 KNOTS THIS AFTERNOON WILL BECOME A
SOUTHWEST WIND 10 TO 15 KNOTS THIS EVENING. WE WILL THEN SEE IT
SHIFT TO THE NORTHWEST WITH A COLD FRONTAL PASSAGE AFTER MIDNIGHT.
SUSTAINED WIND SPEEDS ARE ANTICIPATED TO INCREASE TO 20 TO 25 KNOTS
FOR A FEW HOURS IN THE WAKE OF THE FRONT WITH GUSTS AROUND 30 KNOTS.
SEAS BUILD TO 2-4 FT WITH A FEW 5 FT WAVES. AS A RESULT, A SMALL
CRAFT ADVISORY IS IN EFFECT FOR OUR OCEAN WATERS AND FOR DELAWARE
BAY FROM MIDNIGHT UNTIL 8:00 AM THURSDAY.
SUB-SCA CONDITIONS RESUME THURSDAY WITH NW WINDS SUBSIDING TO AROUND
10 KTS BECOMING LIGHT THURSDAY NIGHT. SEAS 2-4 FT DURING THE DAY
DROP TO 1-2 FT AT NIGHT.
OUTLOOK...
FRIDAY...SMALL CRAFT ADVISORY CONDITIONS DEVELOPING AS SOUTH TO
SOUTHWEST WINDS INCREASE AND SEAS BUILD.
SATURDAY...SMALL CRAFT ADVISORY CONDITIONS LIKELY. A PERIOD OF GALE
FORCE WIND GUSTS POSSIBLE SATURDAY INTO SUNDAY, HOWEVER THIS WILL
DEPEND ON THE VERTICAL MIXING AS A VERY WARM AIR MASS OVER THE
CHILLY OCEAN WATERS WILL BE IN PLACE AHEAD OF A STRONG COLD FRONT.
THE GREATEST CHANCE FOR GALE FORCE WIND GUSTS MAY END UP BEING
DURING SATURDAY NIGHT ALONG AND BEHIND THE COLD FRONT.
SUNDAY...SCA CONDITIONS LIKELY.
MONDAY...SCA CONDITIONS POSSIBLE.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM EDT
THURSDAY FOR ANZ430-431-450>455.
SYNOPSIS...OHARA/WUNDERLIN
NEAR TERM...MJL
SHORT TERM...GORSE
LONG TERM...WUNDERLIN
AVIATION...GORSE/MJL/WUNDERLIN
MARINE...GORSE/IOVINO/MJL/WUNDERLIN
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