067
FXUS61 KPHI 290740
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
340 AM EDT TUE APR 29 2025
SYNOPSIS
A WARM FRONT ARRIVES TODAY, FOLLOWED BY A COLD FRONT OVERNIGHT INTO
WEDNESDAY MORNING. HIGH PRESSURE BRIEFLY RETURNS LATE WEDNESDAY INTO
THURSDAY. ANOTHER LOW PRESSURE SYSTEM TRACKS TO OUR NORTH ON FRIDAY
WITH A COLD FRONT MOVING THROUGH BY EARLY SATURDAY. HIGH PRESSURE
THEN BUILDS IN BY SUNDAY.
NEAR TERM /THROUGH TONIGHT/
A WARM AND BREEZY AFTERNOON WELL AHEAD OF A COLD FRONT.
THE AXIS OF A MID LEVEL RIDGE IS FORECAST TO CREST ACROSS OUR AREA
THROUGH THIS MORNING BEFORE SHIFTING TO OUR EAST AND SOUTH THIS
AFTERNOON INTO TONIGHT. THIS WILL TAKE THE CENTER OF SURFACE HIGH
PRESSURE FARTHER SOUTHEAST OF OUR AREA. A TIGHTENING PRESSURE
GRADIENT WILL DEVELOP ACROSS OUR AREA THROUGH THIS AFTERNOON BETWEEN
HIGH PRESSURE TO OUR SOUTHEAST AND WELL AHEAD OF A COLD FRONT. AS
THE BOUNDARY LAYER WARMS THROUGH THE MORNING, STRENGTHENING WINDS
ABOVE THE SURFACE WILL MIX DOWN TO THE SURFACE AND THIS WILL RESULT
IN A GUSTY SOUTH TO SOUTHWEST WIND. AS THE WINDS INCREASE LATER THIS
MORNING AND PEAK DURING THE AFTERNOON, SUSTAINED WINDS OF 15-20 MPH
ARE FORECAST WITH GUSTS UP TO 30 MPH. THE STRONGEST WINDS MAY OCCUR
FROM ABOUT THE I-95 CORRIDOR ON SOUTH AND EAST WHERE SOME DEEPER
MIXING OCCURS. SOME HIGH LEVEL CLOUDINESS WILL BE CRESTING THE RIDGE
AXIS TODAY, AND IT IS POSSIBLE THAT SOME CUMULUS CLOUDS DEVELOP THIS
AFTERNOON PENDING CONVECTIVE TEMPERATURES BEING REACHED.
THE STRENGTHENING SOUTHWESTERLY FLOW WILL BOOST THE LOW-LEVEL WARM
AIR ADVECTION TODAY AND THIS EVENING AHEAD OF A COLD FRONT. THIS
WILL RESULT IN TEMPERATURES WELL ABOVE AVERAGE, WITH HIGHS IN THE
UPPER 70S TO LOW 80S (COOLER IN THE HIGHER ELEVATIONS). GIVEN A
SOUTH TO SOUTHWEST WIND, IT WILL BE COOLER ALONG MUCH OF THE COASTAL
AREAS. ALONG WITH THE WARM AIR ADVECTION, MOISTURE ADVECTION WILL
GET UNDERWAY AS WELL THROUGH THE DAY. THIS WILL BRING AN INCREASE IN
THE SURFACE DEW POINTS, ALTHOUGH WITH DEEPER MIXING THROUGH THE
AFTERNOON SOME LOWERING OF THE DEW POINTS SHOULD OCCUR ESPECIALLY
ACROSS MUCH OF NEW JERSEY AND DELAWARE.
AS WE GO THROUGH TONIGHT, A MILD NIGHT FOR THE REGION AHEAD OF A
COLD FRONT ALTHOUGH THE COLD FRONT WILL BE WORKING ITS WAY ACROSS
PARTS OF THE REGION OVERNIGHT. AN UPPER-LEVEL TROUGH WILL PIVOT
ACROSS THE EASTERN GREAT LAKES AND ADJACENT CANADA, HOWEVER THE MAIN
FORCING LOOKS TO TRACK TO OUR NORTH. A COLD FRONT TIED TO THIS
FEATURE THOUGH WILL ARRIVE IN OUR AREA. A LINE OF SHOWERS AND
THUNDERSTORMS OR EVEN A FEW CLUSTERS ARE EXPECTED TO DEVELOP THIS
AFTERNOON WITH OR AHEAD OF THE COLD FRONT WELL TO OUR WEST. THE
TIMING INTO OUR AREA IS NOT IDEAL AS ANY CONVECTION DOES NOT LOOK TO
ARRIVE INTO OUR FAR WESTERN ZONES UNTIL THIS EVENING. THE MODEL
FORECAST SOUNDINGS INDICATE AN INCREASE IN SHEAR AS A LOW-LEVEL JET
INCREASES AHEAD OF THE COLD FRONT, HOWEVER THE INSTABILITY IS ON THE
LOWER SIDE. GIVEN DIMINISHING FORCING WITH TIME, THE ORGANIZED
CONVECTION WELL TO OUR WEST LOOKS TO BE WEAKENING QUITE A BIT AS IT
APPROACHES AND MOVES INTO OUR FAR WESTERN ZONES. IF THE CONVECTION
REMAINS ORGANIZED ENOUGH AND THEREFORE DOES NOT WEAKEN AS QUICKLY,
THEN THERE IS SOME POTENTIAL FOR LOCALLY STRONG/DAMAGING WINDS
ACROSS THE POCONOS TO PERHAPS PARTS OF THE LEHIGH VALLEY AND BERKS
COUNTY. THIS IS MOSTLY DUE TO LINGERING DRY AIR IN THE BOUNDARY
LAYER AND EVEN SOME MID LEVEL DRY AIR THAT COULD ACCELERATE DOWNWARD
MOMENTUM WITHIN A DOWNDRAFT. THE SPC CONTINUES WITH A MARGINAL RISK
(LEVEL 1 OUT OF 5) FOR POSSIBLE SEVERE THUNDERSTORMS ACROSS THE
POCONOS TO PARTS OF THE LEHIGH VALLEY AND BERKS COUNTY. THE GRADIENT
SURFACE WINDS WILL ALSO SETTLE DOWN SOME TONIGHT AS THE DEEPER
MIXING WANES AFTER SUNSET. LOW TEMPERATURES ARE FORECAST TO BE IN
THE 50S AND 60S.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
COLD FRONT WILL BE CONTINUING TO SINK SOUTH AS WEDNESDAY BEGINS.
THERE REMAINS A BIT OF UNCERTAINTY IN HOW QUICKLY THE FRONT WILL
BE SOUTH OF THE REGION. IF IT DOESN'T GET SOUTHEAST OF SE NJ AND
S DE UNTIL CLOSER TO MID DAY, THAN HIGHS ON WEDNESDAY IN
DELMARVA AND THE COASTAL PLAIN OF NJ WILL BE CLOSE TO IF NOT A
FEW DEGREES WARMER THAN TUESDAY.
HIGH PRESSURE WILL THEN BE THE DOMINANT FEATURE THROUGH
THURSDAY. EVEN WITH THE COLD FRONT, DAY TIME TEMPERATURES ARE
EXPECTED TO BE UP TO 5 DEGREES WARMER THAN NORMAL.
THE WARM FRONT ASSOCIATED WITH THE NEXT LOW PRESSURE SYSTEM
COULD ARRIVE AS EARLY AS LATE THURSDAY, BRINGING THE NEXT CHANCE
FOR SHOWERS AND STORMS.
LONG TERM /FRIDAY THROUGH MONDAY/
WARM FRONT WILL CONTINUE TO LIFT NORTH THROUGH THE REGION ON
FRIDAY. SHOWERS AND THUNDERSTORMS BECOME MORE LIKELY FRIDAY
INTO FRIDAY NIGHT AS THE WARM FRONT WILL BE FOLLOWED CLOSE
BEHIND BY A COLD FRONT. STILL LOTS OF UNCERTAINTY ABOUT
INTENSITY, BUT WE'LL BE WATCHING ANY SEVERE WEATHER RISK
CLOSELY.
SOME OF THE LATEST GUIDANCE IS A BIT SLOWER WITH THE COLD FRONT,
DEPICTING IT CROSSING THROUGH THE REGION DURING THE DAY ON
SATURDAY. CONSEQUENTLY, THERE IS HIGH UNCERTAINTY IN THE
PRECIPITATION CHANCES AND TEMPERATURES ON SATURDAY. HOWEVER, BY
SUNDAY INTO MONDAY, EXPECT TEMPERATURES TO BE SLIGHTLY BELOW
NORMAL
AVIATION /07Z TUESDAY THROUGH SATURDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TODAY...VFR. SOUTH TO SOUTHWEST WINDS NEAR 5 KNOTS OR LOCALLY LIGHT
AND VARIABLE TO CALM EARLY, THEN SOUTHWEST WINDS INCREASE TO AROUND
15 KNOTS WITH GUSTS UP TO 25 KNOTS BY LATER THIS MORNING THROUGH THE
AFTERNOON. HIGH CONFIDENCE.
TONIGHT...VFR OVERALL WITH AN INCREASE IN MAINLY MID TO HIGH LEVEL
CLOUDS. SOME SHOWERS OR A THUNDERSTORM CANNOT BE RULED OUT
ESPECIALLY AROUND KABE AND KRDG, AND GIVEN CHANCES LOOK LOW ENOUGH
JUST INCLUDED A VCSH THERE FOR NOW. SOUTHWEST WINDS 10-15 KNOTS
DIMINISHING TO 5-10 KNOTS AND BECOMING WEST TO NORTHWEST CLOSER TO
DAYBREAK WEDNESDAY. LOW CONFIDENCE ON TIMING/COVERAGE OF ANY SHOWERS
AND THUNDER, ESPECIALLY WITH AN EASTWARD EXTENT.
OUTLOOK...
WEDNESDAY INTO THURSDAY...VFR EXPECTED.
THURSDAY NIGHT THROUGH SATURDAY...PERIODS OF MVFR AND EVEN IFR
WITH SHOWERS AND THUNDERSTORMS POSSIBLE.
MARINE
SMALL CRAFT ADVISORY CONDITIONS ARE FORECAST TO DEVELOP THIS
AFTERNOON AS SOUTHWESTERLY WINDS INCREASE WITH GUSTS 25-30 KNOTS ON
THE OCEAN ZONES. THIS WILL CONTINUE MOST OF TONIGHT. IT MAY TAKE
SOME TIME HOWEVER FOR THE STRONGER WINDS TO REACH THE SURFACE GIVEN
MUCH WARMER AIR MOVING OVER THE COOL OCEAN WATER (WATER TEMPERATURES
MOSTLY IN THE 50S). SEAS WILL ALSO BUILD IN RESPONSE TO THE PERIOD
OF STRONGER WINDS. FOR DELAWARE BAY, OPTED TO ISSUE A SMALL CRAFT
ADVISORY FOR THIS AFTERNOON INTO EARLY THIS EVENING AS GUSTS TO
AROUND 25 KNOTS ARE ANTICIPATED TO OCCUR ESPECIALLY CLOSER TO THE
COAST.
OUTLOOK...
WEDNESDAY THROUGH THURSDAY NIGHT...ONCE SEAS SUBSIDE BELOW 5 FT
WEDNESDAY MORNING, WINDS AND SEAS SHOULD STAY BELOW SCA
CRITERIA.
FRIDAY...SOUTHERLY WINDS ABOVE 25 KT AND SEAS ABOVE 5 FT ARE
POSSIBLE.
SATURDAY...WINDS AND SEAS ARE FORECAST TO REMAIN BELOW SCA
CRITERIA.
FIRE WEATHER
FOR TODAY, WHILE THE DEW POINTS WILL BE MUCH HIGHER THAN YESTERDAY,
THEY WILL REMAIN LOW ENOUGH AND WHEN COMBINED WITH VERY WARM
TEMPERATURES THIS AFTERNOON WILL RESULT IN THE RELATIVE HUMIDITY
DROPPING TO AROUND 30 PERCENT ACROSS MOST OF NEW JERSEY AND
DELAWARE. THE RELATIVE HUMIDITY LOOKS TO STAY HIGHER IN MOST OF
EASTERN PENNSYLVANIA AND MARYLANDS EASTERN SHORE. IN ADDITION, SOUTH
TO SOUTHWEST WINDS WILL INCREASE TO 15-20 MPH WITH GUSTS UP TO 30
MPH. THE STRONGEST WINDS MAY END UP BEING FROM ABOUT I-95 SOUTH AND
EAST. BASED ON THE LATEST FORECAST AND EARLIER COORDINATION WITH
STATE FIRE PARTNERS, A SPECIAL WEATHER STATEMENT WILL BE ISSUED FOR
MOST OF NEW JERSEY AND ALL OF DELAWARE TO COVER THE ELEVATED RISK OF
RAPID FIRE SPREAD THIS AFTERNOON.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 7 PM EDT THIS EVENING
FOR ANZ430-431.
SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 AM EDT WEDNESDAY FOR
ANZ450>455.
SYNOPSIS...JOHNSON/RCM/STAARMANN
NEAR TERM...GORSE
SHORT TERM...JOHNSON/STAARMANN
LONG TERM...JOHNSON/STAARMANN
AVIATION...GORSE/JOHNSON
MARINE...GORSE/JOHNSON
FIRE WEATHER...
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