405
FXUS61 KPHI 261440
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1040 AM EDT SAT APR 26 2025
SYNOPSIS
AS LOW PRESSURE TRACKS TO OUR NORTH TODAY, A COLD FRONT WILL CROSS
OUR REGION THIS AFTERNOON INTO THIS EVENING. LOW PRESSURE MAY THEN
MEANDER NEAR COASTAL NEW ENGLAND SUNDAY AS HIGH PRESSURE SLOWLY
APPROACHES OUR AREA FROM THE WEST. THE HIGH SLIDES ACROSS OUR AREA
DURING MONDAY BEFORE SHIFTING TO OUR SOUTH AND EAST. A WARM FRONT
MOVES THROUGH LATER TUESDAY FOLLOWED BY A COLD FRONT ON WEDNESDAY.
HIGH PRESSURE SLIDES BY TO OUR NORTH THURSDAY, THEN A COLD FRONT
ARRIVES DURING FRIDAY.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGE: ROUNDS OF SHOWERS AND STORMS, WITH A FOCUS ON A
LINE OF STORMS JUST AHEAD OF THE COLD FRONT THIS AFTERNOON AND
INTO THE EARLY EVENING THAT COULD BRING LIGHTNING AND GUSTY
WINDS.
ONE AREA OR SHOWERS REACHED FROM THE SOUTHERN POCONOS AND NORTH
NJ AND IT EXTENDS SW ACROSS THE LEHIGH VALLEY AND FURTHER SOUTH
INTO THE EASTERN SHORE OF MD. THESE SHOWERS ARE MOVING EAST AND
WILL AFFECT THE AREA MUCH OF THE REST OF THE MORNING AND INTO
THE EARLY AFTERNOON. A FEW OF THE HOURLY POPS WERE ADJUSTED UP A
BIT TO ACCOUNT FOR THIS. ALSO, A FEW MINOR ADJUSTMENTS TO WINDS
AND TEMPS TOO.
THE MAIN FOCUS IN THIS PERIOD WILL BE A SECOND ROUND OF SHOWERS
AND THUNDERSTORMS EXPECTED JUST AHEAD OF THE COLD FRONT THIS
AFTERNOON. WITH THIS ROUND, EXPECTING A LINE OF SHOWERS AND
STORMS TO PROGRESS QUICKLY FROM WEST TO EAST THROUGH THE
AFTERNOON AND EVENING (APPROXIMATELY 1 PM TO 8 PM).
THERE IS A CONDITIONAL THREAT (5%) THAT THERE WILL BE GUSTY
WINDS WITH THIS SECOND ROUND OF STORMS, ESPECIALLY FOR AREAS
ALONG AND EAST OF THE INTERSTATE 95 CORRIDOR. MODEL SOUNDINGS
DEPICT A BRIEF WINDOW OF A LONG AND SKINNY CAPE PROFILE. WHILE
THE CAPE VALUES WILL BE LIMITED, IT COULD BE ENOUGH TO MIX DOWN
SOME OF THE STRONGER WINDS ALOFT. ADDITIONALLY, A LAYER OF DRY
AIR BETWEEN 700 AND 500 MB COULD LEAD TO SOME DRY AIR ENTRAINMENT
AND POTENTIAL FOR DOWNBURSTS. MODEL DCAPE VALUES IN MANY AREAS
ARE HIGHER THAN THE CAPE VALUES.
IN THE WAKE OF THE COLD FRONT, SHOWERS WILL CLEAR OUT QUICKLY, AND
WINDS WILL INCREASE OUT OF THE NORTHWEST. EXPECT TO STAY RELATIVELY
WELL MIXED OVERNIGHT, BUT WITH STRONG COLD AIR ADVECTION IN THE WAKE
OF THE COLD FRONT, SHOULD STILL BE ABLE TO DROP DOWN INTO THE 30S
AND 40S FOR MOST OF THE AREA.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/
MUCH COOLER WITH STRONG WINDS SUNDAY, THEN TEMPERATURES REBOUND
MONDAY WITH LESS WIND.
A CLOSED LOW IS FORECAST TO PIVOT ACROSS THE NORTHEAST SUNDAY WITH
SURFACE LOW PRESSURE POSSIBLY MEANDERING NEAR COASTAL NEW ENGLAND
FOR A TIME. AS THIS OCCURS, HIGH PRESSURE WILL BE BUILDING INTO THE
UPPER OHIO VALLEY. THIS WILL PLACE OUR AREA WITHIN CYCLONIC FLOW AND
A TIGHT PRESSURE GRADIENT. GIVEN COLD AIR ADVECTION AND A DEEPER
MIXING LAYER DURING THE DAY, BREEZY TO WINDY CONDITIONS ARE EXPECTED
DURING SUNDAY. MODEL FORECAST SOUNDINGS VIA BUFKIT SHOW STEEPENING
OF THE LOW-LEVEL LAPSE RATES WITH 30 TO NEARLY 40 KNOTS OF WIND
WITHIN THE MIXING LAYER. NORTHWEST SURFACE WINDS 15-25 MPH WITH
GUSTS 30-40 MPH LOOK TO OCCUR, WHICH WILL THEN START TO DIMINISH
SUNDAY EVENING AS THE MIXING HEIGHTS LOWER AND WE START LOOSING THE
INFLUENCE OF THE CYCLONIC FLOW. WENT AHEAD AND INCREASED THE WIND
AND WIND GUSTS QUITE A BIT FOR THE DAYTIME HOURS OF SUNDAY. A MUCH
DRIER AIR MASS WILL ALSO BE ADVECTING IN DURING SUNDAY WITH DEW
POINTS FALLING THROUGH THE 30S. DUE TO THE COLDER AIR ALOFT THERE
SHOULD BE A DECENT AMOUNT OF STRATOCUMULUS DEVELOPMENT FOR A TIME
FOR MUCH OF THE AREA, WHICH IS SUPPORTED BY THE MODEL FORECAST
SOUNDINGS. THE SKY WILL CLEAR SUNDAY NIGHT AND TEMPERATURES DROP
INTO THE 40S ACROSS THE REGION.
AS WE GO THROUGH MONDAY, SOME MID LEVEL RIDGING ARRIVES FROM THE
WEST AND THIS WILL ALLOW SURFACE HIGH PRESSURE TO SLIDE OVER OUR
AREA ALTHOUGH THE CENTER OF THE HIGH LOOKS TO BECOME MORE FOCUSED TO
OUR SOUTH WITH TIME. THIS WILL RESULT IN LESS WIND AND WITH HEIGHTS
ON THE RISE IT WILL BE A WARMER AFTERNOON. HIGH TEMPERATURES LOOK TO
BE ABOUT 10 DEGREES HIGHER THAN SUNDAY. NORTHWEST WINDS WILL BE LESS
AND AS THE FLOW TURNS EVEN LIGHTER A SEA/BAY BREEZE SHOULD DEVELOP
DURING THE COURSE OF THE AFTERNOON. TEMPERATURES MONDAY NIGHT LOOK
TO DROP BACK INTO THE MID/UPPER 40S TO SOME LOW 50S.
LONG TERM /TUESDAY THROUGH FRIDAY/
SUMMARY...MILD/WARM TEMPERATURES OVERALL ALONG WITH SOME CHANCES FOR
SHOWERS.
SYNOPTIC OVERVIEW...A MID LEVEL RIDGE IS FORECAST TO CREST ACROSS
OUR AREA TUESDAY, THEN AN UPPER-LEVEL TROUGH SLIDES ACROSS THE
NORTHEAST LATE TUESDAY INTO WEDNESDAY. SOME BRIEF RIDGING ALOFT
MOVES THROUGH THURSDAY FOLLOWED BY AN UPPER-LEVEL TROUGH DURING
FRIDAY. AT THE SURFACE, HIGH PRESSURE SHIFTS TO OUR SOUTH AND EAST
TUESDAY THEN A COLD FRONT ARRIVES WEDNESDAY. HIGH PRESSURE SLIDES BY
TO OUR NORTH THURSDAY, THEN A COLD FRONT ARRIVES DURING FRIDAY.
FOR TUESDAY AND WEDNESDAY...AS A MID LEVEL RIDGE AXIS SHIFTS SOUTH
AND EAST OF OUR AREA, SURFACE HIGH PRESSURE WILL AS WELL. A WARM
FRONT LOOKS TO LIFT ACROSS OUR AREA LATER TUESDAY. AN UPPER-LEVEL
TROUGH SHIFTS EAST INTO THE NORTHEAST FROM THE GREAT LAKES AND
ADJACENT CANADA, WITH A COLD FRONT CROSSING OUR AREA DURING
WEDNESDAY. THIS MAY BE A QUICK MOVING SYSTEM WITH NOT MUCH TIME FOR
DEEPER MOISTURE RETURN AND THEREFORE SHOWERS MAY BE LIMITED WITH IT.
SOME SHOWERS LOOK TO BE POSSIBLE TUESDAY WITH THE WARM FRONT, THEN
THE COLD FRONT ITSELF LOOKS TO BE SPEEDING UP SOME AND MAY CROSS
MOST IF NOT ALL OF THE AREA DURING THE FIRST PART OF WEDNESDAY. IT
MAY COME THROUGH MAINLY DRY. A SOUTH TO SOUTHWEST BREEZE SHOULD
INCREASE DURING TUESDAY AS THE PRESSURE GRADIENT TIGHTENS SOME AHEAD
OF THE ADVANCING COLD FRONT, THEN A WEST TO NORTHWEST BREEZE OCCURS
WEDNESDAY IN THE WAKE OF THE COLD FRONT. TEMPERATURES TUESDAY SHOULD
TOP OUT AROUND 80 DEGREES FOR MUCH OF THE AREA, THEN SOME COOLING
STARTS TO TAKE PLACE DURING WEDNESDAY ALONG WITH MUCH DRIER AIR
ADVECTING IN.
FOR THURSDAY AND FRIDAY...SURFACE HIGH PRESSURE IS FORECAST TO BE
SLIDING BY TO OUR NORTH THURSDAY ALTHOUGH STILL EXTENDING ACROSS OUR
AREA. AS THE FLOW VEERS FROM SOUTHEAST TO SOUTH AND SOUTHWEST
THOUGH, WARM AIR ADVECTION GETS UNDERWAY ESPECIALLY AS A WARM FRONT
APPROACHES. THE INCREASING ISENTROPIC LIFT IN ADVANCE OF THE WARM
FRONT AND AHEAD OF AN APPROACHING UPPER-LEVEL TROUGH MAY RESULT IN
SOME SHOWERS LATER THURSDAY AND THURSDAY NIGHT. SOME ELEVATED
INSTABILITY CANNOT BE RULED OUT, HOWEVER THE CHANCE FOR SOME THUNDER
IS LOW CONFIDENCE AS OF NOW. THE AFOREMENTIONED UPPER-LEVEL TROUGH
DRIVES SURFACE LOW PRESSURE ACROSS THE EASTERN GREAT LAKES AND
VICINITY FRIDAY, AND THIS PULLS A COLD FRONT ACROSS OUR AREA LATER
FRIDAY. INCREASING FORCING FOR ASCENT TIED TO THIS INCOMING UPPER-
LEVEL TROUGH AND COLD FRONT SHOULD RESULT IN AN INCREASE IN SHOWERS
FOR A TIME. SOME THUNDER IS POSSIBLE, HOWEVER THIS LOOKS TO BE MORE
TIED TO HOW FAR NORTH THE MAIN WARM SECTOR GETS AND ALSO HOW MUCH
INSTABILITY CAN BE ACHIEVED IN ADVANCE OF THE COLD FRONT. HIGH
TEMPERATURES THURSDAY ARE FORECAST TO BE IN THE 60S TO LOW 70S, AND
THEN ON FRIDAY THE HIGHS WILL DEPEND ON THE NORTHWARD PLACEMENT OF
THE MAIN WARM SECTOR.
AVIATION /15Z SATURDAY THROUGH WEDNESDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
THIS AFTERNOON...MOSTLY VFR BUT PERIODS OF MVFR CONDITIONS
(MOSTLY DUE TO CEILINGS) ARE POSSIBLE. SHOWERS ARE PROCEEDING
WEST TO EAST ACROSS THE TERMINALS FROM THE LATE MORNING AND
INTO THE AFTERNOON. ANOTHER ROUND OF SHOWERS WITH SCATTERED
THUNDERSTORMS ARE EXPECTED TO MOVE FROM W TO E BETWEEN 17Z AND
00Z. ONCE THIS ROUND (AND THE ASSOCIATED COLD FRONT PASSES),
EXPECT A QUICK RETURN TO VFR AND AN ABRUPT WIND SHIFT TO
NORTHWESTERLY WINDS WITH GUSTS UP TO 25 KT.
TONIGHT...VFR CONDITIONS EXPECTED WITH NORTHWESTERLY WINDS
CONTINUING TO GUST NEAR 20 KT.
OUTLOOK...
SUNDAY...VFR. NORTHWEST WINDS 15-20 KNOTS WITH GUSTS 30-35 KNOTS,
DIMINISHING AT NIGHT.
MONDAY...VFR.
TUESDAY AND WEDNESDAY...TIMES OF SUB-VFR CONDITIONS POSSIBLE,
ESPECIALLY TUESDAY NIGHT INTO WEDNESDAY MORNING.
MARINE
THE SMALL CRAFT ADVISORY CONTINUES WITH BREEZY SOUTH TO SOUTHWEST
WINDS THROUGH THIS AFTERNOON, BEFORE A COLD FRONT WILL BRING AN
ABRUPT SHIFT TO NORTHWESTERLY WINDS LATER THIS AFTERNOON INTO
THIS EVENING. NORTHWESTERLY WINDS GUSTING NEAR 30 KT ARE EXPECTED
IN THE WAKE OF THE COLD FRONT CONTINUING THROUGH THE OVERNIGHT
HOURS. THERE IS A SMALL CHANCE (LESS THAN 20%) THAT WINDS WILL
GUST AS HIGH AS 35 KT, BUT CONFIDENCE IS TOO LOW TO ISSUE A GALE
WARNING AT THIS TIME.
OUTLOOK...
SUNDAY...SMALL CRAFT ADVISORY CONDITIONS, WITH NORTHWEST WIND GUSTS
TO 30 KNOTS. THE CONDITIONS IMPROVE AT NIGHT.
MONDAY...THE CONDITIONS ARE ANTICIPATED TO BE BELOW SMALL CRAFT
ADVISORY CRITERIA.
TUESDAY AND WEDNESDAY...SMALL CRAFT ADVISORY CONDITIONS PROBABLE,
ESPECIALLY TUESDAY NIGHT INTO WEDNESDAY MORNING.
FIRE WEATHER
SHOWERS AROUND THE AREA INTO THIS EVENING. OVERALL, QPF OF 0.20-0.40
INCHES OF RAIN ACROSS MOST OF THE AREA, ALTHOUGH 0.50-1.00 INCHES
OF RAIN POSSIBLE FOR ABOUT THE I-80 CORRIDOR. SOME THUNDERSTORMS
POSSIBLE ESPECIALLY THIS AFTERNOON AND EARLY THIS EVENING, WHICH
CAN RESULT IN LOCALLY HIGHER RAINFALL AMOUNTS. GIVEN THIS AND HIGHER
RELATIVE HUMIDITY, THERE ARE NO CONCERNS FOR RAPID FIRE SPREAD TODAY.
FOR SUNDAY, NORTHWEST WINDS 15-25 MPH WITH GUSTS 30-40 MPH. IN ADDITION,
RELATIVE HUMIDITY VALUES ARE FORECAST TO DROP TO ABOUT 30-35 PERCENT
NEAR AND ESPECIALLY SOUTH OF I-78 (40 PERCENT AND HIGHER NORTH OF
I-78). HOW QUICKLY THE FUELS DRY OUT FROM THE SHOWERS TODAY WILL
DETERMINE ANY RAPID FIRE SPREAD RISK.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT SUNDAY FOR ANZ430-431-
450>455.
SYNOPSIS...GORSE
NEAR TERM...JOHNSON/PO
SHORT TERM...GORSE
LONG TERM...GORSE
AVIATION...GORSE/JOHNSON/PO
MARINE...GORSE/JOHNSON/PO
FIRE WEATHER...
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