613
FXUS61 KPHI 172040
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
340 PM EST TUE DEC 17 2024
SYNOPSIS
WEAK HIGH PRESSURE WILL BUILD INTO THE AREA TONIGHT. ANOTHER
AREA OF LOW PRESSURE AND ASSOCIATED COLD FRONT IMPACT THE AREA
WITH ANOTHER ROUND OF RAINFALL LATE WEDNESDAY INTO WEDNESDAY
NIGHT. HIGH PRESSURE RETURNS ON THURSDAY WITH A WEAK DISTURBANCE
PASSING THROUGH ON FRIDAY. OTHERWISE, COLD CANADIAN HIGH
PRESSURE ARRIVES FOR THE WEEKEND INTO EARLY NEXT WEEK.
NEAR TERM /THROUGH WEDNESDAY NIGHT/
THE COLD FRONT CONTINUES TO PUSH OFFSHORE THIS EVENING, BEFORE
IT STALLS TO OUR SOUTH OVERNIGHT. WEAK HIGH PRESSURE WILL
BRIEFLY MOVE INTO THE AREA TONIGHT PROVIDING FAIR WEATHER
OVERNIGHT. THERE IS A SLIGHT CHANCE SOME PATCHY FOG MAY DEVELOP
LATE IN THE OVERNIGHT, BUT WE HAVE KEPT THIS OUT OF THE FORECAST
FOR NOW.
ON WEDNESDAY, THE HIGH PRESSURE SHIFTS OFFSHORE WHILE THE FRONT
TO OUR SOUTH BEGINS TO LIFT BACK NORTHWARD AS A WARM FRONT
THROUGH THE DAY. MEANWHILE, AN AREA OF LOW PRESSURE WILL BE
LIFTING TOWARD OUR AREA FROM THE SOUTHWEST. WE EXPECT RAIN TO
BEGIN TO MOVE INTO PORTION OF THE AREA LATE IN THE AFTERNOON,
BEFORE SPREADING ACROSS THE ENTIRE AREA AS THE LOW PRESSURE
MOVES ACROSS THE AREA. THE RAINFALL COULD BECOME MODERATE TO
HEAVY AT TIMES, BUT RAINFALL AMOUNTS ARE FORECAST TO BE AROUND
0.25-0.50 INCHES ACROSS THE AREA. THE RAIN SHOULD BEGIN TO END
DURING THE OVERNIGHT HOURS AS THE LOW LIFTS TO OUR NORTHEAST AND
A COLD FRONT SHIFTS ACROSS THE AREA.
SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/
HIGH PRESSURE WILL BUILD TO OUR NORTH ON THURSDAY, AND ANOTHER
LONG WAVE TROUGH WILL TAKE SHAPE TO OUR WEST INTO THURSDAY
NIGHT. BENIGN AND SEASONABLE WEATHER CONDITIONS CAN BE EXPECTED.
HIGHS IN THE 40S AND LOWS IN THE 20S TO NEAR 30 DEGREES.
LONG TERM /FRIDAY THROUGH TUESDAY/
POTENTIAL FOR SOME LIGHT PRECIPITATION FRIDAY OR FRIDAY NIGHT
HAS INCREASED A BIT GIVEN THE TRENDS IN THE LATEST GUIDANCE.
WE'LL BE ON THE FRINGES OF BROAD LOW PRESSURE DEVELOPING WELL
OFFSHORE, AND SOME SURFACE TROUGHING COMBINED WITH THE TROUGH
AXIS PASSING OVERHEAD COULD YIELD SOME LIGHT RAIN AND SNOW.
GUIDANCE CONTINUES TO SHOW A RELATIVE LACK OF MOISTURE
ASSOCIATED WITH THIS SYSTEM, THOUGH THERE WAS AN INCREASE IN QPF
ACROSS THE BOARD (ALBEIT VERY LIGHT). HAVE ADVERTISED GENERALLY
CHANCE POPS (~40-50%) ACROSS THE AREA DURING THIS TIMEFRAME.
FORTUNATELY, WITH THE INITIAL LOW WEAKENING AND STRONG LOW
PRESSURE DEVELOPING SEVERAL HUNDRED MILES OFFSHORE, THERE DOES
NOT LOOK TO BE ANY SIGNIFICANT IMPACTS TO THE AREA AT THIS TIME.
OTHERWISE, BEHIND THIS SYSTEM WILL BE THE WELCOMING OF A STRONG
CANADIAN HIGH THAT WILL BUILD INTO THE REGION FOR THE WEEKEND
INTO THE START OF NEXT WEEK. A COUPLE OF DRY SECONDARY COLD
FRONTS WILL USHER IN COLDER AIR AT TIMES, WITH THE "PEAK" OF THE
COLD AIR OCCURING SATURDAY NIGHT THROUGH SUNDAY NIGHT. DURING
THIS TIME, TEMPERATURES WILL RANGE ANYWHERE BETWEEN 10-15
DEGREES BELOW NORMAL. THIS WILL LIKELY BE THE COLDEST AIRMASS SO
FAR THIS SEASON, WITH 850 MB TEMPERATURES FALLING TO AROUND -12C
TO -18C ON SUNDAY. THIS IS EXPECTED TO RESULT IN THE FIRST
DAYTIME PERIOD WITH SUB-FREEZING TEMPERATURES. SOME MODERATING
IS THEN EXPECTED ON MONDAY, BUT OVERALL THE LONG TERM PERIOD
WILL REMAIN BELOW- NORMAL AND DRY.
AVIATION /20Z TUESDAY THROUGH SUNDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS...
REST OF TODAY...THE LOW CLOUDS AND FOG HAVE BEGUN TO LIFT AND
DISSIPATE, AND ALL SITES WILL IMPROVE TO VFR BETWEEN 18Z-19Z.
WEST TO SOUTHWEST WINDS AROUND 5 TO 10 KTS WILL BECOME WEST TO
NORTHWEST THROUGH THIS AFTERNOON. OCCASIONAL GUSTS AROUND 15-20
KNOTS POSSIBLE. HIGH CONFIDENCE.
TONIGHT...VFR CONDITIONS EXPECTED. THERE IS A SMALL CHANCE OF
PATCHY FOG LATE IN THE NIGHT, HOWEVER THIS HAS BEEN KEPT OUT OF
THE TAFS AT THIS TIME. HIGH CONFIDENCE.
WEDNESDAY...VFR (UNLESS PATCHY FOG DOES DEVELOP) WILL REMAIN
FOR MUCH OF THE DAY. HOWEVER, LOWER CLOUDS AND LOWER VISIBILITY
(LIKELY IFR) WILL MOVE IN LATER IN THE DAY AS RAIN MOVES INTO
THE AREA. MODERATE CONFIDENCE.
WEDNESDAY NIGHT...LOWER CLOUDS AND LOWER VISIBILITY (LIKELY
IFR) WILL BEGIN THE PERIOD DURING THE EVENING HOURS, BEFORE
IMPROVING TO MVFR OR VFR OVERNIGHT AS THE RAIN EXITS. MODERATE
CONFIDENCE.
OUTLOOK...
THURSDAY THROUGH THURSDAY NIGHT...VFR. NO SIGNIFICANT WEATHER.
FRIDAY THROUGH FRIDAY NIGHT...SUB-VFR CONDITIONS POSSIBLE WITH
A CHANCE FOR RAIN/SNOW SHOWERS.
SATURDAY AND SUNDAY...VFR. NO SIGNIFICANT WEATHER.
MARINE
THE SMALL CRAFT ADVISORY HAS BEEN CANCELLED FOR TONIGHT AND
CONDITIONS WILL REMAIN BELOW ADVISORY LEVELS TONIGHT THROUGH
WEDNESDAY. SMALL CRAFT ADVISORY CONDITIONS BECOME LIKELY AGAIN
WEDNESDAY NIGHT.
OUTLOOK...
WEDNESDAY NIGHT THROUGH THURSDAY...SCA CONDITIONS PROBABLE.
WIND GUSTS UP TO 25-30 KT AND SEAS AROUND 5 FEET. RAIN LIKELY
WEDNESDAY NIGHT.
THURSDAY NIGHT THROUGH FRIDAY...FAIR WEATHER. NO MARINE
HEADLINES EXPECTED. WINDS UP TO 15 KT AND SEAS OF 3-4 FEET.
FRIDAY NIGHT THROUGH SATURDAY...SCA CONDITIONS PROBABLE. WIND
GUSTS UP TO 25 KT AND SEAS AROUND 5 FEET.
SUNDAY...NO MARINE HEADLINES EXPECTED.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.
SYNOPSIS...DESILVA/STAARMANN
NEAR TERM...ROBERTSON
SHORT TERM...DESILVA/STAARMANN
LONG TERM...DESILVA/STAARMANN
AVIATION...DESILVA/ROBERTSON
MARINE...DESILVA/ROBERTSON
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