038
FXUS61 KPHI 172321
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
621 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/
PATCHY FOG IS DEVELOPING OVER EAST AND SOUTHEAST NEW JERSEY, AS
WELL AS PORTIONS OF DELMARVA AS A COOLER AIRMASS SPREADS OVER
RELATIVELY SATURATED GROUND DUE TO RECENT RAINFALL. FOR NOW,
THIS MAY PERSIST UNTIL MIDNIGHT OR SO, BUT IT MAY LAST LONGER,
AND MAY SPREAD FARTHER WEST.
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 /23Z TUESDAY THROUGH SUNDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS...
TONIGHT...SOME FOG HAS BEGUN TO DEVELOP OVER EASTERN AND
SOUTHEAST NEW JERSEY AND DELAWARE. VSBYS AT KMIV HAVE
VACILLATED FROM AS LOW AS 1/2SM TO 3SM. WILL GO AHEAD AND TEMPO
LIFR CONDS UNTIL 04Z, AND IF THIS TREND CONTINUES, WILL HAVE TO
EXTEND BR/FG IN THE TAF. FOR THE REST OF THE TAFS, CONFIDENCE
IS LOW THAT FOG WILL DEVELOP IN THESE AREAS AS SURFACE
TEMPERATURES MAY NOT LOWER DOWN TO THE DEW POINT TEMPERATURE.
WILL MONITOR, AND AMD AS NECESSARY. LGT/VRB WINDS. LOW
CONFIDENCE.
WEDNESDAY...UNLESS FOG DEVELOPS LATE TONIGHT, VFR CONDS UNTIL
20Z. MVFR CONDS THEN DEVELOP IN RA. POTENTIAL FOR IFR CONDS JUST
PRIOR TO 00Z, BUT WILL LEAVE OUT OF THE TAFS, EXCEPT FOR KPHL,
AT THIS TIME. LGT/VRB WINDS MOST OF THE DAY, THEN SE WINDS
AROUND 5 KT AFTER 18Z. LOW CONFIDENCE.
WEDNESDAY NIGHT...MVFR/IFR CONDS IN RA/STRATUS. IMPROVEMENT TO
VFR AFTER 06Z AS RAIN ENDS AND A COLD FRONT PASSES THROUGH THE
TERMINALS. WINDS BECOME W-NW AROUND 10 KT AFTER 00Z. 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...MPS/ROBERTSON
SHORT TERM...DESILVA/STAARMANN
LONG TERM...DESILVA/STAARMANN
AVIATION...DESILVA/MPS/ROBERTSON
MARINE...DESILVA/ROBERTSON
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