Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 180725 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 325 AM EDT FRI APR 18 2014 .SYNOPSIS... HIGH PRESSURE WILL CONTINUE TO EXTEND ACROSS THE EASTERN SEABOARD THROUGH TODAY. THE HIGH WILL RETREAT AS A WEAKENING FRONTAL BOUNDARY MOVES ACROSS THE AREA TONIGHT INTO SATURDAY MORNING. HIGH PRESSURE REESTABLISHES ITSELF ACROSS EASTERN CANADA OVER THE WEEKEND AND BUILDS SOUTHWARD ALONG THE EASTERN SEABOARD SUNDAY INTO MONDAY. ANOTHER FRONTAL BOUNDARY IS EXPECTED TO AFFECT THE AREA NEXT TUESDAY, FOLLOWED BRIEFLY BY HIGH PRESSURE WEDNESDAY NIGHT INTO THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 230 AM ESTF...DROPPED THE REMAINING FROST HEADLINE IN SE PA. EARLY THIS MORNING...MOSTLY CLOUDY WITH A FEW BREAKS IN THE OVC. TEMPS MOSTLY 35 TO 40. ISO FREEZING TEMPS KSMQ TO KMPO SHOULD BE WARMING SEVERAL DEGREES DURING THESE PREDAWN HOURS. A LIGHT NE-E WIND CONTINUES. ELY MARINE LAYER OF HIGH RH SATURATING JUST BELOW THE INVERSION AROUND 2200-2400 FT. NOT NEARLY AS COLD AS THURSDAY MORNING WHEN A RECORD LOW WAS SET AT ALLENTOWN PA. TODAY...FCST BASIS IS MOSTLY NAM 3RLY TEMPS AND MAX T DURING THE DAY AND THE HIGHER OF THE NCEP 3 HRLY MOS DEWPOINTS. 50 50 BLENDED SFC SUSTAINED WINDS. LOW CLOUDS RECEDE EWD AS THE BL WARMS BUT LOW CLOUDS SHOULD DOMINATE MOST OF THIS FRIDAY MORNING. THEN CONSIDERABLE HIGH CLOUD DURING THE AFTN. E WIND G NEAR 15 KT BECOMING S-SE LATE IN THE DAY. MAX TEMPS NEAR 5 PM THIS AFTN IN THE INTERIOR AS THE LOW CLOUDS DISSIPATE DURING THE AFTN AND TEMPS MAY RISE 5 DEGREES BETWEEN 2P AND 5P VCNTY PHILADELPHIA. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... TONIGHT...FCST BASIS IS A 50 50 BLEND OF THE 00Z/18 NCEP MOS GUIDANCE WITH THE COLDER OF THE LOW TEMPS NEAR 10Z/SAT. CONSIDERABLE MOSTLY HIGH CLOUD WITH A SMIDGE OF CFP CLOUD NEAR 4000 FT TOWARD DAWN SATURDAY. LIGHT SE-S WIND DURING THE EVENING TURN W OR NW LATE AT NIGHT. && .LONG TERM /SATURDAY THROUGH THURSDAY/... WE EXPECT DRY WEATHER TO BUILD IN ACROSS THE AREA SATURDAY BEHIND THE WEAKENING FRONTAL BOUNDARY THAT WILL CROSS THE AREA EARLY SATURDAY MORNING AS HIGH PRESSURE BEGINS TO BUILD SOUTHWARD OUT OF CANADA. THE HIGH SHOULD SUPPRESS THE LOW TO OUR SOUTH OFF THE SOUTHEAST COAST WHICH SHOULD PREVENT ANY PRECIPITATION FROM REACHING OUR AREA. THIS HIGH WILL REESTABLISH ITSELF ACROSS EASTERN CANADA AND BUILD SOUTHWARD ALONG THE EASTERN SEABOARD SUNDAY AND MONDAY. THIS WILL CONTINUE TO PROVIDE DRY WEATHER OVER THE WEEKEND INTO MONDAY OF NEXT WEEK. WITH SLIGHT RIDGING ALOFT TAKING PLACE, TEMPERATURES WILL RETURN CLOSER TO NORMAL OVER THE WEEKEND INTO EARLY NEXT WEEK. SUNDAY WILL LIKELY BE THE COOLEST DAY WHEN THICKNESSES AND 925 MB TEMPERATURES ARE AT THEIR LOWEST. THE HIGH WILL WEAKEN AND RETREAT MONDAY NIGHT AHEAD OF AN APPROACHING STORM SYSTEM. AN AREA OF LOW PRESSURE IS FORECAST TO MOVE OUT OF THE GREAT LAKES REGION AND STRENGTHEN AS IT MOVES INTO NEW ENGLAND TUESDAY INTO TUESDAY NIGHT. AS THIS OCCURS, A COLD FRONT WILL SWEEP THROUGH THE AREA LATE TUESDAY INTO TUESDAY NIGHT, WHICH WILL BRING THE NEXT CHANCE OF PRECIPITATION ACROSS THE AREA. THEREFORE WE MAINTAIN CHANCE POPS ACROSS THE AREA DURING THIS TIME PERIOD. THIS LOW IS EXPECTED TO SLOWLY PULL TO OUR NORTHEAST THROUGH WEDNESDAY AND THURSDAY AS HIGH PRESSURE BEGINS TO BUILD SOUTHWARD OUT OF CANADA ONCE AGAIN. WEDNESDAY AND THURSDAY ARE EXPECTED TO BE DRY, BUT SHOULD BE QUITE GUSTY WITH THE TIGHTENING PRESSURE GRADIENT. WINDS COULD EASILY GUST 25-30 MPH, IF NOT HIGHER. && .AVIATION /07Z FRIDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THROUGH 12Z...CIGS 2000-2500 FT. LIGHT EAST WIND. AFTER 12Z...THE MVFR CIG IS EXPECTED TO DISSIPATE RAPIDLY EASTWARD LATE THIS MORNING OR MIDDAY WITH A VFR CIRRUS DECK ABOVE IT DURING THE AFTERNOON. SYNOPTIC SCALE WINDS OVERALL SHOULD BE LIGHTER (GENERALLY AN EASTWARD COMPONENT) THAN THURSDAY AND A SEA BREEZE FRONT MAY FORM DURING THE AFTERNOON AS THE WIND TENDS TO TURN SE-S. TONIGHT...VFR CIRRUS WITH CHC OF A SCT-BKN DECK NEAR 4000 FT TOWARD 10Z SATURDAY ASSOCIATED WITH A WEAK COLD FRONTAL PASSAGE (CFP). OUTLOOK... SATURDAY-MONDAY NIGHT...MOSTLY VFR. GUSTY N-NW WINDS 15-20 KNOTS SATURDAY. TUESDAY...MVFR CONDITIONS POSSIBLE WITH SHOWERS WITH A FRONTAL PASSAGE. && .MARINE... SEAS 9 FT AT 44009 AT 2 AM. GFS WW4 GUIDANCE HAS BEEN TOO LOW BY A FOOT OR 2 ON THE ATLANTIC WATERS AND SO HAVE RAISED THAT GUIDANCE THRU THIS FRIDAY EVENING. SCA CONTINUES OPEN ATLC WATERS...MAINLY FOR SEAS AND HAVE CONVERTED THAT SCA HEADLINE TO SCA FOR HAZARDOUS SEAS HERE AT THE 3 AM ISSUANCE. DE BAY WATERS NO HEADLINE THRU TONIGHT. E-NE WIND G 15 KT AND SEAS LESS THAN 3 FT TODAY. WINDS AND SEAS DIMINISH/SUBSIDE TONIGHT. THE WIND TURN S TOWARD SUNSET FRIDAY THEN SHIFT TO W OR NW TOWARD DAWN SATURDAY. OUTLOOK... SATURDAY...SUB-SMALL CRAFT ADVISORY CRITERIA EXPECTED, THOUGH WINDS MAY GUST NEAR 20 KNOTS. SATURDAY NIGHT-SUNDAY NIGHT...WINDS AND SEAS INCREASING TO SMALL CRAFT ADVISORY CRITERIA OVERNIGHT SATURDAY AND CONTINUE INTO SUNDAY. SEAS MAY REMAIN ELEVATED INTO SUNDAY NIGHT. MONDAY-MONDAY NIGHT...A RETURN TO SUB-SMALL CRAFT ADVISORY CRITERIA. TUESDAY...FRONTAL PASSAGE EXPECTED WITH NEAR ADVISORY CONDITIONS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EDT SATURDAY FOR ANZ450>455. && $$ SYNOPSIS...ROBERTSON NEAR TERM...DRAG SHORT TERM...DRAG LONG TERM...ROBERTSON AVIATION...DRAG/ROBERTSON MARINE...DRAG/ROBERTSON

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