600 FXUS61 KPHI 291957 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 357 PM EDT SUN SEP 29 2013 .SYNOPSIS... HIGH PRESSURE WILL REMAIN IN CONTROL OF OUR WEATHER THROUGH MUCH OF THE FIVE DAYS. A WEAK WARM FRONT WILL PASS EASTWARD ACROSS THE MID ATLANTIC STATES TUESDAY. A SUBSTANTIAL FRONTAL SYSTEM WILL APPROACH FROM THE WEST FRIDAY AND SATURDAY AND MAY MOVE OFF THE COAST SUNDAY. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... AN 18Z SURFACE ANALYSIS PLACED HIGH PRESSURE CENTERED NEAR COASTAL NEW ENGLAND, ALTHOUGH IT IS WEDGED SOUTHWESTWARD ALL THE WAY TO THE SOUTHEASTERN U.S. A COOL FRONT WAS FROM NEAR HUDSON BAY TO THE EASTERN GREAT LAKES THEN ALL THE WAY DOWN TO EASTERN TEXAS. LOW PRESSURE WAS WELL EAST OF THE NORTH CAROLINA COAST. AN UPPER AIR ANALYSIS SHOWED A WEAK RIDGE FROM THE TENNESSEE VALLEY TO NEW ENGLAND. A LARGE TROUGH WAS NEAR THE PACIFIC NORTHWEST, WITH A WEAKER SHORT WAVE TROUGH NEAR THE CENTRAL GREAT LAKES. OUR SENSIBLE WEATHER WILL CONTINUE TO BE DOMINATED OVERALL BY HIGH PRESSURE THAT EXTENDS FROM NEW ENGLAND ALL THE WAY DOWN TO THE SOUTHEASTERN U.S. THIS AREA OF HIGH PRESSURE IS GETTING SQUEEZED THOUGH FROM THE WEST AND EAST, AS LOW PRESSURE CONTINUES TO ORGANIZED WELL OFF THE EAST COAST AND A COOL FRONT MOVES ACROSS THE EASTERN GREAT LAKES AND OHIO VALLEY. THE WATER VAPOR IMAGERY THIS AFTERNOON SHOWS AN UPPER-LEVEL LOW EAST OF NORTH CAROLINA. THIS IS TRYING TO TOSS SOME OF THE CLOUDINESS WELL OFF OF OUR COAST WESTWARD, HOWEVER ENOUGH SUBSIDENCE SHOULD HOLD TO KEEP MOST OF THIS OFF THE COAST. THE CUMULUS FIELD THAT DEVELOPED DURING THE DAY AS THE SHALLOW ONSHORE FLOW OCEAN MOISTURE WAS LIFTED ON LAND DUE TO HEATING. THIS MOISTURE SHOULD DISSIPATE OR MIX OUT WITH DRIER AIR ALOFT, RESULTING IN THE CUMULUS FIELD DISSIPATING THROUGH THIS EVENING FROM EAST TO WEST. THE VISIBLE SATELLITE IMAGERY TRENDS THIS AFTERNOON SHOW THIS UNDERWAY IN MUCH OF NEW JERSEY. OTHERWISE, THERE COULD BE SOME HIGH LEVEL CLOUDS ARRIVING MAINLY ASSOCIATED WITH THE COOL FRONT TO OUR WEST GIVEN THE NARROW MOISTURE TRAIL FROM SOUTH TO NORTH SEEN ON THE WATER VAPOR IMAGERY. WHILE THERE COULD BE SOME MAINLY GROUND FOG LATE, IT MAY BE LIMITED DUE TO JUST ENOUGH DRY AIR. BASED ON THIS, PATCHY FOG WAS JUST CONFINED TO THE NORTHWEST ZONES TOWARD DAYBREAK. AS FOR LOW TEMPERATURES, MAINLY AN EVEN BLEND OF THE GFS/NAM MOS WAS USED WITH JUST SOME MINOR TWEAKS. THE LAMP/LAV GUIDANCE WAS INCORPORATED INTO THE HOURLY GRIDS THROUGH THIS EVENING TO HELP ASSIST WITH TRENDS. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... THE OVERALL SYNOPTIC PATTERN DOES NOT CHANGE MUCH DURING MONDAY. A RIBBON OF SURFACE HIGH PRESSURE REMAINS OVER OUR AREA ALTHOUGH IT IS FORECAST TO WEAKEN SOME. MEANWHILE, LOW PRESSURE WILL REMAIN WELL TO OUR EAST. AN UPPER-LEVEL TROUGH LIFTING NORTH OF THE GREAT LAKES WILL WEAKEN, THEREFORE LITTLE IN THE WAY OF DYNAMICS ARE LEFT FOR THE SURFACE COOL FRONT. AS A RESULT, THE FRONT SHOULD TEND TO WEAKEN FURTHER OR EVEN DISSIPATE AS IT APPROACHES OUR AREA. AS THE MAIN SYNOPTIC FEATURES SHIFT EASTWARD A BIT, THE PERSISTENT NORTHEASTERLY LOW-LEVEL FLOW SHOULD SHIFT TO A MORE SOUTHERLY FLOW ALTHOUGH ON THE LIGHT SIDE. A NARROWING PLUME OF MID TO UPPER LEVEL MOISTURE LINGERING WITH THE APPROACHING WEAKENING FRONT AND UPPER-LEVEL TROUGH, MAY ALLOW FOR SOME HIGH LEVEL CLOUDINESS ACROSS OUR AREA. HOWEVER, A DECENT AMOUNT OF SUNSHINE IS ANTICIPATED ALTHOUGH AT LEAST SOME SHORT CUMULUS WILL PROBABLY DEVELOP OVER LAND DUE TO ENOUGH HEATING. THE HIGH TEMPERATURES WERE MAINLY AN EVEN GFS/NAM MOS BLEND. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... 500 MB: A LARGE WARM RIDGE BUILDS ALONG THE EAST COAST BY THURSDAY IN THE WAKE OF MONDAYS DEPARTING OFFSHORE LOW TROUGH. SIGNIFICANT TROUGHING EVOLVES IN THE GREAT LAKES REGION NEXT WEEKEND AND DEPENDING ON ITS SOUTHWARD MERIDIONAL AMPLITUDE...IT COULD SCOOP A BIT OF TROPICAL MOISTURE NORTHWARD ALONG THE EAST COAST OVER THE WEEKEND. THAT COULD ASSIST TO BREAK THE IN-PROGRESS 11 TO 12 DAY DRY SPELL THAT BEGAN EARLY 9/22 AND IS PROJECTED TO LAST THROUGH AT LEAST THE 3RD IF NOT THE 4TH AND 5TH OF OCTOBER. THE 12Z/29 GEFS SUGGESTS THAT THE RIDGE MAY NOT BREAK DOWN ALONG THE EAST COAST FRIDAY AND SATURDAY...DELAYING ANY COLD FRONTAL PASSAGE AND KEEPING IT RATHER WARM LONGER THAN NOW FCST. TEMPERATURES: THE CALENDAR DAY AVERAGE WILL BE AROUND 5 DEGREES ABOVE NORMAL TUESDAY...THEN 8 TO 15 DEGREES ABOVE NORMAL WED-FRI AND POSSIBLY SATURDAY TOO. SUNDAY IS FRAUGHT WITH UNCERTAINTY. THE PRIMARY GFS/ECMWF DETERMINISTIC MODELS ARE FLIP FLOPPING THEIR DAY 7-8 FORECASTS AND GEFS IS NOW APPEARING MUCH SLOWER THAN THE 12Z/29 DETERMINISTIC ECMWF...MORE LIKE THE 00Z/29 VERSION. HAVE BOUGHT INTO THE OVERALL WARMEST AVBL GUIDANCE FOR DAYTIME MAX TEMPS WED-SAT RELYING HEAVILY ON THE CONSISTENTLY WARMEST 2M TEMPS FROM THE ECMWF WITH PERSISTENT 14C 850MB TEMPS OVERHEAD WED-SAT. FORECAST BASIS: MONDAY NIGHT THROUGH TUESDAY NIGHT IS A 50 50 BLEND OF 12Z/29 GFS/NAM MOS. WEDNESDAY IS STRAIGHT 12Z/29 GFS MEXMOS. WEDNESDAY NIGHT THROUGH THU NIGHT IS STRAIGHT 12Z/29 GFS MEX MOS BLENDED WARMER ON THURSDAYS MAX WITH THE 12Z/29 WARM 2M TEMPS OF THE ECMWF. THU NIGHT IS A 500 BLEND OF WPC AND THE MEX GUIDANCE. FRIDAY AND SATURDAY ARE A 50 50 BLEND OF THE WPC AND WARM 12Z 2M TEMPS OF THE ECMWF. SUNDAY IS WPC GUIDANCE. THE POPS WERE CHECKED AGAINST BOTH THE 09Z/29 SREF 3HR PROB FOR.01 AND 12Z/29 GEFS 6 HR PROB FOR .05. BASICALLY RAISED SLIGHTLY AVBL GUIDANCE TUESDAY AND FRIDAY. THE DAILIES... MONDAY NIGHT...CLEAR THEN INCREASING CLOUDS LATE. PATCHY FOG POSSIBLE IN THE COUNTRYSIDE LATE WITH LIGHT WIND AND SHALLOW LEFTOVER BOUNDARY LAYER MOISTURE FROM THE ONSHORE FLOW OF THIS WEEKEND. TUESDAY...A WEAK WARM FRONT WITH THE PWAT AXIS BUILDING NEWD TO 1.1 INCHES BUT KI ONLY 20-25C. NAM/GFS SPITTING OUT .01 NW PTN OF OUR AREA AND A MID LVL SPRINKLE COULD OCCUR N AND NW OF KPHL FORENOON - MIDDAY. TSECS SHOW THE ATTEMPTED LIFT THROUGH A SPIKE IN DEEP RH. W WIND MAY GUST 10-15 MPH IN THE AFTN AS SKIES CLEAR AND TEMPS WARM LATE. WED-THU...GORGEOUS! MID 80S WARMTH LIKELY WEDNESDAY WITH AN OFFSHORE W WIND GUSTING 15 MPH WED AFTN. THEN FOR THURSDAY A LIGHT VARIABLE WIND WITH PROBABLE COOLING AFTERNOON COASTAL SEA BREEZES AND LESS MIXING...PLUS SOME CIRRUS...SO TEMPS SLIGHTLY COOLER BUT STILL 10 DEGREES ABOVE NORMAL. FRI...PROBABLY A NICE WARM DAY BUT THE ECMWF IN 3 OF THE 4 MOST RECENT DETERMINISTIC CYCLES HAS BEEN SPITTING OUT A FEW SHOWERS IN THE NW PTN OF OUR FORECAST AREA (POCONOS AND NW NJ) DURING THE DAY AS ANOTHER WARM FRONT FORMS IN THE MID ATLANTIC STATES. THE 00Z-12Z/29 ECMWF HAS OUR KI UP TO 32..WITH UNSTABLE SWI. WE MAY NEED TO INCLUDE A 30 POP UP THERE FOR AN AFTN SHOWER OR TSTM BUT FOR NOW MORE CONSERVATIVE KNOWING THIS BURST COULD BE TOO ROBUST. SW WIND GUSTING 15 MPH IN THE AFTN. SAT SUN...DEPENDING ON YOUR MODEL OF CHOICE...IT SHOULD RAIN ON ONE OF THESE DAYS. THE 12Z/29 GFS AND ECMWF NOW SAY LATE SATURDAY WHILE THE ENSEMBLES DELAY TIL LATE SUNDAY WITH POSSIBLE INGEST OF TROPICAL MOISTURE FROM DOWN OVER GMEX. FOR NOW THINK ABNORMALLY WARM AND HUMID SATURDAY AND POSSIBLE SHOWERS/TSTMS LATE DAY OR AT NIGHT BUT WITH LESS THAN AVG CONFIDENCE ON TIMING THE APPROACHING CFP AND SO SATURDAY STILL COULD BE RAINFREE ALL DAY WITH ALL RAIN DELAYED TIL SAT NIGHT OR SUNDAY??? DEWPOINTS SHOULD BE 65-70 SATURDAY! CONFIDENCE IS ABOVE AVERAGE FOR THE TEMP FCST TUESDAY-SATURDAY (USING THE WARMEST OF THE AVBL GUIDANCE) AND BELOW AVERAGE SUNDAY. THE POP FORECAST MAY BE TOO CONSERVATIVE TUE MORNING (MID LVL WAA SHOWER), FRIDAY IN MORE GENERAL DEEPER WAA AND SAT NIGHT AHD OF THE CF. && .AVIATION /20Z SUNDAY THROUGH FRIDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. REST OF THIS AFTERNOON...CEILINGS NEAR 4000 FEET ARE ANTICIPATED TO SCATTER OUT FROM EAST TO WEST. EASTERLY WINDS MAINLY NEAR 10 KNOTS. TONIGHT...OVERALL VFR. LIGHT NORTHEAST TO CALM WINDS. SOME LOCALIZED MVFR FOG MAY DEVELOP TOWARD DAYBREAK, HOWEVER CONFIDENCE IS ON THE LOWER SIDE PARTIALLY DUE TO THE DRYNESS OF THE AIRMASS. MONDAY...PERHAPS LOCALIZED MVFR DUE TO FOG TO START, OTHERWISE VFR. WINDS NEAR 5 KNOTS BUT THEY MAY BE VARIABLE, THEN FAVOR A SOUTH OR SOUTHWESTERLY DIRECTION IN THE AFTERNOON. OUTLOOK... MONDAY THROUGH THURSDAY... MONDAY NIGHT THROUGH FRIDAY...MAINLY VFR CONDITIONS EXPECTED. SOME PATCHY MORNING FOG IS POSSIBLE EACH DAY...MAINLY COUNTRYSIDE. TUESDAY...A PERIOD OF CIGS AOA 5000 FT...ESPECIALLY MORNING MIDDAY. CHANCE OF A SPRINKLE POCONOS AND NW NJ. WEST WIND MAY GUST 10-15 KT IN THE AFTN. CONFIDENCE: ABOVE AVERAGE. WEDNESDAY...HARDLY A CLOUD IN THE SKY. WSW WIND GUST 15 KT DURING THE AFTN. CONFIDENCE: WELL ABOVE AVERAGE. THURSDAY...CIRRUS POSSIBLE. LIGHT AND VARIABLE WIND WITH AFTERNOON COASTAL SEA BREEZES. CONFIDENCE: WELL ABOVE AVERAGE. FRIDAY...SCT-BKN CLOUDS AOA 5000 FT WITH A POSSIBLE SHOWER OR TSTM N OF KPHL. SSW WIND GUST 15 KT IN THE AFTERNOON. CONFIDENCE: ABOVE AVERAGE EXCEPT BELOW AVERAGE ON WHETHER ANY SHOWERS OCCUR NEAR AND NW OF KRDG AND KABE. && .MARINE... AN ONSHORE FLOW CONTINUES DUE TO HIGH PRESSURE CENTERED NEAR COASTAL NEW ENGLAND, AND LOW PRESSURE ORGANIZING WELL EAST OF THE ATLANTIC COASTLINE. THE TIGHTER PRESSURE GRADIENT SHOULD REMAIN TO OUR EAST, HOWEVER IT MAY TRY TO BACK IN A BIT FROM THE EAST TONIGHT INTO MONDAY. DESPITE THIS, THE WINDS ARE ANTICIPATED TO REMAIN UNDER 25 KNOTS. THE LOW-LEVEL FLOW TRAJECTORY HOWEVER IS FAVORING SEAS RIGHT AROUND 5 FEET ACROSS OUR SOUTHERN OCEAN ZONES. THIS SHOULD CONTINUE FOR AWHILE, ALTHOUGH THE SEAS MAY SUBSIDE JUST ENOUGH LATE TONIGHT OR DURING MONDAY. BASED ON THIS AND LOWER CONFIDENCE THAT SOLID 5 FOOTERS REMAIN LONGER, THE SMALL CRAFT ADVISORY WAS NOT EXTENDED BEYOND 12Z MONDAY. ELSEWHERE, CONDITIONS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA THROUGH MONDAY. OUTLOOK... NO HEADLINES ANTICIPATED MONDAY NIGHT AND TUESDAY...LEFTOVER ELY SWELL OF 3-4 FT ON THE ATLC WATERS WITH VERY LITTLE IF ANY ADDITIONAL WIND WAVE CHOP. CONFIDENCE: ABOVE AVERAGE. WEDNESDAY...THE NEARSHORE WEST WIND MAY GUST 15-20 KT IN THE AFTN BUT OVERALL ATLC SEAS AOB 3 FT. CONFIDENCE: ABOVE AVERAGE. THURSDAY...ALMOST CALM WITH SEAS AOB 2 FT AND LIGHT WIND BECOMING AFTERNOON COASTAL SE SEA BREEZES. CONFIDENCE: WELL ABOVE AVERAGE. FRIDAY...THE WIND TURNS SSW WITH GUSTS 20 KT POSSIBLE. SOME MODEL GUIDANCE SUGGESTS POTENTIAL FOR 25 KT NEARSHORE WIND LATE IN THE DAY. CONFIDENCE BELOW AVERAGE ON MAX WIND SPEEDS. && .RIP CURRENTS... GIVEN THE PERSISTENT ONSHORE FLOW AND STRONG ENOUGH SWELL COMPONENT, A MODERATE RISK OF RIP CURRENTS CONTINUES THROUGH THIS EVENING. LOW PRESSURE TRACKING NORTHWARD IS FORECAST TO REMAIN WELL OFF THE COAST THROUGH MONDAY. SWELLS HOWEVER ASSOCIATED WITH THE LOW WILL AFFECT OUR COASTLINE, RESULTING IN A CONTINUED MODERATE RISK OF RIP CURRENTS. OUR SURF ZONE FORECAST SEASON ENDS ON MONDAY, 9/30. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 AM EDT MONDAY FOR ANZ453>455. && $$ SYNOPSIS...DRAG 357P NEAR TERM...GORSE 357P SHORT TERM...GORSE 357P LONG TERM...DRAG 357P AVIATION...DRAG/GORSE 357P MARINE...DRAG/GORSE 357P RIP CURRENTS...GORSE 357P