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