-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 081223
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
823 AM EDT WED SEP 8 2010

.SYNOPSIS...
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A COLD FRONT IS CURRENTLY CROSSING OUR REGION AS LOW PRESSURE
MOVES INTO NORTHERN NEW ENGLAND THROUGH TONIGHT. AN AREA OF HIGH
PRESSURE THEN GRADUALLY BUILDS INTO OUR AREA DURING THURSDAY AND
FRIDAY. THIS HIGH PRESSURE SYSTEM WILL MOVE OFFSHORE DURING
SATURDAY, THEN A COLD FRONT WILL CROSS THE AREA SUNDAY. ANOTHER
HIGH PRESSURE SYSTEM THEN BUILDS IN FOR MONDAY AND TUESDAY.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
A FEW LIGHT SHOWERS OR SPRINKLES CONTINUE ALONG THE COLD FRONT,
WHICH WAS CROSSING THE DELAWARE RIVER FROM TRENTON TO WILMINGTON
AT 8 AM. THE GRIDS HAVE BEEN UPDATED TO SHOW THIS. HAVE TAKEN OUT
THE MENTION OF THUNDER, SINCE THE PORBABILITY OF THIS OCCURRING
IS VERY LOW. THE FRONT, SHOWERS, AND CLOUDS WILL EXIT THE COAST
BETWEEN 13 AND 15Z.

SYNOPTICALLY, A STRONG UPPER-LEVEL TROUGH WILL BE MIGRATING FROM THE
GREAT LAKES REGION TO THE NORTHEAST THROUGH TODAY. THE CYCLONIC
FLOW BEHIND THE SURFACE COLD FRONT WILL ALLOW FOR INCREASING CAA
WITH TIME. THE MAIN FOCUS TODAY IS THE PASSAGE OF A STRONG BUT
MAINLY MOISTURE STARVED COLD FRONT. A DECENT AMOUNT OF CONVECTION
FORMED AHEAD OF THE BOUNDARY EARLY LAST EVENING FROM THE EASTERN
GREAT LAKES TO THE UPPER OHIO VALLEY, AS A RIBBON OF DEEPER
MOISTURE COINCIDED WITH A RATHER IMPRESSIVE MIDLEVEL WIND MAX AND
AN AXIS OF MLCAPE. THE BULK OF THIS IS LIFTING UP TO OUR NORTH,
WEAKENING AND HEADED INTO NEW ENGLAND, HOWEVER SOME MODEST
MIDLEVEL FLOW IS FORECAST TO CROSS OUR AREA. THIS IS THE DRIVING
FORCE FOR THE SHOWERS THAT ARE CURRENTLY ACCOMPANYING THE FRONT.

OTHERWISE, MAINLY MID TO HIGH LEVEL CLOUDS ALONG AND AHEAD OF THE
COLD FRONT /PROBABLY BE ABLE TO ADVECT OR DEVELOP SOME CUMULUS AS
WELL/, THEN FAIRLY QUICK CLEARING BEHIND THE COLD FRONT AS MUCH
DRIER AIR ADVECTS IN ALONG WITH DEVELOPING CAA AND DOWNSLOPING FLOW.
SOME GUSTINESS IN THE SOUTHERLY FLOW AHEAD OF THE COLD FRONT, THEN
ADDITIONAL GUSTY WINDS BEHIND THE COLD FRONT AS THE LOW-LEVEL LAPSE
RATES STEEPEN WITH THE DEVELOPING CAA ABOVE SURFACE HEATING. THE
FORECAST SOUNDINGS INDICATE THAT THE WINDS INCREASE TO NEARLY 30
KNOTS AT THE TOP OF THE DEEPENING BOUNDARY LAYER. THIS WOULD
TRANSLATE TO 30 TO 35 MPH WIND GUSTS BEHIND THE FRONT. THIS WILL
PROBABLY BE DELAYED ACROSS THE SOUTHERN AND SOUTHEASTERN ZONES AS
THE FRONT ARRIVES HERE LATER. OVERALL, THE SITUATION LOOKS TO BE
BELOW WIND ADVISORY CRITERIA. THE WINDS COMBINED WITH THE DRIER AIR
SURGING IN BEHIND THE FRONT WILL LEAD TO FIRE WEATHER CONCERNS,
THEREFORE SEE THE FIRE WEATHER SECTION BELOW FOR MORE DETAILS.

AS FOR TEMPERATURES, GIVEN THE MILD START ACROSS THE BULK OF THE CWA
UNDER WAA AHEAD OF THE COLD FRONT, LEANED TOWARD THE WARMER NAM MOS.
THIS POINTS TOWARD WARMER TEMPERATURES ESPECIALLY ACROSS THE EASTERN
AND SOUTHERN ZONES AS THE CAA WILL ARRIVE HERE IN EARNEST LATER IN
THE DAY.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
AN AREA OF LOW PRESSURE IS FORECAST TO BE NEAR NORTHERN NEW ENGLAND
AS A CLOSED MIDLEVEL LOW SETS UP SHOP IN THAT VICINITY. THE
ASSOCIATED LARGE TROUGH ENCOMPASSING THE NORTHEAST AND MID ATLANTIC
STATES WILL RESULT IN A CYCLONIC FLOW BRINGING COOLER AIR TO THE
REGION. THE NORTHWESTERLY FLOW OF THIS COOL AND DRY AIRMASS WILL
ALLOW FOR LITTLE CLOUDS TO OCCUR TONIGHT. THE EXCEPTION SHOULD BE
THE NORTHWESTERN ZONES WHERE THE CAA, COMBINED WITH THE FLOW OFF THE
WARM EASTERN GREAT LAKES, CYCLONIC FLOW AND MOISTURE BECOMING
TRAPPED UNDER AN INVERSION TO TOSS STRATOCUMULUS SOUTHEASTWARD.
THEREFORE WE WILL CARRY MORE CLOUDS THERE THROUGH THE NIGHT AND ALSO
DURING THURSDAY.

THE WIND TONIGHT SHOULD DECOUPLE AT LEAST SOME, ALTHOUGH A COMPLETE
DECOUPLING IS NOT ANTICIPATED GIVEN THE TIGHTENED PRESSURE GRADIENT
AND CAA. THEREFORE, WE WILL GRADUALLY THROTTLE BACK ON THE WINDS. A
FEW SHOWERS/SPRINKLES CANNOT BE RULED OUT MAINLY THURSDAY AFTERNOON
THROUGH FRIDAY, THEREFORE SLIGHT CHC POPS WILL BE MAINTAINED AT
TIMES FOR THE NORTHWESTERN ZONES. WE ARE SEEING A LITTLE INSTABILITY
IN THE FORECAST SOUNDINGS THURSDAY AFTERNOON FARTHER SOUTH,
THEREFORE CAA STRATOCUMULUS/CUMULUS WILL PROBABLY DEVELOP BUT
POTENTIALLY FIGHT THE DOWNSLOPING FLOW /AS OF NOW WE ARE NOT
ANTICIPATING ANY SPRINKLES OR BRIEF SHOWERS TO BE ABLE TO DEVELOP
FROM THIS/. WE TRIED TO INDICATE THIS IN THE SKY COVER GRIDS FROM
NORTHWEST TO SOUTHEAST. FOR FRIDAY, THE PRESSURE GRADIENT IS
FORECAST TO GRADUALLY RELAX THEREFORE THE WINDS SHOULD NOT BE AS
GUSTY COMPARED TO TODAY AND THURSDAY.

AS FOR TEMPERATURES, WE GENERALLY UTILIZED AN EVENLY WEIGHTED BLEND
OF THE NAM/GFS MOS BUT MADE A FEW ADJUSTMENTS FOR LOCAL AFFECTS.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
THIS TIME FRAME IS COMPRISED OF SEVERAL MODERATE AMPLITUDE BUT
PROGRESSIVE UPPER AIR FEATURES AFFECTING OUR AREA. THIS FORECAST
PACKAGE SIDES WITHE A COMPROMISE TIMING BETWEEN THE GFS AND ECMWF,
PRETTY SIMILAR TO THE CANADIAN GGEM MODEL.

HIGH PRESSURE SHOULD BE BUILDING OVER OUR CWA AT THE START OF THE
LONG TERM. PENDING ON A FASTER TIMING, LOW TEMPERATURES MIGHT NEED A
DOWNWARD ADJUSTMENT IN SUBSEQUENT FORECASTS ACROSS THE SOUTHEASTERN
PART OF OUR CWA. BEING OF A PROGRESSIVE NATURE, THE HIGH PRESSURE
SYSTEM SHOULD MOVE OFFSHORE RATHER QUICKLY.

GOING WITH A CONSENSUS TIMING, WE HAVE SHOWERS AND THUNDERSTORMS
CHCS ARRIVING DURING THE DAY ON SUNDAY. THERE ARE INSTABILITY
DIFFERENCES BETWEEN THE GFS AND ECMWF WITH RESPECT TO THUNDER WITH
THE GFS MORE BULLISH OF IT OCCURRING IN NEARLY ALL OF OUR CWA.
BECAUSE OF THE BETTER TIMING WE DID ADD THE CHANCE FOR THUNDER FOR
SUNDAY DAY INTO SUNDAY EVENING. MANY DECENT LOOKING PRECIPITATION
EVENTS HAVE GONE THE WAY OF THE PASSENGER PIGEON THIS WARM SEASON.
THE LATEST GFS SHOWS PROMISE WITH SOME HERMINE RESIDUALS GETTING
ENTRAINED INTO AND A WAVE FORMING ON THE FRONT. WE WILL HAVE TO SEE
IF THIS CONTINUES IN FUTURE MODEL RUNS.

CONSENSUS SOLUTION WOULD KEEP MONDAY DRY AND SOMEWHAT COOLER FOR
NOW. ANOTHER REINFORCING COLD FRONT SHOULD BE APPROACHING OUR CWA ON
TUESDAY. THIS ONE IS NOT FORECAST TO HAVE AS MUCH DEEP MOISTURE OR
INSTABILITY, SO JUST SOME LOW GRADE SHOWER SLIGHT CHC/CHC WERE ADDED
ATTM. TEMPERATURE-WISE DOES NOT LOOK LIKE MUCH EXTREMES IN EITHER
DIRECTION WITH READINGS PRETTY CLOSE TO AVERAGE. ONLY DAY THAT MIGHT
VERIFY WARMER WOULD BE SUNDAY IF THE COLD FRONT IS SLOWER IN
ARRIVING. OVERALL, WE DID NOT MAKE ANY SIGNIFICANT CHANGES TO
CONTINUITY. HOWEVER, WE DID BLEND IN A SMALL PERCENTAGE OF THE 00Z
MOSGUIDE TO SOME FIELDS TO INTRODUCE A LITTLE BIT OF NEW GUIDANCE
INTO THE FORECAST.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

11Z-14Z...VFR. A LINE OF SCT ELEVATED CONVECTION WILL PUSH EWD
ACROSS THE FCST AREA. MOST OF IT SHOULD BE A 20 MINUTE SHOWER OR
SPRINKLE HOWEVER...ISOLATED THUNDER IS EXPECTED. LINE "MAY"
REIGNITE AS IT CROSSES THE COAST AROUND 1130Z-13Z?

AFTER 14Z TODAY...VFR QUICKLY BECOMING SKC WITH W WIND GUSTING
25-33KTS.

AFTER 00Z THU...WINDS DIMINISH RAPIDLY WITH VFR CONDS EXCEPT KPHL
AND KACY WHERE NW GUSTS 20 KTS MAY PERSIST INTO THE NIGHT WITH
DECENT CAA.

OUTLOOK...
THURSDAY AND FRIDAY: VFR. GUSTY WNW WINDS 20-28 KTS DAYLIGHT HOURS
DIMINISH AT NIGHT.

CYCLONIC FLOW DOMINATES OUR WEATHER THROUGH FRIDAY WITH A SECONDARY
WEAK COOL FRONTAL PASSAGE THURSDAY AFTERNOON OR EVENING. DIURNALLY
HEAT DRIVEN CONSIDERABLE CLOUD COVER 3500 TO 5500 FT THURSDAY AND
FRIDAY DAYLIGHT HOURS TENDS TO CLEAR AT NIGHT. MOST OF THE CLOUDINESS
EASTERN PA AND NORTHERN TWO THIRDS OF NJ.

SCT SHOWERS OR SPRINKLES POSSIBLE THURSDAY AFTERNOON POCONOS AND
NORTHERN NJ WITH SHORT WAVE ROTATING SEWD THRU THE AREA AND A WEAK
WIND SHIFT.

SATURDAY...VFR LIGHT WIND AND HIGH PRESSURE OVERHEAD.

SUNDAY...CONDITIONS MAY DEGRADE IN POTENTIAL LOW PRESSURE PASSAGE
WITH MVFR CONDS IN SHOWERS.

&&

.MARINE...
SCA THROUGH 00Z THU FOR NEAR SHORE /WITHIN 5 MI OF THE LAND/
GUSTS 25-30 KTS AFTER THE MORNING CFP.

TONIGHT...WINDS MAY CONTINUE OCCASIONALLY GUSTING 25 KTS VIRTUALLY
ALL WATERS WITH CAA OVER WARM SST...TRANSFER EXTENDS OUTWARD FROM
THE COAST. THE EXCEPTION FOR TONIGHT MIGHT BE THE UPPER PORTION
OF DELAWARE BAY.

THURSDAY AND FRIDAY...NW WIND GUSTS 20-25 KNOTS.  MIGHT BE A SECONDARY
WEAK CFP LATE IN THE DAY THAT ENHANCES WIND TRANSFER INTO THU NIGHT.

SATURDAY...HIGH PRESSURE WILL THEN BUILD INTO THE AREA BRINGING FAIR
WEATHER AND RATHER TRANQUIL CONDITIONS.

SUNDAY...DEGRADING CONDITIONS IN POTENTIAL SHOWERS AND LOW PRESSURE.

&&

.FIRE WEATHER...
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FOLLOWING THE PASSAGE OF THE COLD FRONT THIS MORNING, MUCH DRIER AIR
AND INCREASING WINDS WILL ARRIVE ACROSS THE AREA. THIS WILL ALLOW
THE DEW POINTS TO TUMBLE AS WINDS INCREASE FROM THE WEST. MODEL
FORECAST SOUNDINGS SUGGEST MIXING FROM 850 MB COULD DROP DEW
POINTS INTO THE MID AND UPPER 40S THIS AFTERNOON. MODEL FORECAST
SOUNDINGS ALSO SHOW THAT ABOUT 30 KNOTS OF WIND WILL BE AVAILABLE
AT THE TOP OF THE DEEPENING BOUNDARY LAYER THIS AFTERNOON IN THE
WAKE OF THE FRONT. THIS SHOULD TRANSLATE INTO WIND GUSTS OF 30 TO
35 MPH, MAINLY FROM LATE MORNING ON. GIVEN THE RATHER DRY
CONDITIONS ACROSS THE REGION AND FORECAST WINDS AND RELATIVE
HUMIDITY VALUES, THE START TIME FOR THE RED FLAG WARNING HAS BEEN
MOVED UP TO NOON TODAY.

WE ARE ANTICIPATING GUSTY WINDS ON THURSDAY, HOWEVER WITH COOLER
TEMPERATURES THE RELATIVE HUMIDITY VALUES LOOK TO BE THE LIMITING
FACTOR FOR FIRE WEATHER RELATED HEADLINES. A MENTION WILL BE
INCLUDED ONLY IN THE FIRE WEATHER FORECAST FOR NOW.
-- End Changed Discussion --

&&

.CLIMATE...
CONSECUTIVE DAYS WITHOUT RAIN /TRACE OR LESS/ THROUGH TUESDAY 9/7:
ABE 15 PHL 15 RDG 15 TTN 14 ILG 14 MPO 14

GED AND ACY HAD OUTER EDGE OF "EARL" SHOWERS ON THE 3RD.

IF IT DOESNT RAIN /MEASURE/ TODAY... WE`RE LIKELY TO EXTEND THE
DRY SPELL THROUGH AT LEAST THIS FRIDAY...I.E. 17-18 CONSECUTIVE
DAYS. OFFICE CLIMATE TOOLS INDICATE THIS IS FAR SHORT OF ANY RECORD.

YEARLY 90 PLUS THROUGH 9/7...

PHL 52 ONE SHORT OF EQUALING THE 1991 RER. RANK #2. POR TO 1873.

ACY 43 TIES 1983 FOR THE MOST. TODAY 9/7 DID NOT EXCEED BUT
WEDNESDAY IS FORECAST TO EXCEED.  POR TO 1906.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
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PA...RED FLAG WARNING FROM NOON TODAY TO 7 PM EDT THIS EVENING FOR
     PAZ060-061-067>071.
NJ...RED FLAG WARNING FROM NOON TODAY TO 7 PM EDT THIS EVENING FOR
     NJZ009-010-012>027.
DE...RED FLAG WARNING FROM NOON TODAY TO 7 PM EDT THIS EVENING FOR
     DEZ001-002.
MD...RED FLAG WARNING FROM NOON TODAY TO 7 PM EDT THIS EVENING FOR
     MDZ008-012-015.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ430-
     431-450>455.
-- End Changed Discussion --

&&

$$
SYNOPSIS...GORSE/RPW
NEAR TERM...DRAG/GORSE/RPW
SHORT TERM...GORSE
LONG TERM...GIGI/GORSE
AVIATION...DRAG
MARINE...DRAG
FIRE WEATHER...HAYES/GORSE/RPW
CLIMATE...637A