712
FXUS61 KPHI 072013
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
313 PM EST SAT NOV 7 2009
SYNOPSIS
A WEAK TROUGH WILL CROSS THE AREA TONIGHT. OTHERWISE, HIGH PRESSURE
OFF THE NORTHERN MID ATLANTIC COAST WILL BE THE MAIN WEATHER
INFLUENCE INTO MONDAY. A COLD FRONT WILL APPROACH THE AREA MONDAY
NIGHT AND MOVE INTO THE AREA ON TUESDAY. HIGH PRESSURE FOLLOW FOR
THE MID TO LATE WORK WEEK.
NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
A MODERATE SOUTHWEST TO WEST FLOW ABOVE THE SURFACE ASSOCIATED WITH
A WEAK SHORT WAVE MOVING OVER THE BUILDING MID LEVEL RIDGE MAY KEEP
TONIGHT FROM BEING THE WHOLESALE RADIATING NIGHT THAT LAST NIGHT
WAS. WE GENERALLY HAVE COMPROMISED BETWEEN MAV AND MET GUIDANCE
WHERE THERE IS A DIFFERENCE. ALSO, BUFKIT SOUNDINGS BRING SOME
MOISTURE IN JUST ABOVE THE SURFACE, WITH THE NAM GENERALLY BEING
MORE EMPHATIC ABOUT THIS THAN THE GFS, AND BOTH DEFINITELY BEING
MORE EMPHATIC ABOUT IT UP NORTH THAN DOWN SOUTH. THEREFORE, WE
EXPECT A DRY AND NOTICEABLY MILDER NIGHT THAN LAST NIGHT UNDER,
PERHAPS, SOME DEVELOPING CLOUDS /NOT A GREAT DEAL SOUTH, AND PERHAPS
A BIT MORE NORTH/.
SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/
AFTER THE SHORT WAVE MOVES THROUGH, THE MID LEVEL RIDGE WILL BUILD
INTO MONDAY MORNING. SURFACE HIGH PRESSURE WILL ANCHOR OFF THE
NORTHERN MID ATLANTIC SEABOARD IN RESPONSE. THERE MAY BE A BIT OF
WARM AIR ADVECTION CLOUDINESS ALOFT FROM TIME TO TIME, BUT EXPECT A
FAIR AMOUNT OF SUNSHINE SUNDAY AND MONDAY. ALSO, SUNDAY NIGHT COULD
BE A FAIR RADIATING NIGHT /THERE CERTAINLY IS A CHOICE REGARDING
MINS BETWEEN THE COOLER MAV AND THE WARMER MET/. THAT SAID, THE
GENERAL TENOR IS FOR DRY AND MILDER CONDITIONS THAT MAY EVENTUALLY
HAVE US REFERRING TO INDIAN SUMMER.
A COLD FRONT AND ASSOCIATED MID LEVEL TROUGH WILL ADVANCE MONDAY
NIGHT INTO TUESDAY ONCE THE MID LEVEL RIDGE AXIS SHIFTS EAST, AND
FOR NOW WE'VE GONE WITH THE TIMING OF THE 00Z ECMWF OVER THE
ATYPICALLY QUICKER 12Z NAM OR THE SLOWER 12Z GFS. ALL THREE OF THESE
MODELS PUSH THE MID LEVEL TROUGH FAR ENOUGH SOUTH TO KEEP MOISTURE
FROM IDA OUT OF OUR AREA, AND THE FRONT WOULD NOT HAVE A LOT OF
MOISTURE TO WORK WITH IF THAT ENDS UP BEING CORRECT.
ON THE OTHER HAND, THERE IS SOME FRONTOGENESIS NEAR THE SURFACE AND
Q-VECTOR CONVERGENCE ALOFT WITH THIS FEATURE. THERE ALSO MAY BE AN
UPPER LEVEL JET PROVIDING SUPPORT, AND WE WON'T YET DISMISS THE
POSSIBILITY THAT THE MODELS KEEP THE IDA MOISTURE TOO FAR SOUTH, SO
WE'LL GO A BIT HIGHER WITH POPS ON TUESDAY THAN HPC IS GOING. WITH
THE ADVANCING FRONT, WE'LL LEAN TOWARD THE MILDER GUIDANCE ON MONDAY
NIGHT ALTHOUGH WE WON'T OVERDO IT AS THE WINDS ABOVE THE SURFACE ARE
NOT PROGGED TO BE THAT STRONG. CONTINUITY WAS FOLLOWED FOR TUESDAY
AS IT SEEMS CONSISTENT WITH OUR TIMING OF THE FRONT.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
LOW PRESSURE WILL MOVE ACROSS EASTERN CANADA ON TUESDAY, STAYING
WELL TO OUR NORTH, BUT THE ASSOCIATED COLD FRONT WILL CROSS THE
REGION ON TUESDAY NIGHT. THIS WILL THEN GIVE WAY TO A VERY STRONG
AND LARGE AREA OF HIGH PRESSURE. THIS HIGH LOOKS TO PUSH EASTWARD
THROUGH THE WEEK KEEPING US HIGH AND DRY THROUGH NEXT WEEKEND.
THE KINK IN THIS FORECAST IS THE POSSIBILITY OF ANY MOISTURE
ASSOCIATED WITH IDA IN THE GULF MAKING ITS WAY UP NORTH. THE GFS
TAKES THE REMNANT SYSTEM AND THEN MOVES IT UP THROUGH THE CAROLINAS
AND OFF THE MIDDLE ATLANTIC COAST. THIS SCENARIO WOULD BRING SOME
DECENT RAIN TOT HE AREA THROUGH WEDNESDAY AND INTO EARLY THURSDAY.
THE ECMWF HAS A DRIER SOLUTION IN WHICH THE HIGH IS STRONG ENOUGH TO
SUPPRESS THE MOISTURE AND KEEP IT TO OUR SOUTH. THE CANADIAN MODEL
HAS SHIFTED BACK TO LOOK MORE LIKE THE ECMWF WITH DRIER CONDITIONS.
WITH THE UNCERTAINTY IN THE MODELS IT WAS THOUGHT THAT THE HIGH WILL
DOMINATE AND KEEP THE REMNANT LOW FROM PUSHING NORTHWARD THUS
KEEPING THE MOISTURE IN THE SOUTHEASTERN STATES.
THEREFORE, WE HAVE FOLLOWED HPC GUIDANCE FOR THE EXTENDED AND HAVE
KEPT THE MAJORITY OF THE FORECAST DRY.
AVIATION /20Z SATURDAY THROUGH THURSDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
A LARGE HIGH PRESSURE SYSTEM WILL CONTINUE TO SLIDE SOUTH AND
EASTWARD THROUGH SUNDAY. THE FLOW ON THE BACKSIDE OF THIS HIGH HAS
BECOME SOUTHERLY AND THE LATEST DATA INDICATES SOME 25 KNOTS OF WIND
JUST ABOVE THE SURFACE. MOST OF THIS WILL NOT MIX DOWN INTO THIS
EVENING DUE TO THE AIR MASS MODERATING, ESPECIALLY ABOVE THE
SURFACE, ALTHOUGH SOME GUSTS HAVE BEEN NOTED THIS AFTERNOON. ANY
GUSTS SHOULD NOT BE SIGNIFICANTLY HIGHER THAN THE SUSTAINED WINDS,
THEREFORE WE JUST BUMPED UP THE SUSTAINED WINDS A BIT THROUGH LATE
THIS AFTERNOON. ONCE WE LOSE THE DAYTIME HEATING, THE VERTICAL
MIXING WILL QUICKLY WANE THEREFORE THE WIND IS EXPECTED TO DROP OFF
TO LIGHT AND VARIABLE AT MANY OF THE TERMINALS. A WEAKENING FRONTAL
BOUNDARY WILL SLIDE ACROSS OUR AREA LATE TONIGHT AND EARLY SUNDAY
MORNING. FOR THOSE TERMINALS THAT ARE ABLE TO HOLD ONTO SOME WIND
THROUGH THE NIGHT WILL HAVE A WIND SHIFT TO THE WEST AND NORTHWEST
LATE. ALL TERMINALS ARE EXPECTED TO HAVE A NORTHWEST WIND SUNDAY OF
10 KNOTS OR LESS BEFORE PERHAPS SHIFTING BACK TO THE SOUTHWEST
TOWARD EVENING. THE FLOW IS FORECAST TO LIGHTER SUNDAY AND WITH
MILDER AIR ARRIVING, THE SURFACE WINDS MAY TURN SOUTH OR EVEN
SOUTHEAST ESPECIALLY AT KILG AND KACY DUE TO A POSSIBLE INFLUENCE
FROM NEARBY WATER.
OTHERWISE, SOME MID TO HIGH LEVEL CLOUDS STREAMING BY FROM TIME TO
TIME THROUGH SUNDAY. ANY STRATOCUMULUS THAT FORMS TO OUR NORTHWEST
WITH THE WEAKENING FRONT LATER TONIGHT SHOULD STAY NORTH OF OUR
TERMINALS. IT APPEARS THE FOG POTENTIAL LATE TONIGHT AND EARLY
SUNDAY MORNING IS RATHER LOW. WHILE A TOUCH OF RIVER FOG IS POSSIBLE
AT KRDG, CONFIDENCE IS NOT HIGH IT ACTUALLY MAKES IT ONTO THE
AIRFIELD /IF IT DOES INDEED DEVELOP/, THEREFORE IT WAS LEFT OUT AT
THIS TIME. OVERALL, VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD.
OUTLOOK...
HIGH PRESSURE IS FORECAST TO MEANDER NEARBY SUNDAY NIGHT THROUGH
MONDAY NIGHT. A COLD FRONT IS THEN FORECAST TO MOVE THROUGH LATE
TUESDAY. THIS SHOULD BRING SOME SHOWERS TO THE AREA ALONG WITH SOME
LOWERED CEILINGS, HOWEVER THERE IS UNCERTAINTY ON HOW MUCH MOISTURE
GETS PULLED NORTHWARD AHEAD OF THIS FRONT. A POSSIBLE GUSTY
NORTHWESTERLY WIND MAY OCCUR TUESDAY NIGHT AND WEDNESDAY PRIOR TO
HIGH PRESSURE GETTING CLOSER INTO THURSDAY.
MARINE
HIGH PRESSURE WILL MEANDER NEAR THE AREA THROUGH MONDAY NIGHT,
HOWEVER WITH IT MAINLY TO OUR SOUTH AND EAST TONIGHT, A SOUTHERLY
FLOW WILL RESULT. THERE WILL BE A WEAKENING FRONTAL BOUNDARY MOVING
THROUGH SUNDAY, WHICH MAY ALLOW THE WINDS TO SHIFT FOR A TIME TO THE
WEST. ON THE BACKSIDE OF THE SURFACE HIGH AND AHEAD OF THE
AFOREMENTIONED FRONT, THE WINDS ABOVE THE SURFACE ARE FORECAST TO
STRENGTHEN SOME RELATED TO A LOW-LEVEL JET. THIS IS WITHIN A WAA
REGIME, THEREFORE IT IS MOSTLY A QUESTION OF VERTICALLY MIXING THIS
WIND DOWN TO THE SURFACE. IT TENDS TO BE MORE DIFFICULT TO DO THIS
IN WAA PATTERNS AND THIS LATEST ONE LOOKS MORE MARGINAL. SINCE OUR
CONFIDENCE IS LOW REGARDING POSSIBLE SMALL CRAFT ADVISORY CONDITIONS
BEING REACHED, WE OPTED TO NOT HOIST THE ADVISORY AND GO WITH GUSTS
TO AROUND 20 KNOTS FOR NOW. THE WINDS ARE EXPECTED TO SETTLE ON
SUNDAY AS THE LOW-LEVEL WIND FIELD WEAKENS AND HIGH PRESSURE
DOMINATES.
THE NEXT FEATURE OF INTEREST WILL BE A COLD FRONT THAT IS FORECAST
TO CROSS THE AREA MAINLY TUESDAY NIGHT. THE PRESSURE GRADIENT WILL
TIGHTEN UP MOSTLY IN ITS WAKE AS A STRONG SURFACE HIGH BEGINS TO
SLIDE EASTWARD TO THE OHIO VALLEY AND A POSSIBLE STORM IS TO OUR
EAST. THIS COUPLED WITH CAA WILL COMBINE FOR MORE EFFICIENT VERTICAL
MIXING AND AN INCREASED CHC OF WINDS/SEAS REACHING ADVISORY
CRITERIA. THERE IS SOME UNCERTAINTY THOUGH ON THE STRENGTH OF THIS
SYSTEM AS ENERGY FROM TROPICAL CYCLONE IDA, CURRENTLY IN THE
NORTHWESTERN CARIBBEAN/, MAY OR MAY NOT GET INVOLVED OR IT COULD
JUST GET STUCK IN THE SOUTHEASTERN UNITED STATES. BASED ON THE
UNCERTAINTY, WE DID NOT GO WITH THE 12Z WAVEWATCH GUIDANCE /GFS
DRIVEN/ TUESDAY NIGHT THROUGH WEDNESDAY NIGHT AS IT LOOKS OVERDONE
DUE TO A STRENGTHENING SURFACE LOW TO OUR EAST AND NORTHEAST. THE
AFOREMENTIONED SURFACE HIGH THEN BUILDS IN FOR THURSDAY WITH A
RELAXING PRESSURE GRADIENT.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.
SYNOPSIS...DELISI
NEAR TERM...DELISI
SHORT TERM...DELISI
LONG TERM...MEOLA
AVIATION...GORSE
MARINE...GORSE
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