000
FXUS61 KPHI 032046
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
346 PM EST WED DEC 3 2008
.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFFSHORE TONIGHT. A COLD FRONT WILL
CROSS THE AREAS FROM THE WEST THURSDAY. COLD HIGH PRESSURE WILL
CROSS THE REGION FRIDAY THROUGH SATURDAY. LOW PRESSURE WILL MOVE
BY TO THE NORTH SATURDAY NIGHT WITH A SECOND AREA OF LOW PRESSURE
FORMING OFF THE CAROLINA COAST. THIS SECOND LOW SHOULD INTENSIFY
RAPIDLY AS IT HEADS NORTH TO COASTAL NEW ENGLAND THROUGH SUNDAY.
ANOTHER COLD HIGH PRESSURE SYSTEM WILL BUILD OVER THE REGION EARLY
NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
AN UPPER AIR TROUGH WILL BE DIGGING OVER THE GREAT LAKES
REGION TONIGHT. IN RESPONSE TO THIS, A COLD FRONT WILL MOVE TO NW
PA BY THURSDAY MORNING. MIDDLE AND HIGH CLOUDS ASSOCIATED WITH THE
TROUGH/FRONT WILL BEGIN TO SPREAD INTO THE AREA BY MIDNIGHT, WITH
MOST OF THE CLOUDS ARRIVING AFTER MIDNIGHT. OVER DELMARVA AND
EXTREME SE NJ, THE THICKER CLOUDS SHOULD BE DELAYED TIL DURING THE
DAY ON THURSDAY. THE BEST DYNAMICS WITH THE SYSTEM ARE WITH AND
BEHIND THE FRONT, SO NO PCPN WILL BE FCST FOR TONIGHT. WITH MOSTLY
CLEAR SKIES AND LIGHT WINDS THIS EVENING, TEMPERATURES WILL HAVE
THEIR BEST CHANCE OF DROPPING AND THE MAV/MET TEMPS LOOK A BIT TOO
HIGH CONSIDERING THE LOW DEWPOINTS IN PLACE.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
THE COLD FRONT MOVES THROUGH FROM THE WEST ON THURSDAY. HOWEVER,
HOW MUCH MOISTURE ACCOMPANIES THE FRONT IS NOT CLEAR CUT. MOISTURE
CURRENTLY WITH THE FRONT IS ASSOCIATED WITH DYNAMICS ALOFT THAT
WILL LIFT INTO CANADA. THIS IN GENERAL MEANS THE PCPN SHOULD BE
DIMINISHING IN THE FRONTAL BOUNDARY. COMPLICATING THE SITUATION IS
AN OLD TROUGH LIFTING OUT OF TEXAS/LOUISIANA ON THE EAST SIDE OF THE
TROUGH AND WEAKENING RAPIDLY. THIS TROUGH WAS TRYING TO DEVELOP
PCPN AROUND ARKANSAS AS SHOWN ON SATL AND REGIONAL RADARS. ANY
MOISTURE THAT DEVELOPS DOWN THERE SHOULD BE ABSORBED BY THE GREAT
LAKES TROUGH AND LIFT NE ACROSS THE MIDDLE ATLANTIC STATES.
FOLLOWING TRENDS, I EXPECT PCPN MOST AREAS THU AFTN/EVENING, BUT
AMOUNTS SHOULD BE LESS THAN 1/10 INCH. THIS IS LESS THAN WHAT THE
MODELS OUTPUT. I WILL FCST POPS OF LIKELY MOST AREAS EXCEPT
DELMARVA WHERE POPS WILL BE LIKELY.
NEXT TO THINK ABOUT IS PTYPE. IN THE POCONOS, MODEL SOUNDINGS FROM
BOTH THE WRF AND THE GFS SHOW RAIN CHANGING TO SNOW. WITH 1/10
INCH ANTICIPATED, THIS WOULD TRANSLATE TO AROUND AN INCH. ACROSS
THE LEHIGH VALLEY AND NORTHERN NJ, SOME MIX/CHANGE TO SNOW IS ALSO
EXPECTED, BUT TEMPERATURES ARE EXPECTED TO BE TOO HIGH TO SUPPORT
ANY ACCUMULATION ASSUMING THE PCPN IS NOT HEAVY. BY THE TIME THE
AIRMASS COLD ENOUGH TO SUPPORT A CHANGE TO SNOW REACHES THE PHL
METROPOLITAN AREA, THE PCPN SHOULD BE ENDING SO ONLY A BRIEF MIX
COULD OCCUR. THE ENDING TIME FOR THE PCPN SHOULD BE BY EVENING
NORTH AND TOWARD MIDNIGHT SOUTH AS DRY COLDER AIR COMES IN FROM
THE NW.
FRIDAY AND SATURDAY LOOK COLD, BUT DRY AS THE HIGH MOVES ACROSS
THE AREA.
IN GENERAL, MAV TEMPS WERE USED, ALTHOUGH SOME ADJUSTMENTS WERE
MADE BASED ON MODEL SOUNDINGS, ESP THURSDAY AND THURSDAY NIGHT.
&&
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
LONG TERM FEATURES WAVE AFTER WAVE OF PRECIP PASSING THROUGH THE
REGION WITH ARCTIC AIR INTRUDING. HIGH PRESSURE HANGS ONTO CONTROL
OF THE REGION FOR THE FIRST PART OF THE WEEKEND AS ITS RIDGE AXIS
SLIDES FURTHER OFFSHORE. WEAK RETURN FLOW SETS UP WITH THE PASSING
RIDGE SATURDAY AFTERNOON AS THE SURFACE HIGH MOVES TO THE NORTH.
FOLLOWING HPC, WHICH IS PRETTY CLOSE TO THE ECMWF FCST SHOWS A
STALLED FRONT SITTING OFF THE CAROLINA COAST. LOW PRESSURE SWINGS
DOWN FROM THE GREAT LAKES AND THEN SECONDARY LOW PRESSURE FORMS ON
THE STALLED FRONT OFF THE CAROLINA COAST. AHEAD OF THE ENTERING
FRONT/LOW PRESSURE AREAS IS SOME WEAK ISENTROPIC LIFT, WHICH HELPS
TO INCREASE THE POSSIBILITY OF PCPN DURING THE EVENING ON
SATURDAY.
SINCE TIMING AND POSITION OF THE DEVELOPING LOWS ARE IN QUESTION
AND THE BULK OF MOITURE MAY STAY TO THE NE, WE HAVE KEPT PCPN
"SHOWERY" FOR NOW.
WITH TEMPS BELOW THE FREEZING MARK HAVE LEFT SNOW SHOWERS TO THE
NORTH WITH A MIX OF RAIN AND SNOW SHOWERS TO THE SOUTH OVERNIGHT
FOR SATURDAY. EVENTUALLY THE FRONT AND LOW MOVE FAR ENOUGH
OFFSHORE THAT WE ARE ABLE TO DRY OUT FOR A DAY OR SO BEGINNING
SUNDAY AFTERNOON/NIGHT.
ARCTIC HIGH MEANDERS ITS WAY DOWN OVER OUR REGION ON MONDAY GIVING
US A NICE BLAST OF COLD AIR. NORTHERNMOST ZONES WILL BE LUCKY TO GET
ABOVE FREEZING FOR DAYTIME HIGHS. AS THE HIGH SLIDES EASTWARD, A
WARM FRONT USHERS IN SOME HIGHER CLOUDS OVERNIGHT MONDAY AND AGAIN
WE SEE DECENT ISENTROPIC FORCING OVER THE REGION. THIS SET UP
BRINGS US TO OUR NEXT SHOT AT SOME PRECIP ON TUESDAY. THIS TIME WE
START WITH A CHANCE OF SNOW WHICH CHANGES OVER TO RAIN FROM SOUTH
TO NORTH AS THE REGION ENTERS INTO THE WARM SECTOR AND WITH THE
HELP OF DIURNAL TRENDS. HIGHER TERRAIN ELEVATIONS WILL LIKELY SEE
A QUICK CHANGE OVER TO RAIN AND THAN BACK TO SNOW ONCE AGAIN.
MODEL CONSENSUS SHOWS THE PRIMARY LOW SLIDING TO THE NORTHEAST ON
WEDNESDAY AND STALLS A FRONT JUST TO OUR WEST WITH A SECONDARY LOW
SKIRTING BY TO OUR SOUTH. WITH THE QUASISTATIONARY FRONT TO OUR WEST
AND A WEAK WAA REGIME, MOISTURE IS PULLED NORTH LEAVING US UNDER
CHANCE POPS OF MOSTLY RAIN.
&&
.AVIATION /20Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
HIGH PRESSURE WILL MOVE EAST OF THE AREA THIS EVENING AS A COLD
FRONT APPROACHES FROM THE WEST.
OVERALL, RELATIVELY QUIET CONDITIONS WILL CONTINUE AT ALL TAF SITES
THROUGH TOMORROW MORNING. WINDS WILL REMAIN OUT OF THE WEST OR
SOUTHWEST THROUGH THE OVERNIGHT HOURS AND INTO TOMORROW. WITH SPEEDS
GENERALLY IN THE 5 TO 10 KT RANGE. CLOUDS WILL BEGIN TO INCREASE
OVERNIGHT WITH THE APPROACH OF THE FRONT BUT CEILINGS WILL REMAIN
ABOVE 4000 FT AND PROBABLY ABOVE 10 THSD FT, WITH NO RESTRICTIONS.
THE COLD FRONT APPROACHES THE AREA WITH RAIN APPROACHING KABE AND
KRDG BY LATE MORNING. LIGHT RAIN IS FCST WITH THE FRONT. THERE
MAY BE BRIEF PERIODS OF MVFR WITH THE FRONTAL PASSAGE ALONG WITH
GUSTY WINDS AND THE RAIN COULD MIX WITH OR CHANGE TO SNOW LATE IN
THE AFTERNOON BEFORE THE PCPN ENDS AT ABE/RDG. THE FRONT SHOULD
PASS THROUGH ALL SITES BY 00Z FRI. WINDS SHOULD SHIFT TO THE
NORTHWEST BEHIND THE FRONT.
OUTLOOK...HIGH PRESSURE WILL BUILD IN FOR FRIDAY AND SATURDAY. A
COMPLEX LOW PRESSURE SYSTEM WILL IMPACT THE REGION MAINLY ON
SUNDAY WITH PRECIPITATION AND THEN FOLLOWED BY STRONG GUSTY WINDS.
&&
.MARINE...
HIGH PRESSURE WILL SHIFT FARTHER OFFSHORE THROUGH EARLY TOMORROW. A
COLD FRONT WILL APPROACH AND CROSS THE COASTAL WATERS THURSDAY
AFTERNOON AND EVENING. WINDS AND SEAS ARE EXPECTED TO INCREASE BOTH
AHEAD OF AND WITH THE FRONTAL PASSAGE. WINDS WILL INCREASE TO 20 TO
30 KT AND REMAIN LARGELY OUT OF THE WEST OR SOUTHWEST BEFORE
SHIFTING TO NORTHWEST BEHIND THE FRONT.
WE HAVE CONTINUED THE SMALL CRAFT ADVISORY WITH NO IMMEDIATE CHANGES
MADE AT THIS TIME. THE WINDS LOOK TO REACH OVER 25 KT THURSDAY
MORNING AND PERSIST THROUGH LATE AFTERNOON OR EARLY EVENING, WITH
THE SEAS, MAINLY ALONG THE OCEAN, REACHING 5 TO 6 FEET DURING THAT
TIME. THE WINDS LOOK TO CALM DOWN A BIT BEFORE PICKING UP AGAIN ON
FRIDAY AND SMALL CRAFT MAYBE NEEDED ONCE AGAIN, DUE PRIMARILY TO
WINDS, BUT WE WILL HOLD OFF ON ISSUING THEM AT THIS TIME AS IT IS IN
THE THIRD AND FOURTH PERIODS. HIGH PRESSURE MOVES IN AND THE
GRADIENT BEGINS TO RELAX ON FRIDAY. ANOTHER COLD FRONT WILL APPROACH
THE COASTAL WATERS LATE IN THE WEEKEND, BRINGING STRONG WINDS AND
HIGHER SEAS, WITH SCA MOST LIKELY NEEDED WITH PERHAPS GALES AS WELL.
THIS LOW WILL BE MONITORED AS IT NEARS THE COASTAL WATERS.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 7 AM TO 7 PM EST THURSDAY FOR ANZ430-
431-450>455.
&&
$$
SYNOPSIS...STAUBER
NEAR TERM...STAUBER
SHORT TERM...STAUBER
LONG TERM...HEAVENER/STAUBER
AVIATION...MEOLA
MARINE...MEOLA
