000
FXUS61 KPHI 201436
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
937 AM EST THU NOV 20 2008
.SYNOPSIS...
A WEAK AREA OF LOW PRESSURE FROM THE GREAT LAKES REGION WILL TRACK
OVER THE REGION LATE TONIGHT AND OFF THE COAST FRIDAY. COLD CANADIAN
HIGH PRESSURE WILL THEN BUILD TOWARD OUR AREA FRIDAY NIGHT INTO
THE WEEKEND. A COLD FRONT IS THEN FORECAST TO MOVE THROUGH THE
FROM THE WEST MONDAY NIGHT OR EARLY TUESDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
FORECAST SOUNDINGS FROM BOTH THE WRF AND THE GFS SHOW CLOUDS WILL
REMAIN OVER THE REGION TODAY AS THEY REMAIN TRAPPED UNDER AN
INVERSION ALOFT THIS MORNING. THE LOWER LEVELS OF THE ATMOSPHERE
GO ADIABATIC THIS AFTERNOON. THIS SHOULD MAINTAIN THE CLOUDS IN
MOST AREAS, HOWEVER, THE MIXING COULD ALLOW THE CLOUDS TO
DISSIPATE A BIT LATE IN THE DAY. WITH THE CLOUDS AND COLD AIR,
THERE WILL BE A CONTINUING THREAT OF SNOW SHOWERS OR FLURRIES TO THE
NORTHWEST OF PHL. FURTHER SOUTHEAST, RADAR SHOWED SOME ECHOES AS FAR
SOUTH AS FAR SOUTHERN NEW JERSEY AND CENTRAL DELAWARE. LATEST MODEL
SOUNDINGS SUGGEST THAT, EVEN WITH THE RELATIVELY MILDER
TEMPERATURES, MOST OF THE VERY LIGHT PRECIP WOULD FALL AS FLURRIES
OVER ALL BUT THE SOUTHERNMOST ZONES AND THE WATER. THE MID-LEVEL
IMPULSE RESPONSIBLE FOR THE PRESENT ACTIVITY WILL MOVE THROUGH THE
AREA LATER IN THE MORNING, BUT OTHERS ARE QUEUED UP TO FOLLOW THIS
AFTERNOON.
THE AIR MASS WON`T BE QUITE AS COLD TODAY AS YESTERDAY WITH THE MAIN
LIMITING FACT THE CLOUDS. THE MAV TEMPS CONTINUE TO LOOK A BIT HIGH,
BUT SEEM BETTER THAN THEY WERE YESTERDAY AT THIS TIME.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
A WEAK AREA OF LOW PRESSURE WILL CROSS THE AREA EARLY FRIDAY
MORNING. MODEL SOUNDINGS SHOW THE BEST MOISTURE FCST TO BE AROUND
THE I95 CORREDOR WITH LIGHT SNOW OR FLURRIES POSSIBLY BEGINNING
AROUND MIDNIGHT FROM PHL WESTWARD AND TOWARD DAYBREAK IN MONMOUTH
COUNTY NJ. THIS MOISTURE IS MOSTLY BELOW 10 THSD FT ON THE
SOUNDINGS BUT BOTH THE WRF AND THE GFS AND IS DUE TO ISENTROPIC
LIFT ALOFT ASSOCIATED WITH A SHORT WAVE MOVING THROUGH THE REGION.
MODEL SOUNDINGS ALSO INDICATE THAT ALL PCPN WOULD BE IN THE FORM
OF SNOW IF IT DEVELOPS. EVEN THE BLYR LOOKS COLD ENOUGH TO SUPPORT
SNOW.
SNOW AMOUNTS SHOULD GENERALLY TOTAL AN INCH OR LESS FROM CECIL
COUNTY MD/CHESTER COUNTY PA EASTNORTHEAST THROUGH MONMOUTH AND
OCEAN COUNTIES IN NJ. ALSO, THE FRIDAY MORNING RUSH SHOULD COULD
SEE SLIPPERY AREAS FROM ANY SNOW THAT WOULD FALL. SINCE AMOUNTS
ARE RELATIVELY LOW, NO HEADLINES WILL BE ISSUED WITH THE PACKAGE.
OVER DELMARVA AND FROM RDG-ABE-SMQ NORTHWARD, ISENTROPIC LIFT IS
WEAKER, SO PCPN POPS ARE LOWER THAN NEAR THE PHL METRO AREA.
FCST TEMPS ARE BASED ON MODEL SOUNDINGS WITH SOME ADJUSTMENT
TOWARD THE MAV GUIDANCE.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
THE AXIS OF THE UPPER TROUGH WILL MOVE OFF TO THE EAST FRIDAY NIGHT.
THIS WILL ALLOW A VERY LARGE HIGH PRESSURE SYSTEM, TO BUILD IN
FOR THE WEEKEND. SATURDAY LOOKS TO BE THE COLDER OF THE 2 WEEKEND
DAYS, AS THERE WILL STILL BE SOME NORTHERLY FLOW AHEAD OF THE
BUILDING HIGH. BY SUNDAY, THE HIGH IS PRETTY MUCH OVERHEAD. BOTH
DAYS LOOK DRY.
THE AREA OF HIGH PRESSURE WILL MOVE TO THE EAST LATER SUNDAY, AND
THERE WILL BE A RETURN FLOW IN ADVANCE OF THE NEXT SYSTEM.
A LOW PRESSURE SYSTEM IS FCST TO MOVE SEWD FROM CNTRL CANADA ON
MONDAY. A WAR FRONT WILL MOVE THROUGH AHEAD OF THIS SYSTEM,
FOLLOWED BY A COLD FRONT MONDAY NIGHT OR EARLY TUESDAY. THIS LOW
LOOKS TO BRING OUR BEST CHANCE OF PRECIP IN THE NEXT WEEK.
FORTUNATELY, MOST, IF NOT ALL OF THE PRECIP IS AHEAD OF THE CDFNT
AND SHOULD BE RAIN IN MOST AREAS, WITH THE EXCEPTION OF THE NRN AND
WRN AREAS.
A COLD H5 TROF THEN ESTABLISHES ITSELF OVER THE AREA ON WEDNESDAY,
BUT THINGS APPEAR DRY ATTM, AS HIGH PRESSURE STARTS TO BUILD IN,
JUST IN TIME FOR THE HOLIDAY TRAVEL PERIOD. THE ECMWF SOLN DOES
PRESENT AN INTERESTING SCENARIO AS WE MOVE INTO THE LEAD-UP TO THE
THANKSGIVING HOLIDAY. IT BRINGS THE CDFNT THROUGH LIKE THE OTHER
MDLS, BUT THEN IT LINGERS THE TROF, GOES NEG TILTED AND DEVELOPS A
COASTAL LOW. OBVIOUSLY, A LOT CAN AND WILL CHANGE WITH THE MODEL
SOLNS BETWEEN NOW AND THEN, SO IT WILL BE INTERESTING TO SEE IF THE
ECMWF IS PICKING UP ON SOMETHING BEFORE THE OTHER MDLS (WHICH IS
OFTEN THE CASE), OR IF THE ECMWF IS PUTTING OUT A TURKEY OF A FCST.
&&
.AVIATION /08Z THURSDAY THROUGH MONDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
SERIES OF SHORT WAVES CONTINUE TO ROTATE AROUND THE UPPER LEVEL LOW
TO OUR NORTH. THE CURRENT WAVE IS ASSOCIATED WITH SURFACE LOW
PRESSURE DROPPING DOWN FROM THE EASTERN GREAT LAKES. THE LOW WILL
REMAIN WEAK AND GIVE US PLENTY OF LOW AND MID CLOUDS TODAY BUT NOT
MUCH IN THE WAY OF PRECIPITATION. THE CLOUDS WILL BECOME SCATTERED
AT TIMES LATE TODAY, ESPECIALLY SOUTHERN AND EASTERN SECTIONS. THE
NEXT SHORT WAVE WILL USHER IN COLDER AIR AND ANOTHER BATCH OF
MOISTURE LATE TONIGHT INTO FRIDAY. EXPECT SC CIGS BY AROUND MIDNIGHT
TONIGHT. SOME LIGHT SNOW OR SNOW SHOWERS ARE POSSIBLE LATE TONIGHT
INTO FRIDAY, POSSIBLY REDUCING CONDITIONS TO MVFR AT TIMES.
OUTLOOK...
HIGH PRESSURE PUSHING IN FROM THE WEST WILL BRING CLEARING FRIDAY
NIGHT AND PROVIDE FAIR WEATHER WITH VFR CONDITIONS THROUGH THE
WEEKEND.
&&
.MARINE...
LOW PRESSURE OVER THE CANADIAN MARITIMES IS CONTINUING TO MOVE OFF
TO THE NORTHEAST. WINDS AND WAVES HAVE DROPPED BELOW SMALL CRAFT
ADVISORY CRITERIA. LATEST BUFKIT INFORMATION IS SUGGESTING SOME
INCREASE IN WINDS DURING THE COURSE OF TODAY FOR OUR SOUTHERN WATERS,
AND WE PERHAPS MAY EVEN SEE SOME ADVISORY LEVEL GUSTS OVER THE
SOUTHERN ATLANTIC WATERS AND DELAWARE BAY. WE WON`T PUT UP AN
ADVISORY IN THE NEAR TERM DOWN THERE, BUT WE WILL FORECAST
NEAR-ADVISORY CONDITIONS.
THESE RELATIVELY TRANQUIL CONDITIONS WILL BE SHORT-LIVED.
AFTER THE WEAK CLIPPER SYSTEM AND REINFORCING COLD FRONT CROSSES THE
WATERS TODAY INTO TONIGHT, OFFSHORE CYCLOGENESIS IS EXPECTED ALONG
THE COLD FRONT ON FRIDAY THANKS TO ANOTHER SHOT OF ENERGY ROTATING
AROUND THE UPPER LOW TO OUR NORTH. WINDS AND SEAS WILL BE INCREASING
FRIDAY, PROBABLY REACHING ADVISORY CRITERIA IN THE AFTERNOON. WILL
RAISE SMALL CRAFT ADVISORIES ON ALL OUR WATERS AT NOON FRIDAY AND
CONTINUE THROUGH FRIDAY NIGHT. LATER SHIFTS MAY NEED TO EXTEND THE
ADVISORY IF CONDITIONS WARRANT. WIND GUSTS COULD APPROACH GALE FORCE
FOR A FEW HOURS FRIDAY EVENING. THE PRESSURE GRADIENT BETWEEN A
LARGE HIGH PRESSURE SYSTEM PUSHING IN FROM THE WEST AND THE
INTENSIFYING LOW PULLING OFF TO OUR EAST WILL BE SLOW TO WEAKEN.
WIND GUSTS OF ADVISORY STRENGTH MAY CONTINUE INTO SATURDAY BEFORE
RELAXING LATE SATURDAY OR SATURDAY NIGHT AS THE HIGH REACHES OUR
AREA.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 12 PM FRIDAY TO 6 AM EST SATURDAY
FOR ANZ430-431-450>455.
&&
$$
SYNOPSIS...STAUBER
NEAR TERM...STAUBER/DELISI
SHORT TERM...STAUBER
LONG TERM...NIERENBERG
AVIATION...RPW
MARINE...RPW/DELISI
