Special Marine Warning 18, NWS Philadelphia/Mount Holly

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
234 PM EDT WED MAY 21 2008

.SYNOPSIS...
A PERSISTENT UPPER LEVEL LOW OVER SOUTHEASTERN CANADA WILL GRADUALLY
MOVE INTO NEW ENGLAND THURSDAY, THEN FINALLY SLIDE TO THE EAST.
ROTATING AROUND THIS UPPER LOW WILL SPOKES OF ENERGY, ONE THIS
EVENING AND ANOTHER ONE THURSDAY WITH PERHAPS ONE LAST ON ON FRIDAY.
TEMPERATURES WILL GRADUALLY WARM OVER THE WEEKEND AND THEN THE
WARMEST DAYS ARE ANTICIPATED EARLY NEXT WEEK BEFORE A COLD FRONT
COMES THROUGH FROM THE NORTHWEST TUESDAY AFTERNOON AND NIGHT.

&&

.NEAR TERM /THROUGH TONIGHT/...
AN UPPER SHORT WAVE COMBINED WITH DAYTIME HEATING AND A
REINFORCING COLD FRONT APPROACING FROM THE WEST HAS RESULTED IN
DEVELOPING SHOWERS MAINLY TO THE NORTH OF PHILADELPHIA. SOUNDINGS
INDICATED AN INVERTED V TYPE LOOK IN THE LOWER LEVELS INDICATING
THAT IF TSTMS DO FORM, SOME GUSTY WINDS TO 35 OR 40 MPH ARE
POSSIBLE, BUT SINCE WINDS ALOFT ARE NOT STRONG, HIGHER WINDS ARE
NOT EXPECTED. BY MIDNIGHT, THE SHOWERS AND TSTMS WILL DISSIPATE
WITH LACK OF HEATING BUT INSTABILITY ALOFT COULD KEEP SOME SHOWERS
GOING NORTH. FCST MINS ARE GENLY CLOSE TO THE MAV FCST.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
VERY COOL AIR COMES DOWN FROM THE NORTH ON THURSDAY AS ANOTHER
SHORT WAVES MOVES THROUGH ALOFT. HOWEVER, THIS SHORT WAVE IS
EXPECT TO MOVE THROUGH LATE MORNING AND SINCE DAYTIME HEATING
SHOULD NOT HAVE A STRONG EFFECT BY THE TIME OF THE SHORT WAVE
PASSAGE, ONLY A CHC OF SHOWERS WILL BE FCST. TEMPS THURSDAY WILL
BE A FEW DEGREES COOLER THAN TODAY WITH COOLER AIR IN PLACE
COMBINED WITH PARTLY CLOUDY SKIES LIMITING THE EFFECTS OF DAYTIME
HEATING.

THURSDAY NIGHT, THE CORE OF THE UPPER TROUGH MOVES OFFSHORE, BUT
ONE LAST SPOKE OF ENERGY/SHORT WAVE IS FCST BY THE MODELS TO MOVE
DOWN THROUGH THE AREA ON FRIDAY. THURSDAY NIGHT SHOULE BE DRY AND
VERY COOL. FOR FRIDAY, I HAVE SOME CLOUDS IN THE FCST DUE TO THE
SHORT WAVE, BUT AM HOLDING OFF ON MENTION OF PCPN AS CONFIDENCE IS
NOT HIGH FOR THIS CONSIDERING THE LOW MOISTURE FCST BY THE MODELS
AND THE ASSOCIATED VERY LOW POPS. EVEN SO, I DID GO FOR 20 POPS
IN THE GRIDS. BY FRIDAY NIGHT, THE UPPER SHORT WAVE SHOULD HAVE
MOVED BY TO THE EAST ALLOWING THE AIRMASS TO FINALLY START TO
MODIFY WARMER.

IN GENERAL A BLEND OF MAV/MET TEMPS WERE USED.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
THE UPPER TROUGH FINALLY GIVES WAY TO RIDGING ALOFT OVER THE
WEEKEND. THIS MEANS DRY WEATHER WITH WARMING TEMPS. BY MONDAY,
TEMPERATURES OVER A GOOD PORTION OF THE REGION SHOULD BE IN THE
80S WITH THE EXCEPTION OF THE COAST AS SEABREEZES SHOULD KEEP THEM
COOLER AND OVER THE POCONOS.

ON TUESDAY, THE MODELS ARE FORECASTING A COLD FROM TO COME THROUGH
FROM THE NW IN THE AFTN OR EVENING. THE 12Z GFS UPPER AIR LOOKS
SUSPECT WITH A SHORT WAVE WELL AHEAD OF THE FRONT BY 18Z. THE
SLOWER MOTION AS DEPICTED ON THE HPC PROGS LOOKS MORE REASONABLE.
THIS MEANS ANOTHER DAY OF WARMTH FOLLOWED BY POTENTIAL TSTMS IN
THE AFTN OR EVENING. THE STRENGTH OF THE TSTMS WILL BE DEPENDENT
ON IF THE TEMPS GET AS WARM AS FCST AND THE TIMING OF THE FRONTAL
BOUNDARY.

TEMPS SHOULD BE COOLER WEDNESDAY BEHIND THE COLD FRONT, BUT THIS
AIRMASS WONT BE NEARLY AS COOL AIR THE ONE CURRENT OVER THE
REGION. SO HIGHS SHOULD BE MOSTLY IN THE 70S.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
SKIES CLEARED RAPIDLY AFTER THIS MORNINGS EARLY MORNING FOG LIFTED.
BY MIDDAY, AC STARTED TO MOVE IN FROM THE W AND SW. FAIR WEATHER CU
ALSO BEGAN POPPING. SCATTERED SHOWERS AND A FEW ISOLATED THUNDERSTORMS
ARE NOW BEGINNING TO FORM AHEAD OF AN APPROACHING COLD FRONT. A MORE
CONCENTRATED AREA OF SHOWERS AND THUNDERSTORMS IS PRECEDING AND
ACCOMPANYING THE FRONT. THE PRECIPITATION WILL CROSS THE AREA THIS
AFTERNOON INTO THE EVENING HOURS BEFORE WEAKENING AND MOVING OFF TO
THE EAST. EXPECT VFR CONDITIONS TO PREVAIL, ALTHOUGH COULD SEE MVFR
OR EVEN BRIEF IFR IN ANY OF THE HEAVIER SHOWERS. EXPECT SCT TO BKN
AC OVERNIGHT WITH MAINLY GOOD VSBYS. WINDS ARE EXPECTED TO DROP TO
5 KT OR LOWER AND IN AREAS THAT RECEIVE RAINFALL, VSBYS COULD DROP
BRIEFLY TO MVFR IN THE PRE-DAWN HOURS. ANOTHER SPOKE OF ENERGY AND
MOISTURE IS EXPECTED TO ROTATE ACROSS THE FORECAST AREA THURSDAY
MORNING, POSSIBLY BRINGING A FEW MORE SHOWERS. AGAIN, VFR CONDITIONS
WILL PREVAIL.

THE UPPER LOW WILL BEGIN TO DRIFT OFF TO THE EAST FRIDAY. THERE COULD
STILL BE ONE LAST SHORT WAVE DROPPING DOWN FROM THE NORTH THAT COULD
BRING SOME CLOUDS AND POSSIBLY A FEW SHOWERS. A LARGE AREA OF HIGH
PRESSURE WILL THEN MOVE IN FOR THE HOLIDAY WEEKEND.

&&

.MARINE...
LOOKS LIKE AN EXTENDED PERIOD OF RELATIVELY QUIET WEATHER FOR THE
MARINE COMMUNITY. SEVERAL SHORT WAVES ROTATING AROUND THE STRONG
UPPER LOW TO OUR NORTH WILL CROSS THE AREA DURING THE NEXT 48 HOURS.
THE FIRST WILL BE EARLY TONIGHT. THE SECOND AROUND MIDDAY THURSDAY.
AND THE THIRD FRIDAY AFTERNOON. NONE OF THESE ARE EXPECTED TO
PRODUCE SMALL CRAFT ADVISORY CONDITIONS, ALTHOUGH WINDS MAY GUST
TO NEAR 25 KT LATE THURSDAY INTO THURSDAY NIGHT IF THE NAM GUIDANCE
IS ANYWHERE NEAR CORRECT. A LARGE AREA OF HIGH PRESSURE WILL THEN
BUILD SOUTHEAST INTO THE MID ATLANTIC REGION FOR THE HOLIDAY WEEKEND
INTO THE EARLY PART OF NEXT WEEK.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

SYNOPSIS...STAUBER
NEAR TERM...STAUBER
SHORT TERM...STAUBER
LONG TERM...STAUBER
AVIATION...RPW
MARINE...RPW