Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 301353
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
953 AM EDT MON MAR 30 2015

.SYNOPSIS...
A COLD FRONT WILL PASS THROUGH THE AREA EARLY THIS AFTERNOON. ON
ITS HEALS WILL BE A FAST MOVING LOW PRESSURE SYSTEM WHICH SHOULD
SWEEP THROUGH THE AREA LATE TUESDAY. A HIGH PRESSURE SYSTEM WILL
BUILD INTO THE REGION FOR WEDNESDAY AND MOVE OFFSHORE ON THURSDAY.
THE NEXT COLD FRONT SHOULD MOVE THROUGH THE REGION LATE FRIDAY. A
SECONDARY COLD FRONT SHOULD MOVE THROUGH THE AREA LATE SATURDAY
FOLLOWED BY A HIGH PRESSURE SYSTEM FOR THE START OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE PRECIPITATION FROM EARLIER HAS EXITED OFF THE COAST. A COLD
FRONT WILL CROSS THE AREA THROUGH THE AFTERNOON. DRIER AIR WILL
ARRIVE BEHIND THE FRONT AND BRING A RETURN TO PARTLY TO MOSTLY
SUNNY SKIES LATER TODAY. WINDS WILL SHIFT FROM S/SW TO W/NW AND
BECOME GUSTY LATER. TEMPERATURES FROM EARLIER LOOKED OK AND WERE
NOT CHANGED MUCH.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
AN UPPER-LEVEL TROUGH IS FORECAST TO SWING ACROSS THE AREA THIS
EVENING. THIS MAY MAINTAIN SOME CLOUDS ESPECIALLY ACROSS THE
NORTHERN AREAS, HOWEVER ENOUGH DRYING SHOULD TAKE PLACE FOR THE SKY
TO CLEAR OUT. THE FAST NORTHWEST FLOW WILL THEN DRIVE THE NEXT SHORT
WAVE /CLIPPER SYSTEM/ ACROSS THE GREAT LAKES LATE. THIS WILL BE
TRACKING ALONG A THERMAL GRADIENT ALOFT WITH SOME DOWNSTREAM WAA
OCCURRING. AS A RESULT, SOME INCREASE IN CLOUDS MAY START TO TAKE
PLACE TOWARD MORNING FROM WEST TO EAST. AS A LOW PRESSURE SYSTEM
MOVES FARTHER AWAY TO OUR NORTHEAST, THE PRESSURE GRADIENT WILL
RELAX AND SO WILL THE MIXING. THEREFORE, THE WINDS ARE EXPECTED TO
DIMINISH FAIRLY QUICKLY IN THE EVENING.

AS FOR THE LOW TEMPERATURES, WE USED MAINLY AN EVEN BLEND OF THE
NAM/GFS MOS.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
THE GFS AND WRF-NMMB INITIALIZATION LOOKED CLOSER TONIGHT, STILL
AN EDGE TO THE GFS AT 500MB. AT 850MB AND 925MB THERE ARE SOME
1-2C ERRORS WITH A SLIGHT EDGE TO THE GFS AGAIN. THE DP/DT VS
LAST NIGHT OVERALL LOOKS SLIGHTLY MORE PROGRESSIVE, AS THE PENDULUM
HAS SWUNG THE OTHER WAY.

THE 00Z MODEL SUITE HAS MERGED SLIGHTLY WITH OUR CLIPPER LOW,
STILL A FAIRLY WIDE SPREAD FOR SO CLOSE IN TIME EVENT. AS THE
ECMWF AND NAM/WRF-NMMB HAVE RESPECTIVELY REPRESENTED THE
DRIEST/SOUTHERNMOST AND WETTEST/NORTHERNMOST SOLUTIONS, WE ARE
GOING TO REMAIN CLOSER TO THE ENSEMBLE MEAN UNTIL WE GET MORE
CONTINUITY. IN REALITY THE OP GFS RUN IS CLOSE TO BOTH THE SREF
AND GEFS ENSEMBLE MEAN. SLIGHTLY ON THE WET SIDE. ITS PBLY GOING
TO BE TOUGH WITH PWAT VALUES PREDICTED TO GET TO 0.5 INCHES FOR
SOME OF THOSE WETTER SOLUTIONS TO VERIFY. NOT SURE IF IT WILL
HAPPEN AGAIN, BUT WOULDNT BE A SHOCKER IF THE 00Z OP WRF/NAM IS
AMONG THE WETTEST OF THE SREF ENSEMBLE MEMBERS.

LIKE LAST NIGHT, THE ECMWF MASS FIELDS (QVEC, FGEN AND
JET LOCATION) ARE NOT THAT DIFFERENT FROM THE GFS. THERMALLY THE
TRACK IS ALSO A CHALLENGE, BUT THERE IS MORE CONSENSUS
WITH PRECIPITATION GETTING INTO THE NORTHERN PART OF OUR
CWA AND BETTER CONSENSUS EXCEPT FOR THE NAM FOR HIGHER TERRAIN
LOCATIONS NORTHWEST TO LEAN MOSTLY SNOW.

AFTER THE SNOW TALK TO END MARCH, MILDER WEATHER WILL GREET US
FOR THE START OF APRIL. THE BACK END OF THE LONG TERM HAS ITS
ISSUES TOO WITH THE THE UKMET EXTREMELY PROGRESSIVE AND THE CAN
GGEM AND GFS RIDING IN THE CABOOSE. THE 500MB PATTERN LOOKS
PROGRESSIVE AND WITH THE INHERENT DEMISE OF THE +EPO RIDGE,
BELIEVE THE WPC ROUTE OF A MORE PROGRESSIVE SOLUTION FOR THE COLD
FRONT IS PREFERRED.

TUESDAY AND TUESDAY NIGHT TIMING WE ARE GOING TO LEAN TOWARD THE GFS
TIMING DUE TO THE MORE PROGRESSIVE DP/DT AND ALSO WAA PRECIP LIKES TO
START EARLY (LOOK AT NOW). THE ANTECEDENT AIR MASS IN THE SOUTHERN HALF
OF OUR CWA LOOKS TO BE WARM ENOUGH FOR MAINLY RAIN ON TUESDAY. COULD
GET SOME SLEET AT THE ONSET, BUT PROBABILITY TOO LOW TO INCLUDE. UP
NORTH, THE WAA IS EXPECTED TO ONLY GET TO ABOUT I80 BEFORE IT
STARTS PIVOTING AS THE CLIPPER TRACKS FARTHER TO THE EAST. GIVEN
THE NARROW FGEN BANDING PREDICTED WITH THIS SYSTEM, ITS TOUGH EVEN
AT THIS POINT TO PICK THE AXIS OF HEAVIER PCPN. GFS DIAGS SUGGEST
BETWEEN MASON DIXON AND THE I78 CORRIDOR AND WE HAVE SEEN THE
ECMWF REMAIN EVEN FURTHER SOUTH. SO WHILE HIGHER TERRAIN LOCATIONS
FAR NORTH WERE KEPT MAINLY SNOW, NOT CONFIDENT ENOUGH THAT THEY
WOULD HAVE ADVISORY LEVEL ACCUMS AT THIS POINT TO ISSUE ONE.
MENTION WILL CONTINUE IN THE HWO.

TEMPERATURES ARE NEARLY A STRAIGHT GFS MOS PLAY GIVEN ITS COMPROMISE
TRACK POSITION. CONFIDENCE THOUGH REMAINS LESS THAN AVERAGE. WE
COULD BE TOO LOW IN DELMARVA WITH MAX TEMPS. AS THE CLIPPER PULLS
OFFSHORE, COLDER AIR WILL START ADVECTING DEEPER INTO OUR CWA.
MOST OF THE TIME AT THIS JUNCTURE OF THE SEASON THIS MEANS
PRECIPITATION ENDS BEFORE OR RIGHT ABOUT THE TIME OF THE
TRANSITION TO SNOW.

WEDNESDAY HAS TRENDED COLDER. GIVEN THE OP GFS LOOKS SLIGHTLY AMPED
VS ITS ENSEMBLE MEAN, OUR PREDICTED MAX TEMPS ARE WARMER THAN ITS
STAT GUIDANCE. ALSO THE WRF/NAM NORMALLY DOES BETTER WITH STRATOCU/CU
LEVEL CLOUDS AND ITS SOUNDINGS ARE NOT BRINGING US TO THE CONVECTIVE
TEMPERATURE, EVEN IN THE POCONOS.

YET ANOTHER CHILLY NIGHT ON WEDNESDAY NIGHT. THE HIGH PRESSURE SYSTEM
FADES OVERNIGHT AND A GRADIENT MIGHT INCREASE OR DEVELOP TOWARD MORNING.
WE SHOWED SOME OUTLYING AREA RADIATIONAL DIFFERENCES TO THE MINS,
BUT NOT AS MUCH AS CLIMO.

A WARMER DAY ON THURSDAY WITH THE INCREASING SOUTHWEST GRADIENT. MAX
TEMPS ARE CLOSER TO THE PREDICTED SOUNDINGS MID AFTN SUGGESTIONS THAN
OFF THE SUB 850 THERMALS WHICH LOOK TO HANG ONTO A COOL WEDGE TOO
LONG FOR DECENT SOUTHWEST FLOW. GIVEN BETTER MODELING FRONT END
CONSENSUS, WE LOWERED POPS FURTHER FOR THURSDAY AFTERNOON.

TIMING UNCERTAINTIES ENOUGH TO KEEP CHANCE POPS IN FOR THURSDAY NIGHT.
ALTHOUGH BETTER CHANCES FOR SHOWERS AND THUNDERSTORMS (STILL UNSTABLE
AT THE SHOWALTER LEVEL) IS ON FRIDAY AND FRIDAY NIGHT. THERE ARE
MODELING DIFFERENCES AS TO WHETHER OR NOT A WAVE WILL FORM ON THE COLD
FRONT AND ALSO WHEN AND WHERE. GEFS MEAN IS VERY SUPPORTIVE OF
THE CURRENT OP ECMWF, SO REASONING FOR HIGHEST POPS AND ALSO WHY
WE HAVE SATURDAY AFTERNOON DRY.

A SECOND COLD FRONT IS PREDICTED TO MOVE THROUGH EARLY ON EASTER
SUNDAY. FOR NOW WE ARE PASSING IT THROUGH DRY. NET EFFECT IS TO
KEEP SLIGHTLY COOLER THAN NORMAL TEMPS GOING THROUGH THE WEEKEND.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY, AND SURROUNDING AREAS.

TODAY...MOSTLY VFR CEILINGS. A FRONTAL BOUNDARY WILL CROSS THE
REGION BY ABOUT MIDDAY WITH SOME SNOW TO RAIN SHOWERS. SOME BRIEF
VISIBILITY RESTRICTIONS ALONG WITH SOME LOCAL MVFR CEILINGS THIS
MORNING. SOUTH-SOUTHWEST WINDS 5-10 KNOTS WILL INCREASE TO 15
KNOTS WITH GUSTS TO ABOUT 25 KNOTS FROM LATE MORNING ON, AND ALSO
SHIFT TO THE WEST AND NORTHWEST.

TONIGHT...VFR, WITH NORTHWEST WINDS QUICKLY DIMINISHING TO ABOUT 4-8
KNOTS DURING THE EVENING.

OUTLOOK...
TUESDAY AND TUESDAY NIGHT...CEILINGS AND VISIBILITIES DECREASING
TO MVFR, POSSIBLY IFR, WITH INCOMING RAIN AND SOME SNOW.
SNOW MOST LIKELY IN THE HIGHER TERRAIN. CONDITIONS IMPROVING
TUESDAY NIGHT.

WEDNESDAY AND WEDNESDAY NIGHT...MOSTLY VFR CONDITIONS.

THURSDAY...MOSTLY VFR. SOUTHWEST WIND GUST SHOULD INCREASE DURING
THE AFTERNOON. REDUCED CONFIDENCE LATER IN THE DAY DUE
TO COLD FRONTAL TIMING.

THURSDAY NIGHT AND FRIDAY...PREDOMINATELY VFR, CHANCE FOR
SHOWERS AND SLIGHT CHANCE FOR THUNDERSTORMS. WITH PRECIPITATION,
MVFR CONDITIONS POSSIBLE.

&&

.MARINE...
A FRONTAL BOUNDARY WILL MOVE THROUGH THE AREA AROUND MIDDAY. THIS
FRONT IS WEAK AS A WARMER AIRMASS IS TO FOLLOW FOR TODAY. A LOW-
LEVEL JET OF ABOUT 40 KNOTS IS MOVING ACROSS THE AREA THIS MORNING
ESPECIALLY THE CENTRAL AND SOUTHERN ZONES. WHILE THE AIRMASS IS
COOLER TO START, IT WILL BE WARMING TODAY. AS A RESULT, THE BETTER
MIXING SHOULD BE THIS MORNING FOR A TIME THEN SHIFT TO ALONG THE
COAST DURING THE COURSE OF THE DAY AS THE BOUNDARY LAYER WARMS. AS A
RESULT, THE STRONGEST WIND GUSTS SHOULD BE MOSTLY THIS MORNING FOR A
TIME FROM THE SOUTH AND SOUTHWEST. THERE IS SOME UNCERTAINTY THOUGH
HOW MUCH MIXING IS ACTUALLY REALIZED, HOWEVER GIVEN THE POTENTIAL
AND ALSO THAT SEAS ON THE OCEAN SHOULD BUILD TO ABOUT 5 FEET WE WILL
KEEP THE SMALL CRAFT ADVISORY GOING. THE WINDS ARE EXPECTED TO
DIMINISH THIS EVENING WITH THE SEAS ALSO SUBSIDING. AS A RESULT, THE
CONDITIONS ARE EXPECTED TO RETURN TO SUB-ADVISORY LEVELS DURING
TONIGHT.

OUTLOOK...
TUESDAY...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED.

TUESDAY NIGHT AND WEDNESDAY...WINDS SHOULD REMAIN BELOW SCA
CRITERIA UNLESS THE LOW IS STRONGER THAN FORECAST. SEAS WILL BE
DEPENDENT ON THE WIND FORECAST BUT AT THIS POINT ARE GENERALLY
EXPECTED TO REACH CLOSE TO SMALL CRAFT ADVISORY CRITERIA ON
THE OCEAN.

WEDNESDAY NIGHT...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED.

THURSDAY THROUGH FRIDAY...SOUTHERLY AND SOUTHWESTERLY WINDS WILL
LIKELY INCREASE ABOVE 25 KT FOR AT LEAST PART OF THIS PERIOD. SEAS
ON THE OCEAN WILL LIKELY INCREASE TO SCA CRITERIA AS WELL. WE WENT
BELOW WAVE WATCH GUIDANCE AS IT NORMALLY IS TOO BULLISH IN SOUTHWEST
FLOW REGIMES ESPECIALLY IN THIS INSTANCE THAT THE AIR SHOULD BE MUCH
WARMER THAN THE WATER TEMPS.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT TUESDAY FOR ANZ450>455.
     SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ430-
     431.

&&

$$
SYNOPSIS...GIGI/JOHNSON
NEAR TERM...O`HARA
SHORT TERM...GORSE
LONG TERM...GIGI
AVIATION...GIGI/GORSE/JOHNSON
MARINE...GIGI/GORSE/JOHNSON


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