Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 281837
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
237 PM EDT SAT MAR 28 2015

.SYNOPSIS...
A HIGH PRESSURE SYSTEM OVER THE GREAT LAKES WILL SINK SOUTHEAST
AND REACH THE SOUTHEAST COAST SUNDAY. A COLD FRONT ASSOCIATED
WITH A LOW PRESSURE SYSTEM WILL MOVE THROUGH THE REGION ON
MONDAY. THIS WILL BE FOLLOWED QUICKLY BY AN ALBERTA CLIPPER
TYPE LOW PRESSURE SYSTEM PASSING NEAR OR THROUGH THE AREA
LATE ON TUESDAY. A HIGH PRESSURE SYSTEM SHOULD THEN BUILD INTO
THE REGION FOR WEDNESDAY. A COLD FRONT IS PREDICTED TO REACH THE
WESTERN GREAT LAKES ON THURSDAY MORNING AND APPROACH OUR AREA ON
FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
REGIONAL RADAR IS NOT SHOWING MUCH IN THE WAY OF SNOW SHOWERS
ACROSS THIS AFTERNOON. THE MORNING SHOWERS ACROSS THE DELMARVA
HAVE ALL BUT WEAKENED AND WITH SURFACE TEMPERATURES CLIMBING CLOSE
TO 40F, ITS DOUBTFUL ANYTHING IS ACTUALLY STICKING ANYMORE. THAT
BEING SAID, THE UPPER LEVEL ENERGY STILL IS PIVOTING THROUGH THE
REGION AS WE SPEAK. A BIT MORE LOW-LEVEL INSTABILITY IS PRESENT
COINCIDING WITH THE COLD POOL ALOFT DRIFTING THROUGH SO WE COULD
STILL SEE WIDELY SCATTERED SNOW SHOWERS ACROSS THE AREA. HI-RES
GUIDANCE HAS BEEN SHOWING THE BETTER AREAS ARE ONCE AGAIN THE
DELMARVA AND PARTS OF THE PHILLY METRO AREA. IT IS POSSIBLE,
CLOSER TO THE NJ COAST, THAT A WEAK TROUGH-LIKE FEATURE TRIES TO
SPARK A FEW BETTER ORGANIZED SHOWERS. THE RGEM IS THE MORE ROBUST
WITH THIS FEATURE BUT SOME OF THE SREF CORE MEMBERS SHOW THIS AS
WELL. NOT ENTIRELY SURE, IF IT FORMS, IT WOULD HAVE MUCH LAND
BASED IMPACTS, SO WE CONTINUE TO ADVERTISE THE CHANCE POPS THROUGH
THE EVENING HOURS FROM PHILLY SOUTHWARD.

THE GUSTY WINDS WILL BE AROUND MOST OF THE NIGHT AND WITH A
SECONDARY SURGE OF COLDER AIR IN THE LOW-LEVELS WE COULD SEE GUSTS
INCREASE SLIGHTLY STRONGER THAN THEY WERE DURING THE DAY. NONE-THE-
LESS THE PRESSURE GRADIENT WILL BE TIGHT ENOUGH TO KEEP US WELL
MIXED SO NOT EXPECTING MUCH IN THE WAY OF RADIATIONAL COOLING AS
THE CLOUDS DISSIPATE. WENT WITH A STRAIGHT BLEND OF THE MET/MAVMOS
TONIGHT.


&&

.SHORT TERM /SUNDAY/...
HIGH PRESSURE MOVES IN ALOFT AND AT THE SURFACE TO PROVIDE A RATHER
TRANQUIL DAY WITH DRY CONDITIONS. SKIES WILL REMAIN MOSTLY SUNNY
WITH THE MASSIVE AMOUNT OF SUBSIDENCE TAKING PLACE BUT THIS WILL
ALSO LIMIT THE HEIGHTS TO WHICH WE CAN MIX. THE AIRMASS ALOFT STARTS
TO MODERATE LATER IN THE DAY AND AS THE WINDS BACK TOWARDS THE WEST-
SOUTHWEST WE SHOULD SEE TEMPERATURES SEVERAL DEGREES WARMER THAN ON
SATURDAY. WE EDGED CLOSER TO THE WARMER MAVMOS FOR HIGHS TOMORROW
THOUGH IT IS QUITE POSSIBLE THAT WITH ANY DOWNSLOPING ADDITION WE
COULD TACK ON ANOTHER DEGREE...EXPECTING MID TO UPPER-40S.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
AN ACTIVE LONG TERM WITH A COUPLE OF PCPN SHOTS POSSIBLE. THE
WRF-NMMB INITIALIZATION AT 500MB LOOKED BETTER THAN THE GFS, BOTH
MODELS WERE ABOUT THE SAME AT 850MB AND 925MB WITH ANY ERRORS
ON THE COLD SIDE BY ABOUT 1C. THE DP/DT WITH THE MODELS OVER
THE PAST 24 HOURS WAS SHOWING A DEEPER EAST COAST TROF. BASED
ON THIS MOVING FORWARD WE WERE SLOWER WITH THE EVOLUTION OF
EVENTS.

AN AIR MASS MODIFICATION WITH DECREASING WINDS IS PREDICTED FOR
SUNDAY. GIVEN THE COLD START, CHANCES ARE THAT THE MAX TEMPS
WILL OCCUR LATER IN THE AFTERNOON THAN USUAL. GIVEN FULL
SUN AND A DOWNSLOPING WIND, WE WENT FULL ADIABATIC
WITH MAX TEMPS CLOSE TO END OF THE AFTERNOON SOUNDING
SUGGESTED MAX TEMPS.

THE WEAKER OF THE NEXT TWO SYSTEMS WILL APPROACH OUR AREA ON MONDAY
NIGHT. THERE WILL BE DECENT MID LEVEL QVEC CONVERGENCE, BUT THE
PREDICTED ISENTROPIC LIFT AND FGEN FORCING ARE MORE MUTED. THE JET IS
NOT IN A BAD POSITION. GIVEN THE OVERALL DRYNESS OF THE INITIAL
AIR MASS, MODELS ARE NOT PREDICTING MUCH PCPN. BECAUSE OF THE DPVA
AND THE MID LEVEL QVEC CONVERGENCE, PCPN SHOULD BE FALLING FROM A
MID CLOUD DECK. NOT SURE IF IT WILL MAKE IT TO THE GROUND, BUT FOR
NOW WE WENT HIGHER THAN STAT GUIDANCE BECAUSE OF THE FORCING. WHILE
A LLJ WILL BE WARMING THE SUB CLOUD LAYER AND MIGHT BE ABLE TO OFFSET
EVAPORATIONAL COOLING EFFECTS, SNOW AS A PTYPE IS A POSSIBILITY IN
THE NORTHERN PART OF OUR CWA. BECAUSE QPF AMOUNTS ARE LOW, ANY ACCUMS
ARE EXPECTED TO BE LESS THAN AN INCH. MIN TEMPS WILL LIKELY OCCUR
EARLIER IN THE NIGHT AND RISE TOWARD MORNING.

USUALLY THE CASE WITH THESE WEAK SYSTEMS, ANY PCPN OCCURS IN THE WAA
PHASE WITH LITTLE IF ANY WITH THE CFP ITSELF. MODELS ARE PRETTY CLOSE
ON THAT DURING THE DAY ON MONDAY. WITH THE LAGGING STRONGER
CAA, THE DOWNSLOPING WINDS SHOULD MORE THAN COMPENSATE FOR COOLING ALOFT.
A STAT GUIDANCE COMBO LOOKS DECENT FOR MAX TEMPERATURES. IT WILL
BECOME WINDIER WIND PEAK GUSTS LIKELY REACHING AT LEAST 20 TO 30 MPH.

THE RIDGING FROM THE NEXT HIGH PRESSURE SYSTEM PASSES OVER OUR FORECAST
AREA ON MONDAY NIGHT. BUT WE MAY REMAIN IN A BIT OF A GRADIENT AND
DID NOT BOTTOM MIN TEMPERATURES.

AT LEAST ON PAPER TODAY, THE NEXT ALBERTA TYPE LOW PRESSURE SYSTEM
LOOKS MORE ROBUST. A MUCH BETTER PREDICTED COUPLET OF MID LEVEL FGEN
AND QVEC FORCING IN OUR AREA. THIS CAN BE SEEN WITH IN THE QPF
FIELD BY ITSELF. THERE ARE TRACK DIFFERENCES WITH DIFFERENCES
IN OPINION AS TO THE GREATER IMPACT. FOR NOW WE HAVE COMPROMISED
BETWEEN THE DATASETS, THUS ONSET OF UPPED PCPN CHANCES IS TUESDAY
AFTERNOON AND CONTINUING INTO TUESDAY NIGHT. WHILE THE BOUNDARY
LAYER WILL GET WARMED ON TUESDAY, IT IS STILL COLD ALOFT AND A
CHANGE TO SNOW, ESPECIALLY OVER THE HIGHER TERRAIN NORTH WOULD
BE THE LOGICAL OUTCOME FOR SUCH A SCENARIO. THIS ONE COULD BE
SNOWIER. BECAUSE OF DIFFERENCES WITH THE TRACK AND THE
INHERENT UNCERTAINTY OF TIMING, THERE EXISTS THE POTENTIAL
FOR SOME BIG ERRORS WITH MAX TEMPS ON TUE. WE ARE TOWARD THE
HIGHER END OF THE GUIDANCE SPECTRUM.

WEAKER HIGH PRESSURE SYSTEM TO FOLLOW ON WEDNESDAY WHICH MEANS LITTLE IF ANY
DROP IN MAXIMUM TEMPERATURES. THE REST OF THE LONG TERM WE SHIED AWAY
FROM THE FASTER GFS CFP TIMING. THUS OUR MAX TEMPS THURSDAY ARE HIGHER
THAN ITS STAT GUIDANCE. WE ALSO PUSHED BACK THE ONSET OF SHOWER CHANCES
CLOSER TO THE ECMWF`S TIMING AND PERSISTED IT THROUGH FRIDAY.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY, AND SURROUNDING AREAS.

THIS EVENING - TONIGHT...VFR. BROKEN DECK AROUND 5KFT. WIDELY
SCATTERED SNOW SHOWERS THIS AFTERNOON AND EVENING MAY OCCUR. NOT
CONFIDENT ON DIRECT TERMINAL IMPACTS SO WE WILL NOT CARRY A TEMPO
AT THIS TIME. BEST CHANCES MAY BE SOUTH AND WEST OF ILG. NORTHWEST
WINDS AROUND 15 KNOTS WITH GUSTS INTO THE LOW-20 KTS RANGE.

SUNDAY...VFR. CEILINGS LIFT A BIT AND SKIES BEGIN TO
SCATTER/CLEAR OUT LATE TONIGHT. ANOTHER, BETTER, SURGE OF COLD AIR
SHOULD ALLOW FOR SLIGHTLY STRONGER GUSTS THEN SATURDAY AFTERNOON
PRODUCED. BY MID- SUNDAY MORNING THE GUSTS BEGIN TO WANE AND WINDS
SLACKEN UNDER CLEAR SKIES. WINDS BACK TOWARDS THE WEST-SOUTHWEST.

OUTLOOK...
SUNDAY NIGHT AND MONDAY...SOME LOWER MVFR CIGS AND VSBYS IN
SCATTERED RAIN, HIGHER TERRAIN SNOW, SHOWERS. THERE IS A CHANCE
FOR LLWS AT SOUTHERN AIRPORTS. NORTHWEST WINDS ON MONDAY SHOULD
GUST TO AROUND 25 KNOTS.

MONDAY NIGHT...VFR.

TUESDAY AND TUESDAY NIGHT...POTENTIAL MVFR OR IFR RESTRICTIONS
IN RAIN AND POSSIBLY SNOW AT HIGHER TERRAIN AIRPORTS.

WEDNESDAY...VFR OR BECOMING VFR AS THE DAY PROGRESSES.

&&

.MARINE...
TONIGHT...WE CONTINUE WITH THE SCA THROUGH MID-SUNDAY AS
WINDS AND SEAS ARE EXPECTED TO REMAIN ELEVATED. GUSTS UPWARDS OF 25
KNOTS ARE STILL EXPECTED ACROSS THE WATERS, AND WITH A SECONDARY
SURGE OF COLDER AIR TONIGHT, WE COULD GUSTS CLIMB UPWARDS OF 30
KNOTS TONIGHT.

SUNDAY...SUB-SCA EXPECTED BY SUNDAY AFTERNOON AS HIGH PRESSURE
SETTLES IN OVERHEAD. WE LOSE THE GUSTS RATHER QUICKLY AND WITH THE
OFFSHORE WINDS THE SEAS SHOULD QUICKLY DROP AS WELL. WINDS BEGIN TO
VEER TOWARDS THE WEST-SOUTWHEST BY SUNDAY AFTERNOON.

OUTLOOK...
SUNDAY NIGHT AND MONDAY...ANOTHER ROUND OF SCA CONDITIONS IS
POSSIBLE IN THE INCREASING SW FLOW PRECEDING THE NEXT CFP. WHILE
AIR TEMPERATURES WILL BE WARMING MONDAY, MIXING NEAR COASTAL AREAS
COULD KEEP SCA CONDITIONS PERSISTING EVEN AFTER THE CFP.

MONDAY NIGHT...SUB SCA CONDITIONS OUTLOOKED TO RETURN AS THE
PRESSURE GRADIENT WEAKENS AGAIN.

TUESDAY THROUGH WEDNESDAY...PRIMARILY SUB SMALL CRAFT ADVISORY
CONDITIONS ARE OUTLOOKED. THE ONE CAVEAT IS THAT WITH A CLIPPER LOW
PRESSURE SYSTEM PASSING THROUGH OR NEAR OUR COASTAL WATERS, WE
WILL HAVE TO MONITOR A STRONGER OVERALL LOW THAT MIGHT INCREASE
BOTH WINDS AND SEAS INTO SMALL CRAFT ADVISORY CRITERIA.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT SUNDAY FOR ANZ430-431-
     450>455.

&&

$$
SYNOPSIS...GAINES/GIGI
NEAR TERM...HEAVENER
SHORT TERM...HEAVENER
LONG TERM...GIGI
AVIATION...GAINES/GIGI/HEAVENER
MARINE...GAINES/GIGI/HEAVENER


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