Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KPHI 291954
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
354 PM EDT SUN MAR 29 2015

.SYNOPSIS...
A COLD FRONT IS EXPECTED TOMORROW. ON ITS HEALS WILL BE A FAST
MOVING LOW PRESSURE SYSTEM WHICH SHOULD SWEEP THROUGH THE AREA LATE
TUESDAY. HIGH PRESSURE WILL BUILD INTO THE REGION FOR WEDNESDAY AND
MOVE OFFSHORE ON THURSDAY. THE NEXT COLD FRONT WILL COME LATE IN THE
WEEK.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
THE GFS AND NAM BOTH INITIALIZED TOO WARM AT 850MB UPSTREAM ACROSS
THE LAKES BUT THE NAM WAS BETTER TO OUR SOUTH AND EAST, WHERE THE
COLD POOL SITS. AT 925MB THE GFS LOOKED BETTER THAN THE NAM AS A
STARTING POINT FOR OVERNIGHT LOWS.

SURFACE RIDGING CRESTS TO OUR SOUTH AND EAST LATER THIS EVENING AS
THE WINDS ACROSS OUR REGION BACK FURTHER TOWARDS THE SOUTH-
SOUTHWEST. AN POSITIVE FLUX IN MOISTURE IS EXPECTED TO OCCUR TONIGHT
AS THE RETURN FLOW AND 40 KNOT LOW-LEVEL JET MOVES IN OVERHEAD,
THOUGH WE DO HAVE A RELATIVE MINIMUM STARTING POINT WITH OUR SURFACE
DEWPOINTS.

WEAK COLD FRONT CONTINUES TO PUSH TOWARDS THE REGION LATE TONIGHT
AND CROSSES MOST OF THE AREA BY LATER MONDAY MORNING. THERE IS NOT
MUCH MOISTURE ASSOCIATED WITH THIS SYSTEM BUT THE FARTHER SOUTH ONE
HEADS THE BETTER CHANCES EXISTS FOR SOME ACCUMULATING RAIN. FROM THE
PHILLY METRO AREA NORTHWARD, WHERE WE HAVE TO OVERCOME THE LARGEST
DEWPOINT DEPRESSIONS TONIGHT, WE ARE CARRYING LOW-CHANCE POPS FOR A
TIME PERIOD, AS THE PTYPES TRANSITION FROM SNOW TO RAIN/SNOW AND
EVENTUALLY ALL RAIN BY LATE MONDAY MORNING...IF ANY MOISTURE REMAINS
IN PLACE.

AHEAD OF THE FRONTAL PASSAGE, HOWEVER, TEMPERATURES SHOULD BE QUICK
TO DROP OFF AS THE PRESSURE GRADIENT RELAXES FOR SEVERAL HOURS
BEFORE TIGHTENING BACK UP LATE. THE CLEAR SKIES AND LIGHTER WINDS
WILL HELP TO RADIATE SOME AREAS BEFORE THE STRONGER SOUTHERLY FLOW
KICKS IN AND HELPS TO WARM THE BOUNDARY LAYER BACK UP. MOST OF THIS
MODERATION TONIGHT, FROM RADIATIVE COOLING TO WARMING AGAIN, SHOULD
TAKE PLACE RIGHT AS THE FRONT BEARS DOWN ON THE REGION. THAT BEING
SAID MOST OF THE LOCATIONS ACROSS THE CWA SHOULD BE ABOVE FREEZING
TO NOT ALLOW FOR FREEZING RAIN ISSUES. THE LOCATIONS THAT ARE BELOW
FREEZING WILL MORE THAN LIKELY BE DRY.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
THE FRONT WILL CLEAR THE REGION BY LATE MORNING HELPING TO PULL ANY
LINGERING MOISTURE OFF TO OUR EAST...RATHER QUICKLY. DRYING AND
WARMING TREND IS EXPECTED FOR MONDAY AS WE MAINTAIN THE SOUTHWEST-
WEST SURFACE FLOW. TEMPERATURES SHOULD BE ABLE TO CLIMB BACK TO
AVERAGE, IF NOT ABOVE ONCE WE START TO CLEAR SOME OF THE STRATOCU
OUT OF THE REGION. WENT WITH THE WARMER MAV GUIDANCE.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
STILL CONSIDERABLE UNCERTAINTY WITH THIS FORECAST ESPECIALLY AS
THE SPLIT FLOW PATTERN CONTINUES FOR MUCH OF THE WEEK.

TUESDAY AND WEDNESDAY...THE BIG QUESTION THROUGH THIS PERIOD WILL
BE THE TRACK OF THE FAST MOVING CLIPPER SYSTEM TUESDAY INTO
TUESDAY NIGHT. MOST MODELS BRING THE CENTER OF THE SURFACE LOW
ACROSS DELMARVA AND SOUTHERN NJ, WITH THE EXCEPTION OF THE NAM,
WHICH TAKES A NORTHERN TRACK, BRINGING THE CENTER OF THE LOW
ACROSS NORTHERN NJ. WITH MORE MODEL AGREEMENT ON THE SOUTHERN
TRACK, FORECAST FAVORS THE SOUTHERN TRACK, KEEPING HIGHER POPS
ACROSS THE SOUTH AND FAVORING THE COLDER GUIDANCE FOR HIGHS ON
TUESDAY. BY WEDNESDAY, A SURFACE HIGH MOVES IN FOR A BRIEF
APPEARANCE.

THURSDAY THROUGH SATURDAY...THIS CONTINUES TO BE THE MOST
UNCERTAIN PERIOD OF THE FORECAST. THE GFS AND ECMWF CONTINUE TO
SHOW VAST DIFFERENCES IN THE TIMING AND TRACK OF A PAIR OF LOWS.
THE FIRST LOW OVER THE HUDSON BAY REGION LATE IN THE WORK WEEK.
THE QUESTION WILL BE IF AND WHEN THE ASSOCIATED COLD FRONT WILL
TRACK AS FAR SOUTH AS OUR REGION. THE SECOND LOW THE GFS SHOWS
DEVELOPING OVER THE SOUTHERN HIGH PLAINS BY THURSDAY NIGHT AND
SLIDING EAST JUST SOUTH OF REGION THROUGH SATURDAY, KEEPING A
STATIONARY FRONT SOUTH OF US THROUGH THIS TIME. THE ECMWF ON THE
OTHER HAND...SHOWS THE LOW FILLING AND ESSENTIALLY DISAPPEARING
BY FRIDAY. GIVEN THE UNCERTAINTY, STAYED CLOSE TO THE PREVIOUS
FORECAST. HOWEVER, AT THIS POINT, AM CONCERNED THAT THE ECMWF MAY
BE UNDERESTIMATING LEE SIDE CYCLOGENESIS. WITH BOTH SOLUTIONS
THOUGH, THE END RESULT IS THAT IT WILL BE COOLER (40S AND 50S)
FOR THE WEEKEND.

&&

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

TONIGHT...VFR. CLEAR SKIES PREVAIL THROUGH THE EVENING HOURS AS HIGH
PRESSURE CRESTS OVER THE REGION. THE WINDS WILL CONTINUE TO BACK
TOWARDS THE WEST-SOUTHWEST THIS EVENING BEFORE BECOMING SOUTHERLY
LATE TONIGHT. THIS IS AHEAD OF A COLD FRONT PASSAGE MONDAY MORNING.

MONDAY...MOSTLY VFR. THE COLD FRONT WILL CROSS THE REGION MONDAY
MORNING AND COULD PRODUCE A BRIEF PERIOD OF RAIN/SNOW AT THE
TERMINALS. COVERAGE LOOKS SPOTTY AND WAS NOT CONFIDENT ENOUGH TO ADD
PRECIPITATION TO THE TAFS, THOUGH FARTHER SOUTH INTO THE DELMARVA
HAS THE BETTER CHANCES. RIGHT BEHIND THE FRONT THE WINDS VEER
TOWARDS THE SOUTHWEST A BIT AND INCREASE WITH SOME GUSTS INTO THE
LOW-20S. BRIEF MVFR CIGS ARE POSSIBLE RIGHT BEHIND THE FRONT,
OTHERWISE BKN-OVC 5000FT DECK SHOULD PERSIST THROUGH MUCH OF THE
AFTERNOON BEFORE SCATTERING OUT.

OUTLOOK...
TUESDAY...CEILINGS AND VISIBILITIES DECREASING TO MVFR, POSSIBLY
IFR, WITH INCOMING RAIN. SNOW POSSIBLE IN HIGHER TERRAIN.

WEDNESDAY...MOSTLY VFR CONDITIONS.

THURSDAY AND FRIDAY...MOSTLY VFR, CHANCE FOR RA AND SLIGHT CHANCE
FOR TSRA. WITH PRECIPITATION, MVFR CONDITIONS POSSIBLE.

&&

.MARINE...

TONIGHT - MONDAY...SUB-SCA EXPECTED ACROSS THE WATERS THROUGH THE
LATE EVENING HOURS. THEN WINDS BACK TOWARDS THE SOUTH-SOUTHWEST AND
THE SEAS BEGIN TO INCREASE AGAIN. THE PRESSURE GRADIENT TIGHTENS
WITH SOME ENHANCED MIXING AND GUSTS CLOSE TO 30 KNOTS RIGHT AROUND A
COLD FRONT PASSAGE. WINDS VEER TOWARDS THE WEST-SOUTHWEST BEHIND THE
FRONT AND CONTINUE TO GUST FOR A PERIOD. THE GUSTS ON THE BAY AND
OCEAN SHOULD DROP BY MONDAY EVENING WHILE THE SEAS REMAIN SOMEWHAT
ELEVATED ALONG THE OCEANFRONT. SCA IS GOOD FROM 6Z TONIGHT TO 6Z
TUESDAY NIGHT.

OUTLOOK...
TUESDAY...ONCE WAVES DECREASE BELOW 5 FT EARLY TUESDAY MORNING,
WINDS AND SEAS SHOULD REMAIN BELOW SCA CRITERIA FOR THE REST OF
THE DAY.

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 REMAIN NEAR OR BELOW 5 FT.

THURSDAY AND FRIDAY...SOUTHERLY AND SOUTHWESTERLY WINDS WILL
LIKELY INCREASE ABOVE 25 KT FOR AT LEAST PART OF THIS PERIOD. SEAS
WILL LIKELY INCREASE ABOVE SCA CRITERIA AS WELL.

&&

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

&&

$$
SYNOPSIS...JOHNSON
NEAR TERM...HEAVENER
SHORT TERM...HEAVENER
LONG TERM...JOHNSON
AVIATION...HEAVENER/JOHNSON
MARINE...HEAVENER/JOHNSON



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.