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
000
FXUS61 KPHI 230059
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
859 PM EDT FRI APR 22 2016

.SYNOPSIS...
A SLOW MOVING COLD FRONT ENTERING NORTHWEST PENNSYLVANIA WILL MOVE
OFF THE MID ATLANTIC COAST SATURDAY MORNING. CANADIAN HIGH PRESSURE
WILL SETTLE SOUTHEAST INTO THE MID ATLANTIC STATES SUNDAY. A COLD
FRONT WILL EXTEND EAST FROM THE MIDWEST TO SOUTHERN NEW ENGLAND
MONDAY THEN EDGE SOUTH THROUGH THE MID ATLANTIC STATES TUESDAY.
CANADIAN HIGH PRESSURE IS FORECAST TO PUSH THE FRONT JUST SOUTH OF
OUR AREA WEDNESDAY. LOW PRESSURE IN THE MIDWEST THURSDAY WILL HEAD
FOR THE MID ATLANTIC STATES AND EVENTUALLY MOVE OUT TO SEA LATER
FRIDAY.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
A COLD FRONT MOVING ACROSS PA ATTM WILL CROSS OUR FORECAST AREA
OVER THE NEXT 6 HOURS. SCT SHOWERS AND PERHAPS A RUMBLE OF THUNDER
EXPECTED. WINDS WILL SHIFT TO NW OR N OVERNIGHT AS THE FRONT
PASSES THE AREA. GRIDS UPDATED WITH SLIGHTLY SLOWER FROPA TIMING.
LOW TEMPS AND OTHER GRIDS LOOKED OK OVERALL.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
GENERALLY, MODELS SEEM TO HAVE CONVERGED TOWARD A SIMILAR SOLUTION
WITH TODAY`S 12Z RUN, SHOWING THE VORT MAX AT BASE OF H5 SHORTWAVE
TROUGH MOVING ACROSS THE DC AREA IN MORNING AND THEN OFF THE
DELMARVA COAST DURING THE AFTERNOON.

A SLOWER SOLUTION WAS FAVORED WRT THE EXIT OF THE SHORTWAVE TROUGH
AND COLD FRONT SINCE THERE HAS BEEN A PERPETUAL PROGRESSIVE BIAS IN
THE MODELS WITH THIS SYSTEM EVER SINCE IT WAS A CUTOFF LOW OVER THE
SWRN US LAST WEEKEND. ACCORDINGLY, SHOWERS ASSOCIATED WITH THE
REMNANT UPPER LOW MAY PERSIST OVER THE DELMARVA AND SRN NJ THRU THE
MORNING AND POSSIBLY LINGER INTO THE EARLY AFTERNOON.

OTHERWISE, NWLY FLOW BEHIND THE FRONT WILL ADVECT DRIER AND COOLER
AIR INTO THE REGION. SKIES WILL CLEAR ACROSS THE POCONOS INITIALLY
DURING THE MORNING AND EXPAND S/E TOWARD THE I-95 CORRIDOR AROUND
MIDDAY AND S NJ/DE COAST LATE IN THE AFTERNOON. CAA IN THE BOUNDARY
LAYER APPEARS TO BE MODEST AND CERTAINLY NOT STRONG ENOUGH TO
COMPLETELY OFFSET DAYTIME INSOLATION WITH A HIGH SUN ANGLE THIS TIME
OF YEAR. THUS, HIGHS SHOULD STILL BE AT OR EVEN A FEW DEGREES ABOVE
NORMAL, RANGING FROM THE UPPER 50S AT MT POCONO TO AROUND 70F IN
PHILADELPHIA.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
500MB: THE PATTERN IN THIS LONG TERM SECTION IS CHARACTERIZED BY A
STRONGLY NEGATIVE NAO.  A SHORT WAVE CROSSES THE NORTHEAST MONDAY
NIGHT/TUESDAY, ANOTHER LATE THURSDAY INTO FRIDAY.

TEMPERATURES:  THE FIRST 21 DAYS OF APRIL HAVE AVERAGED NEAR NORMAL
AT PHL, TTN AND ABE AND 1-2 TO DEGREES BELOW NORMAL ELSEWHERE.
CALENDAR DAY AVERAGES SHOULD AVERAGE SEVERAL DEGREES BELOW NORMAL
SUNDAY, SEVERAL DEGREES ABOVE NORMAL MONDAY AND TUESDAY, NEAR
OR SLIGHTLY BELOW NORMAL WEDNESDAY. THURSDAY AND FRIDAY ARE MORE
UNCERTAIN BUT LETS SAY FOR NOW, WITHIN 5 DEGREES EITHER SIDE OF
NORMAL.

FORECAST BASIS: UNLESS OTHERWISE NOTED, A 50 50 BLEND OF THE 12Z/22
GFS/NAM MOS GUIDANCE SATURDAY NIGHT-SUNDAY NIGHT, THEREAFTER THE
12Z/22 GFS MEX MOS FOR MONDAY AND MONDAY NIGHT AND WPC GUIDANCE
TUESDAY - FRIDAY. ONE NOTABLE EXCEPTION... SINCE THERE IS SO MUCH
UNCERTAINTY TUESDAY REGARDING THE POSITION OF A STRONG COLD FRONT...
HAVE BLENDED THE MUCH COOLER ECMWF 12Z 2M TEMPS TUESDAY WITH THE
WPC GUIDANCE TO FORECAST A SIGNIFICANT COOLING NE PA AND MUCH OF
NNJ.

THE DAILIES...

SATURDAY NIGHT...CLEAR AND CHILLY WITH FROST POTENTIAL LATE (7Z-
11Z)NEAR AND NW OF I-78. LIGHT NORTH FLOW EXCEPT POSSIBLE GUSTS 15
MPH ALONG THE COASTS. RADIATIONAL COOLING MOST IDEAL LATE AT NIGHT.
LOWERED 12Z/22 NCEP BLENDED GUIDANCE 2-3 DEGS IN THE COUNTRYSIDE
NORTHWEST OF I-95. SCT FROST IS IN THE FCST WHERE ANTICIPATE THE
NEED FOR A FROST ADVISORY IN A FUTURE ISSUANCE WHICH IS BASICALLY
NEAR AND N OF I-78. LOWS ABOUT 4 TO 8 DEGREES BELOW NORMAL.

SUNDAY...SUNNY AND PLEASANT. LIGHT NORTH TO NORTHWEST WIND BACKING
TO SOUTHWEST LATE IN THE DAY. NEAR NORMAL MAX TEMPS.

MONDAY...PARTLY TO MOSTLY SUNNY AND WARMER... GOOD WEATHER. SW WIND
GUST 20 TO 25 MPH IN THE AFTERNOON. MAX TEMPS ABOUT 10 DEGREES ABOVE
NORMAL AWAY FROM THE MARINE INFLUENCE. THERE IS A SMALL CHANCE
THAT WE WILL HAVE FIRE WEATHER CONCERNS ACROSS E PA AND NJ MONDAY
AFTERNOON.

TUESDAY...CONSIDERABLE UNCERTAINTY BUT FOR NOW MORNING MIN TEMPERATURES
ABOUT 10 TO 15 DEGREES ABOVE NORMAL KRDG-KPHL-KACY SOUTH WHILE A SHOWERY
ACTIVE COLD FRONT SEEPS SOUTHWARD BY DAYBREAK, MAYBE TO NEAR I-78.
HOPEFULLY BENEFICIAL RAINFALL. CHANCE OF A THUNDERSTORM PHILLY
AREA SOUTHWARD. WEST WIND SHIFT TO NORTH OR NORTHEAST AND POSSIBLY
GUSTY 20 MPH. LOW TEMPERATURE FOR THE CALENDAR DAY NEAR 1 AM WEDNESDAY
WITH MOST MAX TEMPS FOR THIS CALENDAR DAY POSSIBLY OCCURRING PRIOR
TO 18Z/26. AS IT MODELS NOW, CONSIDERABLE ERROR POTENTIAL FOR THE
MORNING MIN TEMPS AND DAYTIME MAX TEMPS.

TUESDAY NIGHT...CONSIDERABLE CLOUDINESS AS ANY LINGERING SHOWERS
END EARLY. COOL. IF IT CLEARS SOON ENOUGH, THERE COULD BE A FROST
CONCERN IN NW NJ AND NE PA.

WEDNESDAY...BECOMING MOSTLY SUNNY AND PLEASANT. LIGHT WIND.

THURSDAY...LOOKS LIKE RAINY OR SHOWERY WITH CONSIDERABLE UNCERTAINTY
REGARDING TEMPERATURES. BIG ERROR POTENTIAL ONCE AGAIN ON DAYTIME
MAX TEMPS SINCE WE`RE NOT EXACTLY SURE OF THE PATH LOW PRESSURE
TAKES ACROSS THE MID ATLANTIC STATES. THAT ALSO IMPACTS THE WIND
DIRECTION. WHAT WE`RE MOST CONFIDENT OF IS THAT IT WILL RAIN.

FRIDAY...ANY LINGERING RAIN ENDS EARLY WITH A COOL NORTHERLY FLOW
TO FOLLOW.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

AN APPROACHING COLD FRONT HAS LED TO AN INCREASE IN COVERAGE OF
SHOWERS THIS EVENING. THESE SHOWERS AND LOCALLY LOWER CIGS/VSBYS
EXPECTED FOR THE NEXT 6 HOURS OR SO. ONCE THE FRONT PASSES...WINDS
WILL SHIFT TO NW OR N AND DRIER AIR WILL ARRIVE OVER THE AREA.
CIGS WILL INCREASE SAT MORNING WITH VFR EXPECTED MUCH OF THE DAY.

OUTLOOK...
SATURDAY NIGHT...VFR.  LIGHT NORTH WIND MAY GUST 15 KT ALONG THE
COASTS.

SUNDAY...VFR...FEW CIRRUS. LIGHT NORTH NORTHWEST WIND BACKING TO
SOUTHWEST LATER IN THE DAY.

MONDAY...VFR PATCHES OF SCT-BKN AOA 5000FT.  SW WIND GUSTY 20 KT.

TUESDAY...MVFR/IFR LIKELY IN SHRA/TSRA TUE AS A SLOW SOUTHWARD
MOVING COLD FRONT TRAVERSES THE TERMINALS. MVFR CIGS EXPECTED TO
LINGER WELL INTO TUESDAY NIGHT AFTER THE SHOWERS END. WEST WIND
EARLY IN THE MORNING SHIFT GUSTY NORTH TO NORTHEAST.

WEDNESDAY...VFR. LIGHT WIND.

&&

.MARINE...
SCA FLAG FROM EARLIER WAS ALLOWED TO EXPIRE AS SEAS ON THE OCEAN
AND WINDS OVERALL HAVE SLACKENED SINCE THIS AFTERNOON. SCATTERED
SHOWERS EXPECTED OVERNIGHT AND SAT MORNING (SOUTHERN WATERS).

OUTLOOK...
SATURDAY NIGHT...NORTH-NORTHWEST WINDS MAY REACH THE SCA THRESHOLD
FOR A BRIEF PERIOD OF TIME AS HIGH PRESSURE BUILDS OVER THE
COASTAL WATERS.

LATE MONDAY OR TUESDAY...AN SCA WILL LIKELY BE NEEDED AS BOTH WINDS
AND SEAS INCREASE IN ASSOCIATION WITH LOW PRESSURE AND COLD FRONT
PASSING THROUGH THE MID ATLANTIC STATES.

WEDNESDAY...NO MARINE HEADLINES ANTICIPATED AT THIS TIME. LIGHT
NORTH WIND TRENDING ONSHORE.

&&

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

&&

$$
SYNOPSIS...DRAG
NEAR TERM...O`HARA
SHORT TERM...KLEIN
LONG TERM...DRAG
AVIATION...DRAG/KLEIN/O`HARA
MARINE...DRAG/KLEIN/O`HARA



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