Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 131032
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
632 AM EDT SUN APR 13 2014

.SYNOPSIS...
HIGH PRESSURE LOCATED OVER THE WESTERN NORTH ATLANTIC WILL
CONTINUE TO INFLUENCE OUR WEATHER FOR TODAY AND MONDAY. A STRONG
COLD FRONT IS FORECAST TO APPROACH FROM THE WEST ON MONDAY NIGHT
AND TUESDAY AND IT SHOULD PASS THROUGH OUR REGION FROM LATE
TUESDAY AFTERNOON INTO EARLY TUESDAY EVENING. HIGH PRESSURE FROM
THE WEST IS ANTICIPATED TO BUILD ACROSS THE NORTHEASTERN STATES ON
WEDNESDAY AND INTO ATLANTIC CANADA FOR THURSDAY AND FRIDAY. A
FRONTAL BOUNDARY APPROACHING FROM THE WEST IS EXPECTED TO PASS
THROUGH OUR REGION ON SATURDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A FRONTAL ZONE WILL BE DRAPED FROM NEW ENGLAND TO THE GREAT LAKES
THEN DOWN INTO THE MID MISSISSIPPI VALLEY TODAY. LOW PRESSURE IS
FORECAST TO TRACK ALONG THIS FRONT IN THE CENTRAL PLAINS TO MID
MISSISSIPPI VALLEY REGIONS. MEANWHILE, THE CONTINUATION OF
DOWNSTREAM WAA WILL HELP SEND A WARM FRONT NORTHWARD ACROSS OUR
AREA THROUGH ABOUT MIDDAY. THIS WILL SIMPLY ENHANCE THE WARMER
AIR MASS THAT HAS ALREADY BEEN IN PLACE ACROSS OUR CWA. ALONG WITH
THE WAA, MOISTURE ADVECTION WILL ALSO BE UNDERWAY WHICH WILL HELP
INCREASE THE SURFACE DEW POINTS GRADUALLY FROM SOUTH TO NORTH
THROUGH THE DAY. THIS PROCESS IS ALREADY UNDERWAY EARLY THIS
MORNING, AND APPEARS TO BE HELPING COMBINE WITH JUST ENOUGH
ISENTROPIC LIFT FOR A FEW SHOWERS ACROSS THE NORTHWESTERN ZONES.
THESE SHOULD NOT AMOUNT TO MUCH BUT DID INCLUDE A SLIGHT CHC POP
FOR A LITTLE WHILE FOR ISOLATED SHOWERS, THEN A CHC OF SPRINKLES A
LITTLE TO THE EAST OF THERE. THE WAA COMBINED WITH A NOCTURNAL
INVERSION WAS INITIALLY THOUGHT TO HELP FOCUS AREAS OF STRATUS OR
FOG EARLY THIS MORNING, HOWEVER THIS PROCESS HAS BEEN RATHER SLOW.
SO FAR, JUST SOME STRATUS HAS DEVELOPED ALONG PORTIONS OF THE DELAWARE
RIVER WHICH SEEMS TO BE ENHANCED BY THE RIVER/BAY AND ALSO
CHESAPEAKE BAY.

OTHERWISE, BANDS OF MID TO HIGH LEVEL CLOUDS STREAMING BY ESPECIALLY
THIS MORNING DUE TO SOME DEBRIS CLOUDINESS FROM CONVECTION EARLY
THIS MORNING IN THE MIDWEST AND GREAT LAKES. AS THE MOISTURE
INCREASES SOME, WE SHOULD BE ABLE TO DEVELOP SOME CUMULUS THIS
AFTERNOON. THE MAIN FORCING IS TIED TO A BOUNDARY NEAR THE EASTERN
GREAT LAKES, AS THIS IS WHERE A THERMAL GRADIENT ALOFT EXITS.
THEREFORE, ORGANIZED SHOWERS AND EMBEDDED THUNDER WILL BE TO OUR
NORTH ASSOCIATED WITH THIS THERMAL BOUNDARY.

AS THE BOUNDARY LAYER WARMS, THE DEPTH OF THE MIXING LAYER WILL
GREATLY INCREASE. THE FORECAST SOUNDINGS SHOW AS THIS OCCURS THE
LOW-LEVEL LAPSE RATES STEEPEN QUITE A BIT AWAY FROM THE COAST.
THIS WILL PROMOTE BREEZY CONDITIONS DEVELOPING ESPECIALLY FROM
MIDDAY ON. THIS WILL ALSO HOLD BACK ANY SEA BREEZE DEVELOPMENT, AS
THE SYNOPTIC SCALE FLOW IS FROM THE SOUTH AND SOUTHWEST.
THEREFORE, LOCALES ESPECIALLY RIGHT ALONG THE NORTHERN COAST OF
DELAWARE BAY AND THE JERSEY SHORE WILL BE COOLER.

AS FOR HIGH TEMPERATURES, WE USED A BLEND OF THE NAM/GFS 2 METER
TEMPERATURES THEN ADJUSTED UP A LITTLE BIT GIVEN THE EXPECTED
MIXING. THE COASTAL LOCALES WERE KEPT COOLER GIVEN THE SOUTHERLY
FLOW. FOR THE HOURLY GRIDS EARLY THIS MORNING, WE USED A BLEND OF
THE LAMP/LAV GUIDANCE TO HELP ASSIST WITH TRENDS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
OUR REGION WILL REMAIN WITHIN THE WARM SECTOR THROUGH TONIGHT AS
WE ARE BETWEEN A RIDGE TO THE SOUTHEAST AND A SHARPENING UPPER-
LEVEL TROUGH FROM THE MIDWEST TO THE CENTRAL PLAINS. THIS WILL
RESULT IN THE SOUTHERLY FLOW BEING MAINTAINED UNDER A DECENT FLOW
REGIME. THIS WILL MAINTAIN SOME MOISTURE ADVECTION FROM THE SOUTH,
AND THEREFORE HIGHER SURFACE DEW POINTS.

AS THE SOUTHWESTERLY FLOW CONTINUES ALONG WITH THE SHARPENING
TROUGH WELL TO OUR WEST, AT LEAST SOME MID TO HIGH CLOUDS WILL
CONTINUE TO STREAM ACROSS THE AREA. HOWEVER, AS THE MOISTURE
DEEPENS SOME IN THE LOWER LEVELS IT MAY BECOME TRAPPED ENOUGH
UNDER THE NOCTURNAL INVERSION. THIS COULD RESULT IN SOME STRATUS
OR FOG. THE BOUNDARY LAYER WHILE IT WILL COOL, IT SHOULD REMAIN
MILD ENOUGH TO PROMOTE AT LEAST SOME WIND FOR MUCH OF THE AREA.
THIS MAY HELP KEEP THE LOWEST LEVELS MIXED ENOUGH TO KEEP STRATUS
OR FOG MAINLY AT BAY. ONE ITEM OF NOTE THOUGH IS THE FORECAST DEW
POINTS TO GRADUALLY INCREASE THROUGH THE 50S, AND THIS ADVECTS
OVER THE COOLER WATERS IT COULD INDUCE SOME FOG. THEREFORE, WE
ADDED PATCHY FOG FOR NOW LATE OVER THE COASTAL WATERS AND THE
ADJACENT COASTAL LOCALES.

AS FOR LOW TEMPERATURES, WE USED MOSTLY A BLEND OF THE NAM/GFS
MOS.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
THE RIDGE OVER THE WESTERN NORTH ATLANTIC SHOULD CONTINUE TO
INFLUENCE OUR REGION FOR MONDAY, BRINGING FAIR WEATHER AND
AFTERNOON TEMPERATURES IN THE 70S AT MOST LOCATIONS.

THE MAIN WEATHER EVENT FOR THE WEEK IS STILL EXPECTED DURING THE
LATE MONDAY NIGHT THROUGH EARLY TUESDAY NIGHT TIME FRAME.

THE AXIS OF A DEEP MID LEVEL TROUGH IS EXPECTED TO EXTEND FROM
THE WESTERN GREAT LAKES TO THE TEXAS GULF COAST ON TUESDAY
MORNING. THE FEATURE SHOULD LIFT NORTHEASTWARD TAKING ON A
NEGATIVE TILT LATE ON TUESDAY. THE AXIS OF THE TROUGH IS
ANTICIPATED TO PASS OVER OUR REGION LATE ON TUESDAY NIGHT. THE
GUIDANCE SEEMS TO BE FOCUSING ON THE LATE TUESDAY AFTERNOON INTO
EARLY TUESDAY EVENING TIME FRAME FOR THE PASSAGE OF THE STRONG
SURFACE COLD FRONT ASSOCIATED WITH THE MID LEVEL TROUGH.

SHOWERS ARE EXPECTED TO BEGIN MOVING INTO OUR REGION FROM THE
WEST ON MONDAY NIGHT AND THEY SHOULD CONTINUE INTO TUESDAY. IT
APPEARS AS THOUGH THE BEST CHANCE FOR MODERATE TO HEAVY RAINFALL
WILL BE IN THE VICINITY OF THE FRONTAL BOUNDARY. THE MODELS ARE
INDICATING GOOD LIFT WITH THE FEATURE WHICH SEEMS REASONABLE DUE
THE PROGRESSIVE NATURE OF THE BOUNDARY AND THE SHARP TEMPERATURE
CONTRAST.

ALSO, A 60 PLUS KNOT LOW LEVEL SOUTH SOUTHWESTERLY JET IS
FORECAST TO DEVELOP OVER OUR REGION IN ADVANCE OF THE FRONT ON
TUESDAY. THE LOW LEVEL JET WILL DRAW ADDITIONAL MOISTURE INTO THE
SYSTEM. PRECIPITABLE WATER VALUES ARE EXPECTED TO RISE NEAR OR
ABOVE 1.5 INCHES.

THE GUIDANCE CONTINUES TO FOCUS MAINLY ON THE 0.75 TO 1.25 INCH
RANGE FOR RAINFALL AMOUNTS WITH THE FRONT, SO WE WILL KEEP
MENTIONING THE POTENTIAL FOR MODERATE TO HEAVY RAIN. THE GUIDANCE
HAS BEEN A BIT HIGH ON PRECIPITATION AMOUNTS RECENTLY SO WE ARE
HOPEFUL THAT THOSE NUMBERS WILL BE AT THE HIGH END OF THE RANGE
FOR OUR AREA WHICH WOULD LIMIT THE THREAT OF FLOODING.

THE STORM PREDICTION CENTER HAS PLACED THE CENTRAL AND SOUTHERN
PARTS OF OUR REGION IN ITS GENERAL THUNDERSTORM AREA FOR TUESDAY.
THE STRONG LIFT MAY VERY WELL RESULT IN SCATTERED THUNDER,
ESPECIALLY NEAR THE FRONT.

THE CONSENSUS OF THE LATEST GUIDANCE SUGGESTS THAT THE
PRECIPITATION WILL BE OFF THE COAST BEFORE MIDNIGHT, IN ADVANCE OF
THE MID LEVEL TROUGH AXIS. THE EXPECTED TIMING WOULD NOT ALLOW
ENOUGH COLD AIR TO ARRIVE BEFORE THE PRECIPITATION ENDS TO CAUSE
THE RAIN TO CHANGE TO SNOW ANYWHERE IN OUR COUNTY WARNING AREA.

COOL HIGH PRESSURE FROM THE WEST IS FORECAST TO BUILD ACROSS THE
NORTHEASTERN STATES ON WEDNESDAY AND INTO ATLANTIC CANADA LATE IN
THE WEEK. A SURFACE RIDGE AXIS IS ANTICIPATED TO DEVELOP DOWN THE
LEE OF THE APPALACHIANS. THE PATTERN WILL KEEP OUR REGION IN A
COOL NORTH TO NORTHEAST SURFACE FLOW. TEMPERATURES WILL BE BELOW
NORMAL.

A PARTLY CLOUDY TO MOSTLY CLEAR SKY IS ANTICIPATED FOR BOTH
WEDNESDAY NIGHT AND THURSDAY NIGHT. THE WIND MAY BECOME LIGHT
ENOUGH ALONG THE INTERSTATE 95 CORRIDOR AND INTO SOUTHEASTERN
PENNSYLVANIA TO RESULT IN THE DEVELOPMENT OF SOME PATCHY FROST
THERE DURING THE EARLY MORNING HOURS ON BOTH THURSDAY AND FRIDAY.

AS THE HIGH PULLS TO THE NORTHEAST AND FARTHER AWAY FROM OUR
REGION A MID LEVEL TROUGH AND ITS ASSOCIATED SURFACE FRONT ARE
EXPECTED TO APPROACH FROM THE WEST AND AFFECT OUR REGION FROM
FRIDAY NIGHT INTO SATURDAY. WE HAVE MENTIONED A CHANCE OF RAIN
SHOWERS.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

TODAY...VFR OVERALL. HOWEVER, SOME LOCAL STRATUS AROUND 1,000 FEET
EARLY THIS MORNING ESPECIALLY FROM KTTN TO KABE AND THE KPHL
METRO. LIGHT SOUTHERLY WINDS OR LIGHT AND VARIABLE, BECOMING
SOUTH-SOUTHWEST AND INCREASING TO 10 TO 15 KNOTS WITH GUSTS UP TO
25 KNOTS. THE MAJORITY OF THE GUSTS SHOULD OCCUR FROM MIDDAY ON.

TONIGHT...VFR OVERALL. HOWEVER, THERE SHOULD BE SOME STRATUS AND/OR
FOG DEVELOPING TOWARD DAYBREAK MONDAY. OUR CONFIDENCE IS ON THE
LOWER SIDE REGARDING THE TIMING AND COVERAGE. SOUTHERLY WINDS
NEAR 10 KNOTS, BUT A BIT GUSTY EARLY.

OUTLOOK...
MONDAY...MAINLY VFR. PATCHY EARLY MORNING LOW CLOUDS AND FOG MAY
LOWER CONDITIONS INTO THE MVFR AND IFR RANGES.

MONDAY NIGHT...LOWERING CONDITIONS LATE AT NIGHT AS RAIN SHOWERS
BEGIN TO MOVE INTO OUR REGION FROM THE WEST.

TUESDAY...MVFR AND IFR CONDITIONS IN RAIN SHOWERS. THE RAIN MAY
BECOME HEAVY AT TIMES, ESPECIALLY IN THE AFTERNOON.

TUESDAY NIGHT...MVFR AND IFR CONDITIONS IN RAIN SHOWERS,
IMPROVING TO VFR LATE AT NIGHT.

WEDNESDAY THROUGH THURSDAY...MAINLY VFR.

&&

.MARINE...
A WARM FRONT WILL LIFT NORTH ACROSS OUR AREA TODAY, MAINTAINING
AN ALREADY WARM AIR MASS ACROSS THE MID ATLANTIC. THE SOUTHERLY
FLOW WILL INCREASE THROUGH TONIGHT, HOWEVER AS IS THE CASE THIS
TIME OF THE YEAR, A MUCH WARMER AIR MASS ABOVE THE COOLER WATERS
WILL RESULT IN A SHARP LOW-LEVEL INVERSION. THE FORECAST SOUNDINGS
INDICATE THAT WINDS TO ABOUT 25 KNOTS ARE JUST ABOVE THE SURFACE,
HOWEVER THE MIXING SHOULD BE LIMITED ESPECIALLY AWAY FROM THE
COAST. WE ARE MORE CONFIDENT ABOUT NEAR SHORE GUSTS TO ABOUT 25
KNOTS DURING THE COURSE OF THIS AFTERNOON AND TONIGHT, BUT THIS
DECREASES FARTHER OFFSHORE. WE WILL MAINTAIN THE SMALL CRAFT
ADVISORY AS THE SUSTAINED SOUTHERLY FLOW IS EXPECTED TO BUILD THE
SEAS TO ABOUT 5 FEET THROUGH TONIGHT. WE DID SLOW THIS DOWN A BIT
AS THE MODELS MAY BE MIXING THE WINDS DOWN A BIT TO MUCH. SINCE
NEAR SHORE GUSTS SHOULD REACH UP TO 25 KNOTS, WE OPTED TO ADD A
SMALL CRAFT ADVISORY FOR DELAWARE BAY THIS AFTERNOON AND THIS
EVENING.

OUTLOOK...
MONDAY...A SMALL CRAFT ADVISORY IS IN EFFECT FOR OUR OCEAN
WATERS. WE ARE EXPECTING GUSTY SOUTHERLY WINDS AND WAVE HEIGHTS
AROUND 5 FEET.

MONDAY NIGHT AND TUESDAY...SMALL CRAFT ADVISORY CONDITIONS ARE
EXPECTED. THE WIND WILL BE FROM THE SOUTH.

TUESDAY NIGHT AND WEDNESDAY...SMALL CRAFT ADVISORY CONDITIONS ARE
EXPECTED. THE WIND WILL VEER FROM THE NORTHWEST TO THE NORTH.

WEDNESDAY NIGHT AND THURSDAY...SMALL CRAFT ADVISORY CONDITIONS
ARE EXPECTED. THE WIND WILL BE FROM THE NORTHEAST.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 PM EDT MONDAY FOR
     ANZ450>455.
     SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO MIDNIGHT EDT
     TONIGHT FOR ANZ430-431.

&&

$$
SYNOPSIS...IOVINO
NEAR TERM...GORSE
SHORT TERM...GORSE
LONG TERM...IOVINO
AVIATION...GORSE/IOVINO
MARINE...GORSE/IOVINO




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