Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 121340
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
940 AM EDT SAT APR 12 2014

.SYNOPSIS...
A FRONTAL BOUNDARY WILL REMAIN TO OUR SOUTH TODAY BEFORE LIFTING
BACK TO THE NORTH TONIGHT. HIGH PRESSURE LOCATED OVER THE WESTERN
NORTH ATLANTIC IS FORECAST TO INFLUENCE OUR WEATHER FROM SUNDAY
INTO MONDAY. A STRONG COLD FRONT IS EXPECTED TO APPROACH FROM THE
WEST EARLY IN THE NEW WEEK, AND IT SHOULD PASS THROUGH OUR REGION
ON TUESDAY. HIGH PRESSURE IS ANTICIPATED TO BUILD ACROSS THE
NORTHEASTERN STATES AND SOUTHEASTERN CANADA FOR THE SECOND HALF OF
THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE AREAS OF FOG ACROSS THE NORTHERN PORTION OF THE CWA ARE
QUICKLY ERODING GIVING WAY TO MOSTLY CLEAR SKIES ABOVE. THIS WILL
ALLOW TEMPERATURES ACROSS THE NORTH TO QUICKLY JUMP SEVERAL
DEGREES WHICH THE LAMP/LAV GUIDANCE SHOWS PRETTY WELL FOR THIS UPDATE.

OTHERWISE, AS A SHORT WAVE TROUGH QUICKLY SHIFTS TO OUR
NORTHEAST THIS MORNING, THE UPPER-LEVEL FLOW WILL TEND TO BE
ZONAL. THIS WILL ALLOW HIGH PRESSURE AT THE SURFACE TO QUICKLY
BUILD ACROSS OUR AREA, HOWEVER IT WILL ALREADY BE SHIFTING
OFFSHORE BY THE EVENING HOURS. THIS WILL RESULT IN A LIGHT
NORTHERLY WIND BECOMING SOUTHERLY. AS THIS OCCURS, A STRONG WA
REGIME AT 850 MB IS FORECAST TO OCCUR UP THE OHIO VALLEY AND INTO
MUCH OF THE GREAT LAKES REGION. THIS WILL ALSO DRIVE A WARM FRONT
NORTHBOUND LATE TODAY. THE FORECAST SOUNDINGS GENERALLY SUGGEST
MAINLY SOME HIGH CLOUDS THROUGH THE DAY ONCE ANY LOWER CLOUDS
DISSIPATE. THE FLOW IS FORECAST TO BECOME EVEN LIGHTER DURING THE
COURSE OF THE DAY, AND WITH A GROWING TEMPERATURE CONTRAST BETWEEN
THE WATER AND LAND, A SEA AND BAY BREEZE SHOULD DEVELOP AROUND
MIDDAY AND POTENTIALLY BE ENHANCED SOME FROM THE LIGHT SYNOPTIC
SOUTHERLY FLOW. THIS WILL KEEP THE COASTAL LOCALES ON THE COOLER
SIDE.

OVERALL, A QUIET DAY IS IN STORE AS HIGH PRESSURE SLIDES ACROSS.
THE AIR MASS IS FORECAST TO BE COOLER ALOFT COMPARED TO YESTERDAY,
THEREFORE WHILE ANOTHER MILD DAY IS EXPECTED IT SHOULD NOT BE AS
WARM AS WHAT WAS OBSERVED YESTERDAY. WE GENERALLY USED A BLEND OF
THE NAM/GFS MOS FOR HIGH TEMPERATURES.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
HIGH PRESSURE WILL CONTINUE TO SHIFT FARTHER AWAY FROM THE MID
ATLANTIC COAST. MEANWHILE, LOW PRESSURE IS FORECAST TO TRACK UP
ACROSS THE CENTRAL GREAT LAKES OVERNIGHT. A WARM FRONT ATTACHED TO
THIS SURFACE LOW SHOULD LIFT WELL TO OUR NORTH, WITH THE 850 MB
THERMAL GRADIENT MORE NOTABLE NEAR THE U.S. AND CANADIAN BORDER. A
STRENGTHENING SOUTHWESTERLY FLOW ALOFT WILL INCREASE THE OVERALL
WAA PATTERN ACROSS THE MID ATLANTIC REGION. THEREFORE, SOME
INCREASE IN CLOUDS ARE ANTICIPATED THROUGH THE NIGHT, ESPECIALLY
ACROSS THE WESTERN AREAS. THE STRONGER ISENTROPIC LIFT APPEARS TO
MORE FOCUSED TO OUR NORTHWEST, THEREFORE WE MAINTAINED A DRY
FORECAST.

AS THE FLOW WILL BE SOUTH TO SOUTHEAST AT THE SURFACE, THE LOW-
LEVEL MOISTURE IS EXPECTED TO INCREASE SOME. WHILE THE SURFACE
WINDS SHOULD BE ON THE LIGHT SIDE, THE WAA ALOFT WILL ALLOW FOR A
SHARPENING LOW-LEVEL INVERSION TO DEVELOP ESPECIALLY AS THE
BOUNDARY LAYER COOLS. THE FORECAST SOUNDINGS INDICATE THAT SOME
LOW CLOUDS AND/OR FOG DEVELOPS LATE TONIGHT, HOWEVER THE MOIST
LAYER LOOKS TO BE RATHER SHALLOW. IF THIS IS THE CASE, THEN ANY
LOW CLOUDS/FOG WOULD TEND TO BE LOCALIZED. AS OF NOW WE BROUGHT IN
SOME INCREASE IN CLOUDS, HOWEVER WILL LEAVE OUT A FOG MENTION AS
IT IS NOT ALL THAT CLEAR IF ANY FOG WOULD BE WIDESPREAD ENOUGH FOR
AN IMPACT.

AS FOR LOW TEMPERATURES WE USED A NAM/GFS MOS BLEND, BUT THEN
MADE SOME ADJUSTMENTS ESPECIALLY FOR THE NORMALLY COOLER LOCALES
AND A SEA BREEZE INFLUENCE EARLY ON.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
A BUILDING RIDGE OVER THE WESTERN NORTH ATLANTIC WILL CONTINUE TO
BRING WARM AIR INTO OUR REGION FOR SUNDAY AND MONDAY ALONG WITH
FAIR WEATHER CONDITIONS. DAYTIME HIGHS SHOULD BE MAINLY IN THE 70S
ON BOTH DAYS WITH OVERNIGHT LOWS IN THE 50S.

THE AXIS OF A MID LEVEL TROUGH APPROACHING FROM THE WEST IS
EXPECTED TO BE LOCATED OVER THE MISSISSIPPI RIVER VALLEY ON MONDAY
NIGHT. THE FEATURE IS FORECAST TO FLATTEN AS IT MOVES OVER THE
EASTERN STATES. THE GFS REMAINS MORE PROGRESS WITH THE TROUGH THAN
THE ECMWF.

A STRONG SURFACE COLD FRONT ASSOCIATED WITH THE MID LEVEL TROUGH
SHOULD EXTEND FROM THE EASTERN GREAT LAKES TO THE LOWER
MISSISSIPPI RIVER VALLEY ON MONDAY EVENING. THE FRONT WILL
PROGRESS EASTWARD AND IT IS EXPECTED TO PASS THROUGH OUR REGION
AROUND TUESDAY AFTERNOON. WE HAVE TAKEN A COMPROMISE IN THE TIMING
OF THE PRECIPITATION WITH THE SYSTEM BETWEEN THE GFS AND THE
ECMWF. BOTH MODELS ARE SUGGESTING RAINFALL AMOUNTS IN THE 0.75 TO
1.25 INCH RANGE AT THIS POINT. HOWEVER, THE MODELS HAVE BEEN
RUNNING A LITTLE HIGH OF LATE. WE WILL CONTINUE TO MONITOR THE
TRENDS FOR ANY FLOODING POTENTIAL. FOR NOW, WE WILL SIMPLY MENTION
THAT THE RAIN COULD BECOME HEAVY AT TIMES.

AS THE MAIN AREA OF PRECIPITATION MOVES OFF THE COAST ON TUESDAY
NIGHT, COLD AIR WILL BEGIN TO BUILD INTO OUR REGION FROM THE
NORTHWEST. IT CONTINUES TO SEEM QUITE POSSIBLE THAT THE EVENT
COULD END WITH A LITTLE SNOW ACROSS OUR NORTHERN COUNTIES. BASED
ON THE EXPECTED TIMING OF THE BACK EDGE OF THE PRECIPITATION AND
THE ARRIVAL OF THE COLD AIR, WE ARE NOT ANTICIPATING ANY
SIGNIFICANT SNOWFALL AMOUNTS AT THIS POINT.

COOL HIGH PRESSURE IS FORECAST TO BUILD FROM THE EASTERN GREAT
LAKES TO ATLANTIC CANADA DURING THE PERIOD FROM WEDNESDAY THROUGH
FRIDAY WITH A SURFACE RIDGE AXIS DEVELOPING 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 WEDNESDAY
NIGHT ALONG WITH A RELATIVELY LIGHT WIND. AS A RESULT, PATCHY
FROST IS POSSIBLE FOR LATE WEDNESDAY NIGHT INTO EARLY THURSDAY
MORNING.

&&

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

TODAY...VFR. NORTHERLY WINDS AROUND 5 TO 10 KNOTS, THEN SOUTHWEST
AND SOUTH FROM ABOUT MIDDAY ON. THERE SHOULD BE A SEA/BAY BREEZE
DEVELOPING THIS AFTERNOON GIVEN LIGHTER WINDS, AND THIS WILL
AFFECT KACY, KMIV TO KILG.

TONIGHT...VFR OVERALL. A STRONG LOW-LEVEL INVERSION THOUGH ESPECIALLY
LATE MAY RESULT IN SOME LOW CLOUDS AND/OR FOG DEVELOPMENT UNDER A
LIGHT SOUTH TO SOUTHEAST WIND. AS OF NOW OUR CONFIDENCE IS ON THE
LOWER SIDE, THEREFORE WE WILL JUST HINT AT THIS POTENTIAL IN THE
12Z TAFS.

OUTLOOK...
SUNDAY THROUGH MONDAY...MAINLY VFR. PATCHY LATE NIGHT AND 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. THE RAIN MAY BECOME
HEAVY AT TIMES.

TUESDAY NIGHT...MVFR AND IFR CONDITIONS WITH RAIN TAPERING TO
SHOWERS.

WEDNESDAY...MAINLY VFR.

&&

.MARINE...
HIGH PRESSURE WILL SLIDE ACROSS THE AREA TODAY HOWEVER BE
SHIFTING TO OUR EAST BY EARLY THIS EVENING. THIS WILL RESULT IN A
NORTHERLY WIND BECOMING SOUTHERLY THROUGH THE AFTERNOON. THIS MAY
BE SOMEWHAT ENHANCED NEAR SHORE AND UP DELAWARE BAY AS A SEA/BAY
BREEZE DEVELOPS. OVERALL THOUGH THE WINDS ARE EXPECTED TO REMAIN
BELOW ADVISORY CRITERIA THROUGH TONIGHT. THE SEAS HAVE SUBSIDED
AND DESPITE THE FLOW BECOMING SOUTHERLY, WE ARE ANTICIPATING THIS
TO REMAIN LIGHT ENOUGH TO KEEP SEAS BELOW 5 FEET. AN INCREASE IN
THE LOW-LEVEL MOISTURE AND WARMER AIR ABOVE A STRENGTHENING
INVERSION COULD RESULT IN SOME FOG DEVELOPMENT LATER TONIGHT. AS
OF NOW, THIS WAS NOT INCLUDED DUE TO SOME LOWER CONFIDENCE.

OUTLOOK...
SUNDAY...NO MARINE HEADLINES ARE ANTICIPATED.

SUNDAY NIGHT AND MONDAY...WAVE HEIGHTS ON OUR OCEAN WATERS MAY
BUILD TO 5 FEET OR GREATER IN THE PERSISTENT SOUTHERLY FLOW.

MONDAY NIGHT AND TUESDAY...WIND GUSTS OF 25 KNOTS OR GREATER FROM
THE SOUTH AND WAVE HEIGHTS OF 5 FEET OR GREATER ARE POSSIBLE ON
OUR OCEAN WATERS.

TUESDAY NIGHT...WAVE HEIGHTS ON OUR OCEAN WATERS MAY REMAIN AT 5
FEET OR GREATER AS A STRONG COLD FRONT MOVES OUT TO SEA.

WEDNESDAY...NO MARINE HEADLINES ARE ANTICIPATED.

&&

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

&&

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






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