Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 151641
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1241 PM EDT WED APR 15 2015

.SYNOPSIS...
HIGH PRESSURE WILL BUILD ACROSS OUR REGION TODAY AND TONIGHT, THEN
SHIFT OFFSHORE THURSDAY INTO FRIDAY. A COLD FRONT WILL MOVE THROUGH
FRIDAY AS LOW PRESSURE DEVELOPS NEAR THE NORTH CAROLINA COAST, THEN
A SECONDARY COLD FRONT ARRIVES DURING SATURDAY. HIGH PRESSURE IS
SCHEDULED TO BRIEFLY BUILD IN FOR SUNDAY, THEN THE NEXT COLD FRONT
AND LOW PRESSURE SYSTEM MOVES IN FOR LATER MONDAY AND TUESDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

HIGH PRESSURE WILL CONTINUE TO BUILD TOWARD THE REGION TODAY. THIS
WILL ALLOW FOR A CONTIUATION OF MOSTLY SUNNY SKIES AND STRONG
NORTHERLY WINDS. DEWPOINTS HAVE BEEN DROPPING ACROSS MOST OF THE
REGION THIS MORNING AND RUNNING QUITE A BIT LOWER THAN WHAT THE
SOME OF THE GUIDANCE SUGGESTS. IN THE NEAR TERM CONTINUED TO LEAN
CLOSER TO THE MET GUIDANCE BUT EVEN THIS IS TO HIGH, LOWERED
DEWPOINTS ON THE 12:30PM UPDATE TO ACCOUNT FOR THE DRY AIRMASS.
WITH MOSTLY SUNNY CONDITIONS TODAY, TEMPERATURES HAVE REPSONDED
NICELY ACROSS THE REGION SOME MINOR ADJUSTMENTS WERE MADE WITH THE
UPDATE OTHERWISE MOST OF US SHOULD SEE HIGHS WELL INTO THE 60`S.
THE MAIN WEATHER PLAYER WILL BE THE STRONG NORTHERLY WIND GUSTS
AROUND 25 MPH. HRRR AND RAP SOUNDINGS CONTINUE TO SUGGEST WIND
GUSTS MAY PERSIST THROUGH THE AFTERNOON AND DID RAISE THEM A BIT
WITH THE LATEST UPDATE. FIRE WEATHER CONCERNS, EXIST AS WELL WITH
A RED FLAG WARNING UP FOR CENTRAL AND NORTHERN NJ ALONG WITH
EASTERN PA, PLEASE SEE FIRE WEATHER SECTION FOR MORE.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
500 MB SHORT WAVE RIDGE SLIDES OVER THE REGION, AS THE SURFACE HIGH
BUILDS CLOSER. ADDITIONALLY, THE 250MB LEVEL JET SLIDES FURTHER OFF
SHORE, ALL OF THIS WILL COMBINE FOR CLEARING SKIES OVERNIGHT. WINDS
SHOULD BE LIGHT, AND WITH THE RELATIVELY LOW DEW POINT TEMPERATURES,
SHOULD SEE CONSIDERABLE RADIATIONAL COOLING. AS A RESULT, EXPECT
LOWS IN THE UPPER 30S TO LOWER 40S. AT THIS TIME, HOWEVER, DO NOT
EXPECT FROST ADVISORY CONDITIONS IN LOCATIONS WHERE THE GROWING
SEASON HAS ALREADY STARTED (IN THESE AREAS EXPECT LOWS MOSTLY IN THE
LOWER 40S).

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
THE SYNOPTIC SETUP IS COMPRISED OF AN INITIAL RIDGE IN THE EAST THAT
TRANSITIONS TO SOME TROUGHING. AS THIS OCCURS, A CLOSED LOW ACROSS
THE WEST DROPS EAST-SOUTHEAST EVENTUALLY EJECTING ACROSS THE PLAINS.
THIS FEATURE BUILDS SOME RIDGING DOWNSTREAM, HOWEVER IT ALSO FORCES
SOME AMPLIFICATION OF THE TROUGH ACROSS THE NORTHEAST FOR A PORTION
OF THE WEEKEND. THE CLOSED LOW MAY THEN GET ABSORBED INTO A LARGE
SCALE TROUGH FROM THE MIDWEST AS IT UNDERGOES AMPLIFICATION EASTWARD
EARLY NEXT WEEK. PRIOR TO THIS OCCURRING, A SURFACE LOW IS FORECAST
TO DEVELOP NEAR THE NORTH CAROLINA COAST THURSDAY AND THEN TRACK
NORTHEASTWARD. THE DETAILS WITHIN THIS SETUP IS OF LOWER CONFIDENCE
AS THE MODEL GUIDANCE IS HAVING TROUBLE HANDLING THE SPLIT FLOW. THE
INTERACTION OF THE EJECTING CLOSED LOW AND THE NORTHERN STREAM
TROUGH AND ASSOCIATED ENERGY WILL HAVE AN IMPACT ON THE DOWNSTREAM
WEATHER. THIS IS MOST NOTED FOR OUR AREA DURING THE WEEKEND AND
ESPECIALLY EARLY NEXT WEEK. GIVEN THE LOWER CONFIDENCE, WE USED A
MODEL BLEND WITH CONTINUITY FOR WEDNESDAY THROUGH FRIDAY THEN WENT
WITH MOSTLY THE 00Z WPC GUIDANCE /BLEND OF THE MEANS SATURDAY, THEN
MOSTLY A NAEFS/ECMWF ENSEMBLE MEAN BLEND THEREAFTER/. SOME
ADJUSTMENTS WERE THEM MADE FOLLOWING ADDITIONAL COLLABORATION WITH
OUR NEIGHBORING OFFICES.

FOR THURSDAY...HIGH PRESSURE AT THE SURFACE IS FORECAST TO SHIFT TO
OUR EAST DURING THIS TIME FRAME. THIS WILL SET THE STAGE FOR
SOUTHEASTERLY LOW-LEVEL FLOW THAT WILL ALLOW FOR MOISTURE ADVECTION
TO INCREASE. IT APPEARS THAT A PRESSURE TROUGH DEVELOPS ALONG THE
NORTH CAROLINA COAST AS DEPARTING HIGH PRESSURE WEDGES SOUTHWESTWARD
FOR A TIME. AS A RESULT, LOW PRESSURE IS FORECAST TO DEVELOP NEAR OR
ALONG THE NORTH CAROLINA COAST. THERE MAY BE A CONDUIT OF MOISTURE
PULLED NORTHWESTWARD FROM THIS SURFACE LOW AS IT SLOWLY TRACKS
NORTHEASTWARD. OTHERWISE, AN INCOMING COLD FRONT SHOULD ALSO HAVE
SOME SHOWERS WITH IT. OVERALL, MUCH OF THIS TIME FRAME SHOULD BE DRY
WITH ANY SHOWERS TENDING TO HOLD OFF UNTIL LATER THURSDAY NIGHT AND
THIS IS WHEN THE POPS INCREASE.

FOR FRIDAY AND SATURDAY...IT MAY START OUT RATHER UNSETTLED FRIDAY
AS MOISTURE GETS PULLED NORTHWARD FROM LOW PRESSURE NEAR THE NORTH
CAROLINA COAST. THIS FEATURE WILL THEN TRACK FARTHER AWAY FROM THE
COAST LATER FRIDAY AND SATURDAY, ALTHOUGH A SECONDARY COLD FRONT
SHOULD ARRIVE DURING SATURDAY. THERE IS LESS CONFIDENCE IN THE
AMOUNT OF SHOWERS FRIDAY AS IT WILL DEPEND ON HOW MUCH INTERACTION
THE SURFACE LOW TO OUR SOUTH HAS WITH ENERGY SLIDING BY FARTHER TO
THE NORTH. AS A RESULT, WE KEPT POPS BELOW LIKELY AND WENT WITH
SCATTERED WORDING FOR NOW. THE SECONDARY FRONT ON SATURDAY MAY NOT
HAVE MUCH MOISTURE LEFT TO WORK WITH, THEREFORE WE KEPT POPS ON THE
LOWER SIDE. IT DOES APPEAR THAT THE AIRMASS MODERATES PRIOR TO THE
COLD FRONTAL PASSAGE WITH MANY AREAS GETTING TO AROUND 70 DEGREES
DURING THE DAY.

FOR SUNDAY THROUGH TUESDAY...HIGH PRESSURE AT THE SURFACE SHOULD
BUILD IN BRIEFLY SUNDAY. AS ENERGY EJECTS EASTWARD FROM A CLOSED LOW
AND ALSO FROM THE MIDWEST, A COMPLEX SYSTEM MAY EVOLVE EASTWARD WITH
TIME. WE KEPT SUNDAY DURING THE DAY DRY DUE TO THE PRESENCE OF HIGH
PRESSURE, THEN WAA AND MOISTURE ADVECTION BEGINS TO OVERTAKE THE
AREA AT NIGHT. THIS MAY ALLOW FOR SOME SHOWERS TO ARRIVE, ALTHOUGH
IT STILL LOOKS LIKE THE MORE UNSETTLED TIME FRAME MAY BE MONDAY AND
TUESDAY. THIS WILL DEPEND ON THE EVOLUTION OF THE SPLIT FLOW AS IT
MAY TURN INTO AN AMPLIFIED UPPER-LEVEL TROUGH IN THE EAST. AS OF
NOW, THE HIGHEST POPS ARE FOR MONDAY HOWEVER THIS WILL PROBABLY
CHANGE. GIVEN THE UNCERTAINTY WITH THE DETAILS, WE DID NOT GO ANY
HIGHER THAN HIGH CHC POPS. SOME COOLER TEMPERATURES SHOULD RESULT,
ESPECIALLY IF THE RAIN IS MORE WIDESPREAD.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. ONLY LINGERING
HIGH CIRRUS CLOUDS ARE POSSIBLE. NORTHERLY WINDS WILL LIKELY GUST
AT MOST LOCATIONS FROM 18-23 KNOTS THIS AFTERNOON. THE GUSTS WILL
TAPER OFF AFTER SUNSET. WINDS ARE EXPECTED TO GRADUALLY SHIFT TO
EAST NORTHEASTERLY OVERNIGHT TONIGHT UNDER 10 KNOTS THEN TO
EASTERLY IN THE MORNING FROM 8-10 KNOTS. THE WINDS WILL THEN SHIFT
SOUTHEASTERLY BY THURSDAY AFTERNOON.

OUTLOOK...
THURSDAY NIGHT THROUGH SATURDAY... CONDITIONS TENDING TO LOWER TO
MVFR WITH SCATTERED SHOWERS LATER THURSDAY NIGHT AND FRIDAY. OUR
CONFIDENCE IS ON THE LOWER SIDE WITH THE TIMING AND HOW MUCH RAIN
OCCURS. A SECONDARY COLD FRONT MOVES THROUGH DURING SATURDAY,
HOWEVER THIS MAY HAVE LIMITED MOISTURE WITH IT.

SUNDAY...OVERALL VFR AS HIGH PRESSURE BRIEFLY BUILD IN.

&&

.MARINE...
SMALL CRAFT ADVISORY HAS BEEN CANCELLED. WINDS AND SEAS HAVE
DROPPED BELOW CRITERIA. A FEW GUSTS NEAR 20 KT WILL BE POSSIBLE
THROUGH THE DAY ON THE COASTAL WATERS, BUT SHOULD REMAIN BELOW
SCA CRITERIA.

OUTLOOK...
THURSDAY AND FRIDAY...THE WINDS AND SEAS ARE EXPECTED TO BE BELOW
SMALL CRAFT ADVISORY CRITERIA AS THE FLOW OVERALL IS FORECAST TO BE
LIGHT ENOUGH.

SATURDAY AND SUNDAY...A COLD FRONT MOVES THROUGH DURING SATURDAY
THEN HIGH PRESSURE ARRIVES BRIEFLY FOR SUNDAY. THE WINDS APPEAR TO
REMAIN BELOW ADVISORY CRITERIA, HOWEVER THE SEAS COULD NEAR 5 FEET
FOR A TIME ON THE OCEAN MAINLY IF THE NORTHERLY FLOW AHEAD OF HIGH
PRESSURE LASTS LONG ENOUGH AND IS A BIT STRONGER.

&&

.FIRE WEATHER...
ALMOST ALL OF THE REGION (WITH THE EXCEPTION OF A FEW COASTAL
LOCATIONS) WILL SEE MINIMUM RELATIVE HUMIDITY VALUES NEAR OR BELOW
20 PERCENT.  MUCH OF DELMARVA AND FAR SOUTHERN NJ HAD RAIN TOTALS
NEAR OR ABOVE 1 INCH YESTERDAY, LEADING TO HIGHER FUEL MOISTURES.
FOR THE REST OF THE REGION HOWEVER, THE LIGHT RAIN YESTERDAY DID
NOT HAVE MADE A SIGNIFICANT IMPACT ACROSS CENTRAL/NORTHERN NJ AND
EASTERN PA ON FUEL MOISTURE AND DRYING OF THE FUEL MOISTURE WILL
CONTINUE TODAY.

AS FOR WINDS, GUSTS NEAR 25 MPH ARE LIKELY ACROSS THE REGION.
HOWEVER, THE TIGHTEST PRESSURE GRADIENT, AND THUS THE STRONGEST
WINDS ARE EXPECTED IN THE MORNING BUT WILL LINGER INTO THE
AFTERNOON. WE HAVE ISSUED A RED FLAG WARNING FOR EASTERN PA,
NORTHERN/CENTRAL NJ UNTIL 7 PM DUE TO A COMBINATION OF LOW
MOISTURE IN FINE FUELS, LOW RH 20% OR LOWER AND WIND GUSTS AROUND
25 MPH THROUGH THE AFTERNOON.

FOR THURSDAY, THE RELATIVE HUMIDITY VALUES ARE FORECAST TO DROP TO
25-35 PERCENT IN THE AFTERNOON MAINLY FOR NEW JERSEY /AWAY FROM THE
COAST/ AND EASTERN PENNSYLVANIA, HOWEVER THE WINDS ARE CURRENTLY
FORECAST TO BE 15 MPH OR LESS.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...RED FLAG WARNING UNTIL 7 PM EDT THIS EVENING FOR PAZ054-055-
     060>062-070-071-101>106.
NJ...RED FLAG WARNING UNTIL 7 PM EDT THIS EVENING FOR NJZ001-
     007>010-012>015.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...GORSE
NEAR TERM...GAINES/JOHNSON
SHORT TERM...JOHNSON
LONG TERM...GORSE
AVIATION...GAINES/GORSE/JOHNSON
MARINE...GORSE/JOHNSON
FIRE WEATHER...GAINES/JOHNSON



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