-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 140802
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
402 AM EDT MON APR 14 2014

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

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
OUR REGION REMAINS BETWEEN A RIDGE TO THE EAST AND SOUTHEAST AND
A SHARPENING UPPER-LEVEL TROUGH TO THE WEST. AS THE LATTER
GRADUALLY SLIDES EASTWARD THROUGH TODAY, THE RIDGE WILL BE PUSHED
FARTHER OFFSHORE. THIS WILL RESULT IN THE HEIGHTS LOWERING SOME
THROUGH THE COURSE OF THE DAY. MEANWHILE, A DEEP SOUTH-SOUTHWEST
FLOW OF WARM AIR WILL BE MAINTAINED ACROSS THE ENTIRE REGION. THIS
WILL RESULT IN ANOTHER WARM DAY, HOWEVER WITH SOME COOLING
FORECAST TO START TAKING PLACE ALOFT, HIGH TEMPERATURES SHOULD BE
A LITTLE COOLER THAN WHAT WAS OBSERVED YESTERDAY. DESPITE THIS, WE
DID GO A LITTLE BIT ABOVE GUIDANCE /CLOSER TO CONTINUITY/
ESPECIALLY AS THE BOUNDARY LAYER IS FORECAST TO BE WELL MIXED ONCE
AGAIN. THE SOUTHERLY WIND COMPONENT THOUGH WILL ALLOW FOR COOLER
TEMPERATURES ONCE AGAIN ALONG THE ATLANTIC COAST AND ALSO THE
NORTH COAST OF DELAWARE BAY.

THE LOW-LEVEL MOISTURE WHILE INCREASING, THE OVERALL FLOW IS
STILL ON THE STRONGER SIDE AND IS ACTUALLY FORECAST TO INCREASE
SOME THROUGH THE DAY. THERE LOOKS TO BE A BATTLE BETWEEN THE
INVERSION AND THE MOISTURE TRYING TO POOL BENEATH IT. IT APPEARS
THAT JUST ENOUGH TURBULENT MIXING BELOW AND NEAR THE INVERSION
WILL KEEP ANY STRATUS DEVELOPMENT LIMITED EARLY THIS MORNING. WE
ARE ALSO BANKING ON MOST PLACES STILL MAINTAINING SOME WIND
THROUGH DAYBREAK TO KEEP ANY FOG RATHER LIMITED.

A STRONG COLD FRONT IS FORECAST TO REMAIN WELL TO OUR WEST
THROUGH TODAY, AND THIS IS WHERE THE GREATEST FORCING IS LOCATED.
THERE IS THE POTENTIAL FOR SOME SHOWERS TO EITHER DEVELOP ACROSS
OUR WESTERN ZONES OR APPROACH FROM THE WEST ESPECIALLY LATER THIS
AFTERNOON. THIS MAY BE ASSOCIATED WITH AN UPTICK IN THE LOW-LEVEL
WIND FIELD AS THE BOUNDARY LAYER MOISTENS SOME MORE BELOW A DRY
LAYER. BASED ON THE SOUNDINGS AND SOME GUIDANCE RUNNING A BIT TO
HIGH WITH THE SURFACE DEW POINTS SO FAR, THIS MAY END UP STAYING
TO OUR WEST AND DELAYED MORE FOR THE NIGHTTIME HOURS. THEREFORE,
WE OPTED TO MAINTAIN A DRY FORECAST THROUGH THE DAYTIME HOURS.

ANOTHER ROUND OF DEEP MIXING IS EXPECTED TO DEVELOP AS THE
BOUNDARY LAYER WARMS AND THE LOW-LEVEL LAPSE RATES STEEPEN QUITE A
BIT. GIVEN ABOUT 30 KNOTS OF WIND AVAILABLE TO BE MIXED DOWN,
SURFACE GUSTS SHOULD NEAR 35 MPH AT TIMES ESPECIALLY FROM MIDDAY
ON. THE HOURLY GRIDS WERE ADJUSTED EARLY THIS MORNING USING THE
LAMP/LAV GUIDANCE TO ASSIST WITH TRENDS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
THE STRETCH OF DRY AND WARM WEATHER WILL START TO COME TO AN END
TONIGHT AS A STRONG COLD FRONT GRADUALLY APPROACHES FROM THE WEST
LATE. THE STRENGTHENING LOW TO MID LEVEL FLOW WILL HELP DRIVE
ADDITIONAL MOISTURE NORTHWARD. IT APPEARS THAT SOME INITIAL
SHOWERS MAY BE SIMPLY TIED TO THE INCREASE IN THE LOW-LEVEL JET IN
COMBINATION WITH A SURGE IN THETA-E ADVECTION. THE BULK OF THE
FORCING APPEARS TO BE LINKED CLOSER TO THE ACTUAL COLD FRONT AND
AS THE REAR RIGHT QUADRANT OF THE 250 MB JET ARRIVES. THEREFORE,
WHILE SHOWERS ARE ANTICIPATED TO DEVELOP AND INCREASE IN COVERAGE
SOME, THE BULK OF THE WET WEATHER SHOULD BE AT AND AFTER DAYBREAK
TUESDAY. WE THEREFORE GRADUALLY INCREASED THE POPS FROM WEST TO
EAST WITH THE HIGHER VALUES TOWARD DAYBREAK. SOME OF THE HIGH
RESOLUTION GUIDANCE INDICATE A DECENT RAMP UP IN SHOWERS
OVERNIGHT, WITH AN AREA ACROSS THE WESTERN ZONES AND ANOTHER ALONG
THE COAST ASSOCIATED WITH THETA-E SURGES AND INCOMING SHORT WAVE
ENERGY, THEN CONGEALING TOWARD DAYBREAK. IF THIS OCCURS THEN POPS
WILL NEED TO BE INCREASED ESPECIALLY FARTHER EAST.

AS THE MOISTURE ADVECTION INCREASES THROUGH THE NIGHT AND
BOUNDARY LAYER WARMTH IS MAINTAINED ENOUGH, THE FORECAST SOUNDINGS
INDICATE THAT SOME INSTABILITY DEVELOPS THROUGH THE NIGHT. THIS
HOWEVER DOES NOT APPEAR TO BE ALL THAT HIGH, WHICH RAISES THE
QUESTION REGARDING CHARGE SEPARATION. AS OF NOW, WE DO NOT THINK
THE INSTABILITY WILL BE SUFFICIENT ENOUGH FOR CHARGE SEPARATION
AND THEREFORE LIMITED THE SLIGHT CHC OF THUNDER TO THE WESTERN
AREAS TOWARD DAYBREAK.

OTHERWISE, CLOUDS WILL CONTINUE TO THICKEN AND LOWER THROUGH THE
NIGHT AS THE LOWER LEVELS TURN A BIT MORE HUMID. THIS MAY ALLOW
FOR A STRATUS DECK TO OVERSPREAD THE AREA ESPECIALLY AS THE
THETA-E SURGE ARRIVES LATER ON. THIS AGAIN THOUGH COULD BE
HINDERED SOME BY ENOUGH TURBULENT MIXING BEING MAINTAINED. BASED
ON THIS IDEA, WE DID NOT CARRY A FOG MENTION. AS FOR LOW
TEMPERATURES, WE GENERALLY USED AN EVEN BLEND OF THE GFS/NAM MOS.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
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 WITH ITS AXIS
PASSING OVER OUR REGION LATE ON TUESDAY NIGHT. THE GUIDANCE
CONTINUES TO FOCUS 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.

WE HAVE GONE WITH A 100 PERCENT CHANCE OF RAIN SHOWERS FOR
TUESDAY. THERE WILL LIKELY BE PERIODS OF MODERATE TO HEAVY
RAINFALL THROUGH THE DAY ALONG WITH A CHANCE OF THUNDER DUE TO THE
ROBUST NATURE OF THE SYSTEM.

THE 0000 UTC NAM AND THE 0000 UTC GFS ARE BRINGING GENERALLY ONE
TO TWO INCHES OF RAIN TO OUR REGION ON TUESDAY AND TUESDAY
EVENING. THE 0000 UTC ECMWF IS MORE CONSERVATIVE WITH AMOUNTS
MAINLY IN THE 0.6 TO 1.0 INCH RANGE. WE WILL CONTINUE TO FOCUS ON
THE 0.75 TO 1.25 INCH RANGE FOR RAINFALL AMOUNTS. THE EXPECTED
AMOUNTS COULD PRODUCE SOME FLOODING IN AREAS OF POOR DRAINAGE AND
PONDING OF WATER ON ROADWAYS. SPOTTY SMALL STREAM FLOODING IS
POSSIBLE. HOWEVER, THE ANTICIPATED AMOUNTS WOULD PRECLUDE ANY
CONCERN FOR WIDESPREAD FLOODING BASED ON ANTECEDENT CONDITIONS.

A 60 PLUS KNOT LOW LEVEL SOUTH SOUTHWESTERLY JET IS FORECAST TO
DEVELOP OVER OUR REGION IN ADVANCE OF THE FRONT ON TUESDAY. WHILE
THE STRONGEST OF THE WINDS ARE NOT EXPECTED TO MIX TO THE SURFACE,
CONDITIONS SHOULD BECOME QUITE BREEZY WITH SOUTHERLY WIND GUSTS
GETTING AT LEAST INTO THE 30 TO 35 MPH RANGE FOR A TIME.

THE LATEST GUIDANCE SUGGESTS THAT MOST OF THE PRECIPITATION WILL
BE OFF THE COAST BEFORE MIDNIGHT ON TUESDAY NIGHT, IN ADVANCE OF
THE MID LEVEL TROUGH AXIS. HOWEVER, SOME LIGHT SHOWERS MAY LINGER
IN PARTS OF NEW JERSEY AND DELAWARE UNTIL ABOUT 2:00 OR 3:00 AM.

AFTER THE FRONT PASSES, TEMPERATURES WILL BEGIN TO DROP SHARPLY
AS A GUSTY NORTHWEST WIND DEVELOPS. IT CONTINUES TO APPEAR AS
THOUGH THE PRECIPITATION WILL END AS A BRIEF PERIOD OF SNOW
SHOWERS IN MUCH OF THE POCONO REGION, THE LEHIGH VALLEY AND
NORTHWESTERN NEW JERSEY. A FEW SNOW FLAKES COULD FALL AS FAR SOUTH
AS SOUTHEASTERN PENNSYLVANIA AND CENTRAL NEW JERSEY. AMOUNTS
SHOULD BE NEGLIGIBLE EXCEPT PERHAPS IN THE ELEVATED TERRAIN OF THE
POCONOS AND NORTHWESTERN NEW JERSEY WHERE A FEW TENTHS OF AN INCH
OF SNOW MAY ACCUMULATE.

THE NORTHERN AND MOST OF THE CENTRAL PART OF OUR FORECAST AREA
SHOULD FALL BELOW FREEZING LATE ON TUESDAY NIGHT. OUR RECENT WARM
SPELL HAS CAUSED PLANTS TO START FLOWERING, ESPECIALLY IN
SOUTHEASTERN PENNSYLVANIA, CENTRAL NEW JERSEY AND POINTS TO THE
SOUTH. THE COLD TEMPERATURES COULD HAVE A NEGATIVE IMPACT AND WE
MAY NEED TO CONSIDER ISSUING A FREEZE WATCH FOR PARTS OF OUR AREA.

COOL HIGH PRESSURE FROM THE WEST IS FORECAST TO BUILD ACROSS THE
NORTHEASTERN STATES ON WEDNESDAY AND OVER ATLANTIC CANADA AND THE
ADJACENT WATERS FOR 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 MOSTLY CLEAR SKY IS ANTICIPATED FOR WEDNESDAY 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 THURSDAY.

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. THE FRONTAL BOUNDARY MAY PASS
THROUGH OUR REGION ON SATURDAY NIGHT. WE HAVE MENTIONED A CHANCE
OF RAIN SHOWERS FROM FRIDAY NIGHT INTO SATURDAY NIGHT.
TEMPERATURES ARE FORECAST TO RETURN TO NEAR NORMAL LEVELS FOR THE
WEEKEND.

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

TODAY...A CHANCE FOR SOME LOCAL STRATUS/FOG EARLY. OTHERWISE, VFR
WITH CEILINGS MOSTLY AT OR ABOVE 10,000 FEET. SOUTH-SOUTHWEST
WINDS 5 TO 10 KNOTS, INCREASING TO AROUND 15 KNOTS WITH GUSTS UP
TO 30 KNOTS. THE HIGHEST GUSTS SHOULD OCCUR FROM MIDDAY ON.

TONIGHT...VFR TO START, THEN CEILINGS LOWERING TO MVFR AND THEN
PROBABLY IFR LATE. THE MOISTURE WILL BE ON THE INCREASE AS THE LOW
TO MID LEVEL WIND FIELDS STRENGTHEN. SURFACE WINDS SHOULD REMAIN
IN THE 10 TO 15 KNOT RANGE, WITH MOST OF THE GUSTINESS DROPPING
OFF DURING THE EVENING. HOWEVER, A SOUTHWEST FLOW AROUND 2,000
FEET WILL BE IN THE 40 TO 50 KNOT RANGE. AS OF NOW, WE HELD OFF
INCLUDING A LOW-LEVEL WIND SHEAR MENTION IN THE TAFS. SOME SHOWERS
ARE EXPECTED TO OVERSPREAD THE AREA ESPECIALLY LATE FROM WEST TO
EAST.

OUTLOOK...
TUESDAY...MVFR AND IFR CONDITIONS IN RAIN SHOWERS. THE RAIN WILL
BECOME MODERATE TO HEAVY AT TIMES. SCATTERED THUNDER IS POSSIBLE.
A SOUTH TO SOUTHWEST WIND AT 15 TO 20 KNOTS MAY GUST NEAR OR IN
EXCESS OF 30 TO 35 KNOTS AT TIMES.

TUESDAY NIGHT...MVFR AND IFR CONDITIONS IN RAIN SHOWERS IN THE
EVENING, IMPROVING TO VFR OVERNIGHT. A NORTHWEST WIND AT 15 TO 20
KNOTS GUSTING TO 25 OR 30 KNOTS AT TIMES.

WEDNESDAY THROUGH FRIDAY...MAINLY VFR.

&&

.MARINE...
A SOUTHERLY FLOW WILL BE MAINTAINED THROUGH TONIGHT WELL IN
ADVANCE OF A STRONG COLD FRONT. THE FLOW ABOVE THE SURFACE IS
FORECAST TO STRENGTHEN, ESPECIALLY TONIGHT WITH 925 MB WINDS ON
THE ORDER OF 40 TO 50 KNOTS. THIS WILL ALLOW FOR THE SURFACE WINDS
TO INCREASE THROUGH THE DAY, HOWEVER A WARM AIR MASS REMAINS AND
THIS WILL ONCE AGAIN TEND TO LIMIT THE VERTICAL MIXING. THE BEST
MIXING WILL GENERALLY BE NEAR SHORE, AND THEREFORE THE HIGHER GUSTS
TO ADVISORY LEVELS. IT MAY TAKE SOME TIME TO OCCUR, ESPECIALLY
ACROSS DELAWARE BAY, HOWEVER WE WILL MAINTAIN THE SMALL CRAFT
ADVISORY FOR ALL AREAS THROUGH TONIGHT. THE SEAS WILL ALSO
GRADUALLY RESPOND TO THE PERSISTENT SOUTHERLY FLOW, WITH THE OCEAN
SEAS GETTING TO 5 FEET OR ABOVE THROUGH TONIGHT.

OUTLOOK...
TUESDAY...SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED. THE WIND
WILL BE FROM THE SOUTH. ISOLATED GALE FORCE GUSTS ARE POSSIBLE.

TUESDAY NIGHT AND WEDNESDAY MORNING...A STRONG NORTHWEST WIND IS
FORECAST WITH FREQUENT GALE FORCE GUSTS. A GALE WATCH IS IN
EFFECT.

WEDNESDAY AFTERNOON THROUGH FRIDAY...SMALL CRAFT ADVISORY
CONDITIONS ARE EXPECTED ON OUR OCEAN WATERS. A NORTHEAST FLOW WILL
KEEP SEAS AT OR IN EXCESS OF 5 FEET. OCCASIONAL WIND GUSTS NEAR 25
KNOTS ARE POSSIBLE.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...GALE WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY MORNING FOR
     ANZ430-431-450>455.
     SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR ANZ430-431-
     450>455.

&&

$$

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