929
FXUS61 KPHI 191628
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1228 PM EDT SUN MAY 19 2013
SYNOPSIS
A FRONTAL BOUNDARY TO OUR SOUTH IS EXPECTED TO WEAKEN AND
DISSIPATE AS IT REMAINS NEARLY STATIONARY THROUGH MONDAY. MEANWHILE,
HIGH PRESSURE SHOULD REMAIN TO OUR NORTHEAST AND EAST. ANOTHER
FRONTAL BOUNDARY FROM THE NORTH IS FORECAST TO DROP INTO OUR
REGION LATE ON TUESDAY AND IT SHOULD LIFT BACK TO THE NORTH ON
WEDNESDAY AND THURSDAY. A COLD FRONT FROM THE WEST IS THEN EXPECTED
TO ARRIVE ON FRIDAY, FOLLOWED BY HIGH PRESSURE FOR SATURDAY.
NEAR TERM /UNTIL 6 PM THIS EVENING/
THE ONSHORE LOW LEVEL FLOW WILL CONTINUE THIS AFTERNOON WITH A
WEALTH OF LOW LEVEL CLOUDINESS EXPECTED. AN AREA OF SHOWERS
PRESENTLY OVER ERN NJ WILL CONTINUE THROUGH EARLY AFTERNOON
BEFORE MOVING OFF TO THE EAST. SOME SHOWERS ARE EXPECTED TO
DEVELOP ACROSS THE SRN AREAS AND MOVE OVER THE AREA LATER TODAY.
THE LATEST HRRR AND NAM RUNS HOWEVER HAVE LIMITED COVERAGE OF
THESE SHOWERS AND HAVE REDUCED POPS TO HIGH CHANCE. IF A FEW
BREAKS IN THE CLOUDS DEVELOP ACROSS THE DELMARVA...A FEW POP-UP
TSTMS MAY OCCUR. THE POSSIBILITY OF THIS LOOKS LOW ENOUGH ATTM TO
KEEP OUT OF THE FCST.
TEMPERATURES WILL REMAIN IN CHECK...WITH THE ABUNDANCE OF CLOUDS.
READINGS IN THE MID/UPPER 60S ACROSS THE NRN AREAS AND UPPER 60S
TO LOW 70S OVER THE SRN AREAS. WINDS WILL BE EAST/SOUTHEAST AT 5
TO 10 MPH MUCH OF THE AFTERNOON.
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/
THE AFOREMENTIONED MID LEVEL FEATURE LOOKS TO LINGER NEAR THE MID
ATLANTIC TONIGHT, AS A RIDGE ALOFT GRADUALLY SLIDES EASTWARD. HIGH
PRESSURE AT THE SURFACE AS A RESULT IS FORECAST TO SLIDE FARTHER
TO OUR EAST, WHICH WILL ALLOW THE LOW-LEVEL FLOW TO VEER FROM
SOUTHEAST TO MORE SOUTH OR SOUTHWEST OVERNIGHT. THIS MAINTAINS
THETA-E ADVECTION THROUGH THE NIGHT WITH AT LEAST SOME WAA AS
WELL. THERE DOES NOT APPEAR TO BE MUCH IN THE WAY OF ORGANIZED
LIFT MOVING THROUGH, THEREFORE THE SHOWERS DURING THE DAY SHOULD
DECREASE IN AREAL COVERAGE.
HOWEVER, AS THE FLOW VEERS AND MOISTURE INCREASES IN THE LOWER
LEVELS SOME MODEL GUIDANCE INDICATES THAT THIS MOISTURE GENERALLY
BECOMES LOCKED IN THE LOWEST LEVELS. IF ENOUGH DRYING CAN OCCUR
ABOVE THIS, THEN SOME DRIZZLE MAY BE THE MAIN PRECIPITATION TYPE
DURING THE COURSE OF THE NIGHT. THIS COULD BE MAINLY FOR OUR
CENTRAL AND NORTHERN ZONES, AS FARTHER SOUTH ENOUGH WARMING MAY
RESULT IN THE CLOUD BASES RISING SOME AND A LESS CONDUCIVE SETUP
FOR DRIZZLE. WE NOTICED THAT SOME OF THE HIGH RESOLUTION GUIDANCE
INDICATES LITTLE TO NO PRECIPITATION OCCURRING DURING THE NIGHT,
WITH PERHAPS SOME SHOWERS DEVELOPING TOWARD DAYBREAK AS SOME
PVA/LIFT ARRIVES FROM THE SOUTHWEST WITH THE MID LEVEL FEATURE. AS
A RESULT, WE LOWERED POPS INTO THE CHC RANGE AND CARRIED SHOWERS
FAR SOUTH WITH LIGHT RAIN/DRIZZLE FARTHER NORTH. WE ALSO ADDED IN
PATCHY FOG, FIRST STARTING IN THE HIGHER TERRAIN THEN TO OTHER
AREAS.
AS FOR LOW TEMPERATURES, WE MAINLY USED AN EVEN GFS/NAM MOS
BLEND. TEMPERATURES SHOULD BE ON THE MILD SIDE GIVEN THE CLOUDS
AND CONTINUED WAA. THERE IS A CHC THAT ESPECIALLY THE FAR SOUTHERN
AREAS HAVE SOME INCREASE IN THE TEMPERATURES OVERNIGHT.
LONG TERM /MONDAY THROUGH SATURDAY/
THE MID LEVEL PATTERN IS EXPECTED TO FEATURE THE POLAR VORTEX WELL
TO OUR NORTHEAST WITH A CLOSED LOW OVER THE MIDDLE MISSOURI RIVER
VALLEY ON MONDAY. THERE SHOULD BE A RIDGE EXTENDING FROM THE
SOUTHEASTERN STATES TO THE GREAT LAKES. THE POLAR VORTEX WILL
REMAIN THE DOMINANT FEATURE OVER EASTERN CANADA DURING THE NEW
WEEK. MEANWHILE, THE CLOSED LOW TO OUR WEST AND ITS ASSOCIATED
TROUGH WILL PROGRESS EASTWARD, GRADUALLY SQUEEZING THE RIDGE AND
PUSHING IT OUT OVER THE ATLANTIC. AS THE TROUGH BEGINS TO MOVE
TOWARD THE EASTERN STATES, IT SHOULD START TO INTERACT WITH THE
POLAR VORTEX AROUND WEDNESDAY AS THAT FEATURE'S INFLUENCE BEGINS
TO EXPAND TO THE WEST AND SOUTH. THE RESULTING MID LEVEL TROUGH
WILL LIKELY MOVE EASTWARD ACROSS THE GREAT LAKES AND THE
NORTHEASTERN STATES IN THE THURSDAY THROUGH SATURDAY TIME FRAME.
THE SURFACE FLOW IS FORECAST TO VEER TO THE SOUTH AND SOUTHWEST
FOR MONDAY AND MONDAY NIGHT CAUSING THE CLOUDS TO LIFT AND
TEMPERATURES TO WARM, RESULTING IN THE DEVELOPMENT OF UNSTABLE
CONDITIONS, ESPECIALLY AWAY FROM THE OCEAN. SURFACE BASED CAPE
VALUES ARE ANTICIPATED TO RISE NEAR 1000 J/KG IN OUR WESTERN
COUNTIES DURING THE AFTERNOON. A FAIR AMOUNT OF LOW LEVEL MOISTURE
WILL REMAIN IN OUR REGION. AS A RESULT, WE WILL CONTINUE TO
MENTION A CHANCE OF SHOWERS FOR MONDAY AND WE WILL ALSO INCLUDE
THE POTENTIAL FOR AFTERNOON THUNDERSTORMS. THE GUIDANCE IS
INDICATING A DECREASE IN PRECIPITATION FOR MONDAY NIGHT WITH THE
LOSS OF DAYTIME HEATING AND WITH THE LACK OF ANY FOCUSING
MECHANISM.
TEMPERATURES ARE FORECAST TO RISE NEAR +15C AT 850 HPA FOR
TUESDAY. A SOUTH TO SOUTHWEST SURFACE FLOW WILL CONTINUE AND
TEMPERATURES ARE EXPECTED TO RISE INTO THE LOWER AND MIDDLE 80S IN
MUCH OF OUR FORECAST AREA. LINGERING LOW LEVEL MOISTURE WILL HELP
ENHANCE THE INSTABILITY AND WE ARE ANTICIPATING SCATTERED SHOWERS
AND THUNDERSTORMS, ESPECIALLY IN THE AFTERNOON AND EVENING.
SURFACE BASED CAPE VALUES IN THE 1500 J/KG NEIGHBORHOOD ARE
POSSIBLE IN OUR SOUTHWESTERN COUNTIES. THE MOST UNSTABLE AREAS
WILL LIKELY HAVE PRECIPITABLE WATER VALUES IN EXCESS OF 1.5 INCHES
WITH THERE BEING THE POTENTIAL FOR LOCALIZED DOWNPOURS.
A FRONTAL BOUNDARY IS FORECAST TO DROP INTO OUR REGION FROM THE
NORTH LATE ON TUESDAY. THERE IS A FAIR AMOUNT OF UNCERTAINTY AS TO
HOW FAR SOUTH THE BOUNDARY WILL PROGRESS. IT SHOULD CONTINUE TO
HAVE A LEAST A LITTLE MOMENTUM INTO WEDNESDAY. HOWEVER, AS THE MID
LEVEL RIDGE AXIS PASSES OVERHEAD ON WEDNESDAY OR WEDNESDAY NIGHT,
THE BOUNDARY IS EXPECTED TO BEGIN LIFTING BACK TO THE NORTH.
REGARDLESS, UNSETTLED CONDITIONS WILL LIKELY CONTINUE.
AS THE MID LEVEL TROUGH BEGINS TO INFLUENCE OUR REGION LATE IN
THE WEEK IT SHOULD MOVE A COLD FRONT ACROSS THE NORTHEASTERN
STATES ON FRIDAY. AS A RESULT, WE WILL CARRY A CHANCE OF SHOWERS
AND AFTERNOON THUNDERSTORMS FOR FRIDAY.
WHILE THERE WILL BE A CHANCE OF PRECIPITATION IN THE FORECAST FOR
EACH DAY FROM MONDAY THROUGH FRIDAY, THE WEEK SHOULD NOT BE A
TOTAL WASHOUT. ACTUALLY, MOST OF THE TIME PRECIPITATION WILL NOT
BE FALLING. OVERALL, TEMPERATURES FOR THE WEEK SHOULD AVERAGE
ABOVE NORMAL FOR THIS TIME OF THE YEAR.
AFTER THE COLD FRONT PASSES, DRY AIR IS ANTICIPATED TO BEGIN
BUILDING INTO OUR REGION FROM THE NORTHWEST AND NORTH FOR FRIDAY
NIGHT AND SATURDAY.
AVIATION /18Z SUNDAY THROUGH FRIDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TODAY...MVFR/IFR CEILINGS PREVAIL THROUGH THE DAY, AND THERE IS
LOWER CONFIDENCE REGARDING ANY IMPROVEMENTS. IT IS POSSIBLE THAT
TERMINALS WITH IFR CEILINGS IMPROVE TO MVFR IN THE AFTERNOON, AND
THE VISIBILITIES SHOULD BE MOSTLY DEPENDENT ON THE SHOWERS.
SOUTHEAST WINDS GENERALLY NEAR 10 KNOTS.
TONIGHT...IFR CEILINGS, WITH A CHANCE FOR IMPROVEMENT TO MVFR
AT TIMES MAINLY SOUTH AND EAST OF KILG. OVERALL, SOME SHOWERS
SHOULD BE AROUND ESPECIALLY IN THE EVENING WITH EVEN THIS PERHAPS
TRANSITIONING TO SOME DRIZZLE, THEREFORE TIMES OF LOCAL VISIBILITY
RESTRICTIONS SHOULD OCCUR. SOME FOG IS ANTICIPATED WHICH WILL ALSO
LOWER THE LOCAL VISIBILITY, ALTHOUGH WE ARE CURRENTLY NOT
ANTICIPATING FOG TO REDUCE THE VISIBILITY TO UNDER 1SM. SOUTHEAST
WINDS 4-8 KNOTS, SHOULD TURN MORE SOUTH-SOUTHWEST.
OUTLOOK...
MONDAY THROUGH THURSDAY...MAINLY VFR. HOWEVER, MVFR AND IFR
CONDITIONS ARE POSSIBLE ESPECIALLY DURING THE LATE NIGHT AND EARLY
MORNING HOURS EACH DAY. ALSO, THERE WILL BE A CHANCE OF SHOWERS
AND THUNDERSTORMS THROUGH THE PERIOD WHICH COULD LOWER CEILINGS
AND REDUCE THE VISIBILITY AT TIMES.
MARINE
HIGH PRESSURE REMAINING TO OUR NORTHEAST TODAY WILL MAINTAIN A
SOUTHEASTERLY FLOW, ALTHOUGH THIS SHOULD START TO TURN MORE FROM
THE SOUTH LATER TODAY ACROSS THE SOUTHERN WATERS. THIS SHIFT TO
SOUTHERLY SHOULD THEN OVERSPREAD ALL THE WATERS TONIGHT. THIS FLOW
REGIME, WHICH IS ANTICIPATED TO REMAIN UNDER 25 KNOTS, WILL ALLOW
THE SEAS TO BUILD SOME MORE THOUGH. THE WAVEWATCH GUIDANCE HAS
BEEN RUNNING 1-2 FEET TO HIGH, HOWEVER IT IS CATCHING UP AS SEAS
REACHED 5 FEET EARLIER AT BUOY 44009. THESE HIGHER SEAS ARE
ANTICIPATED TO SPREAD NORTHWARD TODAY, HOWEVER CONFIDENCE IS NOT
ALL THAT HIGH THEY GET ABOVE 6 FEET. THEREFORE, THE SMALL CRAFT
ADVISORY REMAINS IN EFFECT FOR OUR OCEAN ZONES THROUGH TONIGHT.
THE CONDITIONS ARE ANTICIPATED TO REMAIN BELOW ADVISORY CRITERIA
ON DELAWARE BAY. SOME ADDITIONAL INCREASE IN THE DEW POINTS
TONIGHT COULD RESULT IN SOME FOG DEVELOPMENT.
OUTLOOK...
HIGH PRESSURE TO OUR NORTHEAST AND EAST WILL CONTINUE TO
INFLUENCE THE COASTAL WATERS OF NEW JERSEY AND DELAWARE INTO
TUESDAY. A FRONTAL BOUNDARY FROM THE NORTH IS FORECAST TO DROP
INTO OUR REGION ON TUESDAY NIGHT BEFORE RETREATING BACK TO THE
NORTH ON WEDNESDAY AND THURSDAY.
WIND SPEEDS ARE FORECAST TO REMAIN LESS THAN 25 KNOTS FROM MONDAY
THROUGH THURSDAY. WAVE HEIGHTS ON OUR OCEAN WATERS COULD REMAIN
AROUND 5 FEET ON MONDAY INTO MONDAY NIGHT AND THE CURRENT SMALL
CRAFT ADVISORY MAY NEED TO BE EXTENDED TO COVER THAT PERIOD. A
LULL IN WAVE HEIGHTS IS POSSIBLE FOR TUESDAY AND WEDNESDAY WITH 5
FOOT SEAS FORECAST TO RETURN TO OUR OCEAN WATERS FOR THURSDAY AS A
LONG SOUTHERLY FETCH BECOMES ESTABLISHED ALONG THE EAST COAST.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT MONDAY FOR ANZ450>455.
SYNOPSIS...IOVINO
NEAR TERM...GAINES/GORSE/O'HARA
SHORT TERM...GORSE
LONG TERM...IOVINO
AVIATION...GORSE/IOVINO
MARINE...GORSE/IOVINO
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