-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 142003
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
403 PM EDT FRI JUN 14 2013

.SYNOPSIS...
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HIGH PRESSURE WILL CONTINUE TO BUILD OVER THE MID ATLANTIC STATES
THROUGH TONIGHT AND SATURDAY, EVENTUALLY PUSHING TO OUR SOUTHEAST BY
THE END OF THE WEEKEND. EARLY NEXT WEEK, AN AREA OF LOW PRESSURE
WILL APPROACH FROM THE WEST MONDAY, AND ITS ASSOCIATED COLD FRONT
WILL CROSS OUR REGION TUESDAY. ANOTHER AREA OF HIGH PRESSURE IS THEN
EXPECTED TO BUILD ACROSS THE REGION THROUGH THE END OF THE WEEK.
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&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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AN 18Z SURFACE ANALYSIS PLACED LOW PRESSURE EAST OF CAPE COD. A
TROUGH WAS DRAPED FROM THE HUDSON VALLEY SOUTH-SOUTHWESTWARD ACROSS
EASTERN PENNSYLVANIA. HIGH PRESSURE WAS OVER THE UPPER GREAT LAKES.
AN UPPER AIR ANALYSIS SHOWED A TROUGH IN THE EAST WITH A RIDGE
ACROSS THE MIDWEST TO THE SOUTHERN PLAINS. THERE WAS ANOTHER TROUGH
IN THE NORTHERN ROCKIES AREA. THERE WERE SOME POCKETS OF FOCUSED 850
MB WAA FROM NEAR NEW JERSEY INTO SOUTHERN NEW ENGLAND, THEN OTHER
AREAS FROM THE CENTRAL PLAINS TO THE MIDWEST. A 250 MB CYCLONICALLY
CURVED JET WAS FROM THE UPPER GREAT LAKES DOWN TO THE CAROLINAS THEN
TO FAR EASTERN NEW ENGLAND.

AN UPPER-LEVEL TROUGH AXIS WILL CONTINUE TO SHIFT TO OUR EAST
THROUGH TONIGHT, ALONG WITH A STRONG SHORT WAVE ROUNDING THE BASE OF
THIS TROUGH. AN AREA OF CONVERGENCE HAS SET UP THIS AFTERNOON ON THE
WEST SIDE OF THE UPPER-LEVEL TROUGH, WITH A SURFACE TROUGH DRAPED
FROM THE HUDSON VALLEY INTO EASTERN PENNSYLVANIA. THE COLDER AIR
ALOFT IS CONTRIBUTING TO JUST ENOUGH INSTABILITY TO ASSIST IN AREAS
OF LOW-LEVEL LIFT. THIS IS RESULTING IN SOME SHOWERS DROPPING
SOUTHWARD. THERE HAS BEEN OCCASIONAL LIGHTNING STRIKES SHOWING UP
WITH SOME OF THE STRONGER CORES IN EASTERN NEW YORK STATE, AND GIVEN
THE COLDER AIR ALOFT SOME LOCALIZED SMALL HAIL CANNOT BE RULED OUT
INTO EARLY THIS EVENING. THE BEST CHC OF THIS IS WITH STRONGER CORES
THAT ARE ABLE TO SUSTAIN THEMSELVES LONGER. THIS ACTIVITY IS
PRIMARILY DRIVEN BY DAYTIME HEATING, THEREFORE DISSIPATION IS
EXPECTED EARLY THIS EVENING AS THE BOUNDARY LAYER COOLS AND ALSO
SOME FURTHER DRYING WORKS IN. AS A RESULT, WE MAINTAINED SLIGHT CHC
TO LOW CHC POPS THROUGH EARLY EVENING TO ACCOUNT FOR THIS ACTIVITY.

OTHERWISE AS THE UPPER-LEVEL TROUGH SHIFTS EAST, SURFACE HIGH
PRESSURE WILL APPROACH THE AREA TOWARD MORNING. THE PRESSURE
GRADIENT WHILE IT REMAINS SOMEWHAT TIGHTENED THROUGH THE NIGHT,
THE LACK OF VERTICAL MIXING WILL RESULT IN LESS WIND TONIGHT. THE
CLOUDS ARE ANTICIPATED TO THIN OUT AND DISSIPATE WITH THE LOSS OF
DAYTIME HEATING, THEREFORE WE FOLLOWED THE TREND OF CONTINUITY WITH
THE COVERAGE LOWERING IN THE SKY GRIDS.

AS FOR TEMPERATURES, WE USED AN EVEN GFS/NAM MOS BLEND WITH JUST
SOME MINOR TWEAKS. THE HOURLY TEMPERATURE GRIDS HAS SOME
INCORPORATION OF THE LAMP/LAV GUIDANCE TO HELP ASSIST WITH TRENDS
THIS AFTERNOON.
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&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL TROUGH
THAT CONTINUES TO LIFT NORTHEASTWARD AND FARTHER AWAY FROM OUR AREA.
MEANWHILE, A RIDGE MOVES INTO THE EASTERN GREAT LAKES AND OHIO
VALLEY REGION BY LATE IN THE DAY. THIS WILL ALLOW SURFACE HIGH
PRESSURE TO SLIDE EAST AND SOUTHEASTWARD. IT APPEARS THAT THE CENTER
OF THE SURFACE HIGH SETTLES TO OUR SOUTH BY LATE IN THE DAY. THIS
WILL RESULT IN NORTHWEST WINDS TENDING TO TURN WESTERLY OR EVEN
SOUTHWEST. THE FLOW ALOFT IS STILL NORTHWESTERLY, HOWEVER THE
BOUNDARY LAYER WINDS MAY BECOME LIGHT TO ALLOW SOMEWHAT OF A SEA
BREEZE TO DEVELOP AND PROBABLY HOLD CLOSER TO THE IMMEDIATE COAST.

THERE ARE SOME SHORT WAVES FORECAST TO BE ROUNDING THE TOP OF THE
RIDGE TO OUR WEST, AND WITH INCREASING WAA UP THE OHIO VALLEY
COMBINED WITH A NORTHWESTERLY FLOW ALOFT, SOME HIGHER LEVELS CLOUDS
MAY ARRIVE DURING THE COURSE OF THE DAY. THERE SHOULD ALSO BE AT
LEAST SOME CUMULUS DEVELOPMENT WITH JUST ENOUGH LOW-LEVEL MOISTURE
IN PLACE. OVERALL THOUGH, WE ARE ANTICIPATING A GOOD AMOUNT OF
SUNSHINE.

AS FOR TEMPERATURES, A GFS/NAM MOS BLEND WAS USED WITH SOME LOCAL
MODIFICATIONS.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
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TO START THE LONG TERM PERIOD, AN AREA OF HIGH PRESSURE WILL BEGIN
PUSHING TO OUR SOUTH AND EAST DURING SATURDAY NIGHT, AND WE STILL
EXPECT DRY CONDITIONS TO LAST THROUGH SATURDAY NIGHT WITH SOME
INCREASE IN CLOUDS FROM THE WEST BY SUNDAY MORNING. AS THE HIGH
PRESSURE CONTINUES TO SETTLE OFF TO OUR SOUTHEAST DURING SUNDAY,
BOTH THE GFS AND ECMWF SHOW A FAIRLY ZONAL FLOW ALOFT BRINGING A MID
LEVEL SHORTWAVE EASTWARD FROM AROUND THE GREAT LAKES. THIS FEATURE
WILL BRING AN INCREASING CHANCE FOR SCATTERED SHWRS/T-STORMS TO OUR
REGION BY SUNDAY AFTERNOON INTO SUNDAY EVENING; ALTHOUGH THE TIMING
AND STRENGTH OF THIS FEATURE DIFFER SOMEWHAT IN MODEL GUIDANCE. WE
HAVE KEPT MAINLY CHANCE POPS IN PLACE AT THIS TIME, GRADUALLY
INCREASING THROUGH THE COURSE OF SUNDAY.

EARLY NEXT WEEK, MOST OF THE MODEL GUIDANCE INDICATES AN AREA OF LOW
PRESSURE PROGRESSING EASTWARD FROM AROUND THE GREAT LAKES FROM
MONDAY INTO TUESDAY. AHEAD OF THIS SYSTEM ON MONDAY, A COUPLE OF MID
LEVEL SHORTWAVES MAY PASS ACROSS OUR REGION, AND WITH ENOUGH
INSTABILITY AROUND, WE MAY HAVE MORE SCATTERED SHWR/T-STORM
ACTIVITY. BY TUESDAY, THE MODELS BECOME MORE DIVERGENT; ALTHOUGH,
MOST GUIDANCE TAKES THE LOW PRESSURE FROM AROUND THE GREAT LAKES
EASTWARD TOWARD THE NEW ENGLAND REGION, WITH A TRAILING COLD FRONT
APPROACHING AND CROSSING OUR REGION FROM TUESDAY AFTERNOON THROUGH
TUESDAY NIGHT. OF NOTE, THE LATEST GFS RUN NOW DEVELOPS AN AREA OF
LOW PRESSURE ALONG THE FRONTAL BOUNDARY AROUND THE UPPER OHIO VALLEY
REGION, WITH THIS LOW THEN INTENSIFYING SOME AS IT PASSES OVER OUR
REGION TUESDAY AFTERNOON THROUGH TUESDAY NIGHT. AS NOTED BY THE
PREVIOUS SHIFT, PWAT VALUES STEADILY RISE ACROSS OUR REGION FROM
MONDAY INTO TUESDAY, AND WITH A SURFACE LOW POSSIBLY DEVELOPING
ALONG THE FRONTAL BOUNDARY AS IT TRACKS ACROSS OUR REGION TUESDAY,
THERE IS THE POTENTIAL FOR ANOTHER HEAVY RAIN EVENT. WHILE THE FINER
DETAILS OF THE TIMING AND STRENGTH OF THE COLD FRONT PASSAGE AND
POSSIBLE SURFACE LOW WILL BE ADJUSTED AS MODEL SOLUTIONS BECOME
CLOSER IN AGREEMENT, WE HAVE KEPT HIGH CHANCE POPS IN PLACE FOR NOW
WITH THE FRONTAL PASSAGE TUESDAY.

BY EARLY WEDNESDAY, BOTH THE ECMWF AND GFS SHOW THE COLD FRONT
PROGRESSING EAST AND OFFSHORE AS SURFACE HIGH PRESSURE FROM AROUND
THE GREAT LAKES AND MIDWEST STATES BEGINS TO SPREAD EASTWARD TOWARD
OUR REGION. THIS HIGH PRESSURE IS FORECAST TO REMAIN NEARBY AND
INFLUENCE OUR REGION THROUGH THE END OF THE WEEK.
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&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

REST OF THIS AFTERNOON...OVERALL VFR. SOME SHOWERS WILL MOVE FROM
NORTH TO SOUTH, ALTHOUGH COVERAGE SHOULD BE NO MORE THAN SCATTERED.
AN ISOLATED THUNDERSTORM WILL BE AROUND, HOWEVER GIVEN THE LOW
COVERAGE THIS WAS NOT INCLUDED. ANY SHOWER CAN BRIEFLY REDUCE THE
LOCAL VISIBILITIES, HOWEVER GIVEN THE SCATTERED NATURE JUST A VCSH
WAS USED. SOME AMENDMENTS MAY BE NEEDED TO INCLUDE A VISIBILITY
RESTRICTION IF A SHOWER LOOKS TO AFFECT A TERMINAL. NORTHWESTERLY
WINDS AROUND KNOTS WITH SOME GUSTS TO NEAR 20 KNOTS, WILL DIMINISH
TOWARD EVENING.

TONIGHT...VFR. ANY REMAINING CEILINGS ARE FORECAST TO DISSIPATE
AFTER A FEW EARLY EVENING SHOWERS. NORTHWEST WINDS DIMINISHING TO
AROUND 5 KNOTS.

SATURDAY...VFR, WITH SOME CUMULUS OR HIGH CLOUDS. NORTHWEST WINDS
MAINLY 5-10 KNOTS, BECOMING WEST OR SOUTHWEST LATER IN THE DAY.

OUTLOOK...
SATURDAY NIGHT...VFR CONDITIONS EXPECTED.

SUNDAY AND MONDAY...MOSTLY VFR CONDITIONS. SOME LOWERING TO MVFR
POSSIBLE IN SCATTERED SHWRS/T-STORMS, ESPECIALLY EACH AFTN/EVE.

TUESDAY...MAINLY VFR CONDITIONS TO START THE DAY, BUT SHWRS/T-STORMS
WILL INCREASE IN COVERAGE BY AFTN TO TUESDAY NIGHT WITH SOME
LOWERING TO MVFR.

WEDNESDAY...VFR CONDITIONS EXPECTED.
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&&

.MARINE...
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AN UPPER-LEVEL TROUGH WILL CONTINUE TO SHIFT EAST AND NORTHEAST OF
THE AREA THROUGH SATURDAY. AN AREA HIGH PRESSURE IS FORECAST TO
SETTLE SOUTHEASTWARD FROM THE UPPER GREAT LAKES TONIGHT, THEN SLIDE
TO OUR SOUTH DURING THE DAY SATURDAY. THE WINDS HAVE SETTLED SOME
MORE AND THEY ARE FORECAST TO REMAIN BELOW ADVISORY CRITERIA THROUGH
SATURDAY AND THE ADVISORY WAS DROPPED FOR THE LOWER DELAWARE BAY.
THE NORTHWEST FLOW WILL SHIFT TO THE WEST AND SOUTHWEST THROUGH
SATURDAY. THE SEAS ARE HIGHER ACROSS THE SOUTHERN OCEAN ZONES DUE TO
THE NORTHERLY FLOW. IT WILL TAKE AWHILE LONGER FOR THESE TO SUBSIDE,
AND THIS IS ALREADY OCCURRING ACROSS THE NORTHERN WATERS. THE SMALL
CRAFT ADVISORY FOR THE OCEAN REMAINS IN EFFECT UNTIL 00Z AS SEAS
SHOULD BE DROPPING BELOW 5 FEET BY THEN.

OUTLOOK...
THROUGH THE WEEKEND, WE ANTICIPATE WINDS AND SEAS TO REMAIN BELOW
SCA CRITERIA AS OUR REGION AND COASTAL WATERS WILL BE INFLUENCED BY
NEARBY HIGH PRESSURE. DURING EARLY NEXT WEEK, A PROLONGED SOUTHERLY
FLOW IS EXPECTED TO DEVELOP ACROSS OUR COASTAL WATERS, AND WHILE
WIND GUSTS SHOULD REMAIN SUB-SCA, SEAS MAY APPROACH 5 FEET AT TIMES
FROM MONDAY THROUGH WEDNESDAY.
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&&

.PHI WATCHES/WARNINGS/ADVISORIES...
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PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR
     ANZ450>455.
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&&

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