-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 141852
AFDPHI

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

.SYNOPSIS...
HIGH PRESSURE WILL GRADUALLY BUILD INTO THE REGION LATER TODAY,
SLIDING TO OUR SOUTHEAST OVER THE WEEKEND. A LOW PRESSURE SYSTEM
WILL APPROACH FROM THE WEST ON MONDAY, DRAGGING A COLD FRONT
THROUGH THE AREA ON TUESDAY. HIGH PRESSURE WILL BUILD INTO THE
REGION FOR THE REST OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
-- Changed Discussion --
SUNDAY IS BEGINNING TO LOOK A BIT WETTER THAN IT HAS THE PAST FEW
DAYS. WHILE THE SURFACE HIGH SLIDES TO OUR SOUTHEAST, WE START TO
DEVELOP A MORE SOUTHERLY FLOW. THIS FLOW WILL INCREASE MOISTURE
ACROSS OUR REGION. THERE IS AN INDICATION IN THE MODELS THAT A
TROUGH MAY DEVELOP AT THE SURFACE BY SUNDAY AFTERNOON. IN
ADDITION, A CONVECTIVE COMPLEX ASSOCIATED WITH A MID LEVEL
SHORTWAVE WILL ROTATE INTO OUR AREA ON SUNDAY. WHILE THE WAVE
APPEARS TO WEAKEN AS IT HEADS EAST, THERE IS THE POTENTIAL FOR IT
TO HOLD TOGETHER AND MAKE IT TO OUR AREA. TIMING AND STRENGTH OF
THIS WAVE DIFFER AMONGST THE MODELS SO CONFIDENCE IS NOT VERY HIGH
THAT IT HOLDS TOGETHER ALL THE WAY TO OUR COAST. REGARDLESS, THERE
WILL REMAIN A CHANCE FOR SOME SHOWERS AND THUNDERSTORMS TO DEVELOP
ON SUNDAY, MAINLY IN THE AFTERNOON AS THEY WILL LIKELY BE MORE
DIURNALLY DRIVEN.

MONDAY LOOKS TO BE SIMILAR TO SUNDAY IN THE FACT THAT A TROUGH
DEVELOPS ACROSS OUR REGION. WHILE THE MID LEVEL FLOW DOES HAVE A FEW
SHORTWAVES MOVING THROUGH, THEY DO NOT APPEAR TO BE AS STRONG AS
THOSE ON SUNDAY AT THIS TIME. SHOWERS AND THUNDERSTORMS WILL AGAIN
BE POSSIBLE AS WE HEAT UP AT THE SURFACE AND MAY HAVE JUST ENOUGH
INSTABILITY TO SPARK OFF SOME STORMS. AGAIN, THESE MAY END UP BEING
MORE DIURNALLY DRIVEN.

TUESDAY WILL BE THE DAY WE SEE OUR NEXT FRONTAL SYSTEM MOVE THROUGH.
LOW PRESSURE ACROSS THE GREAT LAKES WILL DRIVE A COLD FRONT
SOUTHWARD INTO OUR AREA ON TUESDAY. THE FRONT STARTS TO PUSH INTO
OUR NORTHWESTERN ZONES DURING THE MORNING BUT APPEARS TO SLOW DOWN
AND TAKE THE REST OF THE DAY TO CLEAR THE COAST. IN ADDITION, A WAVE
WILL MOVE ALONG THE FRONTAL BOUNDARY AS IT MOVES THROUGH OUR AREA.
THE SOUTHWEST FLOW THAT DEVELOPS LATE IN THE WEEKEND WILL CONTINUE
THROUGH TUESDAY. AS A RESULT, WE WILL SEE AN INCREASE IN MOISTURE
AND PRECIPITABLE WATER VALUES WILL START TO RISE ONCE AGAIN, NEARING
2 INCHES ACROSS MUCH OF THE REGION. THIS GIVES AN INDICATION THAT
YET ANOTHER HEAVY RAIN EVENT MAY BE ON TAP FOR OUR ALREADY
WATERLOGGED REGION. THIS WILL NEED TO BE FOLLOWED CLOSELY AS WE HAVE
SEEN CONSIDERABLE RAIN THIS PAST WEEK AND FLOODING WILL REMAIN A
CONCERN.

WITH THE SOUTHWEST FLOW ON SUNDAY AND MONDAY, WE WILL SEE SOME
WARMER AIR ADVECT INTO THE REGION, ESPECIALLY ACROSS OUR SOUTHERN
AREAS. MAXIMUM TEMPERATURES WILL RISE INTO THE LOW TO MID 80S, WITH
SOME UPPER 80S POSSIBLE ACROSS THE DELMARVA. TEMPERATURES ON TUESDAY
WILL BE SLIGHTLY COOLER WITH THE FRONT MOVING THROUGH, MAINLY IN THE
LOW TO MID 80S.

WEDNESDAY STARTS TO DRY OUT BEHIND THE DEPARTING COLD FRONT AND ANY
LINGERING SHOWERS SHOULD EXIT THE REGION BY WEDNESDAY MORNING. HIGH
PRESSURE WILL BUILD IN FROM THE WEST AND WILL MOVE DIRECTLY OVER THE
REGION ON THURSDAY. A MID LEVEL TROUGH STARTS TO DEVELOP ACROSS THE
EASTERN UNITED STATES ON WEDNESDAY AND WILL PERSIST THROUGH
THURSDAY. WHILE THE HIGH WILL KEEP US DRY, THE MID LEVELS WILL BE
COOLER AND TEMPERATURES WILL REMAIN ON THE COOL SIDE. MAXIMUM
TEMPERATURES ON BOTH DAYS WILL GENERALLY BE IN THE MID TO UPPER 70S.
-- End Changed Discussion --

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
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...MAINLY VFR CONDITIONS EXPECTED. MVFR
CONDITIONS POSSIBLE IN SHOWERS AND THUNDERSTORMS, MAINLY IN THE
AFTERNOON.

TUESDAY...MAINLY VFR CONDITIONS EXPECTED. SHOWERS AND THUNDERSTORMS
WILL INCREASE IN COVERAGE THROUGH THE DAY AS A COLD FRONT MOVES
THROUGH WITH MVFR CONDITIONS POSSIBLE.
-- End Changed Discussion --

&&

.MARINE...
THE WINDS ARE LOWERING SOME NEAR THE UPPER DELAWARE BAY,
THEREFORE THE SMALL CRAFT ADVISORY WAS DISCONTINUED. THE NORTHERLY
FLOW IS GUSTING TO AROUND 25 KNOTS STILL IN THE LOWER PORTION OF
THE BAY ESPECIALLY NEAR THE BAY MOUTH, THEREFORE WE EXTENDED THE
ADVISORY HERE THROUGH THE AFTERNOON. THE SMALL CRAFT ADVISORY
REMAINS IN EFFECT THROUGH 8 PM FOR THE OCEAN ZONES AS THE SEAS
TAKE LONGER TO LOWER. QUIETER CONDITIONS SHOULD PREVAIL OVER ALL
WATERS FOR TONIGHT.

OUTLOOK...
FOR SATURDAY THROUGH TUESDAY, WINDS AND SEAS WILL REMAIN BELOW SMALL
CRAFT CRITERIA. AS A PROLONGED SOUTHERLY FLOW DEVELOPS EARLY NEXT
WEEK, SEAS WILL START TO INCREASE AND MAY BEGIN TO APPROACH 5 FEET.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR
     ANZ450>455.
     SMALL CRAFT ADVISORY UNTIL 5 PM EDT THIS AFTERNOON FOR ANZ431.

&&

$$
SYNOPSIS...MEOLA
NEAR TERM...GORSE
SHORT TERM...GORSE
LONG TERM...MEOLA
AVIATION...GORSE/MEOLA
MARINE...AMC/GORSE/MEOLA