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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 170159
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
959 PM EDT SUN JUN 16 2013

.SYNOPSIS...
AN AREA OF LOW PRESSURE WILL TRACK FROM THE GREAT LAKES INTO
SOUTHEASTERN CANADA INTO MONDAY. A WEAK COLD FRONT ASSOCIATED WITH
IT IS FORECAST TO SETTLE ACROSS OUR AREA TONIGHT. A SECONDARY COLD
FRONT SHOULD THEN ARRIVE TUESDAY WITH A WEAK LOW PRESSURE SYSTEM
FORMING ALONG IT. HIGH PRESSURE WILL THEN BUILD INTO THE AREA
WEDNESDAY AND THURSDAY, BEFORE SHIFTING TO OUR EAST FRIDAY INTO
SATURDAY. A WARM FRONT MAY THEN LIFT NORTHWARD NEAR OUR AREA
SATURDAY, WITH A COLD FRONT WELL TO OUR WEST SUNDAY.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --
MOST OF THE SHOWER/THUNDERSTORM ACTIVITY HAS MOVED OFF THE COAST,
EXCEPT FOR AN AREA OF SHOWERS/THUNDERSTORMS ACROSS SOUTHERN
DELMARVA, AS A WEAK SURFACE TROUGH HAS PASSED THROUGH THE AREA.
THERE IS ALSO A FEW SHOWERS MOVING THROUGH SOME OF THE NORTHERN
COUNTIES LATE THIS EVENING WHICH SHOULD CONTINUE TO DISSIPATE AS
THEY SLIDE TO THE SOUTHEAST. A WEAK FRONTAL BOUNDARY IS FORECAST
TO SETTLE ACROSS THE AREA TONIGHT WHILE ANOTHER PIECE OF VORTICITY
IS FORECAST TO SLIDE ACROSS THE SOUTHERN AREAS OVERNIGHT.
THEREFORE, THERE WILL REMAIN SOME ACTIVITY ACROSS SOUTHERN
PORTIONS OF THE DELMARVA FOR A FEW MORE HOURS. THERE ARE A FEW
SCATTERED SHOWERS/THUNDERSTORMS ACROSS WESTERN AND CENTRAL
PENNSYLVANIA ASSOCIATED WITH A LITTLE PIECE OF VORTICITY TO OUR
WEST. HOWEVER, NEAR TERM MODEL GUIDANCE DISSIPATES THIS ACTIVITY
BEFORE REACHING OUR AREA; BUT WE WILL CONTINUE TO MONITOR THESE
SHOWERS.

TEMPERATURES TONIGHT WILL BE QUITE MILD COMPARED TO THE PAST COUPLE
OF MORNINGS. WITH AMPLE LOW-LEVEL MOISTURE IN PLACE AND HIGH CLOUDS
OVERHEAD WE COULD SEE SOME GROUND FOG OR HAZE DEVELOPMENT BY LATE
TONIGHT. TEMPERATURE WISE WE SHOULD ONLY BE ABLE TO DROP BACK INTO
THE UPPER-60S ACROSS THE AREA AS WE USED A BLEND OF THE MET/MAVMOS
TONIGHT.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
MUCH CAN BE SAID OF TOMORROW THAT CAN BE SAID OF SUNDAY WITH AN
ALMOST IDENTICAL SYNOPTIC SETUP. STILL HAVE THE ZONAL FLOW ALOFT
KICKING THROUGH MULTIPLE SHORTWAVES TO OUR NORTH AND POSSIBLY
ANOTHER WEAK OR REMAINING TROUGH TO OUR SOUTH. THESE TWO AREAS COULD
SEE MORE WIDELY SCATTERED SHOWERS AND THUNDERSTORMS. TOMORROW DOES
NOT LOOK MUCH BETTER IN TERMS OF CONVECTION THOUGH THE THERMAL
PROFILES ARE MORE CONDUCIVE WITH BETTER SURFACE BASED CAPE AND LESS
CLOUD COVER, THOUGH THE WEAKER WINDS/SHEAR WOULD PROHIBIT BETTER
UPDRAFT STRENGTH. STILL MAINTAIN THE CHANCE POPS LATER IN THE
AFTERNOON WITH THUNDER BUT THIS WILL ONCE AGAIN HAVE TO BE
REASSESSED TO THE POTENTIAL FOR HOW STRONG ANY OF THE STORMS, IF
THEY FORM, WILL BE.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF GRADUALLY RISING HEIGHTS
AS A PACIFIC NORTHWEST CLOSED LOW DRIFTS NORTHEASTWARD INTO SOUTHERN
CANADA. A RIDGE OVER THE PLAINS BUILDS INTO THE MISSISSIPPI VALLEY,
AND THE TROUGH IN THE EASTERN U.S. RELAXES. GIVEN THIS FLOW REGIME,
SYSTEMS LOOK TO BE ON THE WEAKER SIDE AS THEY SLIDE ACROSS THE AREA.
A FRONT SHOULD CLEAR THE AREA LATER TUESDAY, FOLLOWED BY A DRIER
AIRMASS. THE EVOLUTION OF SYSTEMS LATE IN THE WEEK AND NEXT WEEKEND
IS SOMEWHAT UNCERTAIN, GIVEN TIMING OF ENERGY EJECTING INTO THE
NORTHERN PLAINS AND ACROSS THE GREAT LAKES. THIS MAY HANG BACK
AWHILE AS HIGH PRESSURE SITS NEAR THE EAST COAST. WE USED A MODEL
BLEND FOR MONDAY NIGHT INTO WEDNESDAY, THEN WPC GUIDANCE THEREAFTER.
SOME ADJUSTMENTS WERE MADE AFTER ADDITIONAL COLLABORATION WITH OUR
NEIGHBORING OFFICES. WPC USED A BLEND OF THE 06Z GEFS/ECMWF ENSEMBLE
MEANS.

FOR MONDAY NIGHT AND TUESDAY...LOW PRESSURE WILL BE TRACKING TO OUR
NORTH AS A CLOSED LOW SLIDES EASTWARD ACROSS SOUTHERN CANADA. AN
ASSOCIATED COLD FRONT WILL GRADUALLY SETTLE SOUTHEASTWARD ACROSS OUR
CWA DURING THIS TIME FRAME. AS AN UPPER-LEVEL TROUGH AMPLIFIES SOME
SOUTHWARD, STRONGER DEEP LAYER SHEAR SLIDES MAINLY ACROSS THE GREAT
LAKES REGION. THERE SHOULD BE ONGOING CONVECTION WITHIN THIS
CORRIDOR, HOWEVER SOME OF THIS ACTIVITY MAY ARRIVE ACROSS OUR
NORTHERN DURING MONDAY EVENING. IF THIS WERE TO OCCUR, IT SHOULD
WEAKEN WITH THE LOSS OF DAYTIME HEATING THEN WE PERHAPS AWAIT FOR
OTHER CONVECTION IN THE UPPER OHIO VALLEY AND EASTERN GREAT LAKES TO
SLIDE EAST-SOUTHEASTWARD. IN ADDITION, MODEL GUIDANCE SUGGESTS A LEE
SIDE TROUGH COULD BE IN PLACE WHICH MAY ALLOW FOR ISOLATED/SCATTERED
CONVECTION MONDAY EVENING TO PUSH ACROSS PORTIONS OF OUR SOUTHERN
ZONES BEFORE DISSIPATING.

A WEAK WAVE OF LOW PRESSURE THEN LOOKS TO DEVELOP ALONG THE BOUNDARY
AND TRACK NEAR OUR AREA TUESDAY. OUR REGION LOOKS TO REMAIN ON THE
SOUTHERN PERIPHERY OF THE STRONGEST 500 MB FLOW, HOWEVER SOME
INCREASE IS FORECAST ALONG WITH ENOUGH INSTABILITY TO RESULT IN SOME
SHOWERS AND THUNDERSTORMS. WE ALSO LOOK TO BECOME SITUATED WITHIN
THE FAVORABLE ENTRANCE REGION OF THE 250 MB JET DURING THE
AFTERNOON, ALLOWING FOR SOME ASSISTANCE IN THE LARGE SCALE LIFT. THE
THUNDERSTORM COVERAGE AND/OR INTENSITY MAY END UP BEING TEMPERED BY
THE CLOUD COVER AROUND. WE MAINTAIN CHC POPS FOR AT LEAST SCATTERED
COVERAGE DURING THE DAY AS THE FRONT SETTLES SOUTHEASTWARD AND THE
WEAK WAVE MOVES NEARBY. WHILE THE HIGHER PW VALUE AIR LOOKS TO SLIDE
SOUTH AND EAST OF THE AREA, THE PW IS FORECAST TO BE ABOUT 1.25-1.50
INCHES ACROSS OUR AREA. THIS CAN STILL PRODUCE LOCAL DOWNPOURS
ESPECIALLY WITH ANY STRONGER CONVECTIVE ELEMENTS. OUR CONFIDENCE IS
A BIT LOW REGARDING TEMPERATURES AS A FAIR AMOUNT OF CLOUDINESS
COMBINED WITH SOME SHOWERS/THUNDERSTORMS MAY HAVE ENOUGH OF AN
AFFECT.

FOR WEDNESDAY AND THURSDAY...A NARROW UPPER-LEVEL RIDGE IS FORECAST
TO MOVE EAST ACROSS THE PLAINS AND MIDWEST WEDNESDAY AHEAD OF A
LARGE TROUGH IN THE WEST. THIS ALLOWS SURFACE HIGH PRESSURE TO
SETTLE OVER OUR AREA DURING THIS TIME FRAME, AND PUSH A COLD FRONT
TO OUR SOUTH AND EAST. THE ECMWF IS SLOWER WITH THE FRONT AND WANTS
TO MAINTAIN SOME CONVECTION INTO AT LEAST OUR SOUTHERN AREAS. WE
LEANED TOWARD A QUICKER SOUTHWARD PUSH ATTM DUE TO THE INCOMING
SURFACE HIGH. A PERSISTENT UPPER-LEVEL TROUGH HOWEVER IS FORECAST TO
BE ACROSS EASTERN CANADA, THEREFORE THE SURFACE HIGH WILL TEND TO
SETTLE DUE EASTWARD DURING THURSDAY. A NORTH-NORTHEAST LOW-LEVEL
FLOW WEDNESDAY MAY BECOME ONSHORE ESPECIALLY AS THE FLOW ALOFT
LESSENS WITH HIGH PRESSURE ARRIVING. AS A RESULT, A SEA/BAY BREEZE
MAY DEVELOP ESPECIALLY THURSDAY WITH EVEN WEAKER FLOW. IN
ASSOCIATION WITH THE INCOMING SURFACE HIGH, A MUCH DRIER AIRMASS
SHOULD SETTLE IN. SINCE HIGH PRESSURE BECOMES THE DOMINANT FEATURE,
A DRY FORECAST WAS CONTINUED.

FOR FRIDAY AND SATURDAY...THE RIDGE IN THE MIDWEST AREA SHOULD
FLATTEN OUT OR PUSH SOUTHWARD AS ENERGY EJECTS OUT OF THE WEST. AS A
RESULT, LOW PRESSURE IS FORECAST TO TRACK ACROSS THE NORTHERN PLAINS
AND MIDWEST DURING THIS TIME FRAME. MEANWHILE, HIGH PRESSURE IS
SITUATED TO OUR EAST WITH A RETURN FLOW OCCURRING ACROSS THE
NORTHEAST. IT APPEARS THAT A WARM FRONT MAY LIFT NORTHWARD LATE
FRIDAY INTO SATURDAY, ALTHOUGH THE MAIN WAA PUSH MAY END UP STAYING
WELL TO OUR WEST. THERE IS THE POTENTIAL THAT SOME SORT OF WEAKNESS
OR COASTAL TROUGH DEVELOPS NEAR THE CAROLINAS WITH CONVECTION
OCCURRING. SOME OF THIS MOISTURE MAY EVENTUALLY GET DRAWN NORTHWARD
AS LOW-LEVEL WAA AND MOISTURE ADVECTION INCREASES WELL IN ADVANCE OF
THE NEXT SYSTEM. BASED ON SOME UNCERTAINTY WITH THE DETAILS MAINLY
TIED TO A POSSIBLE WARM FRONT, WE WENT DRY FRIDAY THEN CARRIED
SLIGHT CHC POPS IN THE DATABASE ACROSS MUCH OF THE AREA SATURDAY.

FOR SUNDAY...OUR REGION SHOULD BE IN A WARM SECTOR AS HIGH PRESSURE
IN THE ATLANTIC EXPANDS WESTWARD SOME. THIS IS IN RESPONSE TO A
TROUGH SLIDING ACROSS THE NORTHERN PLAINS AND GREAT LAKES. AS THIS
OCCURS, A COLD FRONT WITH POSSIBLY SOME WAVES OF LOW PRESSURE ALONG
IT WILL BE TRAVERSING EASTWARD. FOR NOW, THIS LOOKS TO HANG BACK FAR
ENOUGH TO OUR WEST ALTHOUGH A SMALL CHC OF SOME SHOWERS/THUNDER
CANNOT BE RULED OUT THEREFORE CARRIED SLIGHT CHC POPS IN THE
DATABASE.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

THIS EVENING THROUGH TONIGHT...VFR. NOW THAT THE SHOWERS HAVE MOVED
THROUGH AND THE SUN HAS SET, WINDS WILL BECOME LIGHT, AND GENERALLY
FROM THE SOUTHWEST. WITH A MOIST AIRMASS IN PLACE AND ONLY HIGH
CLOUDS IN PLACE OVERNIGHT, SOME TERMINALS COULD SEE MVFR VSBYS
FORM BY LATE TONIGHT WITH EITHER A LIGHT GROUND FOG OR HAZE.

MONDAY...VFR. ANY GROUND FOG/HAZE WILL DISSIPATE BY LATE MORNING
ONCE WE BEGIN TO MIX. WINDS SHOULD BACK A BIT TOWARDS THE WEST BUT
REMAIN LIGHT. THERE COULD BE SOME GUSTINESS AGAIN TOMORROW AFTERNOON
BUT SHOULD BE IN THE UPPER TEENS RANGE.

OUTLOOK...
MONDAY NIGHT...MOSTLY VFR. LOCALIZED MVFR POSSIBLE WITH A SHOWER OR
THUNDERSTORM IN THE EVENING, THEN PERHAPS WITH LOCAL FOG LATE.

TUESDAY...MVFR OR LOWER AT TIMES WITH SOME SHOWERS AND
THUNDERSTORMS. THERE COULD BE SOME MVFR/IFR LATE AT NIGHT DUE TO
SOME FOG.

WEDNESDAY THROUGH FRIDAY...OVERALL VFR.
-- End Changed Discussion --

&&

.MARINE...
CURRENTLY ACROSS OUR WATERS THE SEAS HAVE NOT RESPONDED AS
ORIGINALLY THOUGHT TO THE STRONGER SOUTHERLY SURGE. THIS MAY BE DUE
TO THE SLIGHTLY OFFSHORE COMPONENT THE WINDS HAVE MAINTAINED. SEEING
THAT THE CONDITIONS SHOULD NOT WORSEN THROUGH THE EVENING AND
OVERNIGHT HOURS DECIDED TO CANCEL THE SCA FOR OUR WATERS. THOUGH
THERE COULD POTENTIALLY BE A 25KT GUST IN PLACES AND SEAS MAY BUILD
UPWARDS OF 4 FEET TONIGHT DID NOT FEEL STRONG ENOUGH TO KEEP THE SCA
GOING. OTHERWISE TOMORROW SHOULD FEATURE SLIGHTLY LESS WIND ACROSS
OUR WATERS WITH SEAS ONCE AGAIN RUNNING AROUND 3 FEET.

OUTLOOK...
A COLD FRONT WILL BE SETTLING ACROSS THE AREA TUESDAY, AND A WEAK
WAVE OF LOW PRESSURE SHOULD TRACK ALONG IT. THERE STILL IS SOME
DIFFERENCES WITH THE SOUTHWARD PUSH OF THE COLD FRONT TUESDAY AND
WEDNESDAY, HOWEVER THE SURFACE LOW LOOKS WEAK ENOUGH TO KEEP THE
WINDS UNDER 25 KNOTS. AS THE WEAK SURFACE LOW DEPARTS, HIGH PRESSURE
STARTS TO BUILD IN AND THE PRESSURE GRADIENT TIGHTENS. A NORTHERLY
WIND SHOULD INCREASE SOME WEDNESDAY BEFORE THE PRESSURE GRADIENT
RELAXES, HOWEVER THE OVERALL FLOW LOOKS TO GENERALLY REMAIN UNDER 25
KNOTS. THERE IS A CHC SEAS REACH 5 FEET FOR A TIME, HOWEVER THIS
POTENTIAL LOOKS MARGINAL ATTM. THE WINDS ARE FORECAST TO BE LIGHTER
LATER WEDNESDAY INTO FRIDAY AS HIGH PRESSURE SETTLES OVERHEAD.
THIS SHOULD RESULT IN THE WINDS TURNING MORE SOUTHERLY, WITH
PERHAPS A SEA/BAY BREEZE CIRCULATION OCCURRING.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...GORSE
NEAR TERM...HEAVENER/ROBERTSON
SHORT TERM...HEAVENER
LONG TERM...GORSE
AVIATION...GORSE/HEAVENER/ROBERTSON
MARINE...GORSE/HEAVENER