Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 162020
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
420 PM EDT THU APR 16 2015

.SYNOPSIS...
LOW PRESSURE EAST OF THE CAROLINA COAST TONIGHT WILL BE PUSHED OUT
TO SEA BY A WEAK COLD FRONT MOVING THROUGH OUR AREA ON FRIDAY NIGHT.
A STRONGER COLD FRONTAL PASSAGE WILL OCCUR SATURDAY AFTERNOON. HIGH
PRESSURE WILL BRIEFLY MOVE IN FROM THE NORTH ON SUNDAY. LOW PRESSURE
IS THEN EXPECTED TO STALL OVER THE GREAT LAKES REGION NEXT WEEK...
LEADING TO A COLD FRONTAL PASSAGE MONDAY NIGHT...WITH ANOTHER COLD
FRONTAL PASSAGE POSSIBLE ON WEDNESDAY OR THURSDAY.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
SURFACE HIGH PRESSURE HAS SHIFTED SOUTHEAST FROM NEW ENGLAND AND IS
NOW EAST OF OUR AREA...WITH A RIDGE AXIS EXTENDING SOUTHWEST ACROSS
THE MID-ATLANTIC REGION. THIS HAS ALLOWED SFC WINDS TO VEER AROUND
TO THE SOUTHEAST IN THE COASTAL ZONES AND MORE SOUTHERLY FARTHER
INLAND. SKIES HAVE BEEN MOSTLY SUNNY THIS AFTERNOON...EXCEPT FOR
SOME CIRRUS...WHICH HAS ALLOWED INLAND TEMPS TO RISE TO THE UPPER
60S MOST AREAS. COASTAL AREAS ARE SOMEWHAT COOLER DUE TO ONSHORE
FLOW FROM THE OCEAN WATER WHERE TEMPS ARE STILL IN THE 40S.

SURFACE WINDS TONIGHT WILL SLACK OFF A BIT WHILE REMAINING SLY...
BUT WINDS AT 850 MB WILL BECOME SOUTHWEST AND INCREASE TO 30-35 KT.
THUS LOW-LEVEL MOISTURE WILL BE ON THE INCREASE. MID LEVEL CLOUDS
ARE ALREADY PRESENT TO OUR WEST FROM WESTERN PA SOUTH INTO VA. THESE
WILL BE SPREADING EAST ACROSS THE AREA THIS EVENING AND CONTINUE TO
THICKEN OVERNIGHT. BY LATE TONIGHT SHOWERS ARE EXPECTED TO DEVELOP
AHEAD OF A SHORTWV TROF MOVING EAST FROM THE GRTLKS/OHIO VLY.
OVERNIGHT POPS GENERALLY INCREASE FROM CHANCE ALONG THE COAST TO
LIKELY IN THE FAR NORTHWEST. THE INCREASING CLOUD COVER WILL ALSO
KEEP OVERNIGHT MIN TEMPS CONSIDERABLY WARMER THAN LAST NIGHT.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
SCATTERED SHOWERS ARE EXPECTED TO CONTINUE ACROSS THE AREA FRIDAY
MORNING WITH A TENDENCY TO SPREAD FARTHER SOUTHEAST INTO SOUTH NJ
AND NORTHERN DELMARVA. SKIES WILL BE CLOUDY IN THE MORNING BUT
PARTIAL CLEARING IS EXPECTED IN THE AFTERNOON AS DEEPER MOISTURE
MOVES OFF TO THE EAST. A FEW HUNDRED J/KG OF CAPE ARE FCST TO
DEVELOP IN THE AFTERNOON ALONG WITH LOW-LVL CONVERGENCE ALONG A
SURFACE TROF...THUS WE HAVE MAINTAINED A CHANCE OF SHOWERS AND
ADDED SOME ISOLD T-STORMS AS WELL. MAX TEMPS FRIDAY AFTERNOON
COULD BE A COUPLE OF DEGREES WARMER THAN TODAY...GIVEN ENOUGH SUN
AND A SLIGHTLY WARMER AIR MASS.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
OVERVIEW...

THE FAIRLY PROGRESSIVE MID-LEVEL PATTERN OVER THE PAST 7+ DAYS
WILL GRADUALLY BECOME MORE BLOCKY THROUGH NEXT WEEK. A GENERAL
SOUTHERN STREAM REX BLOCK WILL BE PARKED INVOF THE CA COAST...AS A
HIGH AMPLITUDE NORTHERN STREAM RIDGE BUILDS INTO THE WESTERN CONUS.
MEANWHILE...A S/WV CURRENTLY OVER THE GULF OF ALASKA WILL TRAVERSE
THIS RIDGE AND DIVE SOUTHEASTWARD INTO THE UPPER MS VALLEY...HEIGHT
FALLS WITH THIS FEATURE WILL BE SUFFICIENT TO EJECT A CLOSED FOUR-
CORNERS LOW NEWD. THE COMBINATION OF THE RIDGE BUILDING INTO THE
WESTERN CONUS AND STRONG DOWNSTREAM BLOCKING DEVELOPING OVER THE
NORTH ATLANTIC WILL LEAD TO A DEEP CLOSED LOW OVER THE UPPER MS
VALLEY DURING THE EARLY-MID NEXT WEEK.

OVERALL...GENERALLY FAIR WEATHER THIS WEEKEND WILL BECOME MORE
ACTIVE DURING THE MON THRU THU TIME FRAME. IN PARTICULAR...LOW
PRESSURE MOVING THROUGH THE GREAT LAKES EARLY NEXT WEEK WILL LEAD TO
REDEVELOPMENT ALONG THE MID-ATLANTIC COASTLINE...WITH HEAVY RAIN AND
GUSTY WINDS POSSIBLE IN THE MON-TUE TIME FRAME. THEREAFTER...WITH
THE UPPER LOW TO THE NORTHWEST...UNSETTLED WEATHER IS PROBABLE THRU
AT LEAST THURSDAY.

DALIES...

FRI NIGHT...LINGERING SHOWERS AND POSSIBLE THUNDER WITH A WEAK COLD
FRONTAL PASSAGE EARLY. BEST CHANCE OF THUNDER IS OVER THE DELMARVA
AND FAR SOUTH JERSEY. SYNOPTIC SETUP AND MODEL SOUNDINGS INDICATE
THE POTENTIAL FOR PATCHY FOG IF ENOUGH CLEARING TAKES PLACE.

SAT...OVERALL A NICE DAY. A STRONGER BUT DRY COLD FROPA IS EXPECTED
DURING THE DAY.

SUN...HIGH PRESSURE BUILDS IN. EXPECTING A DRY DAY WITH SOME MID TO
HIGH LEVEL CLOUDS STREAMING IN FROM THE SOUTHWEST. FLOW WILL BECOME
ONSHORE SO COASTAL LOCALS WILL BE COOLER.

MONDAY AND TUESDAY...LOW PRESSURE MOVING THROUGH THE GRT LAKES WILL
REDEVELOP TO SOME EXTENT OFF THE MID-ATLANTIC COAST. GOOD KINEMATICS
AND THERMODYNAMICS ARE IN PLACE FOR THE POSSIBILITY OF SOME HEAVIER
RAIN DURING THE MON NIGHT THRU TUESDAY MORNING TIME FRAME. SUPPORTING
THIS...PRECIPITABLE WATER VALUES APPROACH 1.5 INCHES...WHICH IS +2
STANDARD DEVIATIONS ABOVE NORMAL FOR THE MONTH OF APRIL. THIS SYSTEM
MAY ALSO MOVE SOMEWHAT SLOWER THAN CURRENTLY MODELED...WHICH WOULD
INCREASE RAINFALL VALUES AS WELL. IT/S TOUGH TO SAY WHETHER WE MAKE
IT INTO THE WARM SECTOR...BUT AT LEAST ELEVATED CONVECTION POSSIBLE
PER MODEL STABILITY INDICES. GUSTY SE WINDS ALONG THE COAST.

WED AND THU...WITH A DEEP CLOSED LOW TO OUR WEST AND CYCLONIC FLOW
ALOFT...EXPECT GENERALLY UNSETTLED WEATHER TO CONTINUE DURING THIS
PERIOD.

&&

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

WINDS THIS AFTERNOON HAVE VEERED TO THE SE FOR NEAR COASTAL AREAS
AND MORE TO THE S OR EVEN SW FARTHER INLAND. THIS HAS OCCURRED IN
RESPONSE TO SFC HIGH PRES SLIDING SEWD OFF OF NEW ENGLAND. SOUTH
WINDS BETWEEN 5 AND 1O KT WILL CONT OVER NIGHT. CLOUDS WILL ALSO BE
INCREASING BUT VFR CONDS SHOULD CONTINUE UNTIL WELL AFTER MIDNIGHT.
CIGS ARE EXPECTED TO LOWER TO MVFR SHORTLY BEFORE SUNRISE FRIDAY
MORN. CIGS AND VSBYS MAY BE LOCALLY LOWER MVFR OR BRIEFLY IFR IN
SCATTERED SHOWERS TOMORROW MORNING. CONDS SHOULD GRADUALLY IMPROVE
DURG THE AFTN BUT THERE IS ALSO A CHANCE FOR SCT TSTMS.

OUTLOOK...
SAT NIGHT...MVFR IN SHRA AND LOW CLOUDS GRADUALLY IMPROVING TO
VFR WITH THE PASSAGE OF A COLD FRONT. ISOLATED THUNDER IS ALSO
POSSIBLE PRIOR TO THE FROPA. GROUND FOG MAY DEVELOP TOWARD
DAYBREAK LEADING TO MVFR CONDITIONS OVER THE INTERIOR.

SUN...MVFR IN GROUND FOG POSSIBLE EARLY. OTHERWISE...VFR CONDITIONS.

MON AND TUE...MVFR/IFR IN LOW CLOUDS...SHRA AND FOG ACROSS THE AREA.
GUSTY SOUTHEAST WINDS MAY ALSO LEAD TO LLWS.

&&

.MARINE...
SUB SCA CONDS ARE EXPECTED THROUGH TONIGHT AND FRIDAY. SWLY WINDS
AND ASSOCD SEAS SHOULD INCREASE SOME ON FRIDAY BUT STILL REMAIN
BELOW SCA CONDS. SLY WINDS TONIGHT WILL BRING INCREASINGLY WARMER
AND MOIST AIR OVER THE COLD WATER WHICH COULD RESULT IN AREAS OF
FOG. VSBY ON FRIDAY COULD BE LOCALLY POOR IN SCT SHOWERS AND ISOLD
TSTMS.

OUTLOOK...

SAT AND SAT NIGHT...SCA MAY BE NEEDED IN POST-FRONTAL GUSTY NW FLOW.

SUN...SUB-SCA CONDITIONS EXPECTED.

MON AND TUE...SOUTHEAST WINDS MAY REACH SCA LEVELS. CONSIDERABLE
UNCERTAINTY DUE TO ULTIMATE TRACK AND STRENGTH OF LOW PRESSURE.
COOL SEA SURFACE TEMPERATURES MAY ALSO LEAD TO AN INVERSION WITH
STRONGER WINDS REMAINING ALOFT.

&&

.FIRE WEATHER...
A STRONGER BUT DRY COLD FROPA IS EXPECTED ON SATURDAY. THIS WILL
LEAD TO VERY DRY CONDITIONS ALONG WITH GUSTY NORTHWEST WINDS. GIVEN
NO HEAVY QPF IN THE FCST LEADING UP TO SATURDAY...AS WELL AS LOW SFC
RELH AND THE GUSTY WINDS...CONDITIONS MAY BE CLOSE TO RED FLAG
CRITERIA DURING THE DAY ON SAT. AGAIN THIS IS DEPENDENT ON THE
FUEL MOISTURE AND ANTECEDENT RAINFALL.

&&

.TIDES/COASTAL FLOODING...
TIDES WILL NEED MONITORING FOR POTENTIAL MINOR COASTAL FLOODING
ISSUES AS POSITIVE DEPARTURES INCREASE SUNDAY THROUGH MONDAY NIGHT
WITH DEVELOPING ONSHORE FLOW. THIS WILL OCCUR IN CONJUNCTION WITH A
NEW MOON THIS WEEKEND SO ASTRONOMICAL TIDES WILL ALREADY BE HIGH.

&&

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

&&

$$
SYNOPSIS...FRANCK
NEAR TERM...AMC
SHORT TERM...AMC
LONG TERM...FRANCK
AVIATION...AMC/FRANCK
MARINE...AMC/FRANCK
FIRE WEATHER...FRANCK
TIDES/COASTAL FLOODING...FRANCK



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