Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 170425
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1225 AM EDT FRI APR 17 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 THIS MORNING/...

SCATTERED LIGHT RAIN SHOWERS COVERED MUCH OF NORTHEASTERN
MARYLAND, EASTERN PENNSYLVANIA AND NORTHWESTERN NEW JERSEY AROUND
MIDNIGHT.

A MID LEVEL TROUGH WAS APPROACHING SLOWLY FROM THE WEST.
MEANWHILE, A 35 TO 40 KNOT LOW LEVEL JET EXTENDING FROM
PENNSYLVANIA TO SOUTHERN NEW ENGLAND WAS CONTRIBUTING TO THE LIFT
AND THE MOISTURE ADVECTION INTO THE AREA OF SHOWERS. THE AREA OF
SHOWERS IS EXPECTED TO EXPAND AS IT LIFTS SLOWLY TO THE EAST
NORTHEAST. AS THE LOW LEVELS OF THE ATMOSPHERE CONTINUE TO
MOISTEN, RAINFALL AMOUNTS WILL INCREASE. PARTS OF EASTERN
PENNSYLVANIA AND NORTHERN NEW JERSEY MAY PICK UP A TENTH OR TWO OF
RAINFALL BY DAYBREAK. LESSER AMOUNTS ARE ANTICIPATED FOR THE
COASTAL PLAIN.

WE HAVE MADE SOME ADJUSTMENTS TO THE FORECAST BASED ON THE
MIDNIGHT RADAR DATA AND ON THE TRENDS IN THE 0200 UTC AND 0300 UTC
RUNS OF THE HRRR. WE HAVE INCREASED THE PROBABILITIES OF
PRECIPITATION A BIT.

TEMPERATURES IN THE REGION WERE MAINLY IN THE 50S AROUND
MIDNIGHT. READINGS WILL DROP A FEW DEGREES WITH THE ONSET OF THE
RAIN BUT THEY ARE NOT EXPECTED TO FALL MUCH AFTERWARD DUE TO THE
THE LIGHT SOUTHERLY SURFACE FLOW.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TODAY/...
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 /TONIGHT 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.

DAILIES...

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 /04Z FRIDAY THROUGH TUESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

OVERNIGHT...SHOWERS OVERSPREADING ALL OF THE TERMINALS. CIGS AND
VSBYS SHOULD LOWER TO MVFR LEVELS TOWARD MORNING. EXCEPTION IS
KABE AND KRDG WHERE THERE IS MORE GUIDANCE UNIFORMITY OF IFR CIGS
OCCURRING. SOUTH WINDS SHOULD REMAIN LESS THAN 10 KNOTS.

FRIDAY MORNING...SHOWERS ENDING. WHILE VSBYS SHOULD BECOME VFR
QUICKLY ONCE SHOWERS END, CIG IMPROVEMENT SHOULD BE SLOW AND MIGHT
TAKE MOST OF THE MORNING INTO EARLY AFTERNOON TO REACH INTO VFR
LEVELS. WINDS SHOULD VEER A BIT MORE TO THE SOUTHWEST AND AVERAGE
10 TO 15 KNOTS.

FRIDAY AFTERNOON VFR CIGS WITH NO VSBY RESTRICTIONS EXPECTED.
WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS ARE POSSIBLE, BUT
CONFIDENCE OF THEM AFFECTING ANY OF THE TERMINALS IS TOO LOW TO
INCLUDE WITH THIS TAF PACKAGE. WINDS WILL VEER A BIT MORE TO THE
WEST AT SPEEDS DECREASING SLIGHTLY, CLOSER TO 10 KNOTS.

OUTLOOK...
FRIDAY 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.

SAT THRU SUN...MVFR IN GROUND FOG POSSIBLE EARLY SAT.
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...IOVINO
SHORT TERM...AMC
LONG TERM...FRANCK
AVIATION...FRANCK/GIGI
MARINE...AMC/FRANCK
FIRE WEATHER...FRANCK
TIDES/COASTAL FLOODING...FRANCK


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