NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at May 23, 2:56 PM EST, 2 hours 34 minutes earlier.
Area forecast discussion, May 23, 2:56 PM EST, 2 hours 34 minutes before
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
356 PM EDT WED MAY 23 2012
.SYNOPSIS...
WEAK HIGH PRESSURE WILL EXTEND INTO THE MID ATLANTIC AND REMAIN
NEARBY THROUGH THE WEEKEND. A WEAK COLD FRONT MAY EDGE SOUTHWARD
FROM NEW YORK STATE LATE SATURDAY INTO EARLY SUNDAY BEFORE
WEAKENING. THIS FRONT IS THEN FORECAST TO ADVANCE NORTHWARD ON
MEMORIAL DAY, FOLLOWED BY LOW PRESSURE AND A COLD FRONT APPROACHING
THE REGION FROM THE WEST ON TUESDAY AND WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
THE WRF-NMMB HAS INITIALIZED SLIGHTLY BETTER THAN THE GFS WITH THE
500MB FLOW, ALTHOUGH THE GFS WAS SLIGHTLY BETTER IN THE NERN CONUS
WITH THE 850MB AND 925MB TEMPS. WE WILL CONT TO USE MORE OF THE
WRF-NMMB FEATURES ALOFT AND THE LOWER LEVEL GFS TEMPS THROUGH THE
SHORT TERM.
THERE ARE TWO TRIGGERS FOR MORE ORGANIZED THUNDERSTORMS PER SE, THE
ONE THE SHORT WAVE AND THE OROGRAPHIC LIFT WORKING IN TANDEM IN THE
NORTHWEST PART OF OUR CWA THIS EVENING. WE ARE SEEING A SECONDARY
CONVERGENCE WITH THE BAY BREEZE FRONTS ON THE DELMARVA PENINSULA.
LATER ITS THE SHORT WAVE ASSOCIATED WITH THE CLOSE LOW OVER THE SERN
CONUS. SOME LOCALLY HEAVY RAIN IS EXPECTED TO PERSIST WITH SHOWERS
AND THUNDERSTORMS INTO THIS EVENING, MAINLY TO THE NORTHWEST OF THE
I95 CORRIDOR. THERE SHOULD THEN BE A POP LULL AROUND MIDNIGHT WITH
AN INCREASE IN POPS SOUTH LATE AS THE SHORT WAVE APPROACHES.
BETWEEN THE STRATUS DECK OVER THE SERN COASTAL WATERS AND THE
LOCALLY HEAVY RAIN ON LAND, WE ARE CONTINUING THE MENTION OF PATCHY
FOG INLAND AND AREAS OF FOG ON THE OCEAN. BECAUSE OF SOME CLOUDS
EXPECTED TO COME NORTH WITH THE SHORT WAVE AND OPENING MID LEVEL
LOW, CONFIDENCE IS NOT HIGH ENOUGH TO INCLUDE AREAS OF DENSE FOG.
AS PER THE CURRENT RELATIVELY HIGH DEW POINTS, WE LEANED MIN TEMPS
TOWARD THE HIGHER STAT GUIDANCE.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
THE SHORT WAVE IS FORECAST TO HUG THE NEW JERSEY COAST DURING THE
DAY ON THURSDAY, BUT THIS IS COINCIDENTAL WITH RELATIVELY LESS
FORECAST INSTABILITY. ELSEWHERE, WE ARE NOT SEEING ANY FORECAST MID
LEVEL QVEC CONVERGENCE OR SHORT WAVES AS WE HAD TODAY. SO WE ARE
EXPECTING THE OVERALL COVERAGE TO BE LESS THAN TODAY AND THUS LOWER
POPS. NOT SURE ABOUT THE WRF-NMMB SCENARIO OF AN EARLY START BEFORE
A CAPPING COMES LATER IN THE DAY EAST. FOR NOW, WE FOLLOWED THE MORE
TYPICAL DIURNAL RISE IN POPS DURING THE AFTERNOON. WITH SLIGHTLY
MORE OF A MARINE INFLUENCE AROUND ON THURSDAY, OVERALL FORECAST
INSTABILITY IS FORECAST TO BE SLIGHTLY LESS. REGARDLESS HIGH
PRECIPITABLE WATER VALUES COUPLED WITH A STILL LAZY FLOW ALOFT WILL
CAUSE SOME LOCALLY HEAVY RAIN TO OCCUR WITH ANY STRONGER
THUNDERSTORMS. THAT AGAIN WOULD APPEAR TO BE THE THREAT OF THE DAY
AS WIND FIELDS ARE FORECAST TO BE WEAK AND NOT MUCH OF A FORECAST
DROP OF THETA E WITH HEIGHT FOR PULSERS.
MAX TEMPS WERE BASED ON MODEL FORECAST 925MB TEMPS WHICH MEANT
LITTLE ADJUSTMENT FROM ONGOING GRIDS AND FORECAST.
&&
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
THE OVERALL PATTERN REMAINS RATHER UNSETTLED THROUGH MUCH OF THE
EXTENDED PERIOD, WITH DAILY CHANCES FOR SHOWERS/T-STORMS ACROSS ALL
OR PART OF THE FORECAST AREA. WHILE WEAK SURFACE HIGH PRESSURE WILL
EXTEND INTO OUR AREA FROM THURSDAY NIGHT INTO FRIDAY, THE GFS AND
EURO SHOW A WEAK UPPER TROUGH AND A VORT MAX OR TWO PASSING OVERHEAD
DURING THIS TIMEFRAME. THE CONVECTION LOOKS TO BE DIURNALLY DRIVEN,
WITH BOTH MODELS INDICATING SUFFICIENT INSTABILITY. THUS, SHWRS WERE
MAINTAINED FOR THE THURS NIGHT TO FRI AM TIMEFRAME, WITH T-STORMS
FOR FRIDAY PM TO EVENING.
FROM THERE, THE EURO AND GFS BOTH SHOW STRENGTHENING LOW PRESSURE
ADVANCING NORTHEASTWARD ACROSS SOUTHERN CANADA, WITH ITS ASSOCIATED
COLD FRONT LIFTING THROUGH THE GREAT LAKES AND NORTHEAST STATES.
THERE ALSO APPEARS TO BE A CONSISTENT SIGNAL AMONG THE MODELS THAT
THIS WEAK COLD FRONT MAY SLIDE SOUTHWARD INTO OUR FORECAST REGION BY
LATE SATURDAY INTO EARLY SUNDAY. THIS ALONG WITH ANOTHER VORT MAX OR
TWO PROGGED TO MOVE OVER THE AREA, WILL BRING ANOTHER CHANCE FOR
SHOWERS/T-STORMS. THE EXACT DETAILS AND TIMING OF THESE FEATURES
REMAIN A BIT UNCERTAIN, BUT WITH ENOUGH INSTABILITY AND A TRIGGER
NEARBY, WE HAVE RETAINED POPS IN THE SATURDAY AFTERNOON AND SUNDAY
PERIODS.
THERE APPEARS TO BE DECENT MODEL AGREEMENT IN SHOWING THIS FRONTAL
BOUNDARY LIFTING BACK NORTHWARD DURING MEMORIAL DAY. THE SPECIFICS
REGARDING TIMING AND ANY UPPER AIR FEATURES THAT MAY HELP TO TRIGGER
CONVECTION ARE A BIT UNCERTAIN AT THIS TIME, BUT WE THERE WILL BE
ENOUGH MOISTURE AND INSTABILITY AROUND FOR SOME SHWR/T-STORM
ACTIVITY, MOST LIKELY DURING THE MONDAY AFTERNOON TIMEFRAME. BEYOND
MONDAY, MODEL DIFFERENCES INCREASE WITH REGARDS TO THE NEXT
POTENTIAL SIGNIFICANT SYNOPTIC FEATURE ON THE HORIZON. THE GFS
DEPICTS A RATHER ORGANIZED AREA OF LOW PRESSURE MOVING ACROSS THE
NORTHERN GREAT LAKES, WITH ITS ASSOCIATED COLD FRONT ADVANCING
THROUGH THE OHIO VALLEY AND APPROACHING OUR REGION BY TUESDAY NIGHT
INTO WEDNESDAY. MEANWHILE, THE EURO DOES NOT REFLECT AS ORGANIZED OF
A SYSTEM. WITH THIS UNCERTAINTY IN MIND, FEW CHANGES WERE MADE TO
POPS IN THIS TIMEFRAME.
INCREASING WARMTH AND HUMIDITY WILL BE FELT ACROSS THE REGION GOING
THROUGH THE LONG TERM PERIOD. GFS AND EURO GUIDANCE HAS DEWPOINTS
CLIMBING INTO THE UPPER 60S AND LOWER 70S BY SUNDAY AND MONDAY.
TEMPERATURES ALSO LOOK TO BE THE WARMEST DURING THAT TIMEFRAME, WITH
A FRONT LIFTING TO THE NORTH ACROSS THE REGION. MAX TEMPERATURES ARE
EXPECTED TO REACH THE UPPER 80S, WITH SOME LOWER 90 DEGREE READINGS
POSSIBLE. THE COMBINATION OF THESE HIGH TEMPERATURES AND DEWPOINTS
MAY LEAD TO HEAT INDEX VALUES IN THE UPPER 90S FOR PORTIONS OF THE
REGION, PERHAPS AROUND 100 DEGREES FOR URBAN AREAS. IN ADDITION,
WITH AN UPPER RIDGE POSSIBLY LINGERING OVER THE REGION TUESDAY, THE
ELEVATED TEMPERATURES AND DEWPOINTS MAY LAST INTO TUESDAY. FOR NOW,
WE WILL HIGHLIGHT THIS CONCERN IN THE HWO, AND WE WILL CONTINUE TO
MONITOR THIS POTENTIAL FOR HEAT OVER THE HOLIDAY WEEKEND INTO EARLY
NEXT WEEK.
&&
.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
WE ARE EXPECTING SCATTERED CONVECTION TO CONTINUE TO AFFECT THE
TERMINALS THIS AFTERNOON AND EVENING FROM KPHL AREA NORTHWESTWARD.
THE STRATUS BANK ALONG THE SE NJ COAST IS HANGING TOUGH. IFR
CONDITIONS ARE EXPECTED TO OCCUR AGAIN LATE TONIGHT AND THURSDAY
MORNING.
FOR THIS AFTERNOON, EXCLUDING KACY, WE ARE EXPECTING VFR CONDITIONS
WITH LIGHT WINDS TO PREVAIL OUTSIDE OF CONVECTION. BEST CHANCES
AND HIGHEST CONFIDENCE FOR CONVECTION ARE AIRPORTS AND TERMINALS
NORTHWEST OF THE KPHL AND I95 CORRIDOR. AT KACY AN IFR STRATUS
CIG IS EXPECTED TO MIX OUT AND DISSIPATE AS THE AFTERNOON
PROGRESSES. WINDS SHOULD BE LIGHT MAINLY FROM THE SOUTHEAST. NO
TRUE DISCERNIBLE SEA BREEZE FRONT IS EXPECTED.
FOR THIS EVENING WE ARE FORECASTING CONVECTIVE COVERAGE TO
DECREASE. THERE IS TOO LOW A CHANCE OF SHOWERS AFFECTING THE AREA
FROM THE SOUTH LATE TO INCLUDE FOR NOW. WITH THE STRATUS CIG AS A
SEEDING GROUND WE ARE EXPECTING A SPREADING OF IFR CONDITIONS THIS
EVENING FROM THE COAST TO ALL AREAS OVERNIGHT. WE ARE BANKING ON
IFR CONDITIONS BEING MORE CIG RELATED THAN VSBY RELATED. OVERALL
CONFIDENCE IS AVERAGE.
CONDITIONS SHOULD IMPROVE AGAIN TO VFR DURING THURSDAY MORNING. WE
USED THE TIMING OF OCCURRENCE THIS MORNING IN THE SERN TERMINAL AREA
(AROUND 14Z) ON THURSDAY AGAIN. WINDS SHOULD BE SLIGHTLY STRONGER
FROM THE SOUTH OR SOUTHEAST THAN TODAY, BUT GENERALLY LESS THAN 10
KNOTS.
OUTLOOK...
THURSDAY NIGHT THROUGH FRIDAY NIGHT...MAINLY VFR CONDITIONS,
ALTHOUGH THERE MAY BE SOME STRATUS OR FOG DURING THE OVERNIGHT TO
EARLY MORNING THAT COULD LOWER CONDITIONS FOR A TIME TO IFR. DURING
FRIDAY AFTERNOON, A FEW SHWRS/T-STORMS COULD ALSO LOWER CONDITIONS
TO MVFR.
SATURDAY THROUGH MONDAY...MAINLY VFR CONDITIONS ARE EXPECTED. MAINLY
AFTERNOON TO EVENING SHWR/T-STORM ACTIVITY COULD LOWER CONDITIONS
FOR A TIME.
&&
.MARINE...
WE ARE NOT EXPECTING SMALL CRAFT ADVISORY CONDITIONS TO OCCUR
NEITHER TONIGHT NOR ON THURSDAY. WHILE THE ONSHORE FLOW IS EXPECTED
TO BE SLIGHTLY STRONGER ON THURSDAY, SEAS SHOULD REMAIN BELOW 5
FEET. THE GREATEST MARINE CONCERN ONCE AGAIN COULD BE SOME DENSE FOG
AS DEW POINT TEMPERATURES ARE AROUND THE WATER TEMPERATURES.
OUTLOOK...
WINDS AND SEAS FOR OUR WATERS ARE EXPECTED TO BE PRIMARILY BELOW SCA
CRITERIA. HOWEVER, WITH AN ALMOST DAILY CHANCE OF SHOWERS OR
THUNDERSTORMS, LOCALLY GUSTY WINDS AND REDUCED VISIBILITIES MAY BE
POSSIBLE WITH THIS ACTIVITY.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.
&&
SYNOPSIS...KLINE
NEAR TERM...GIGI
SHORT TERM...GIGI
LONG TERM...KLINE
AVIATION...GIGI/KLINE
MARINE...GIGI/KLINE