NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Nov 22, 6:47 PM EST, 2 hours 22 minutes earlier.
Area forecast discussion, Nov 22, 6:47 PM EST, 2 hours 22 minutes before
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
647 PM EST TUE NOV 22 2011
.SYNOPSIS...
A WARM FRONT IN SOUTHERN VIRGINIA WILL MOVE THROUGH DELAWARE AND
EASTERN MARYLAND TONIGHT AND INTO CENTRAL NEW JERSEY BY MORNING, AS
INTENSIFYING LOW PRESSURE TRACKS EAST FROM INDIANA. THAT LOW
EMERGES NEAR LONG ISLAND WEDNESDAY AFTERNOON WITH ITS TRAILING
COLD FRONT MOVING SOUTH OF OUR REGION BY EVENING. HIGH PRESSURE
FOLLOWS INTO THE MID ATLANTIC STATES THURSDAY AND FRIDAY THEN
SLIDES EASTWARD FROM THE CAROLINAS THIS WEEKEND. CONSIDERABLE
UNCERTAINTY EXISTS IN THE WEATHER PATTERN HERE EARLY NEXT WEEK,
ALTHOUGH IT APPEARS A LOW PRESSURE SYSTEM SHOULD AFFECT THE AREA.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
THROUGH 600 PM, SOME LOCATIONS IN BERKS COUNTY WERE NEAR THE ONE
INCH MARK FOR A RAINFALL TOTAL FOR THIS EVENT. TOTALS GRADUALLY
TAPERED DOWN TO LESS THAN A QUARTER INCH NEAR THE COAST.
WITH LEAF AND DEBRIS CLOGGED STORM DRAINS, SOME ROADWAY FLOODING WAS
OCCURRING AT LOCATIONS THAT HAVE RECEIVED IN EXCESS OF A HALF INCH
OF RAIN. AS A RESULT, A FLOOD ADVISORY WAS ISSUED FOR MUCH OF
SOUTHEASTERN PENNSYLVANIA SHORTLY BEFORE 600 PM. IT IS IN EFFECT
UNTIL CLOSE TO MIDNIGHT AND IT MAY NEED TO BE EXTENDED OR UPGRADED
DEPENDING UP HOW THINGS UNFOLD THIS EVENING.
WHILE A FAIRLY STEADY RAIN IS EXPECTED TO CONTINUE THROUGH THE NIGHT
IN EASTERN PENNSYLVANIA AND IN NORTHERN AND CENTRAL NEW JERSEY, A
BIT OF A BREAK IS ANTICIPATED TO AFFECT PARTS OF NORTHEASTERN
MARYLAND, DELAWARE AND SOUTHERN NEW JERSEY THIS EVENING. THE RAIN
SHOULD FILL BACK OVER THOSE AREAS LATE TONIGHT.
WE CONTINUE TO EXPECT A FAIR AMOUNT OF RAIN OVER PARTS OF EASTERN
PENNSYLVANIA AND NORTHERN AND CENTRAL NEW JERSEY AND A FLOOD WATCH
REMAINS IN EFFECT BEGINNING AT 1000 PM. AN INCH OR TWO OF RAIN IS
ANTICIPATED WITH LOCALLY HIGHER AMOUNTS.
IN REGARD TO TEMPERATURES, READINGS ARE FORECAST TO RISE SLOWLY
THROUGH THE NIGHT AT MOST LOCATIONS. HOWEVER, SOME LOW LEVEL COLD
AIR MAY REMAIN TRAPPED IN PARTS OF NORTHERN NEW JERSEY AND THE
POCONO REGION.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
THE LOW PRESSURE SYSTEM WILL CROSS OUR AREA WEDNESDAY MORNING AND
MOVE OFF TO THE EAST DURING THE AFTERNOON. RAIN AND AN ISOLATED
THUNDERSTORM WILL CONTINUE UNTIL THE COLD FRONT CROSSES THE AREA.
ONCE THAT OCCURS, THE PRECIPITATION WILL BECOME SHOWERY AND THE
THREAT FOR A THUNDERSTORM WILL END. SKIES WILL BEGIN TO CLEAR
TOWARD EVENING AND THE SHOWERS WILL END FROM WEST TO EAST. WINDS
WILL BECOME SOUTHWEST AROUND 10 MPH AS THE COLD FRONT APPROACHES
AND THEN SHIFT TO NORTHWEST BEHIND THE FRONT. WIND SPEEDS WILL
THEN INCREASE AND BY EVENING, GUSTS INTO THE MID AND UPPER 20S
ARE EXPECTED. HIGH TEMPERATURES WEDNESDAY WILL OCCUR EARLY IN
THE DAY WITH READINGS IN THE 50S TO MID 60S. TEMPERATURES WILL
THEN BEGIN TO FALL ONCE THE FRONT HAS CROSSED THE AREA AND BY
EVENING, READINGS WILL BE IN THE 40S AND LOWER 50S.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
UPPER AIR: SHARP TROUGH DEPARTS SEWD FROM MID ATLC COAST WED EVE TO
BE REPLACED BY RIDGING ALONG THE E COAST THU-SAT. THEREAFTER...VERY
HUGE SPREAD IN SOLNS BETWEEN SUNDAY AND NEXT TUESDAY WITH STILL
SOME 12Z/22 OP MODELS AND ENSEMBLE MEMBERS PEELING OFF A STRONG
SHORT WAVE INTO THE NE USA SUNDAY AND MONDAY WHILE OTHERS DELAY
WITH A HIGH AMPLITUDE TROUGH IN THE MISSISSIPPI VALLEY SUNDAY AND
MONDAY LIFTING AND WEAKENING NEWD INTO THE NE USA TUESDAY...YET
LEAVING BEHIND ANOTHER LARGE AMPLITUDE TROUGH ACROSS LOWER OHIO
VALLEY ON TUESDAY. WHAT TO BELIEVE?
THIS FORECAST WAS POPULATED WITH 12Z/22 HPC GUIDANCE FROM DAY 4-7
AND ALL THE GRIDS FROM 00Z/24 ONWARD ARE A 50 50 BLEND OF NCEP
GUIDANCE.
THE DAILIES...
WEDNESDAY EVENING...MAY HAVE A PERIOD OF NLY GUSTS 28 TO 38 KNOTS
WITH STRONG PRES RISES AND CAA TRAILING THE DEPARTING TROUGH ALOFT
THAT HAS RATHER NOTABLY HIGH TOTAL TOTALS OF OVER 50. SUGGESTS
SOME LEFTOVER CONVECTIVE ELEMENTS IN THE EVENING OVER THE SE
PORTION OF OUR AREA.,,VICINITY DELAWARE BAY SWD.
THURSDAY-SATURDAY...LOOKS VERY VERY NICE FOR THIS TIME OF YEAR WITH
A GRADUAL WARMING TREND. PATCHY FOG POSSIBLE EARLY FRIDAY AND
EARLY SATURDAY IN SOME OF THE COUNTRYSIDE. GENERALLY LIGHT WIND.
BANDS OF CIRRUS PROBABLY ARRIVE FRIDAY NIGHT OR SATURDAY AS THE
RIDGE AXIS ALOFT HEADS FOR THE EAST COAST.
SUNDAY-TUESDAY...SLOWER 12Z/22 HPC GUIDANCE FOLLOWED DESPITE SOMEWHAT
FASTER OP GFS MEX POPS AND FASTER UK/CMC MODELS. THE GEFS POPS ARE
RATHER LOW...AND I DONT BELIEVE THESE.
THE 12Z/22 ECMWF AND GFS MASS FIELDS ARE SLOW. BASICALLY WARMER
THAN NORMAL WITH INCREASING CLOUD COVER AND EVENTUALLY A DECENT
SPIKE OF SE INFLOW AND ASSOCIATED SHOWERY RAINS. TIMING HIGHLY
UNCERTAIN ATTM. FWIW...NAEFS FAVORS MON NIGHT-TUESDAY FOR SOME
SORT OF WIDESPREAD RAIN EVENT. SOME MODEL INDICATIONS OF 5 INCH
TOTALS NEXT 7 DAYS IN NNJ.
NOTE WE DID SEE THE OTHER LOW PRESSURE SYSTEM IN THE ECMWF WELL OFF
THE EAST COAST EARLY NEXT WEEK...NOT SURE WHAT TO MAKE OF THIS AS
A PLAYER IN OUR WEATHER.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
A HIGH IMPACT TO HOLIDAY TRAVEL CONTINUES THROUGH WEDNESDAY MORNING
DUE TO LOW CEILINGS AND VISIBILITIES, ALONG WITH A PERIOD OF
LOW-LEVEL WIND SHEAR.
A WARM FRONT TO OUR SOUTH SHOULD GRADUALLY LIFT NORTHWARD TONIGHT
INTO WEDNESDAY MORNING AS LOW PRESSURE TRACKS NEARLY OVER THE AREA
ON WEDNESDAY. THIS WILL BE ACCOMPANIED BY A ROBUST LOW-LEVEL JET OF
40-55 KNOTS OVERNIGHT INTO WEDNESDAY MORNING. RAIN WILL CONTINUE AS
PLENTY OF LIFT ACCOMPANIES THIS SYSTEM, HOWEVER IT MAY TAPER OFF
SOME OVERNIGHT FOR A TIME MAINLY FOR THE TERMINALS CLOSEST TO THE
COAST. THE POSITION OF THE WARM FRONT MAY IMPACT THE CEILINGS AS
WELL AS MILDER AIR BUILDS IN, WHICH MAY TRY TO ERODE THE LOW-LEVEL
CLOUDINESS SOME ALONG WITH ANY FOG /ESPECIALLY GIVEN THE WIND FIELD
FORECAST JUST ABOVE THE SURFACE/. THEREFORE, OUR CONFIDENCE
REGARDING ANY TIMING OF THIS IS NOT REAL HIGH. THERE APPEARS TO BE A
SOMEWHAT BETTER CHANCE OF A BIT HIGHER CEILINGS FOR KMIV AND KACY
GIVEN THEIR PROXIMITY TO THE WARMER LOW-LEVEL TEMPERATURE SURGE,
WITH RATHER LOW CEILINGS HANGING ON FARTHER INLAND. THEREFORE, MVFR
OR LOWER CEILINGS WILL CONTINUE EVERYWHERE OVERNIGHT AND WEDNESDAY
MORNING BEFORE IMPROVEMENT IS EXPECTED. THE RAIN WILL BE HEAVY AT
TIMES WITH EVEN A FEW ISOLATED THUNDERSTORMS POSSIBLE. SINCE THE
COVERAGE OF ANY CONVECTION LOOKS LOW, WE DID NOT INCLUDE A MENTION
WITH THE 00Z ISSUANCE. THE LOCAL VISIBILITIES WILL BE AFFECTED BY
THE RAIN INTENSITIES. SOME OF THE MILDER LOW-LEVEL AIR COMING IN
FROM THE SOUTH AND SOUTHEAST WILL ALLOW FOR SURFACE GUSTS TO AROUND
20 KNOTS TONIGHT MAINLY AT KACY AND KMIV.
A ROBUST LOW-LEVEL JET FROM THE SOUTH AND THEN SOUTHWEST WILL MOVE
ACROSS THE AREA OVERNIGHT AND FOR A TIME WEDNESDAY MORNING. THIS IS
FORECAST TO BE STRONGEST FROM THE KPHL AREA ON EASTWARD, THEREFORE
THE LOW-LEVEL WIND SHEAR WAS MAINTAINED BUT INCREASED A BIT FOR
THESE TERMINALS AND SHOWN TO BE A BIT WEAKER FOR KABE AND KRDG. THIS
SHOULD END DURING WEDNESDAY MORNING FROM WEST TO EAST AS THE COLD
FRONT SLIDES THROUGH. THE RAIN SHOULD TRANSITION TO SHOWERS
WEDNESDAY AS THE STORM MOVES THROUGH. THERE SHOULD BE A SHARP EDGE
TO THE TRAILING SHOWERS, THEREFORE THESE WERE ENDED IN THE AFTERNOON
ALONG WITH IMPROVING CONDITIONS. AS THE CEILINGS AND VISIBILITIES
IMPROVE, THE WINDS WILL SHIFT FROM THE SOUTHWEST TO THE NORTHWEST
AND INCREASE AND TURN GUSTY.
OUTLOOK...
WEDNESDAY NIGHT...ANY LINGERING MVFR CONDITIONS IN LEFTOVER SHOWERS
SOUTH AND EAST OF KPHL IN THE EVENING QUICKLY SHIFTS SOUTHEASTWARD
AND OUT TO SEA. GUSTY NORTHERLY WINDS DURING THE EVENING /GENERALLY
TO 25 KNOTS/, WILL THEN DIMINISH LATER AT NIGHT.
THURSDAY THROUGH SUNDAY...VFR WITH SOME HIGH LEVEL CLOUDS POSSIBLE
FRIDAY NIGHT AND SATURDAY. NORTHWEST WIND GUSTS TO 20 KNOTS POSSIBLE
DURING THE DAY THURSDAY, THEN LESS WIND FRIDAY AND SATURDAY AS HIGH
PRESSURE SETTLES OVER THE AREA. A SOUTHERLY FLOW DEVELOPS FOR SUNDAY
WITH SOME INCREASE AHEAD OF THE NEXT APPROACHING COLD FRONT.
&&
.MARINE...
E TO SE WINDS 15 TO 20 KT EARLY THIS EVENING WITH SOME GUSTS TO 25
KNOTS WILL CONTINUE TONIGHT. SOME GUSTS TO 25 KT ARE OCCURRING ON
DELAWARE BAY AS WELL. THEREFORE, THE SMALL CRAFT ADVISORY REMAINS
IN PLACE FOR ALL OUR ZONES. LOW PRESSURE, MOVING EAST FROM THE
OHIO VALLEY, WILL CROSS OUR AREA WEDNESDAY AND THEN TRACK OFF TO
THE EAST AND NORTHEAST. WINDS WILL BECOME SOUTHERLY DURING TONIGHT
AND THEN SOUTHWEST AS THE FRONT APPROACHES WEDNESDAY MORNING. THEY
WILL THEN SHIFT TO THE NORTHWEST BEHIND THE FRONT WEDNESDAY
AFTERNOON. THE PRESSURE GRADIENT WILL TIGHTEN BEHIND THE FRONT AND
WIND GUSTS COULD APPROACH GALE FORCE TOWARD EVENING.
OUTLOOK...
THE GALE WATCH IS BASED ON PRIOR MODEL CYCLE INDICATIONS OF GALE
POTENTIAL FOR WEDNESDAY NIGHT AND CONFIRMATION FROM THE 12Z/22 GFS
AND NAM 950MB-SST TRANSFER PROFILES. ATTM...THINKING IS 1-3 HRS OF
NORTHERLY GALE GUSTS IN THE 23Z-03Z TIME FRAME NNJ WATERS VICINITY
SANDY HOOK...AROUND 35 KTS. HOWEVER...S NJ FROM BARNEGAT SOUTHWARD
TO THE DE WATERS...THINKING 02Z-08Z TIME FRAME WHERE THERE IS A
BETTER CHC OF CRITERIA WIND GUSTS FOR 2-5 HRS. THE ECMWF 925 MB
WIND FIELD SHOWS AROUND 35 KNOTS DURING WEDNESDAY NIGHT, ALTHOUGH
THE FORECAST SOUNDINGS DO NOT APPEAR TO BE AS STRONG WITH THE
MIXING. HOWEVER, THE POTENTIAL FOR 35 KNOT SURFACE GUSTS ARE
THERE. WE MAY UPGRADE THE GALE WATCH TO A WARNING LATER THIS
EVENING AFTER CHECKING SOME ADDITIONAL GUIDANCE.
THURSDAY...DIMINISHING WIND AND SEAS AND EVENTUALLY SCA CONDS SHOULD
END...CERTAINLY ON DE BAY BY FORENOON THURSDAY BUT 5 FT SEAS MAY
LINGER TIL THU NIGHT ON THE ATLC WATERS...ESP E OF DELAWARE.
FRIDAY-SATURDAY...NO HEADLINES ANTICIPATED AS A GENERAL LIGHT
WESTERLY FLOW DEVELOPS WITH HIGH PRESSURE BUILDING TO OUR SOUTH.
&&
.HYDROLOGY...
A COMPLEX LOW PRESSURE SYSTEM WILL INTO OUR REGION LATE TONIGHT AND
PRODUCE A COPIOUS AMOUNT OF RAINFALL THROUGH WEDNESDAY AFTERNOON.
PWATS ACROSS SOUTHEAST PENNSYLVANIA AND NORTHERN NEW JERSEY CLIMB TO
NEARLY 1.5 INCHES WHICH QUITE HIGH FOR THIS TIME OF THE YEAR. THIS
COULD LEAD TO A WIDESPREAD 1 TO 3 INCHES OF RAIN ACROSS MUCH OF OUR
CWA THROUGH WEDNESDAY AFTERNOON. MUCH LIKE IN THE PAST, OUR TARGET
AREA IS HONED IN ON SE PA AND N NJ WHICH SEEMS TO ALWAYS TAKE A
BEATING WITH THE HIGHEST RAINFALL AMOUNTS. THE AIRMASS WILL BE
MOISTENING MORE AND WARMING UP TONIGHT AS THE ASSOCIATED WARM FRONT
MOVES OVERHEAD SO WE COULD SEE A FEW ISOLATED THUNDERSTORMS DEVELOP
WHICH COULD PRODUCE 3 PLUS INCH LOCALIZED RAINFALL AMOUNTS.
MAIN CONCERN FOR FLOODING ARE THE SMALLER STREAMS, URBAN AREAS,
AND POOR DRAINAGE AREAS. ROADWAY AND POOR DRAINAGE FLOODING WILL
BE ENHANCED BY ANY LEAVES CLOGGING STORM DRAINS. THE LARGER RIVERS
WILL RISE A BIT BUT FOR THE MOST PART THEY SHOULD REMAIN IN THEIR
BANKS. THERE COULD BE A FEW MORE ISSUES IN NORTHEAST NEW JERSEY
WHERE PARTS OF THE PASSAIC AND RAMAPO NEAR CAUTION/MINOR FLOOD
STAGE, BUT THIS DOES NOT APPEAR TO BE WIDESPREAD.
&&
.TIDES/COASTAL FLOODING...
WE ARE IN A HIGH ASTRONOMICAL HIGH TIDE CYCLE THIS WEEK, AS WE
APPROACH THE NEW MOON. THE HIGH TIDES OF CONCERN, AS FAR AS COASTAL
FLOODING, WILL BE THE EARLY MORNING HIGH TIDES WEDNESDAY AND
THURSDAY. GUIDANCE IS NOW SHOWING THAT WATER LEVELS WILL APPROACH
MINOR TIDAL FLOOD HEIGHTS AROUND THE TIME OF HIGH TIDE WEDNESDAY
MORNING ALONG OUR OCEAN FRONT AND ON DELAWARE BAY, THE BACK BAYS,
AND THE LOWER DELAWARE RIVER. IF FLOODING DOES OCCUR, IT IS NOT
EXPECTED TO BE WIDESPREAD OR CAUSE A SIGNIFICANT AMOUNT OF DAMAGE.
WE HAVE ISSUED A COASTAL FLOOD STATEMENT PERTAINING TO THIS HIGH
TIDE CYCLE. IT DOES NOT APPEAR AS THOUGH TIDAL FLOODING WILL BE A
PROBLEM FOR THE CHESAPEAKE BAY.
THE NEXT TIDE OF INTEREST IS THE THURSDAY MORNING TIDE. WINDS SHOULD
BE NORTH...WHICH MAY RESULT IN AN EKMAN SPIRAL IN THE UPPER PORTION
OF THE OCEAN. THIS WOULD RESULT IN A GENERAL PUSH OF WATER TOWARD
THE BEACH. IN ADDITION...THE HIGH TIDE THURSDAY MORNING IS A BIT
HIGHER THAN WEDNESDAY MORNING. THE PREPONDERANCE SUGGESTS THIS TIDE
WILL ALSO SEE MINOR TIDAL FLOODING...MAINLY ALONG THE OCEAN FRONT...
MAINLY ON THE ORDER OF A HALF A FOOT ABOVE THE MINOR FLOOD STAGE.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...FLASH FLOOD WATCH FROM 10 PM EST THIS EVENING THROUGH
WEDNESDAY AFTERNOON FOR PAZ060>062-067>071.
NJ...FLASH FLOOD WATCH FROM 10 PM EST THIS EVENING THROUGH
WEDNESDAY AFTERNOON FOR NJZ001-007>010-012-015.
DE...NONE.
MD...NONE.
MARINE...GALE WATCH FROM WEDNESDAY EVENING THROUGH LATE WEDNESDAY NIGHT
FOR ANZ431-450>455.
SMALL CRAFT ADVISORY UNTIL 6 PM EST WEDNESDAY FOR ANZ430-431-
450>455.
&&
SYNOPSIS...DRAG
NEAR TERM...IOVINO
SHORT TERM...RPW
LONG TERM...DRAG
AVIATION...DRAG/GORSE
MARINE...DRAG/GORSE/RPW
HYDROLOGY...HEAVENER
TIDES/COASTAL FLOODING...RPW