Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 022046 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 346 PM EST TUE FEB 2 2016 .SYNOPSIS...
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STRONG LOW PRESSURE WAS LOCATED OVER NORTHEASTERN KANSAS THIS AFTERNOON. THE SYSTEM WILL TRACK NORTHEASTWARD ACROSS THE GREAT LAKES ON WEDNESDAY AND INTO EASTERN CANADA FOR WEDNESDAY NIGHT AND THURSDAY. THE LOW IS FORECAST TO PULL A WARM FRONT THROUGH OUR REGION ON WEDNESDAY MORNING FOLLOWED BY A COLD FRONT LATE ON WEDNESDAY NIGHT. HIGH PRESSURE IS EXPECTED TO BUILD ACROSS OUR REGION FROM THE WEST AND SOUTHWEST FOR THURSDAY, FRIDAY AND SATURDAY. A COLD FRONT FROM THE NORTHWEST IS ANTICIPATED TO ARRIVE ON SUNDAY. COMPLEX LOW PRESSURE MAY APPROACH FROM THE WEST AND SOUTH EARLY IN THE NEW WEEK.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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MID-LEVEL RIDGE WILL CREST OVER THE AREA THIS EVENING WITH THE FLOW ALOFT BECOMING SOUTHWEST TOWARD DAWN. HIGH LEVEL CLOUDS NOTED ON SATELLITE WILL OVERSPREAD THE REGION THIS EVENING, WHILE THE LOW- MID LEVELS BEGIN TO SATURATE AFTER MIDNIGHT NORTHWEST OF I-95. WITH SOME RADIATIONAL COOLING EARLY EXPECT TEMPS TO PLUMMET, THEN LEVEL OUT AND RISE TOWARD DAWN, AS CLOUDS LOWER AND THICKEN. THE SURFACE FLOW WILL GRADUALLY VEER, GENERALLY FROM THE NORTHEAST TO SOUTHEAST OVERNIGHT. DO EXPECT SOME FOG TO DEVELOP NORTHWEST OF I95, WHERE THERE IS SNOW COVER, AND WE RADIATE BEST. IN FACT, MAY SEE THE FOG INCREASE TOWARD 12Z, AS HIGHER DEW POINTSBEGIN TO ADVECT IN OVER THE SNOW COVER. IN TERMS OF PRECIP, HAVE SCALED BACK POPS SOME, AND KEPT WEST OF A NEWARK-PHILADELPHIA- GEORGETOWN LINE IN THE 06Z-12Z TIME FRAME.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
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HIGH CONFIDENCE FOR COMBINATION OF BRIEF HEAVY RAIN AND SNOWMELT LEADING TO FLOODING ISSUES, AS WELL AS RECORD WARMTH. A MID-LEVEL CLOSED LOW AND ATTENDANT 995 MB SURFACE LOW TRAVERSES LAKE HURON. OUR REGION WILL BE LOCATED WITHIN THE LEFT EXIT REGION OF THE UPPER LEVEL JET MAXIMA, WHILE A LOW-LEVEL 70 KT SOUTHWESTERLY CRANKS OVERHEAD. THE STRONGEST LIFT WILL OCCUR ALONG/NORTHWEST OF I95, WHERE LOW-LEVEL SOUTH-SOUTHWEST FLOW IS LIFTED ALONG THE TERRAIN, AND NEAR AN APPARENT PRE-FRONTAL TROUGH. THIS IS WHERE WE EXPECT THE HEAVIEST RAINFALL, A GENERAL 1 TO 1.5 INCHES WITH THE HIGHEST AMOUNTS OVER THE LEHIGH VALLEY AND POCONOS, AND AMOUNTS TAPERING TO 0.75 INCHES OVER SOUTHERN DELMARVA. DUE TO SNOWMELT AND TEMPERATURES WELL ABOVE AVERAGE, A FLOOD WATCH REMAINS IN EFFECT FOR PORTIONS OF THE AREA. FURTHER DETAILS IN A SEPARATE HYDRO SECTION BELOW. WE CONTINUE THE CHANCE OF THUNDER IN THE FORECAST WED AFTERNOON AND EVENING, CONFINED TO DELMARVA AND FAR SOUTHERN NJ, WHERE WE EXPECT MAINLY ELEVATED CONVECTION. CANNOT RULE OUT SOME 35 KNOT WIND GUSTS IN HEAVIER SHOWERS AND/OR THUNDERSTORMS ACROSS THIS AREA. FORECAST CONTINUES FOR RECORD HIGH TEMPERATES TOMORROW AT SEVERAL CLIMATE SITES FURTHER DETAILS IN A SEPARATE CLIMATE SECTION BELOW.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
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IT IS LIKELY THAT RAIN WILL STILL BE FALLING IN OUR REGION ON WEDNESDAY EVENING, ESPECIALLY FROM THE INTERSTATE 95 CORRIDOR EASTWARD. THE ENTRANCE REGION OF A 60+ KNOT LOW LEVEL JET IS FORECAST TO BE OVER SOUTHERN NEW JERSEY AND DELAWARE AT THAT TIME ALONG WITH AN AXIS OF 1.5+ INCH PRECIPITABLE WATER VALUES. THE LOW LEVEL JET SHOULD LIFT TO OUR NORTHEAST ON WEDNESDAY NIGHT AND THE HIGH PRECIPITABLE WATER VALUES WILL LIKELY SHIFT TO OUR EAST AND OFF THE COAST. THE COLD FRONT THAT WILL BE APPROACHING FROM THE WEST IS ANTICIPATED TO PASS THROUGH EASTERN PENNSYLVANIA, NORTHEASTERN MARYLAND, DELAWARE AND NEW JERSEY BETWEEN ABOUT 100 AM AND 500 AM THURSDAY. THE RAIN IS EXPECTED TO COME TO AN END FROM WEST TO EAST ACROSS OUR REGION ON WEDNESDAY NIGHT. AN ADDITIONAL 0.10 TO 0.25 INCHES OF RAIN MAY FALL AFTER 700 PM WEDNESDAY TO THE NORTHWEST OF THE INTERSTATE 95 CORRIDOR. ADDITIONAL AMOUNTS OF 0.25 TO 0.50 INCHES ARE POSSIBLE ON THE COASTAL PLAIN. THE POTENTIAL FOR LIGHT RAIN WILL LINGER ALONG AND NEAR THE COAST INTO THURSDAY AS THE COLD FRONT DRIFTS OUT OVER THE OCEAN. THE SOUTHWESTERLY MID LEVEL FLOW WILL SLOW THE PROGRESS OF THE FRONT AND THE ASSOCIATED CLEARING BEHIND IT. THE LAST OF THE MID AND HIGH LEVEL CLOUDS ARE EXPECTED TO PASS TO OUR EAST ON THURSDAY NIGHT AS A MID LEVEL TROUGH APPROACHES FROM THE WEST. THE AXIS OF THE TROUGH IS FORECAST TO PASS OVERHEAD ON FRIDAY MORNING. DRY WEATHER CONDITIONS ARE ANTICIPATED FOR FRIDAY AND SATURDAY AS HIGH PRESSURE FROM THE WEST BUILDS ACROSS THE SOUTHEASTERN AND MIDDLE ATLANTIC STATES. A DRY COLD FRONT IS FORECAST TO DROP INTO OUR REGION ON SUNDAY WITH HIGH PRESSURE NOSING DOWN FROM THE NORTH FOR SUNDAY NIGHT INTO MONDAY. THE GUIDANCE IS IN AGREEMENT IN DEVELOPING LOW PRESSURE OFF THE SOUTHEAST COAST ON SUNDAY AND MOVING IT OUT TO SEA WITH LITTLE IMPACT ON OUR WEATHER. ANOTHER LOW PRESSURE IS EXPECTED TO PASS ACROSS THE GREAT LAKES EARLY IN THE NEW WEEK WITH A SECONDARY LOW POSSIBLY APPROACHING OUR REGION FROM THE SOUTHWEST. AS A RESULT, WE ARE ANTICIPATING SOME PRECIPITATION AT THAT TIME. THE DETAILS ARE A LOW CONFIDENCE FORECAST AT THIS TIME. THE TEMPERATURE PROFILES SUGGEST PRIMARILY RAIN.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TONIGHT...MVFR CEILINGS DEVELOP KPHL NORTHWARD, WHERE -SHRA EXPECTED BY 12Z. SOME FOG MAY DEVELOP AT TTN, RDG, AND ABE, AND VSBYS IN TAFS MAY NEED TO BE ADJUSTED DOWNWARD TO REFLECT THIS. LOW CONFIDENCE DUE TO AIR MASS INTERACTING WITH SNOW COVER OVER AFOREMENTIONED AREA. THE WIND GRADUALLY VEERS NORTHEAST TO SOUTHEAST, GENERALLY AOB 15 KNOTS. WEDNESDAY...OCCASIONAL MVFR AND POSSIBLY IFR CONDITIONS IN SHRA AND FOG. THE FOG WILL BE MAINLY CONFINED TO TTN, RDG, AND ABE. THERE IS ALSO A CHANCE OF LIGHTNING, MAINLY AT ILG, MIV, AND ACY. SOUTHERLY WINDS MAY GUST TO 30 KNOTS, ESPECIALLY AT KPHL AND POINTS SOUTH. WE DID NOT INCLUDE LLWS, PER OUR IN HOUSE TOOL. OUTLOOK... WEDNESDAY NIGHT...MVFR AND IFR CONDITIONS IN THE EVENING DUE TO RAIN, LOW CLOUDS AND FOG. CONDITIONS IMPROVING TO VFR LATE AT NIGHT. THURSDAY THROUGH SUNDAY...MAINLY VFR.
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&& .MARINE...
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TONIGHT...SOUTHEAST WINDS 10 TO 15 KNOTS...WINDS AND SEAS BELOW SMALL CRAFT ADVISORY /SCA/ THRESHOLD. WEDNESDAY...SOUTHERLY LOW-LEVEL JET TRAVERSES THE WATERS, BUT COOLER SSTS WILL LIMIT MIXING. EXPECT WIND GUSTS OF 25 TO 30 KNOTS AND SEAS AROUND 8 FT. LOW PROBABILITY OF GALE FORCE GUSTS, MAINLY IN THE AFTERNOON AND EVENING, WHEN THERE IS A SLIGHT CHANCE OF THUNDERSTORMS OVER THE DE AND SOUTH NJ WATERS. SCA GOES INTO EFFECT AT 11Z WEDNESDAY. OUTLOOK... WEDNESDAY NIGHT...A SMALL CRAFT ADVISORY WILL REMAIN IN EFFECT UNTIL MIDNIGHT ON DELAWARE BAY. A SMALL CRAFT ADVISORY WILL REMAIN IN EFFECT FOR OUR OCEAN WATERS FOR THE ENTIRE NIGHT. THURSDAY...A SMALL CRAFT ADVISORY WILL REMAIN IN EFFECT FOR OUR OCEAN WATERS MAINLY FOR WAVE HEIGHTS IN THE 5 FOOT RANGE. THURSDAY NIGHT AND FRIDAY...A NORTHWEST WIND MAY GUST NEAR 25 KNOTS. FRIDAY NIGHT THROUGH SUNDAY...NO MARINE HEADLINES ARE ANTICIPATED.
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&& .HYDROLOGY...
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IMPACTS...THE THREAT OF MINOR TO MODERATE RIVER FLOODING CONTINUES FOR THE PASSAIC AND RARITAN BASINS IN NJ. THE THREAT OF MINOR RIVER FLOODING CONTINUES FOR THE SCHUYLKILL BASIN IN PA. ADJACENT BASINS(TO THOSE MENTIONED ABOVE) IN NJ AND ACROSS SOUTHEAST PA, SHOULD ALSO KEEP UP WITH THE LATEST FORECASTS IN CASE THE FLOOD POTENTIAL EXPANDS. FORECAST...WHEN THURSDAY ROLLS AROUND, IT APPEARS MUCH IF NOT ALL THE SNOW THAT IS ON THE GROUND ACROSS THE HSA WILL BE GONE. THE SNOW HAS REALLY RIPENED THE LAST 24 HOURS AND IS READY TO GO. THIS SNOWMELT COMBINED WITH 0.75 TO 1.5 INCHES OF RAIN EXPECTED WEDNESDAY INTO WEDNESDAY NIGHT CONTINUES TO RAISE A FEW RED FLAGS. THE THREAT OF FLOODING WILL BE TWO-FOLD, FIRST ON WEDNESDAY INTO WEDNESDAY NIGHT, AND THEN WEDNESDAY NIGHT INTO THURSDAY. THE FIRST THREAT WILL INCLUDE LOW-LYING, POOR DRAINAGE, STREET, AND SMALL CREEK FLOODING. THIS WILL PROBABLY HAVE AN IMPACT ON THE WEDNESDAY EVENING COMMUTE. THE THREAT STEMS FROM RAPIDLY MELTING SNOW, PERIODS OF HEAVY RAIN, A FROZEN GROUND, AND POSSIBLY CLOGGED OR RESTRICTED STORM DRAINS. THE SECOND THREAT STEMS FROM THE RUNOFF MAKING IT TO THE LARGER RIVERS. IT`S AT THIS TIME, WEDNESDAY NIGHT INTO THURSDAY, WHERE WE COULD SEE SOME OUR RIVER FORECAST POINTS EXCEED FLOOD STAGE. SNOW WATER EQUIVALENT, OR SWE, IS HIGHEST RIGHT ALONG THE I78 CORRIDOR AND LOCATIONS JUST TO THE NORTH AND SOUTH. GENERALLY, SWE VALUES ARE RUNNING BETWEEN 1.5 AND 2.0 INCHES HERE. COMBINE THIS WITH THE EXPECTED RAINFALL, THIS AREA COULD HAVE TO DEAL WITH OVER 3.00 INCHES OF POTENTIAL RUNOFF. HEADLINES...A FLOOD WATCH CONTINUES AND WE HAVE ALSO ADDED CECIL COUNTY IN MARYLAND. THE WATCH IS FROM MIDDAY WEDNESDAY THROUGH THURSDAY AFTERNOON COVERING BOTH OF THE POTENTIAL FLOOD THREATS MENTIONED ABOVE. AT THIS POINT, THE MOTIVATION FOR THE WATCH IS TO INITIATE PREPARATION FOR THE POSSIBILITY OF FLOODING. HSA BREAKDOWN...UPPER EASTERN SHORE OF MARYLAND (KENT, QUEEN ANNE`S, TALBOT AND CAROLINE)...SOME NUISANCE FLOODING IS POSSIBLE WEDNESDAY INTO WEDNESDAY NIGHT. THE FLOOD WATCH INCLUDES CECIL COUNTY WHERE BOTH THE HEAVIER RAIN IS EXPECTED AND REMAINING SWE IS HIGHEST. DELAWARE...SOME NUISANCE FLOODING IS POSSIBLE WEDNESDAY INTO WEDNESDAY NIGHT, ESPECIALLY IN NEW CASTLE COUNTY WHERE BOTH THE RAIN IS EXPECTED AND REMAINING SWE IS HIGHEST. SMALL CREEKS AND STREAMS WILL LIKELY SEE RISES APPROACHING BANKFULL OR LEVELS THAT EXCEED BANKFULL, ESPECIALLY ACROSS NORTHERN NEW CASTLE. NEW JERSEY...NUISANCE FLOODING IS LIKELY WEDNESDAY INTO WEDNESDAY NIGHT ACROSS THE WATCH AREA. SMALL CREEKS AND STREAMS WILL LIKELY SEE RISES APPROACHING BANKFULL OR LEVELS THAT EXCEED BANKFULL. IN ADDITION, THERE IS A THREAT OF RIVER FLOODING WEDNESDAY NIGHT INTO THURSDAY. THIS THREAT LIES ACROSS PORTIONS OF THE PASSAIC AND RARITAN BASINS. NO FLOODING IS EXPECTED ALONG THE DELAWARE. PENNSYLVANIA...NUISANCE FLOODING IS LIKELY WEDNESDAY INTO WEDNESDAY NIGHT ACROSS THE WATCH AREA. SMALLER CREEKS AND STREAMS SUCH AS THE NESHAMINY, PERKIOMEN, BRANDYWINE, AND CHESTER WILL LIKELY SEE RISES APPROACH BANKFULL OR LEVELS THAT EXCEED BANKFULL. IN ADDITION, THERE IS A THREAT OF RIVER FLOODING WEDNESDAY NIGHT INTO THURSDAY. THIS THREAT LIES ACROSS THE SCHUYLKILL BASIN. NO FLOODING IS EXPECTED ALONG THE DELAWARE.
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&& .CLIMATE...
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LISTED BELOW ARE THE RECORD HIGH TEMPERATURES AND RECORD RAINFALL FOR WEDNESDAY. THESE RAINFALL AMOUNTS ARE NOT LIKELY TO BE EXCEEDED AT MOST IF NOT ALL 8 SITES LISTED, DUE IN PART TO THE VERY FAST MOVEMENT OF THE RAIN. RECORD MAX RECORD RAIN PERIOD OF RECORD ---------- ----------- ---------------- ACY...66-2006 1.61-1880 1874 PHL...62-2006 1.64-1939 1872 ILG...64-1991 1.40-1939 1894 ABE...63-1991 1.37-1982 1922 TTN...62-2006 1.57-1939 1865 GED...68-2006 1.47-1973 1948 RDG...63-1991 1.40-1939 1869 MPO...52-1973 2.19-1983 1901
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...FLOOD WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY AFTERNOON FOR PAZ060-061-070-071-101>106. NJ...FLOOD WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY AFTERNOON FOR NJZ009-010-012-013-015>019. DE...FLOOD WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY AFTERNOON FOR DEZ001. MD...FLOOD WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY AFTERNOON FOR MDZ008. MARINE...SMALL CRAFT ADVISORY FROM 6 AM WEDNESDAY TO 6 PM EST THURSDAY FOR ANZ450>455. SMALL CRAFT ADVISORY FROM 6 AM WEDNESDAY TO MIDNIGHT EST WEDNESDAY NIGHT FOR ANZ430-431.
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&& $$ SYNOPSIS...IOVINO NEAR TERM...FRANCK SHORT TERM...FRANCK LONG TERM...IOVINO AVIATION...FRANCK/IOVINO MARINE...DRAG/FRANCK/IOVINO HYDROLOGY...KRUZDLO CLIMATE...STAFF

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