Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 012028 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 328 PM EST SUN FEB 1 2015 .SYNOPSIS... LOW PRESSURE WILL MOVE THROUGH THE OHIO VALLEY TONIGHT AND CROSS OUR AREA ON MONDAY BEFORE RACING OFF TO THE NORTHEAST MONDAY NIGHT. HIGH PRESSURE WILL BUILD ACROSS TO THE SOUTH OF OUR AREA TUESDAY THROUGH WEDNESDAY. A CLIPPER SYSTEM WILL MOVE ACROSS THE GREAT LAKES REGION ON WEDNESDAY, DRAGGING A COLD FRONT ACROSS OUR AREA ON THURSDAY. HIGH PRESSURE WILL THEN RETURN FOR FRIDAY. ANOTHER FRONTAL SYSTEM WILL CROSS THE REGION OVER THE WEEKEND. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... A RATHER COMPLEX FORECAST AS SUBTLE CHANGES IN THE THERMAL PROFILES/MICROPHYSICS WILL AFFECT THE PRECIPITATION TYPES. THIS FORECAST CARRIES LOWER CONFIDENCE REGARDING THE TIMING OF THE MIXING OR CHANGEOVER AND THE SOUTHERN EXTENT OF ANY LIGHT ICING. THE WATER VAPOR IMAGERY THIS AFTERNOON SHOWS A WELL DEFINED UPPER-LEVEL LOW NEAR THE MID-MISSISSIPPI VALLEY. THIS FEATURE LOOKS RATHER SHARP AS A STRONGER UPPER-LEVEL JET ROTATES INTO THE BASE OF THE TROUGH. THIS RESULTS IN A BIT MORE RIDGING IN FRONT OF THE STORM, THEREFORE A NORTHWARD TRACK OF THE SURFACE LOW. HOWEVER, A PRONOUNCED AND TIGHTENING BAROCLINIC ZONE IS PRESENT EASTWARD WITH ARCTIC AIR TO THE NORTH. THIS AT TIMES DOES FORCE THE SURFACE LOW TRACK A LITTLE FARTHER TO THE SOUTH, HOWEVER GIVEN THE AMPLITUDE OF THE TROUGH THE WARMING ALOFT LOOKS TO OVERSPREAD THE ENTIRE AREA. AS A RESULT, THE SNOW THAT DEVELOPS WILL MIX WITH AND CHANGE TO SLEET AND FREEZING RAIN NORTHWARD WITH EVEN THE PLAIN RAIN PHASE GETTING RATHER FAR NORTH TOWARD DAYBREAK. BACKING UP A BIT, THE INCREASING WAA AND ISENTROPIC UPGLIDE WILL RESULT IN A SWATH OF OVERRUNNING SNOW AS THE LIFT BECOMES FOCUSED ALONG THE THERMAL GRADIENT. SO FAR THIS IS WEAK WITH ENOUGH DRYING TO ERODE MUCH OF THE INCOMING PRECIPITATION. THE LOWER LEVELS THOUGH ARE MOISTENING SOME, WITH SOME FLURRIES OR LIGHT SNOW AT TIMES INTO PARTS OF OUR WESTERN ZONES THIS AFTERNOON. THIS SNOW COULD THEN COME IN FAIRLY FAST LATER THIS EVENING WITH PERHAPS A THUMP OF SNOW /SNOWFALL RATES AROUND AN INCH PER HOUR/ FARTHER NORTH TAILING OFF TO A PERIOD OF LIGHTER SNOW TO RAIN SOUTHWARD. THERE MAY BE SOME HEAVIER BANDING ACROSS THE NORTH FOR A TIME OVERNIGHT BEFORE WARMING ALOFT GETS MORE INVOLVED. THE WARMING LOOKS PRONOUNCED ALOFT TO ALLOW A QUICKER CHANGEOVER FROM SOUTH TO NORTH OVERNIGHT. THEREFORE, PORTIONS OF SOUTHEASTERN PENNSYLVANIA ON SOUTH AND EAST SHOULD BE EITHER MIXING OR CHANGING TO RAIN WELL BEFORE DAYBREAK AS TEMPERATURES CLIMB TO OR ABOVE FREEZING. SOME PAUSE IS NEEDED THOUGH AS EVEN THE FARTHER NORTH GUIDANCE SHOWS SOME COLD AIR DAMMING HOLDING ON JUST ENOUGH FROM THE LEHIGH VALLEY AREA NORTHWARD WHICH WOULD SLOW THE SURFACE TEMPERATURE RISE. THIS COULD BE ENHANCED BY THE SNOW COVER THAT EXISTS AND THE GROUND BEING COLD. THIS WILL HAVE TO BE WATCHED BECAUSE IF THE WARMER AIR FLOODS NORTHWARD FASTER, THAN MORE OF AN ICING THREAT INCREASES WHILE ACCUMULATING SNOW/SLEET DECREASES. WE LEANED MORE TOWARD A GFS/ECMWF BLEND. THIS TENDS TO FAVOR A QUICKER CHANGEOVER INTO THE PHILADELPHIA METRO, WITH EVEN THE SLEET TO FREEZING RAIN DRIVING FARTHER NORTH FASTER. AS A RESULT OF A MODEL CONSENSUS AND COLLABORATION WITH OUR NEIGHBORING OFFICES, WE CUT BACK ON THE SNOW AMOUNTS AND ADDED MORE ICING. REGARDING THE WINTER WEATHER ADVISORIES AND WINTER STORM WARNINGS, WE WILL MAINTAIN THEM WHERE THEY ARE FOR NOW BUT DID DO SOME REGROUPING ALONG WITH SOME ADJUSTMENTS TO THE END TIMES. WE ARE CONCERNED THAT THE SOUTHERN TIER OF ADVISORIES MAY NOT BE NEEDED BUT WILL HOLD FOR NOW SINCE THERE IS A CHC OF A BRIEF MIX/ICING BEFORE JUST RAIN OCCURS. IF THE GROUND IS COLD ENOUGH, IT DOES NOT TAKE MUCH ICING TO CAUSE ISSUES. THE SOUTHERN TIER OF THE WARNINGS MAY END UP FALLING SHORT OF CRITERIA HOWEVER BASED ON COMBINED IMPACTS OF SNOW AND ICE WE STAYED THE COURSE ATTM. AS FOR THE LOW TEMPERATURES, WE USED A NAM/GFS MOS AND ECMWF BLEND. THE HOURLY GRIDS WERE SET TO SHOW TEMPERATURES RISING OVERNIGHT, WITH THIS TREND MORE PRONOUNCED FROM THE PHILADELPHIA METRO ON SOUTH AND EAST. THIS TREND WILL HAVE TO BE MONITORED AS IT WILL HAVE AN IMPACT ON THE PROJECTED ICING. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... THE AFOREMENTIONED SHORT WAVE TROUGH WILL MOVE ACROSS THE AREA DURING THE DAY MONDAY. THIS WILL TAKE SURFACE LOW PRESSURE RIGHT OVER OUR AREA, AND WITH WARMING OCCURRING MUCH OF THE CWA MAY GO OVER TO PLAIN RAIN FOR AWHILE. HOWEVER, FROM ABOUT THE LEHIGH VALLEY REGION NORTHWARD JUST ENOUGH COLD AIR DAMMING MAY GET TRAPPED DUE TO SNOW COVER AND ICE TO NOT ALLOW THE WARMER AIR ALOFT TO PENETRATE DOWN TO THE SURFACE. THIS COULD RESULT IN MORE ICING ACROSS THESE AREAS. IT APPEARS THAT FARTHER SOUTH, ANY MIXING EARLY SHOULD BE MAINLY RAIN BUT EVEN INTO THE I-95 AREA SOME CAUTION IS ADVISED EARLY AS A COLD GROUND MAY RESULT IN SOME ICY SPOTS DESPITE THE AIR TEMPERATURE RISING. WE THEN TURN OUR ATTENTION TO THE RAPID INCREASE IN CAA AS THE STORM DEPARTS. THE GUIDANCE IS IN GOOD AGREEMENT IN RAPIDLY INCREASING THE CAA, WHICH WOULD RESULT IN THE TEMPERATURES TUMBLING DURING THE AFTERNOON FROM WEST TO EAST. IF THIS OCCURS FAST ENOUGH, ANY RAIN OR MIXED PRECIPITATION WOULD CHANGE TO SNOW BEFORE ENDING. IN ADDITION, THE WET /SLUSHY/ SURFACES MAY UNDERGO A FLASH FREEZE AS TEMPERATURES RAPIDLY DROP BELOW FREEZING BY EVENING. THE EXTENT OF THE CAA SURGE COMBINED WITH PRESSURE RISES AND A TIGHT PRESSURE GRADIENT WILL RESULT IN A SHARP INCREASE IN THE WINDS MONDAY AFTERNOON AS THE LOW-LEVEL INVERSION BREAKS. THIS INCREASED MIXING SHOULD RESULT IN WIND GUSTS ON THE ORDER OF 30-40 MPH. WHILE THIS WILL HELP DRY SOME OF THE SURFACES OUT WITH TIME, A SUDDEN DROP IN TEMPERATURES TO BELOW FREEZING CAN STILL RESULT IN A FREEZE UP OF UNTREATED SURFACES. AS FOR THE HIGH TEMPERATURES, WE USED A NAM/GFS MOS AND ECMWF BLEND WITH SOME TWEAKS. THE TEMPERATURES WERE THEN SHOWN TO FALL IN THE AFTERNOON FROM WEST TO EAST, HOWEVER WE MAY NOT NECESSARILY BE CATCHING THE MAGNITUDE OF THIS DROP IN THE HOURLY GRIDS. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... MONDAY NIGHT...THE SURFACE LOW RACES OFF TO THE NORTHEAST AND WITH HIGH PRESSURE BUILDING IN FROM THE WEST. THE ATMOSPHERE DRIES OUT PRETTY QUICKLY AND THE PRECIPITATION WILL CUT OFF JUST AS FAST AS A RESULT. A FEW FLURRIES MAY CONTINUE INTO THE EVENING BUT EXPECT THEM TO PETER OUT BEFORE MIDNIGHT. SKIES WILL CLEAR AND TEMPERATURES WILL CONTINUE TO FALL OVERNIGHT. A FRESH SNOWPACK IN MANY AREAS WILL CONTRIBUTE TO VERY COLD OVERNIGHT TEMPERATURES AND WE WILL SEE TEMPERATURES PLUMMET INTO THE SINGLE DIGITS ACROSS OUR NORTHERN AREAS AND INTO THE LOWER TO MID TEENS ACROSS THE SOUTHERN AND COASTAL AREAS. IN ADDITION TO THE COLD TEMPERATURES, WE WILL LIKELY SEE FREEZING OF WET SURFACES AS THE TEMPERATURES FALL THROUGH THE NIGHT, MAKING EXPOSED AND UNTREATED SURFACES SLIPPERY. WINDS WILL REMAIN UP THROUGH THE OVERNIGHT PERIOD AND WE WILL LIKELY SEE WIND CHILLS INTO THE NEGATIVE TEENS ACROSS THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY. WIND CHILL ADVISORIES MAY BE NEEDED FOR MONDAY NIGHT INTO TUESDAY MORNING ACROSS THESE AREAS. TUESDAY...HIGH PRESSURE WILL BUILD ACROSS THE REGION TUESDAY, REMAINING CENTERED TO OUR SOUTH, WITH A SHIFT FURTHER SOUTH AND EAST TUESDAY NIGHT. PLENTY OF COLD AIR WILL ACCOMPANY THIS HIGH PRESSURE SYSTEM WITH 850MB TEMPERATURES IN THE -10C TO -15C RANGE. MAXIMUM TEMPERATURES WILL STRUGGLE TO RISE AND GENERALLY REMAIN IN THE 20S, WITH TEENS ACROSS THE LEHIGH VALLEY, SOUTHERN POCONOS AND NORTHWESTERN NEW JERSEY AND SOME LOWER 30S ACROSS OUR SOUTHERNMOST ZONES. THE AIR MASS WILL MODIFY A BIT AS IT SLIDES EASTWARD AND MINIMUM TEMPERATURES WILL NOT BE AS COLD TUESDAY NIGHT AS THEY ARE ON MONDAY NIGHT. IT WILL STILL BE COLD WITH LOWS RANGING FROM THE SINGLE DIGITS ACROSS THE HIGHER ELEVATIONS ACROSS THE NORTH TO THE LOWER 20S ACROSS THE SOUTHERN PART OF THE FORECAST AREA. WEDNESDAY AND THURSDAY...A SURFACE LOW PRESSURE SYSTEM WILL TRACK TO THE THE NORTH OF THE AREA ON WEDNESDAY WITH ITS ATTACHED COLD FRONT MOVING THROUGH OUR REGION ON THURSDAY. ANOTHER SYSTEM WILL DEVELOP IN THE GULF OF MEXICO AND THEN TRACK TOWARD THE CAROLINA COAST ON THURSDAY. THIS SECOND SYSTEM LOOKS TO REMAIN OFFSHORE AT THIS TIME. THE COLD FRONT WILL GET PULLED INTO THE COASTAL SYSTEM AND THEN EXIT QUICKLY TO THE NORTHEAST, REACHING THE CANADIAN MARITIMES BY THURSDAY NIGHT. SOME LIGHT SNOW WILL START TO PUSH INTO THE REGION AHEAD OF THE COLD FRONT ON WEDNESDAY BEFORE STARTING TO OVERSPREAD THE AREA ON THURSDAY. PRECIPITATION TYPE LOOKS TO BE MAINLY SNOW WITH MAYBE SOME RAIN MIXING IN ACROSS OUR FAR SOUTHERN AREAS. THE SNOW WILL END QUICKLY THURSDAY EVENING. TEMPERATURES MAXIMUM TEMPERATURES ON WEDNESDAY WILL BE QUITE WARM, OR AT LEAST FEEL THAT WAY. EXPECT HIGHS TO RISE ONTO THE MID 30S TO MID 40S ACROSS MUCH OF THE AREA. OVERNIGHT LIGHTS INTO THURSDAY MORNING WILL ONLY FALL INTO THE UPPER TEENS 20S ACROSS MOST OF THE REGION. FOR THURSDAY, WE WILL SEE A DEFINITELY DECLINE IN TEMPERATURES AS THE PRECIPITATION IMPACTS OUR AREAS. HIGHS WILL NOT RISE ALL THAT MICH AND WILL STRUGGLE TO REACH 30, ESPECIALLY AREAS ALONG AND TO THE NORTH AND WEST OF THE I-95 CORRIDOR. THURSDAY NIGHT WILL BE ANOTHER COLD ONE AND BUNDLING UP WILL DEFINITELY BE NEEDED. LOWS WILL BE IN THE 10S TO MID TEENS ACROSS OUR SOUTHERN AND COASTAL AREAS AND ONLY INTO THE SINGLE DIGITS AS YOU HEAD TO THE NORTH AND WEST. SOUTHERN POCONOS AND NORTHWEST NEW JERSEY MAY SEE TEMPERATURES FALL INTO THE MINUS SINGLE DIGITS OVERNIGHT. WIND CHILLS OVERNIGHT WILL MAKE IT FEEL EVEN COLDER AND AN ADVISORY MAY BE NEEDED ACROSS THE FAR NORTH. FRIDAY...HIGH PRESSURE WILL SLIDE ACROSS THE OHIO VALLEY AND THEN SHIFT TO OUR SOUTH FRIDAY NIGHT. HIGHS ON FRIDAY LOOK TO BE COLD ONCE AGAIN AS THE HIGH PUSHES TO THE EAST. TEMPERATURES INTO THE 20S CAN BE EXPECTED ACROSS THE FORECAST AREA. AS THE HIGH SLIDES TO THE SOUTH, A SOUTHWESTERLY FLOW WILL DEVELOP AND WE SHOULD SEE A BIT OF WARMER AIR REACH OUR AREA. WITH THIS SOUTHWEST FLOW, OVERNIGHT TEMPERATURES WON`T BE AS COLD AS THURSDAY NIGHT AND SHOULD RANGE FROM THE SINGLE DIGITS ACROSS THE NORTH TO AROUND 20 ACROSS THE SOUTH. SATURDAY AND SUNDAY...A LOW PRESSURE SYSTEM DROPS DOWN FROM CANADA AND TRACKS INTO NEW ENGLAND. ITS ATTACHED COLD FRONT LOOKS TO DROP DOWN INTO OUR AREA FROM THE NORTH SATURDAY INTO SUNDAY. PRECIPITATION THIS FAR OUT LOOKS TO BE SNOW AT THIS TIME. && .AVIATION /21Z SUNDAY THROUGH FRIDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THIS AFTERNOON - TONIGHT...VFR TO START BEFORE DROPPING TO MVFR/IFR AS LIGHT SNOW MOVES IN FROM THE WEST-SOUTHWEST LATER THIS EVENING. THE SNOWIEST TERMINALS WILL BE RDG/ABE WHILE THE I-95 TERMINALS SEE SOME SNOW, WITH A QUICK TRANSITION TO FREEZING RAIN TO RAIN...MIV/ACY SHOULD BE QUICK SNOW TO RAIN...MINIMAL MIXING EXPECTED. WINDS WILL OUT OF THE WEST EARLY AND BACKING TOWARDS THE SOUTH-SOUTHEAST LATE TONIGHT. MONDAY...IFR TRENDING TO MVFR LATE IN THE CYCLE. RDG/ABE WILL BE THE LAST TERMINALS TO CHANGE OVER TO ALL RAIN BY LATER MONDAY MORNING. WINDS BECOME LIGHTER AS THE CENTER OF THE LOW PRESSURE PASSING BY. MODERATE TO HEAVY RAIN MAY OCCUR LATE MORNING INTO THE EARLY AFTERNOON. STRONGER WEST-NORTHWEST WINDS KICK IN BEHIND THE SYSTEM WITH STRONG GUSTS EXPECTED LATE IN THE CYCLE. A CHANGEOVER BACK TO SOME SNOW SHOWERS IS POSSIBLE LATE AFTERNOON, IF ANY MOISTURE REMAINS. OUTLOOK... MONDAY NIGHT...MVFR TO VFR. LINGERING SNOW SHOWERS COME TO AN END WEST TO EAST. GUSTY NORTHWEST WINDS, UPWARDS OF 25 TO 30 KNOTS THROUGH EARLY TUESDAY MORNING BEFORE SUBSIDING. TUESDAY...VFR. WEDNESDAY - CHANCE OF SNOW SHOWERS WITH LOCAL MVFR/IFR RESTRICTIONS. THURSDAY - FRIDAY...VFR && .MARINE... TONIGHT - TUESDAY MORNING...CONVERTED THE GALE WATCH TO A WARNING ACROSS ALL OUR WATERS STARTING MONDAY EVENING. AHEAD OF THE NORTHWEST GALES A PERIOD OF SOUTH-SOUTHWESTERLY SCA GUSTS IS POSSIBLE. A DRAMATIC SHIFT IN THE WINDS IS EXPECTED BY LATE MONDAY AFTERNOON/EARLY EVENING AS A QUICK MOVING COLD FRONT PUSHES THROUGH. BEHIND THIS FRONT IS WHEN THE GALES KICK IN. THE STRONG GUSTS SHOULD BEGIN TO SUBSIDE BY MID-TUESDAY MORNING. LIGHT TO MODERATE FREEZING SPRAY IS LIKELY ON TUESDAY OUTLOOK... TUESDAY - WEDNESDAY...SUB SCA SEAS AND WINDS EXPECTED. THURSDAY - FRIDAY...POSSIBLE SCA CONDITIONS AS ANOTHER COLD FRONT IS EXPECTED TO MOVE THROUGH ON THURSDAY. FREEZING SPRAY IS POSSIBLE ON FRIDAY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 1 PM EST MONDAY FOR PAZ060>062-103-105. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 AM EST MONDAY FOR PAZ070-071. WINTER STORM WARNING FROM 7 PM THIS EVENING TO 4 PM EST MONDAY FOR PAZ054-055. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 10 AM EST MONDAY FOR PAZ101-102-104-106. NJ...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 1 PM EST MONDAY FOR NJZ007>010-012. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 AM EST MONDAY FOR NJZ013-014-016>020-026-027. WINTER STORM WARNING FROM 7 PM THIS EVENING TO 4 PM EST MONDAY FOR NJZ001. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 1 AM EST MONDAY FOR NJZ021-022-025. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 10 AM EST MONDAY FOR NJZ015. DE...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 AM EST MONDAY FOR DEZ001. MD...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 AM EST MONDAY FOR MDZ008. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 1 AM EST MONDAY FOR MDZ012. MARINE...GALE WARNING FROM 4 PM MONDAY TO 6 AM EST TUESDAY FOR ANZ430- 431-450>455. && $$ SYNOPSIS...MEOLA NEAR TERM...GORSE SHORT TERM...GORSE LONG TERM...MEOLA AVIATION...GORSE/HEAVENER MARINE...GORSE/HEAVENER

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