694 FXUS61 KPHI 112027 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 327 PM EST MON FEB 11 2013 .SYNOPSIS... LOW PRESSURE LOCATED OVER THE GREAT LAKES IS FORECAST TO PULL A WARM FRONT INTO OUR REGION TODAY, FOLLOWED BY A COLD FRONT THIS EVENING. WEAK HIGH PRESSURE IS EXPECTED FOR TUESDAY INTO WEDNESDAY. LOW PRESSURE FROM THE WEST IS FORECAST TO TRACK OFF THE MID ATLANTIC COAST WEDNESDAY NIGHT. ANOTHER WEAK AREA OF HIGH PRESSURE IS EXPECTED TO FOLLOW FOR THURSDAY INTO FRIDAY. A COLD FRONT FROM THE WEST IS ANTICIPATED TO ARRIVE FRIDAY NIGHT WITH A COLD NORTHWEST FLOW FORECAST FOR THE COMING WEEKEND. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... A 19Z SURFACE ANALYSIS PLACED LOW PRESSURE JUST NORTH OF THE CENTRAL GREAT LAKES WITH A COLD FRONT ACROSS WESTERN NEW YORK TO WESTERN VIRGINIA AND THE CAROLINAS. A WARM FRONT WAS DRAPED FROM CENTRAL PENNSYLVANIA, ACROSS THE DELMARVA, THEN NORTHWARD ACROSS EASTERN NEW JERSEY. AN UPPER AIR ANALYSIS PLACED A CLOSED LOW OVER THE GREAT LAKES WITH ANOTHER TROUGH ACROSS THE WEST. A STRONG 250 MB JET WAS FROM THE TENNESSEE VALLEY TO SOUTHERN NEW ENGLAND. THE WAA PUSH AT 850 MB WAS LOCATED IN NEW ENGLAND AND OFF OF OUR COAST. AN INTERESTING AND CHALLENGING SETUP TODAY AS THE WARM FRONT PRETTY MUCH HALTED ACROSS THE EASTERN AND FAR SOUTHERN ZONES. DESPITE HIGH PRESSURE TO OUR EAST AND A DEEP SOUTHERLY FLOW OCCURRING, A COLD AIR DAMMING SITUATION UNFOLDED. THIS WAS PROBABLY ENHANCED BY THE LINGERING SNOW COVER OVER PARTS OF THE AREA AND THE COLDER MORE DENSE AIR THAT WAS IN PLACE EARLY THIS MORNING. THE END RESULT WAS THE MILDER AIR STREAMING IN ALOFT STRENGTHENED THE LOW-LEVEL INVERSION AND KEPT THE MIXING FROM ALLOWING THE WARM FRONT TO JUMP NORTHWARD. THE WARM FRONT HAS GOTTEN INLAND ACROSS NEW JERSEY AND DELMARVA WITH THESE LOCALES IN THE 40S AND 50S, AND SOME ADDITIONAL WARMING IS OCCURRING ACROSS SOUTHEASTERN PENNSYLVANIA. FARTHER NORTH, TEMPERATURES HAVE BEEN STUCK IN THE 30S WITH A VERY SLOW RISE SO FAR. A WEALTH OF LOW CLOUDS AND FOG HAVE BEEN STUCK ACROSS THE AREA, WITH EVEN SOME DRIZZLE. THE VISIBLE SATELLITE IMAGERY SHOWS THE WESTERN EDGE OF THE LOW CLOUDS IN CENTRAL PENNSYLVANIA, WHICH HAS SHOWN A VERY SLOW EROSION SO FAR TOWARD NORTHEASTERN PENNSYLVANIA. A STACKED LOW ACROSS THE GREAT LAKES WILL SLIDE EASTWARD AND TRACK WELL TO OUR NORTH THROUGH TONIGHT. THE ASSOCIATED COLD FRONT MAY END UP BEING AN OCCLUSION WHEN IT SLIDES ACROSS OUR AREA LATER THIS EVENING. AS THIS OCCURS, LOCALES THAT REALLY DID NOT GET INTO THE TRUE WARMER AIR MAY ACTUALLY HAVE THEIR TEMPERATURES SPIKE FOR A TIME TONIGHT. THE BULK OF THE LIFT HAS SHIFTED NORTHEAST OF OUR AREA ALONG WITH THE ROBUST LOW-LEVEL JET, WITH JUST A FEW ISOLATED SHOWERS ACROSS THE EASTERN ZONES. THE FLOW AROUND 925 MB IS FORECAST TO GENERALLY REMAIN IN THE 30-40 KNOT RANGE THROUGH THE NIGHT, BUT THIS WILL BE VEERING WITH TIME. THE FORECAST SOUNDINGS MAINTAIN THE RATHER MOIST LOW-LEVEL PROFILE AT LEAST THROUGH EARLY THIS EVENING THEN DRYING OCCURS. WE BELIEVE THE NAM IS OVERDONE WITH SOCKING IN THE LOW CLOUDS MUCH LONGER ACROSS MUCH OF THE CWA. WE THEREFORE MAINTAINED LOTS OF CLOUDS AND CARRIED SOME FOG INTO AT LEAST THE EARLY EVENING. THE FOG IS LOCALLY DENSE, BUT CHECKING TRAFFIC CAMERAS IT APPEARS FOR THE MOST PART THE FOG IS NOT QUITE AS DENSE AS THE REPORTED VISIBILITIES SUGGEST. THEREFORE, WE WILL HOLD WITH THE SPECIAL WEATHER STATEMENT FOR NOW. IT APPEARS THAT SOME RESIDUAL DRIZZLE WILL CONTINUE, ALTHOUGH AN ISOLATED SHOWER CANNOT BE RULED OUT AHEAD OF AN WITH THE FRONT. WE OPTED TO KEEP POPS BELOW SLIGHT CHC FOR MOST AND CARRIED PATCHY DRIZZLE FOR AWHILE LONGER /UNTIL THE FRONT MOVES THROUGH/. THE TIMING OF THE CLEARING IS OF LOWER CONFIDENCE, BUT ONCE THE FRONT MOVES THROUGH AND THE FLOW TURNS WESTERLY THE LOW CLOUDS SHOULD ERODE. THE CAA LATER TONIGHT ALONG WITH A WEST-NORTHWEST FLOW MAY HELP TO BRING SOME CLOUDS AND FLURRIES TOWARD THE POCONOS. AS FOR LOW TEMPERATURES, WE BLENDED THE NAM/GFS MOS WITH JUST SOME TWEAKS MADE. THE HOURLY GRIDS WERE RESET TO THE CURRENT OBS WITH SOME INCORPORATION OF THE LAV/LAMP GUIDANCE TO HELP ASSIST WITH THE ONGOING TRENDS. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... AN UPPER-LEVEL TROUGH WILL BE MOVING THROUGH DURING THE COURSE OF THIS TIME FRAME, WITH ITS AXIS PROBABLY TO OUR EAST BY MIDDAY. LOW PRESSURE WILL TRACK INTO THE CANADIAN MARITIMES WITH CYCLONIC FLOW IN ITS WAKE. THE CAA WILL CONTINUE ESPECIALLY THROUGH THE FIRST HALF OF THE DAY, ALTHOUGH A SECOND SURGE OF THIS COULD SLIDE ACROSS OUR NORTHERN ZONES IN THE AFTERNOON. THE COLDER AIR ALOFT WILL TEAM UP WITH ENOUGH WARMTH IN THE BOUNDARY LAYER, WHICH WILL STEEPEN THE LOW-LEVEL LAPSE RATES THROUGH THE MORNING. THIS IN COMBINATION WITH A TIGHT PRESSURE GRADIENT FOR MUCH OF THE DAY WILL RESULT IN BREEZY TO WINDY CONDITIONS. THE FORECAST SOUNDINGS INDICATE THAT WIND GUSTS SHOULD PEAK AT ABOUT 30 KNOTS. A FRONTAL BOUNDARY LOOKS TO BE STALLED TO OUR SOUTH AND A THERMAL GRADIENT IS FORECAST TO TIGHTEN THERE. THIS MAY RESULT IN SOME OVERRUNNING WELL TO OUR SOUTH AND SOUTHWEST, AND GIVEN THE WESTERLY FLOW THE CLOUDS ASSOCIATED WITH THAT SHOULD TEND TO STAY TO OUR SOUTH. THERE SHOULD BE SOME LAKE EFFECT RESPONSE DURING THE DAY WITH WEST-NORTHWEST FLOW OF COLDER AIR IN PLACE. THE FLOW ABOVE THE SURFACE IS FORECAST TO BE ON THE STRONGER SIDE, THEREFORE PERHAPS MORE CLOUDS MAKE IT TO NORTHEASTERN PENNSYLVANIA ALONG WITH SOME FLURRIES OR A SNOW SHOWER. AS FOR TEMPERATURES, WE GENERALLY TOOK AN EVEN BLEND OF THE NAM/GFS MOS. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... WINDS SHOULD DIMINISH FOR TUESDAY NIGHT AS WEAK HIGH PRESSURE INFLUENCES OUR REGION. THERE REMAINS SOME DIFFERENCE IN THE MODELS REGARDING THE MID WEEK SYSTEM. LOW PRESSURE IS FORECAST TO TAKE SHAPE OVER THE SOUTHEASTERN STATES ON WEDNESDAY BEFORE PASSING OFF THE MIDDLE ATLANTIC COAST ON WEDNESDAY EVENING. PRECIPITATION SHOULD BEGIN TO OVERSPREAD OUR REGION ON WEDNESDAY AFTERNOON. AT THE ONSET, BOUNDARY LAYER TEMPERATURE ARE ANTICIPATED TO SUPPORT RAIN IN ALL BUT OUR FAR NORTH. DURING THE COURSE OF WEDNESDAY NIGHT, COLD AIR SHOULD BE DRAWN INTO OUR REGION ON A NORTHEAST TO NORTH WIND CAUSING THE RAIN TO CHANGE TO SNOW FROM NORTH TO SOUTH. IF PRECIPITATION RATES INCREASE ON WEDNESDAY NIGHT, ADDITIONAL COOLING FROM ALOFT IS POSSIBLE. AS A RESULT, FORECASTING THE CHANGE-OVER TIMES AND AMOUNTS REMAINS QUITE TRICKY AT THIS POINT. NEVERTHELESS, BASED ON THE SYSTEM'S EXPECTED TRACK AND TIMING, IT APPEARS QUITE POSSIBLE THAT WE COULD RECEIVE OF SWATH OF A FEW INCHES OF SNOW ACROSS A PORTION OF OUR REGION, PERHAPS FROM THE PHILADELPHIA METROPOLITAN AREA INTO CENTRAL NEW JERSEY AND POINTS TO THE NORTH. ONCE THE MID WEEK SYSTEM PASSES, WE SHOULD BE IN ANOTHER BRIEF LULL FROM THURSDAY INTO THURSDAY NIGHT. A LONG WAVE TROUGH IS FORECAST TO SETTLE OVER THE EASTERN STATES FOR FRIDAY INTO THE WEEKEND. A COLD FRONT FROM THE WEST IS EXPECTED TO ARRIVE ON FRIDAY NIGHT WITH COLD AIR BUILDING INTO OUR REGION IN STEPS OVER THE WEEKEND. WE ARE ANTICIPATING SOME CLOUDS AND SHOWERS IN THE COLD ADVECTION. WE MAY SEE SNOW SHOWERS IN THE NORTH ON SATURDAY WITH A MIX OF SNOW AND RAIN ELSEWHERE. IT SHOULD BE COLD ENOUGH FOR ALL SNOW SHOWERS ON SUNDAY. && .AVIATION /21Z MONDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. REST OF THIS AFTERNOON...A LOWER CONFIDENCE FORECAST. LOW CLOUDS AND FOG AFFECTING ALL OUR TERMINALS. THIS IS RESULTING IN IFR TO LIFR CEILINGS. THE VISIBILITIES SHOULD VARY FROM MVFR TO IFR. MAINLY SOME DRIZZLE WILL CONTINUE THROUGH AT LEAST EARLY THIS EVENING. THE CEILINGS MAY TRY TO IMPROVE SOME TOWARD EVENING, HOWEVER CONFIDENCE IS RATHER LOW ON THIS. THE INLAND TERMINALS WILL TEND TO HAVE LIGHT AND VARIABLE WINDS THAT SHOULD TURN SOUTHERLY, WITH 10-15 KNOT WINDS MAINLY AT KMIV AND KACY. VISIBLE SATELLITE IMAGERY SHOWING CLOUDS CLEARING IN CENTRAL PENNSYLVANIA TOWARD NORTHEAST PENNSYLVANIA, AND THIS IS EXPECTED TO EVENTUALLY REACH OUR AREA. TONIGHT...A COLD FRONT WILL MOVE THROUGH LATER THIS EVENING, HOWEVER MOISTURE STUCK NEAR THE GROUND MAY NOT MIX OUT UNTIL AFTER THE FRONT SHIFTS TO OUR EAST. AS A RESULT, IMPROVEMENTS WILL PROBABLY DELAYED UNTIL THEN. LOW CONFIDENCE ON THE TIMING OF IMPROVEMENT TO VFR. SOUTH-SOUTHWEST WINDS WILL BECOME WEST-NORTHWEST AT AROUND 10 KNOTS. TUESDAY...VFR. WEST-NORTHWEST WINDS 15-20 KNOTS WITH GUSTS TO 30 KNOTS. OUTLOOK... TUESDAY NIGHT AND WEDNESDAY...MAINLY VFR WITH LIGHT RAIN BUILDING UP FROM THE SOUTH ON WEDNESDAY AFTERNOON. WEDNESDAY NIGHT...RAIN CHANGING TO SNOW FROM NORTH TO SOUTH. WIDESPREAD IFR CONDITIONS ARE POSSIBLE. THURSDAY AND FRIDAY...MAINLY VFR. && .MARINE... LOW PRESSURE WILL TRACK WELL NORTH OF OUR AREA TONIGHT, WITH AN ASSOCIATED COLD FRONT SLIDING ACROSS DURING THIS EVENING. A POTENT LOW-LEVEL JET AROUND 925 MB WILL CONTINUE TO SHIFT TO THE EAST INTO THIS EVENING. THIS HAS HELPED TO MIX DOWN SOME OF THE STRONGER WINDS TO THE SURFACE DESPITE THE WARMING ALOFT. IT APPEARS ITS INFLUENCE HAS BACKED OFF THOUGH AS THE WINDS LOOKED TO ALREADY HAVE PEAKED. THE INCREASED SOUTHERLY FLOW THOUGH HAS ALLOWED THE SEAS TO BUILD TO THE 5-7 FOOT RANGE ON THE OCEAN. THE SOUTHERLY FLOW WILL CONTINUE AHEAD OF THE FRONT, THEN A SHIFT TO THE WEST IS EXPECTED LATER THIS EVENING WITH THE PASSAGE OF THE COLD FRONT. WE THEN WAIT FOR THE CAA TO KICK IN, WHICH LOOKS TO BE THE STRONGEST STARTING AROUND 06Z TONIGHT. AS THIS OCCURS, THE LOW-LEVEL LAPSE RATES WILL STEEPEN AND BE MUCH MORE CONDUCIVE FOR DEEPER MIXING. THE MOST IDEAL TIME FRAME FOR THIS TO OCCUR THOUGH IS DURING THE DAY TUESDAY. ON DELAWARE BAY, WE MAY END UP HAVING TO WAIT FOR THIS TO OCCUR TUESDAY INSTEAD OF LATER TONIGHT. SINCE THE WINDS HAVE COME DOWN FOR THE MOST PART ON THE BAY, WE OPTED TO CANCEL THE CURRENT ADVISORY AND HOIST A NEW ONE FOR THE DAY TUESDAY. THE ADVISORY ON THE OCEAN CONTINUES AT LEAST THROUGH TUESDAY. OUTLOOK... FOLLOWING A BRIEF BREAK, WE MAY APPROACH OR REACH SMALL CRAFT ADVISORY CONDITIONS AGAIN FROM WEDNESDAY NIGHT INTO THURSDAY AS LOW PRESSURE FROM THE WEST PASS OFF THE MIDDLE ATLANTIC COAST. WIND SPEEDS AND WAVE HEIGHTS SHOULD BE BELOW THE SMALL CRAFT ADVISORY CRITERIA FOR THURSDAY NIGHT INTO FRIDAY EVEN AS A COLD FRONT APPROACHES FROM THE WEST. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST TUESDAY FOR ANZ450>455. SMALL CRAFT ADVISORY FROM 5 AM TO 6 PM EST TUESDAY FOR ANZ430- 431. && $$ SYNOPSIS...IOVINO NEAR TERM...GORSE SHORT TERM...GORSE LONG TERM...IOVINO AVIATION...GORSE/IOVINO MARINE...GORSE/IOVINO