Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 281659 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1259 PM EDT TUE OCT 28 2014 .SYNOPSIS... HIGH PRESSURE WILL MOVE FARTHER OFFSHORE THIS AFTERNOON. A COLD FRONT APPROACHES THE AREA OVERNIGHT AND MOVES THROUGH WEDNESDAY. HIGH PRESSURE WILL BRIEFLY BUILD IN FOR THURSDAY BEFORE AN AREA OF LOW PRESSURE MOVES OUT OF THE GREAT LAKES REGION AND COMBINES WITH A DEVELOPING COASTAL LOW OFFSHORE OF THE MID ATLANTIC. HIGH PRESSURE RETURNS FOR THE END OF THE WEEKEND AND EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THICKER CIRRUS THIS MORNING HAS SLOWED THE MIXING AND RISE IN TEMPERATURES IN PA AND NJ. MEANWHILE LOWER DELMARVA ALREADY IN THE LOWER 70S. UPSTREAM CIRRUS DOES NOT LOOK AS THICK AND MODELS SOUNDINGS ARE FORECASTING LESS MOISTURE. SO WE ARE KEEPING TEMPERATURES CLOSE TO MAX TEMP PROJECTIONS, JUST MAKING IT LATER IN THE AFTERNOON. IN DELMARVA, WITH LESS CIRRUS ISSUES TEMPERATURES ARE ALREADY IN THE LOWER 70S WITH PLENTY OF LOWER TO MID 70S IN PLACES FARTHER SOUTHWEST. HERE WE ARE FEELING MORE CONFIDENT ABOUT MAX TEMPS. OTHER THAN ADJUSTMENTS ALREADY MADE TO SKY GRIDS, NO OTHER BIG CHANGES TO WIND OR DEW POINT FORECASTS. HIGH PRESSURE HAS MOVED OFF THE SOUTHEAST AND MID-ATLANTIC COAST EARLY THIS MORNING. MEANWHILE, A SFC LOW WAS LOCATED OVER EXTREME NORTHEAST LAKE SUPERIOR WITH A COLD FRONT EXTENDING SOUTHWESTWARD ACROSS THE MIDWEST AND SOUTHERN PLAINS. THERE ISN`T MUCH EVIDENCE OF A WARM FRONT EAST OF THE APPALACHIANS ON THE LATEST SFC ANALYSIS DESPITE THE SIGNIFICANT WAA ALOFT. HIGH CLOUDS AROUND THE PERIPHERY OF THE RIDGE STREAMING IN FROM THE WEST ARE EXPECTED TO THIN OUT OVER THE MID-ATLANTIC REGION LATER THIS MORNING AS THE BULK OF THE UPPER-LEVEL MOISTURE SHIFTS DOWNSTREAM INTO THE NORTHEAST. AHEAD OF THE MIDWEST COLD FRONT, THE CORE OF THE WARM SECTOR WILL BECOME ESTABLISHED OVER MID-ATLANTIC STATES THIS AFTERNOON. MAJORITY OF MODEL GUIDANCE SHOWS 925 MB AND 850 MB TEMPS FOR PHL INCREASING TO AROUND 21C AND 17C RESPECTIVELY, WHICH IS A +2 SD OCCURRENCE FOR LATE OCTOBER. ASSUMING FULL MIXING DOWN FROM THE 925 MB WARM NOSE, TEMPS WOULD REACH THE LOWER TO MID 80S. MAX TEMP FORECAST IS NOT QUITE THAT WARM (SINCE FULL MIXING NOT EXPECTED OWING TO THE LOW SUN ANGLE) BUT IS SEVERAL DEGREES ABOVE STAT GUIDANCE. FORECAST HIGHS IN LOW 80S IN THE DELMARVA AND MID TO UPPER 70S ELSEWHERE MATCHES UP WELL WITH UPSTREAM OBSERVATIONS YESTERDAY IN THE MIDWEST. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... LOW PRESSURE WILL CONTINUE TO LIFT NORTH OF THE GREAT LAKES TONIGHT AND TOWARDS JAMES BAY. THE COLD FRONT WITH THIS SYSTEM IS EXPECTED TO CROSS THE APPALACHIANS THIS EVENING AND SHOULD BE ON THE FRONT DOOR STEP OF OUR FAR WESTERN ZONES IN EASTERN PA BY DAYBREAK. THE TREND OF RECENT GUIDANCE WAS TO SLOW DOWN THE PROGRESSION OF THE FRONT EVER SO SLIGHTLY. FOLLOWED THIS TREND WITH POPS OVERNIGHT, KEEPING ANY MENTION OF SHOWERS WEST OF THE FALL LINE. POPS FOLLOW CLOSE SUITE TO THE 21Z/03Z SREF RUNS. WENT ABOVE MOS GUIDANCE FOR MIN TEMP AS SOUTHWESTERLY FLOW IN PRE-FRONTAL WARM SECTOR AND INCREASING CLOUD COVER LATE SHOULD LIMIT RADIATIONAL COOLING. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... A COLD FRONT WILL BE MOVING INTO THE AREA AT THE BEGINNING OF THE DAY WEDNESDAY AND PROGRESS ITS WAY THROUGH THE AREA DURING THE DAY AND INTO THE EVENING. POPS WILL INCREASE FROM WEST TO EAST THROUGH THE DAY AS THE FRONT MOVES THROUGH. MODEL GUIDANCE IS IN PRETTY GOOD AGREEMENT WITH THE PRECIP OCCURRING MOSTLY FROM LATE MORNING THROUGH THE AFTERNOON HOURS. THERE IS SOME DIFFERENCES IN QPF AMOUNTS, BUT OVERALL DOES NOT LOOK LIKE A SIGNIFICANT AMOUNT OF RAIN, GENERALLY ONE-TENTH TO ONE-QUARTER OF AN INCH OR LESS. THE FRONT MOVES OFFSHORE BY LATE IN THE DAY, AND THE MAIN SHORT WAVE MOVES THROUGH OVERNIGHT. PRECIP CHANCES WILL DIMINISH FROM WEST TO EAST THROUGH THE LATE AFTERNOON AND EVENING, AND SHOULD BE ALL OUT OF THE AREA BY OR SHORTLY AFTER MIDNIGHT. HIGH PRESSURE IS EXPECTED TO BRIEFLY AFFECT THE AREA THURSDAY INTO THURSDAY NIGHT. DRY WEATHER AND NEAR NORMAL TEMPERATURES ARE EXPECTED BEFORE A CHANGE FOR THE UPCOMING WEEKEND. ON FRIDAY, AND AREA OF LOW PRESSURE WILL BE MOVING OUT OF THE GREAT LAKES REGION, AND APPROACHING THE AREA, WHILE A COASTAL LOW DEVELOPS AND STRENGTHENS TO OUR SOUTHEAST. WE DO NOT EXPECT ANY PRECIPITATION DURING THE DAY AS THE PRECIPITATION TIED TO THE APPROACHING LOW TO THE NORTHWEST SHOULD STILL BE TO OUR NORTHWEST. HOWEVER, AS WE GO INTO FRIDAY NIGHT, THE LOW TO THE NORTHWEST IS EXPECTED TO BEGIN GETTING ABSORBED BY THE COASTAL LOW. AT THE SAME TIME, THE MID/UPPER TROUGH WILL BE DIVING SOUTHWARD INTO THE AREA AS WELL AND WILL ALLOW PRECIPITATION TO FILL IN ACROSS THE AREA. THE MID/UPPER TROUGH WILL SLOWLY SWING ACROSS THE AREA THROUGH SATURDAY, SO THERE COULD STILL BE SHOWERS ACROSS THE AREA THROUGH THE DAY SATURDAY. THERE IS SOME COLD AIR ASSOCIATED WITH THE MID/UPPER TROUGH SWINGING ACROSS THE AREA WITH SUB-ZERO 925/850MB TEMPERATURES LATE FRIDAY NIGHT THROUGH SATURDAY INTO SATURDAY NIGHT. THERE IS THE POTENTIAL FOR SOME SNOW TO MIX WITH RAIN, OR EVEN A COMPLETE CHANCE OVER ACROSS THE HIGHER ELEVATIONS. WINDS WILL ALSO INCREASE SATURDAY INTO SATURDAY NIGHT AS THE PRESSURE GRADIENT TIGHTENS SIGNIFICANTLY BETWEEN THE COASTAL LOW AND HIGH PRESSURE TO THE WEST. THERE IS THE POTENTIAL FOR WINDS TO APPROACH ADVISORY LEVELS, ESPECIALLY FOR COASTAL AREAS, SO WE WILL KEEP A MENTION IN THE HWO. IMPROVING CONDITIONS ARE EXPECTED FOR SUNDAY INTO MONDAY AS HIGH PRESSURE IS EXPECTED TO BUILD INTO THE REGION FROM THE WEST. THE 00Z ECMWF IS SLOWER TO MOVE THE COASTAL LOW TO THE NORTHWEST, WHICH WOULD KEEP THE STRONGER WINDS SLOW TO SUBSIDE AND A CHANCE OF PRECIP FOR NORTHEASTERN AREAS. HOWEVER, THE THOUGHT IS THIS MAY BE TO SLOW, SO WE WEAKEN WINDS AND KEEP THE FORECAST DRY SUNDAY THROUGH MONDAY, ALTHOUGH IT MAY STILL BE A BIT BREEZY. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. 18Z TAFS VFR THRU THIS EVENING, UNCERTAIN ABOUT MVFR/IFR CONDITIONS TOWARD WEDNESDAY MORNING AND A CHANCE OF SHOWERS LATER WEDNESDAY. WE ADDED LLWS FOR KABE AND KRDG. FOR THIS AFTERNOON VFR CIRRUS WITH SOUTH TO SOUTHWEST WINDS AVERAGING CLOSE TO 10 KNOTS. A SLIGHT BACKING OF THE WIND DIRECTION TOWARD EVENING. THIS EVENING INTO THE OVERNIGHT. CONTINUED MAINLY CIRRUS BASED VFR CIGS. VERY LIGHT WINDS FROM THE SOUTH IF NOT CALM. A LOW LEVEL JET IS PREDICTED TO PASS ACROSS OUR NORTHWEST TERMINALS AND AIRPORTS. SINCE THE COMBINATION OF MOST LIKELY CALM WINDS AND LOCATION OF THE LLJ, WE DID ADD A LLWS PERIOD AT KABE AND KRDG AND WILL MONITOR FOR THE REST OF THE TERMINALS. LATE TONIGHT WE DID BRING MOST TERMINALS DOWN TO MVFR CONDITIONS MAINLY DUE TO FOG AND ALSO SOME STRATUS AND STRATOCU AND SOME OF THE MORE INLAND TERMINALS. CONFIDENCE THOUGH IS NOT HIGH AS IT DEPENDS UPON HOW THICK THE CIRRUS WILL BE. ON WEDNESDAY MORNING, VFR CONDITIONS PREDICTED TO RETURN AS A COLD FRONT STARTS MOVING THROUGH THE AREA. WINDS ARE FORECAST TO BECOME WEST. SHOWERS ARE POSSIBLE AT THE MORE INLAND TERMINALS WITH THEM POSSIBLY REACHING THE INTERSTATE 95 CORRIDOR AIRPORTS BY THE END OF THE TAF FCST PERIOD. WITH THE 30HR TAF AT KPHL WE DO SHOW A WINDOW OF MAINLY VFR SHOWERS DURING THE AFTERNOON. OUTLOOK... WEDNESDAY NIGHT-FRIDAY...MOSTLY VFR. FRIDAY NIGHT-SATURDAY...GENERALLY VFR, WITH MVFR CONDITIONS POSSIBLE WITH SHOWERS. SNOW SHOWERS POSSIBLE ACROSS NORTHEAST PENNSYLVANIA AND NORTHWEST NEW JERSEY. STRONG, GUSTY WINDS SATURDAY INTO SATURDAY NIGHT.
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&& .MARINE... SWLY WINDS WILL STRENGTHEN TODAY TO 10-20 KT. THE GRADIENT TIGHTENS A BIT MORE TONIGHT. WARM AIR ATOP THE COOLER OCEAN WATERS DO NOT PROVIDE A PARTICULARLY FAVORABLE MIXING SETUP BUT OCCASIONAL GUSTS TO 25 KT ARE POSSIBLE OVER THE COASTAL WATERS LATE. USING WAVEWATCH GUIDANCE, SEAS WILL INCREASE TO 4-5 FT OVERNIGHT. A SCA WAS ISSUED FOR THE ATLANTIC ZONES STARTING AT MIDNIGHT TONIGHT. OUTLOOK... WEDNESDAY...SMALL CRAFT REMAINS IN EFFECT THROUGH MIDDAY WEDNESDAY, THEN SEAS ARE EXPECTED TO SUBSIDE. WEDNESDAY NIGHT-FRIDAY...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED. FRIDAY NIGHT-SATURDAY...INCREASING WINDS OVERNIGHT INTO SATURDAY AND SATURDAY NIGHT AS A COASTAL LOW STRENGTHENS. AT LEAST SMALL CRAFT CONDITIONS EXPECTED, WITH GALE FORCE WINDS POSSIBLE. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 2 PM EDT WEDNESDAY FOR ANZ450>455. && $$ SYNOPSIS...ROBERTSON NEAR TERM...GIGI/KLEIN SHORT TERM...KLEIN LONG TERM...ROBERTSON AVIATION...GIGI/ROBERTSON MARINE...KLEIN/ROBERTSON

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