Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 070150 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 950 PM EDT WED MAY 6 2015 .SYNOPSIS... HIGH PRESSURE WILL BUILD ACROSS OUR AREA THROUGH THURSDAY. THE HIGH WILL THEN BUILD TO OUR EAST FRIDAY AND THROUGH THE WEEKEND, LEADING TO A RETURN FLOW ACROSS OUR REGION. LOW PRESSURE IS FORECAST TO LIFT THROUGH THE GREAT LAKES REGION EARLY NEXT WEEK AND TOWARD THE NORTHEAST BY WEDNESDAY, PULLING A COLD FRONT TO THE EAST COAST AROUND TUESDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... THE WATER VAPOR IMAGERY SHOWS FAST WEST-NORTHWEST FLOW ALOFT ACROSS THE NORTHEAST, ALTHOUGH RIDGING IS STARTING TO BUILD MORE JUST TO OUR WEST. MEANWHILE, A SURFACE FRONT IS DRAPED JUST TO OUR SOUTH AND SOUTHWEST WITH A LOW-LEVEL MARINE AIRMASS OVER OUR AREA AND CONTINUING TO SPREAD WESTWARD, THUS MORE STABILITY. SOME WEAK LIFT NORTH OF THE AFOREMENTIONED FRONT HAS HELPED TO SUSTAIN SOME LIGHT SHOWERS OR SPRINKLES FOR PARTS OF THE AREA, HOWEVER THESE CONTINUE TO DWINDLE AS THEY TRACK SOUTHEASTWARD. SOME NEW DEVELOPMENT HAS BEEN OCCURRING IN THE HARRISBURG TO LANCASTER CORRIDOR, HOWEVER EVEN THESE ARE WEAKENING WITH A SOUTHEASTERN EXTENT. ANY LINGERING SHOWER/SPRINKLES WILL DISSIPATE TOWARD MIDNIGHT, HOWEVER SOME LINGERING WEAK LIFT AND LOW-LEVEL CONVERGENCE CLOSER TO THE FRONT MAY PRODUCE A FEW MORE SHOWERS OVERNIGHT OR TOWARD DAYBREAK. THIS IS OF LOWER CONFIDENCE AS ANY LIFT GENERALLY LOOKS RATHER WEAK AND DISORGANIZED. THEREFORE, WE CONTINUED TO ADVERTISE A DRY OVERNIGHT. A RIBBON OF CLOUDINESS REMAINS AROUND THE CENTRAL PART OF THE CWA, WITH LESS UP NORTH AND ACROSS PORTIONS OF THE DELMARVA. THE LOW- LEVEL DRY AIR SHOULD HELP KEEP LESS CLOUDS ACROSS THE FAR NORTH, MEANWHILE FARTHER SOUTH THERE IS A CIRRUS CANOPY FROM THE DISORGANIZED SYSTEM OFF THE SOUTHEAST COAST. THE HOURLY GRIDS WERE ADJUSTED WITH THE LATEST OBSERVATIONS /WHICH INCLUDED A BIT FASTER TEMPERATURE DROP THUS FAR ACROSS THE EASTERN ZONES/, AND THEN THE LAMP/LAV GUIDANCE WAS BLENDED IN TO ASSIST THROUGH THE EVENING. NO MAJOR CHANGES WERE MADE TO THE LOW TEMPERATURES ATTM. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... THURSDAY...RIGHT NOW THINK IT SHOULD OVERALL AVERAGE PARTLY CLOUDY WITH CONSIDERABLE CONVECTIVELY DRIVEN MIDDAY CLOUD COVER. 50 50 BLENDED 12Z/6 NCEP MOS GUIDANCE TEMPS/DEWS/WINDS. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... HIGH PRESSURE BUILDS OFFSHORE OF THE EAST COAST THURSDAY NIGHT INTO FRIDAY, AND OUR AREA WILL REMAIN ON THE WESTERN SIDE OF THE HIGH THROUGH THE UPCOMING WEEKEND. MEANWHILE, RIDGING ALOFT BUILDS OVER THE AREA, WHICH WILL ALLOW TEMPERATURES TO REMAIN WARM THROUGH THE UPCOMING WEEKEND. TEMPERATURES THROUGH SUNDAY WILL REMAIN CLOSE TO 10 DEGREES ABOVE NORMAL EACH DAY. MOSTLY DRY WEATHER IS EXPECTED AS THERE IS NO STRONG, DISCERNIBLE SHORT WAVE/VORTICITY IMPULSES FORECAST TO TRAVERSE THE AREA AROUND THE RIDGE ALOFT. HOWEVER, WITH RETURN FLOW IN PLACE AND THE WARM, MOISTENING LOW LEVELS, THERE IS BE SOME DAYTIME INSTABILITY. THIS COULD LEAD TO SOME DIURNAL, INSTABILITY INDUCED SHOWERS/THUNDERSTORMS, ESPECIALLY SATURDAY AND SUNDAY. WE HAVE SLIGHT CHANCE/CHANCE SHOWERS/THUNDERSTORMS POSSIBLE OVER THE WEEKEND. WITH THE ADDED LOW LEVEL MOISTURE AND STABLE AIR OVERNIGHT, THERE IS THE POSSIBILITY OF OVERNIGHT/EARLY MORNING FOG DEVELOPMENT EACH NIGHT FROM FRIDAY NIGHT THROUGH SUNDAY NIGHT. AS WE MOVE INTO MONDAY, A BACKDOOR TYPE FRONT TRIES TO SAG SOUTHWARD FROM THE NORTH, WHILE THE RIDGE ALOFT BEGINS TO BREAK DOWN AND MOVE EASTWARD. THE FRONT MAY NOT MAKE IT INTO OUR AREA, BUT WILL REMAIN INSTABILITY ACROSS THE AREA. IF ANY VORTICITY IMPULSES ARE ABLE TO SLIDE ACROSS THE AREA IN THE SOUTHWEST FLOW ALOFT, THE WOULD HELP ENHANCE OUR SHOWER/THUNDERSTORM POTENTIAL. SO WE WILL CONTINUE WITH LOW END CHANCE POPS FOR MONDAY. AN BROAD AREA OF LOW PRESSURE IS FORECAST TO MOVE OUT OF THE GREAT LAKES MONDAY NIGHT, AND INTO THE NORTHEAST US/SOUTHEASTERN CANADA THROUGH TUESDAY. AS IT DOES SO, IT WILL PULL A COLD FRONT ACROSS THE AREA. SHOWERS AND THUNDERSTORMS CHANCES INCREASE FROM MONDAY NIGHT INTO TUESDAY/TUESDAY NIGHT. THE MOST LIKELY PERIOD OF SHOWERS/THUNDERSTORMS WOULD BE WITH THE FRONTAL PASSAGE WHICH IS CURRENTLY EXPECTED DURING THE DAY TUESDAY. AN AREA OF LOW PRESSURE OFF THE SOUTHEAST COAST IS FORECAST TO MEANDER NEAR THE CAROLINA COASTS THROUGH THE UPCOMING WEEKEND. BY THE TIME IT STARTS TO MOVE NORTHWARD, IT SHOULD GET CAUGHT UP IN THE SOUTHWEST FLOW ALOFT AND BEGIN MOVING OFFSHORE EARLY NEXT WEEK. FOR NOW IT IS EXPECTED TO REMAIN FAR ENOUGH TO OUR SOUTH, BUT WE`LL NEED TO WATCH THE FORECAST OVER THE NEXT SEVERAL DAYS. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. OVERNIGHT...VFR WITH A CEILING AT OR ABOVE 4000 FEET, WHICH MAY SCATTER OUT FOR SOME AREAS ESPECIALLY LATE. NORTHEASTERLY WINDS AROUND 5 KNOTS, POSSIBLY TURNING LOCALLY LIGHT SOUTHEAST. THURSDAY...VFR WITH CLOUD BASES /A CEILING AT TIMES ESPECIALLY IN THE MORNING/ AT OR ABOVE 4000 FEET. EASTERLY WINDS 4-8 KNOTS TURNING SOUTH-SOUTHEAST THEN SOUTHWEST DURING THE AFTERNOON /REMAINING MORE SOUTHEAST MAINLY AT KILG, KACY AND KMIV DUE TO BAY/SEA BREEZE INFLUENCE/. OUTLOOK... THURSDAY NIGHT-FRIDAY NIGHT...GENERALLY VFR EXPECTED. SATURDAY-MONDAY...GENERALLY VFR DURING THE DAY. ISOLATED/SCATTERED SHOWERS/THUNDERSTORMS EACH AFTERNOON. FOG/STRATUS POSSIBLE OVERNIGHT/EARLY MORNING WITH REDUCED CIGS/VSBYS. && .MARINE... WINDS AND SEAS SHOULD REMAIN BELOW SCA CRITERIA THROUGH THURSDAY. NORTHEAST /LOCALLY SOUTHEAST/ THIS EVENING, THEN LIGHT EAST- NORTHEAST OVERNIGHT AND TURNING SOUTHEAST ON THURSDAY. SEAS GENERALLY AOB 2 FEET. OUTLOOK... THURSDAY NIGHT-MONDAY...SUB-SMALL CRAFT ADVISORY CONDITIONS CONTINUE TO BE EXPECTED THROUGH THE WEEKEND. WINDS MAY GUST AROUND 20 KNOTS SATURDAY-MONDAY, WITH SEAS BUILDING TO 4 FEET. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GORSE/ROBERTSON NEAR TERM...GORSE SHORT TERM...DRAG LONG TERM...ROBERTSON AVIATION...GORSE/ROBERTSON MARINE...DRAG/ROBERTSON

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