Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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173 FXUS61 KPHI 290145 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 945 PM EDT THU APR 28 2016 .SYNOPSIS... LOW PRESSURE IN NORTH CAROLINA GRADUALLY SHIFTS OUT TO SEA OFF THE MID ATLANTIC COAST LATER FRIDAY OR FRIDAY NIGHT. HIGH PRESSURE WILL THEN BUILD DOWN FROM THE NORTH SATURDAY INTO SUNDAY. LOW PRESSURE IS FORECAST TO TRACK ACROSS OUR AREA SUNDAY NIGHT AND MONDAY BEFORE SHIFTING OFFSHORE MONDAY NIGHT INTO TUESDAY. HIGH PRESSURE MAY EXTEND INTO OUR AREA TUESDAY INTO WEDNESDAY. THE NEXT COLD FRONT ARRIVES ON THURSDAY. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 930PM ESTF: POPS ADJUSTED HIGHER ON THE DELMARVA OVERNIGHT (03Z- 07Z) PER DYING CONVECTION MOVING EWD FROM VA. ADDED PATCHY DRIZZLE/FOG TO THE FCST. A DAMP COOL NIGHT. THE HEAVIER RAINS OF EARLIER THIS EVENING WERE DIMINISHING ACROSS PA AND NJ. MANY REPS OF .1 TO .3 INCHES SO FAR THIS AFTN/EVE ECENTRAL PA THROUGH CENTRAL NJ. TEMPS SHOULD BE STEADY TONIGHT. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... THE NEXT UPPER LEVEL SHORT WAVE TROUGH CROSSES ESEWD ALONG I-80 LATE TOMORROW AND IS SOMEWHAT IMPRESSIVE (TIGHT 500MB VORT) DESPITE MINOR 30 METER 12 HR 500 MB HFC. HAVE RAISED POPS 30-40 PCT N OF I-78 FRIDAY AFTERNOON PER GFS/EC SUGGESTION OF .1-.2 INCHES. ADJUSTED TEMPS DOWN 2-3F IN SOME PLACES PER OVC CONDITION AND LITTLE IN THE WAY OF MIXING WITHIN THIS FAIRLY MOIST BOUNDARY LAYER. WITH CONTINUED ONSHORE FLOW AND PERSISTENT LOW AND MID LEVEL CLOUDS, KEPT TOMORROWS HIGHS SIMILAR TO WHAT WE`VE SEEN TODAY AND YESTERDAY... GENERALLY UPPER 40S TO MID 50S FOR MOST OF THE REGION...PROBABLY AROUND 12F BELOW NORMAL....POSSIBLY COLDER THAN THAT. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... THE SYNOPTIC PATTERN IS FORECAST TO BE COMPRISED OF A STRONG CLOSED LOW THAT CONTINUES TO SLOWLY EXIT THE CANADIAN MARITIMES FRIDAY NIGHT INTO SATURDAY. THIS ALLOWS THE UPPER-LEVEL FLOW TO BACK MORE WESTERLY/ZONAL OVER THE WEEKEND AS A WEAK RIDGE AXIS MOVES ACROSS. A CLOSED LOW IN THE PLAINS IS FORECAST TO OPEN UP AS IT LIFTS NORTHEAST AND EASTWARD OVER THE WEEKEND. THIS FEATURE IS SCHEDULED TO CROSS OUR AREA SUNDAY NIGHT AND MONDAY. THIS WILL DRIVE LOW PRESSURE EASTWARD, WHICH LOOKS TO TRACK ACROSS OUR AREA ON MONDAY BEFORE SHIFTING OFFSHORE. AS A RIDGE BUILDS OUT WEST, A TROUGH LOOKS TO AMPLIFY INTO THE EAST TUESDAY THROUGH THURSDAY. A COLD FRONT ASSOCIATED WITH THE LEADING EDGE OF THIS LOOKS TO APPROACH LATER WEDNESDAY THEN MOVE THROUGH OUR AREA THURSDAY. WE USED A MODEL/CONTINUITY BLEND THROUGH SUNDAY, THEN BLENDED IN THE 12Z WPC GUIDANCE THEREAFTER. SOME ADJUSTMENTS WERE THEN MADE FOLLOWING ADDITIONAL COLLABORATION WITH OUR NEIGHBORING OFFICES. FOR FRIDAY NIGHT AND SATURDAY...AN UPPER-LEVEL FEATURE IS FORECAST TO TRANSLATE ACROSS OUR AREA TO START FRIDAY NIGHT. THIS SHOULD KEEP SOME SHOWERS GOING, HOWEVER THEY SHOULD BE ON THE WANE AS SOME RIDGING ARRIVES LATER FRIDAY NIGHT AND TO START SATURDAY. THE UPPER- LEVEL FLOW THEN BACKS SOME AS A TROUGH TAKES ON SOME AMPLIFICATION IN THE GREAT LAKES LATE SATURDAY. THIS WILL ALLOW FOR WAA AND INCREASING ISENTROPIC LIFT TO START OVERSPREADING OUR AREA SATURDAY NIGHT. THIS MAY RESULT IN SOME RAIN ARRIVING LATER SATURDAY NIGHT, AND THE MODEL GUIDANCE OVERALL APPEARS TO BE FASTER IN BRINGING IN THE PRECIPITATION. AS A RESULT, WE SPED UP THE POP INCREASE SATURDAY NIGHT. DUE TO SOME BRIEF DRYING SATURDAY, TEMPERATURES SHOULD MODIFY SOME DURING THE DAY. FOR SUNDAY AND MONDAY...AS AN UPPER-LEVEL TROUGH AMPLIFIES EASTWARD, SURFACE LOW PRESSURE IS FORECAST TO ARRIVE IN OUR AREA LATER SUNDAY AND MONDAY. HOWEVER, THERE APPEARS TO BE PLENTY OF WAA AND ISENTROPIC INDUCED LIFT AS A WARM FRONT EDGES CLOSER DURING SUNDAY. GIVEN THE FLOW BACKING TO THE SOUTHWEST, PRECIPITATION MAY QUICKLY MOVE ACROSS THE AREA. LINGERING SURFACE HIGH PRESSURE TO OUR NORTHEAST THOUGH WILL RESULT IN SOME SORT OF A WEDGE INITIALLY AND COULD ALLOW ENOUGH DRY LOW-LEVEL AIR TO HOLD ON A LITTLE LONGER. OVERALL THOUGH, MOISTURE INCREASING FROM THE SOUTHWEST SHOULD OVERTAKE THIS. AS A RESULT, THIS TIME FRAME LOOKS RATHER UNSETTLED WITH RAIN AT TIMES. THE STEADIER RAIN MAY THEN BECOME SHOWERY ON MONDAY AS THE BETTER OVERRUNNING STARTS TO SHIFT TO OUR NORTHEAST. SOME GUIDANCE SUGGESTS LESS PRECIPITATION ON MONDAY WHICH WOULD OCCUR IF THE SURFACE LOW IS FASTER. IT APPEARS THE WARM SECTOR MAY EDGE INTO OUR SOUTHERN AREAS SUNDAY INTO MONDAY. WHILE SOME THUNDER CANNOT BE RULED OUT WITHIN THE WARM SECTOR /PERHAPS SOME ELEVATED INSTABILITY NORTH OF THE WARM FRONT/, IT IS LESS CERTAIN IF IT WOULD BE ENOUGH FOR THUNDER. AS A RESULT, NO THUNDER WAS ADDED ATTM. THE SHOWERS SHOULD END MONDAY NIGHT AS THE SYSTEM SHIFTS OFFSHORE AND THE LOW-LEVEL FLOW TURNS MORE FROM THE NORTH AND NORTHWEST. FOR TUESDAY THROUGH THURSDAY...AN UPPER-LEVEL TROUGH IS FORECAST TO AMPLIFY INTO THE EAST TUESDAY AND WEDNESDAY. AS THIS STARTS TO OCCUR, THE MONDAY FRONTAL BOUNDARY MAY HAVE A WAVE OF LOW PRESSURE RUNNING UP THE FRONT. THIS COULD AT LEAST BRUSH OUR EASTERN AND SOUTHERN ZONES TUESDAY, HOWEVER THERE IS LOW CONFIDENCE WITH THIS. AS THE AFOREMENTIONED TROUGH AMPLIFIES MORE INTO THURSDAY, A COLD FRONT LOOKS TO ARRIVE. THERE SHOULD BE ENOUGH HEATING AND WAA TO ALLOW TEMPERATURES TO MODIFY SOME PRIOR TO THE ARRIVAL OF THE COLD FRONT. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,KMIV, KACY AND SURROUNDING AREAS. REMAINDER OF TONIGHT...CONDITIONS GENERALLY MVFR OR IFR IN ST/DRIZZLE FOG AND GROUPS OF SHOWERY RAINS. LIGHT NE WIND. HIGH CONFIDENCE. FRIDAY...CONDITIONS PROBABLY IMPROVING TO MVFR OR VFR CIGS DURING MIDDAY. MODERATE CONFIDENCE BUT MAY LOWER IN RAIN DURING THE AFTERNOON, ESPECIALLY KRDG/KABE AND KTTN. NE WIND WITH A FEW GUSTS 15-20 KT POSSIBLE I-95 EASTWARD. OUTLOOK... FRIDAY NIGHT...MVFR CONDITIONS IN THE EVENING WITH SOME SHOWERS SHOULD THEN IMPROVE TO VFR. NORTHEAST WINDS 10 KNOTS OR LESS. SATURDAY...VFR DURING THE DAY, THEN LOWER TO MVFR AT NIGHT AS SOME RAIN APPROACHES. EAST-SOUTHEAST WINDS AROUND 10 KNOTS OR LESS. SUNDAY AND MONDAY...MVFR TO POTENTIALLY IFR CONDITIONS ALONG WITH RAIN AT TIMES. THE CONDITIONS MAY START IMPROVING MONDAY NIGHT. TUESDAY...VFR OVERALL. && .MARINE... 930 PM: DELAYED THE START OF THE SCA LOWER DE BAY AND NJ COAST. CONFIDENCE BELOW AVERAGE ON SEAS REACHING 5 FT NJ ATLC WATERS OR GUSTS 25 KT LOWER DE BAY AND NJ ATLC WATERS...BUT ITS STILL POSSIBLE. OUTLOOK... FRIDAY NIGHT...NORTHEASTERLY WIND GUSTS OF 20 TO 25 KNOTS ON THE OCEAN ZONES ALONG WITH SEAS TO AROUND 5 FEET. THESE SHOULD SUBSIDE DURING THE NIGHT AND THEREFORE THE SMALL CRAFT ADVISORY WAS KEPT UNTIL 06Z SATURDAY. SATURDAY AND SUNDAY...THE WINDS AND SEAS SHOULD BE BELOW ADVISORY CRITERIA DESPITE INCOMING LOW PRESSURE LATE SUNDAY. MONDAY AND TUESDAY...NORTHEAST WINDS MONDAY SHOULD SHIFT TO NORTHWEST AT NIGHT INTO TUESDAY BEFORE SHIFTING BACK EASTERLY. IT APPEARS THAT THE WINDS REMAIN UNDER 25 KNOTS, HOWEVER SEAS MAY BUILD TO 5 FEET FOR A TIME ON THE OCEAN ZONES. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FROM 4 AM FRIDAY TO 2 AM EDT SATURDAY FOR ANZ450>453. SMALL CRAFT ADVISORY UNTIL 2 AM EDT SATURDAY FOR ANZ454-455. SMALL CRAFT ADVISORY FROM 4 AM TO 10 AM EDT FRIDAY FOR ANZ431. && $$ SYNOPSIS...DRAG/GORSE NEAR TERM...DRAG 945P SHORT TERM...DRAG/JOHNSON 945P LONG TERM...GORSE AVIATION...DRAG/GORSE 945P MARINE...DRAG/GORSE 945P

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