Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 210728 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 328 AM EDT TUE OCT 21 2014 .SYNOPSIS... LOW PRESSURE WILL PASS OFF THE MID ATLANTIC COAST TONIGHT. THE LOW IS THEN EXPECTED TO MOVE SLOWLY NORTH AND NORTHEASTWARD, REACHING THE WATERS OFF CAPE COD AROUND THURSDAY NIGHT AND ARRIVING IN NOVA SCOTIA ON FRIDAY NIGHT. HIGH PRESSURE IS ANTICIPATED TO BUILD INTO OUR REGION FROM THE SOUTHWEST FOR FRIDAY INTO SATURDAY. A COLD FRONT IS EXPECTED TO ARRIVE SATURDAY NIGHT WITH ANOTHER AREA OF HIGH PRESSURE FOLLOWING FOR SUNDAY AND MONDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... AN UPPER-LEVEL TROUGH WILL CONTINUE TO AMPLIFY INTO THE NORTHEAST THROUGH TODAY. AN INITIAL STRONG AND COMPACT SHORT WAVE CARVING OUT THE TROUGH CONTINUES TO WORK ITS WAY ACROSS PENNSYLVANIA EARLY THIS MORNING. THIS FEATURE IS WELL EVIDENT ON THE WATER VAPOR IMAGERY AS IT LIFTS EAST-NORTHEASTWARD, AND APPEARS TO BE STRONGER THAN EARLIER GUIDANCE INDICATED. AS A RESULT, THE DOWNSTREAM WAA AND LOWER LEVEL CONVERGENCE/LIFT HAS BEEN STRONG ENOUGH TO DEVELOP AND ORGANIZE SOME SHOWERS. THIS IS WITHIN A MOISTENING AIRMASS AS IT WAS INITIALLY RATHER DRY ACROSS OUR AREA. THE AIRMASS WILL CONTINUE TO MOISTEN UP SOME MORE TODAY AS THE UPPER-LEVEL TROUGH AMPLIFIES FURTHER. A STRONGER MID/UPPER LEVEL JET DIVING DOWN THE WEST SIDE OF THE TROUGH WILL PUSH STRONGER SHORT WAVE ENERGY ALONG. THIS WILL ASSIST IN CUTTING OFF THE TROUGH FROM THE MAIN FLOW, THEREFORE THIS UPPER-LEVEL TROUGH WILL BE CLOSING OFF DURING THE COURSE OF THE DAY. THIS WILL ALSO TAKE LOW PRESSURE NEAR THE EASTERN GREAT LAKES EARLY THIS MORNING, AND THEN MOVE IT OVER OUR AREA BEFORE IT STARTS TO EVENTUALLY CONSOLIDATE OFFSHORE. THE MAIN FORECAST CHALLENGE IS THE TIMING AND COVERAGE OF THE ASSOCIATED SHOWERS. AFTER SOME INITIAL SHOWERS EARLY THIS MORNING MAINLY ACROSS THE WESTERN ZONES, THERE COULD BE A BREAK BEFORE ADDITIONAL SHOWERS DEVELOP ESPECIALLY LATER THIS AFTERNOON AS ANOTHER STRONG SHORT WAVE ROUNDS THE BASE OF THE TROUGH. THE SOUNDINGS SHOW SOME INSTABILITY DEVELOPING, BUT THIS IS MOSTLY CONFINED TO THE LOWEST LEVELS. AS A RESULT, WE HELD OFF ON ADDING A THUNDER MENTION ATTM. WE CONTINUED CHC POPS FOR SCATTERED SHOWERS THROUGH THE DAY, ALTHOUGH A TIME OF LIKELY POPS ACROSS THE WESTERN AREAS CLOSER TO THE INCOMING TROUGH. THE AIRMASS IS MODERATING AHEAD OF THE MAIN UPPER-LEVEL TROUGH AND THE ASSOCIATED WAA WILL YIELD WARMER AFTERNOON TEMPERATURES. THERE MAY BE A SQUEEZE PLAY THOUGH AS THE WARMEST AIR MAY SLIDE UP ACROSS OUR DELMARVA AND EASTERN ZONES. THEREFORE, A BLEND OF THE NAM/GFS MOS RESULTED IN THE WARMEST HIGH TEMPERATURES IN THESE AREAS. OTHERWISE, THE FLOW SHOULD START TO SHIFT AROUND FROM THE SOUTHWEST TO THE NORTHWEST DURING THE COURSE OF THE DAY AS LOW PRESSURE DEVELOPS OVER OUR AREA BEFORE CONSOLIDATING SOME JUST TO OUR EAST TOWARD EVENING. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... A CLOSED LOW WILL STRENGTHEN ACROSS THE MID ATLANTIC AND NORTHEAST THROUGH TONIGHT. AS THIS OCCURS, SURFACE LOW PRESSURE SHOULD CONSOLIDATE SOME MORE OFF OF OUR COAST. THE MODEL GUIDANCE OVERALL SHOWS A SIGNIFICANT SHORT WAVE ROUNDING THE BASE OF THE CLOSED LOW OVERNIGHT. THIS FEATURE LOOKS TO NEAR OUR SOUTHEASTERN ZONES TOWARD DAYBREAK. AS THIS OCCURS, LARGE SCALE LIFT IN CONJUNCTION WITH SOME POTENTIAL FRONTOGENETIC FORCING ON THE WEST SIDE OF THE SURFACE LOW SHOULD ORGANIZE AND AREA OF RAIN. THIS LOOKS TO GENERALLY BE ACROSS THE EASTERN HALF OF THE CWA. AS A RESULT, LIKELY POPS ARE CARRIED ACROSS MUCH OF THE CWA ESPECIALLY LATE WITH THE SLIGHTLY HIGHER VALUES ACROSS THE EASTERN ZONES. WHILE ISOLATED THUNDER CANNOT BE RULED OUT ESPECIALLY ACROSS THE EASTERN AREAS AS AT LEAST SOME MID LEVEL INSTABILITY COULD BE PRESENT, THE CHC APPEARS TO BE RATHER LOW AND THEREFORE IT WAS NOT CARRIED ATTM. THE POTENTIALLY DEVELOPING RAIN AREA HAS THE SIGNATURE OF WHAT COULD BE THE START OF A PIVOT REGION ACROSS AT LEAST A PORTION OF OUR AREA STARTING NEAR DAYBREAK. THIS WOULD BE DUE TO THE CLOSED LOW MOVING OVERHEAD AND THE STRONG SHORT WAVE PIVOTING UP FROM THE SOUTHWEST AS THE SURFACE LOW ORGANIZES SOME MORE OFFSHORE. AS FOR LOW TEMPERATURES, WE UTILIZED MAINLY AN EVEN NAM/GFS MOS BLEND. WHILE THE WINDS SHOULD BE LIGHT FOR MOST, A NORTHERLY WIND SHOULD START TO INCREASE SOME MAINLY LATE AS THE SYSTEM AS A WHOLE STARTS TO BECOME BETTER ORGANIZED TO OUR EAST. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... A MID LEVEL LOW IS EXPECTED TO PASS OFF THE DELMARVA COAST ON WEDNESDAY MORNING. THE FEATURE IS THEN ANTICIPATED TO MEANDER OFF OUR COAST FROM WEDNESDAY AFTERNOON INTO THURSDAY EVENING BEFORE LIFTING NORTHEASTWARD AND REACHING THE WATERS OFF CAPE COD ON FRIDAY MORNING. A SURFACE LOW IS FORECAST TO FOLLOW THE MID LEVEL LOW CLOSELY DURING THE PERIOD. WE ARE EXPECTING THE POTENTIAL FOR RAIN FROM WEDNESDAY THROUGH THURSDAY MORNING. THE POSSIBILITY OF MODERATE TO HEAVY RAINFALL SHOULD BE MOSTLY ON THE EAST SIDE OF THE DEVELOPING MID LEVEL LOW. AS A RESULT, WE ARE NOT ANTICIPATING MUCH MODERATE TO HEAVY RAINFALL IN OUR REGION. THE ONLY EXCEPTION IS IN OUR COASTAL AREAS WEDNESDAY WHERE RAINFALL AMOUNTS MAY APPROACH AN INCH AT SOME LOCATIONS. ALSO, MARGINAL INSTABILITY IN THAT AREA MAY TRANSLATE INTO ISOLATED LIGHTNING AND THUNDER. REGARDLESS, THE EXPECTED RAINFALL TOTALS SHOULD NOT RESULT IN ANY FLOODING PROBLEMS. AS THE LOW BEGINS TO PULL AWAY TO OUR NORTHEAST ON THURSDAY NIGHT, THE POTENTIAL FOR RAIN SHOWERS SHOULD END GRADUALLY IN OUR AREA. A COUPLE OF REINFORCING MID LEVEL SHORT WAVES SHOULD DROP OVER OUR REGION FROM THE NORTHWEST IN THE CYCLONIC FLOW AROUND THE DEPARTING MID LEVEL LOW OVER THE COMING WEEKEND. THE SHORT WAVES ARE NOT EXPECTED TO HAVE MUCH MOISTURE ASSOCIATED WITH THEM. THEREFORE, WE ARE NOT ANTICIPATING ANY PRECIPITATION AT THAT TIME. A MID LEVEL RIDGE FROM THE WEST SHOULD BUILD TOWARD OUR REGION FOR SUNDAY AND MONDAY. DAYTIME HIGHS ARE FORECAST TO BE A BIT BELOW NORMAL WITH THE RAIN ON WEDNESDAY AND THURSDAY. READINGS SHOULD RETURN TO NEAR NORMAL FOR THE PERIOD FROM FRIDAY THROUGH MONDAY. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TODAY...MOSTLY VFR. SOME SHOWERS WILL BE AROUND THE AREA AS LOW PRESSURE DEVELOPS OVERHEAD BEFORE CONSOLIDATING SOME JUST TO OUR EAST TOWARD EVENING. WHILE MVFR CONDITIONS CAN OCCUR FOR A TIME WITH SHOWERS, THERE IS SOME LOWER CONFIDENCE ON THE TIMING AND AREAL COVERAGE. A SOUTH-SOUTHWEST WIND WILL SHIFT TO THE WEST AND NORTHWEST DURING THE COURSE OF THE DAY, HOWEVER SPEEDS ARE EXPECTED TO BE LESS THAN 10 KNOTS. TONIGHT...VFR CEILINGS OVERALL. THERE IS THE POTENTIAL FOR MVFR VISIBILITIES AT TIMES WITH SOME SHOWERS. A MORE ORGANIZED AREA OF RAIN MAY DEVELOP LATE ESPECIALLY EAST OF KPHL, WHERE SOME MVFR CEILINGS COULD START TO DEVELOP. LOW CONFIDENCE ON THE MVFR CEILINGS. THE WINDS ARE ANTICIPATED TO BECOME NORTH TO NORTHEAST AROUND 5 KNOTS. OUTLOOK... WEDNESDAY THROUGH THURSDAY...CONDITIONS VARYING BETWEEN VFR AND MVFR IN PERIODS OF RAIN. THURSDAY NIGHT...MAINLY VFR WITH A CHANCE OF SHOWERS. FRIDAY THROUGH SATURDAY...MAINLY VFR. && .MARINE... TODAY AND TONIGHT...LOW PRESSURE DEVELOPING OVERHEAD WILL START TO CONSOLIDATE SOME OFFSHORE TONIGHT. THIS WILL RESULT A SOUTHWESTERLY WIND TURNING TO THE WEST AND NORTHWEST TODAY THEN NORTH-NORTHEAST DURING TONIGHT. GIVEN THE NEARBY LOCATION OF THE ORGANIZING SURFACE LOW, THE FLOW IS FORECAST TO BE ON THE LIGHTER SIDE. AFTER SOME SURGE IN THE SEAS OFFSHORE EARLIER, THE SEAS ARE EXPECTED TO BE BELOW ADVISORY CRITERIA THROUGH TONIGHT. THE NORTHERLY WINDS MAY START TO INCREASE THOUGH TOWARD DAYBREAK WEDNESDAY. OUTLOOK... WEDNESDAY...NORTHERLY WIND GUSTS OF 25 TO 30 KNOTS ARE POSSIBLE. WEDNESDAY NIGHT THROUGH FRIDAY NIGHT...NORTHWESTERLY WIND GUSTS OF 25 TO 30 KNOTS ARE POSSIBLE. SATURDAY...NO MARINE HEADLINES ARE ANTICIPATED. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...GALE WATCH FROM WEDNESDAY AFTERNOON THROUGH LATE WEDNESDAY NIGHT FOR ANZ431-450>455. SMALL CRAFT ADVISORY FROM NOON WEDNESDAY TO 6 AM EDT THURSDAY FOR ANZ430. && $$ SYNOPSIS...IOVINO NEAR TERM...GORSE SHORT TERM...GORSE LONG TERM...IOVINO AVIATION...GORSE/IOVINO MARINE...GORSE/IOVINO

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