Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 010424 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1224 AM EDT WED OCT 1 2014 .SYNOPSIS... LOW PRESSURE IN PENNSYLVANIA WILL REDEVELOP SOUTHEAST OF NEW ENGLAND LATE TODAY THROUGH THURSDAY. STRENGTHENING HIGH PRESSURE IN EASTERN CANADA WEDGES DOWN INTO THE MID ATLANTIC STATES LATER TODAY THROUGH THURSDAY. THE HIGH WILL SLIDE TO OUR EAST FRIDAY WITH A POTENT COLD FRONT MOVING THROUGH OUR AREA FRIDAY NIGHT INTO SATURDAY MORNING. ANOTHER COLD FRONT PASSES BY NEXT MONDAY. && .NEAR TERM /THROUGH WEDNESDAY/... TROUGH AXIS SHOWERS AND TSTMS IN EASTERN PA TO CHESAPEAKE BAY AT MIDNIGHT WILL ROTATE EASTWARD INTO SOUTH PA...NE MD DURING THE NIGHT WHILE THE NORTHERN PORTION IS STATIONARY WEST OF HAZELTON. THIS IN RESPONSE TO STEERING WIND FIELDS ALOFT...WESTERLY FLOW TO THE SOUTH AND NEARLY E OR SE FLOW N OF 178. ALSO LOW TOP SHOWERS WITH SIGNIFICANT INTENSITY ARE SWEEPING WESTWARD OFF THE ATLANTIC INTO NE NJ. POPS AND WX HAVE BEEN ADJUSTED OVERNIGHT...REFLECTING HIGHER POPS NE NJ. MODELS ARE NOW CARRYING UNSTABLE SWI`S ACROSS NJ OVERNIGHT AND WED MORNING AND IT WILL NOT SURPRISE TO SEE SHOWERS BECOME MORE WIDESPREAD OVER THE FCST AREA BY DAWN. MODEL QPF HAS JUST NOT BEEN VERY GOOD IN THIS INFREQUENTLY OCCURRING PATTERN. GUIDANCE WAS ALSO INDICATING THE POTENTIAL FOR PATCHY FOG, AND WE KEPT THIS IN THE FORECAST WITH THE EAST-NORTHEAST FLOW AND AMPLE MOISTURE. FOR OVERNIGHT TEMPERATURES, WE MOSTLY TOOK A BLEND OF MET/MAV GUIDANCE AND EXPECT LOWS MOSTLY IN THE 50S, EXCEPT SOME LOWER 60S ALONG THE COAST AND IN MORE URBAN AREAS. LIGHT NORTH TO EAST WIND. WEDNESDAY...INSTABILITY SCT SHOWERS ANTICIPATED...AT LEAST THROUGH EARLY AFTN. PWAT CONTINUES 1.2 INCHES SO SOME AREAS WILL RECEIVE BENEFICIAL RAINFALL. SKIES WILL BE MAINLY CLOUDY THROUGH MIDDAY BEFORE SOME SLOW THINNING OCCURS LATE-DAY. MAXIMUM TEMPERATURES WERE A BLEND OF MET/MAV GUIDANCE WITH CONTINUITY, AND WE EXPECT HIGHS MOSTLY IN THE LOW TO MID 70S. LIGHT NORTHEAST WIND. && .SHORT TERM /WEDNESDAY NIGHT/... LOW CLOUDS AND PATCHY FOG RE-EXPAND ACROSS OUR AREA IN LIGHT WIND FIELD ASSOCIATED WITH THE WEDGE OF HIGH PRESS TUCKED DOWN THE COAST FROM EASTERN CANADA. && .LONG TERM /THURSDAY THROUGH TUESDAY/... OPERATIONAL MODELS ARE IN PRETTY GOOD AGREEMENT WITH THE LARGE SCALE FEATURES THROUGH THE WEEKEND. THE FIRST SUCH FEATURE BEING THE DEPARTING UPPER LEVEL CUT-OFF LOW THAT SHOULD BE TO OUR IMMEDIATE EAST. THEN WE HAVE THE POTENTIAL PHASING OF A STRONG NORTHERN AND SOUTHERN STREAM SYSTEM TO OUR WEST THAT CARVES OUT A VERY LARGE AND DEEP CLOSED LOW/TROUGH ACROSS THE UPPER MID-WEST BY LATE FRIDAY NIGHT. THURSDAY...RATHER DRY DAY EXCEPT FOR SOME LINGERING SHOWERS EARLY ON ACROSS OUR EASTERN PORTIONS. THERE COULD STILL BE SOME MID-LEVEL INSTABILITY TO WORK WITH AS THE MID-LEVEL COLD POOL SCRAPES BY BUT NOT EXPECTING MUCH QPF WITH. MID AND UPPER LEVEL RIDGING BECOME MORE PROMINENT ON THURSDAY WHICH SHOULD GIVE WAY TO LATE DAY SUNSHINE. TEMPERATURES WILL BE IN THE LOW-70S; AT OR SLIGHTLY BELOW NORMAL. FRIDAY...MODEL GUIDANCE MAY BE BREAKING DOWN THE RIDGING OVERHEAD A BIT TOO FAST, ESPECIALLY GIVEN THE DOWNSTREAM UPPER LEVEL LOW IS STILL LINGERING BY AND THE APPROACH OF A DEEPENING TROUGH UPSTREAM, THE RIDGE SHOULD BUILD SLIGHTLY BEFORE BREAKING. ONSHORE FLOW AHEAD OF THE NEXT TROUGH AND ATTENDANT SURFACE FRONT MAY ALLOW FOR SCATTERED SHOWERS TO BREAK OUT ALONG THE HIGHER ELEVATION LOCATIONS ACROSS OUR WESTERN ZONES BY LATER FRIDAY AFTERNOON. DO NOT SEE MUCH IN THE WAY OF CONVECTION WITH THIS ACTIVITY GIVEN THE STABLE LOWER ATMOSPHERE. WE SEE A INCREASE IN SHOWER COVERAGE AND POSSIBLY INTENSITY BY LATE FRIDAY NIGHT AS A STRONGER COLD FRONT INCHES CLOSER. DAYTIME TEMPERATURES SHOULD REMAIN MUCH THE SAME, LOW-70S WITH INCREASING COLD COVER. SATURDAY...TRANSITION DAY WITH A STRONG FRONT EXPECTED TO SWEEP THROUGH DURING THE MORNING HOURS. DEEP SOUTHWEST FLOW AHEAD OF THE FRONT WILL ALLOW PWATS TO CLIMB TO WELL ABOVE NORMAL MAKING FOR HEAVIER RAINFALL. ANTECEDENT CONDITIONS ARE STILL PRETTY DRY ACROSS THE REGION SO NOT EXPECTING ANYTHING OUT OF THE ORDINARY TO OCCUR WITH THE POSSIBLE HEAVIER RAIN. LOTS OF CLOUD COVER AND COLD AIR ADVECTION OCCURRING DROPPING TEMPERATURES BACK INTO THE MID TO UPPER-60S. SUNDAY - TUESDAY...CLOSED MID-LEVEL LOW ESTABLISHES ITSELF OVER NORTHERN ONTARIO DURING THE SATURDAY THROUGH TUESDAY TIMEFRAME. PREFERRED THE CMC AND UKMET EVOLUTION OF THE MID-LEVEL HEIGHT FIELD OVER THE GFS AND ECMWF...BOTH OF WHICH HAVE A MORE NEGATIVELY TILTED TROUGH AND PLACEMENT OF THE CLOSED LOW FURTHER SOUTH AND EAST. THERE IS STILL QUITE A BIT UNCERTAINTY AS SHOWN BY BOTH THE GEFS AND ECENS SPREAD IN MID-LEVEL HEIGHT FIELDS FROM THE MEAN AND THIS THINKING IS SUPPORTED BY THE LATEST MODEL VERIFICATIONS WHICH INDICATE A LESS AMPLIFIED SOLUTION. EXPECT WINDS TO DECREASE SATURDAY NIGHT AS A RIDGE OF HIGH PRES NOSES INTO THE REGION. IF THE BOUNDARY LAYER DECOUPLES ENOUGH W/ LIGHT WINDS...COULD SEE LOW TEMPS IN THE 35-40 RANGE IN THE NORTHWEST INTERIOR OF OUR CWA. SUNDAY IS SHAPING UP TO BE THE COOLEST DAY OF THE PERIOD...WITH 850 HPA TEMPS SUPPORTING HIGHS SEVERAL DEGREES BELOW NORMAL...MID 50S IN THE POCONOS TO MID 60S IN SOUTH JERSEY. A WEAK COLD FRONT IS PROGGED TO MOVE THROUGH THE REGION EARLY ON TUESDAY...PRESENTING THE BEST CHANCE OF PRECIPITATION DURING THIS TIMEFRAME. TEMPERATURES WILL RETURN TO SEASONABLE LEVELS ON MONDAY AND CONTINUE THROUGH TUESDAY && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. OVERNIGHT THROUGH 12Z...VFR CONDITIONS WEST AND MVFR CIGS EAST DEGRADING TO IFR CONDITIONS EAST AND POTENTIAL IFR CIGS WEST. SHOWERS COASTAL NNJ AND SHOWERS VCNTY KRDG AND KMPO WITH CHANCE OF THUNDER VCNTY KRDG. WEDNESDAY...POSSIBLE MVFR/IFR CONDITIONS WILL LIKELY LAST THROUGH THE MORNING, BEFORE BECOMING VFR AROUND MIDDAY TO EARLY AFTERNOON FOR THE TAF SITES. AN ISOLATED TO SCATTERED SHOWER REMAINS POSSIBLE THROUGH THE MORNING. NORTHEASTERLY WINDS ARE EXPECTED, MOSTLY IN THE 8 TO 10 KNOT RANGE. WEDNESDAY NIGHT...MVFR OR IFR CONDITIONS REDEVELOP IN LOW CLOUDS/PATCHY FOG. OUTLOOK... THURSDAY...MVFR EARLY BECOMING VFR. EASTERLY WINDS EXPECTED. POSSIBLE LINGERING SHOWER EARLY AT MIV/ACY, OTHERWISE DRY. FRIDAY...MOSTLY VFR. RAIN, HEAVY AT TIMES LATE, OVERSPREADS THE AREA FROM THE WEST. REDUCED VSBYS AND CIGS IN HEAVY SHOWERS. WINDS BACK SOUTH-SOUTHWEST. SATURDAY...MVFR/IFR EARLY IN HEAVY RAIN, TRENDING VFR. WINDS CONTINUE TO BACK TO THE WEST-NORTHWEST. && .MARINE... TWO WEEKS AFTER RESTORATION OF A LENGTHY BUOY 44065 OUTAGE...DATA TRANSMISSION TOPPED AT 4PM THIS PAST TUESDAY AFTERNOON. NDBC HAS BEEN CONTACTED AND THEY WILL LET US KNOW WHAT THE PROBLEM IS. IN THE MEANTIME...MARGINAL SCA CONDITIONS ARE FCST FOR THE NNJ WATERS TODAY. WE DONT REALLY KNOW WHAT THE SEAS ARE DOING OFF THE NNJ COAST. NO EXPANSION OF THE SCA IS ANTICIPATED ATTM FOR THE REMAINDER OF THE WATERS IN OUR 330 AM FCST. BASICALLY NE FLOW CONTINUES THROUGH WEDNESDAY NIGHT WITH MAX GUSTS AROUND 20 KT. SEAS BUILD TO NEAR 5 FT NORTHERN WATERS...NEAR 4 FT SOUTHERN WATERS AND GENERALLY 1-2 FT DELAWARE BAY. OUTLOOK... THURSDAY - FRIDAY...SCA CONDITIONS WILL LIKELY PERSIST ON OUR WATERS THROUGH EARLY FRIDAY AS WE CONTINUE WITH THE EASTERLY ONSHORE FLOW. SEAS WILL CONTINUE TO RUN AROUND 5 FEET. WINDS BEGIN TO BACK TOWARDS THE SOUTH-SOUTHEAST BY FRIDAY AHEAD OF THE NEXT COLD FRONT. SATURDAY...STRONG COLD FRONT MOVES THROUGH. WINDS BACK TOWARDS THE WEST-NORTHWEST LATER IN THE DAY AND WITH STRONGER COLD AIR ADVECTION OCCURRING, WE COULD SEE A RETURN TO SCA CONDITIONS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FROM 11 AM WEDNESDAY TO 6 AM EDT THURSDAY FOR ANZ450>452. && $$ SYNOPSIS...HEAVENER/DRAG 1224A NEAR TERM...DRAG/KLINE/ROBERTSON 1224A SHORT TERM...DRAG/KLINE 1224A LONG TERM...FRANCK/HEAVENER AVIATION...DRAG/HEAVENER/KLINE/ROBERTSON 1224A MARINE...DRAG/HEAVENER/KLINE 1224A

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