Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 121030 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 630 AM EDT SAT APR 12 2014 .SYNOPSIS...
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A FRONTAL BOUNDARY WILL REMAIN TO OUR SOUTH TODAY BEFORE LIFTING BACK TO THE NORTH TONIGHT. HIGH PRESSURE LOCATED OVER THE WESTERN NORTH ATLANTIC IS FORECAST TO INFLUENCE OUR WEATHER FROM SUNDAY INTO MONDAY. A STRONG COLD FRONT IS EXPECTED TO APPROACH FROM THE WEST EARLY IN THE NEW WEEK, AND IT SHOULD PASS THROUGH OUR REGION ON TUESDAY. HIGH PRESSURE IS ANTICIPATED TO BUILD ACROSS THE NORTHEASTERN STATES AND SOUTHEASTERN CANADA FOR THE SECOND HALF OF THE WEEK.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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LIGHT WINDS, JUST ENOUGH LOW-LEVEL MOISTURE, BOUNDARY LAYER COOLING AND CLEARING HAS ALLOWED SOME FOG TO DEVELOP. THIS IS MOST COMMON WHERE THE CLOUDS THINNED OUT SOONER AND ALSO WHERE SOME RAIN FELL YESTERDAY /I.E. OUR WESTERN ZONES/. WHILE SOME FOG MAY BE LOCALLY DENSE, IT APPEARS IT SHOULD REMAIN LOCALIZED HOWEVER WE WILL MONITOR. THE FOG IS EXPECTED TO DISSIPATE BY MID MORNING. MEANWHILE, A WEAK COLD FRONT CONTINUES TO EASE OFF THE COAST WITH THE LAST OF THE ISOLATED SHOWERS DISSIPATING. AS A SHORT WAVE TROUGH QUICKLY SHIFTS TO OUR NORTHEAST EARLY THIS MORNING, THE UPPER-LEVEL FLOW WILL TEND TO BE ZONAL. THIS WILL ALLOW HIGH PRESSURE AT THE SURFACE TO QUICKLY BUILD ACROSS OUR AREA, HOWEVER IT WILL ALREADY BE SHIFTING OFFSHORE BY THE EVENING HOURS. THIS WILL RESULT IN A LIGHT NORTHERLY WIND BECOMING SOUTHERLY. AS THIS OCCURS, A STRONG WAA REGIME AT 850 MB IS FORECAST TO OCCUR UP THE OHIO VALLEY AND INTO MUCH OF THE GREAT LAKES REGION. THIS WILL ALSO DRIVE A WARM FRONT NORTHBOUND LATE TODAY. THE FORECAST SOUNDINGS GENERALLY SUGGEST MAINLY SOME HIGH CLOUDS THROUGH THE DAY ONCE ANY LOWER CLOUDS DISSIPATE. THE FLOW IS FORECAST TO BECOME EVEN LIGHTER DURING THE COURSE OF THE DAY, AND WITH A GROWING TEMPERATURE CONTRAST BETWEEN THE WATER AND LAND, A SEA AND BAY BREEZE SHOULD DEVELOP AROUND MIDDAY AND POTENTIALLY BE ENHANCED SOME FROM THE LIGHT SYNOPTIC SOUTHERLY FLOW. THIS WILL KEEP THE COASTAL LOCALES ON THE COOLER SIDE. OVERALL, A QUIET DAY IS IN STORE AS HIGH PRESSURE SLIDES ACROSS. THE AIR MASS IS FORECAST TO BE COOLER ALOFT COMPARED TO YESTERDAY, THEREFORE WHILE ANOTHER MILD DAY IS EXPECTED IT SHOULD NOT BE AS WARM AS WHAT WAS OBSERVED YESTERDAY. WE GENERALLY USED A BLEND OF THE NAM/GFS MOS FOR HIGH TEMPERATURES. THE LAMP/LAV GUIDANCE WAS USED TO ASSIST WITH ADJUSTMENTS MADE TO THE HOURLY GRIDS EARLY THIS MORNING.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... HIGH PRESSURE WILL CONTINUE TO SHIFT FARTHER AWAY FROM THE MID ATLANTIC COAST. MEANWHILE, LOW PRESSURE IS FORECAST TO TRACK UP ACROSS THE CENTRAL GREAT LAKES OVERNIGHT. A WARM FRONT ATTACHED TO THIS SURFACE LOW SHOULD LIFT WELL TO OUR NORTH, WITH THE 850 MB THERMAL GRADIENT MORE NOTABLE NEAR THE U.S. AND CANADIAN BORDER. A STRENGTHENING SOUTHWESTERLY FLOW ALOFT WILL INCREASE THE OVERALL WAA PATTERN ACROSS THE MID ATLANTIC REGION. THEREFORE, SOME INCREASE IN CLOUDS ARE ANTICIPATED THROUGH THE NIGHT, ESPECIALLY ACROSS THE WESTERN AREAS. THE STRONGER ISENTROPIC LIFT APPEARS TO MORE FOCUSED TO OUR NORTHWEST, THEREFORE WE MAINTAINED A DRY FORECAST. AS THE FLOW WILL BE SOUTH TO SOUTHEAST AT THE SURFACE, THE LOW- LEVEL MOISTURE IS EXPECTED TO INCREASE SOME. WHILE THE SURFACE WINDS SHOULD BE ON THE LIGHT SIDE, THE WAA ALOFT WILL ALLOW FOR A SHARPENING LOW-LEVEL INVERSION TO DEVELOP ESPECIALLY AS THE BOUNDARY LAYER COOLS. THE FORECAST SOUNDINGS INDICATE THAT SOME LOW CLOUDS AND/OR FOG DEVELOPS LATE TONIGHT, HOWEVER THE MOIST LAYER LOOKS TO BE RATHER SHALLOW. IF THIS IS THE CASE, THEN ANY LOW CLOUDS/FOG WOULD TEND TO BE LOCALIZED. AS OF NOW WE BROUGHT IN SOME INCREASE IN CLOUDS, HOWEVER WILL LEAVE OUT A FOG MENTION AS IT IS NOT ALL THAT CLEAR IF ANY FOG WOULD BE WIDESPREAD ENOUGH FOR AN IMPACT. AS FOR LOW TEMPERATURES WE USED A NAM/GFS MOS BLEND, BUT THEN MADE SOME ADJUSTMENTS ESPECIALLY FOR THE NORMALLY COOLER LOCALES AND A SEA BREEZE INFLUENCE EARLY ON. && .LONG TERM /SUNDAY THROUGH FRIDAY/... A BUILDING RIDGE OVER THE WESTERN NORTH ATLANTIC WILL CONTINUE TO BRING WARM AIR INTO OUR REGION FOR SUNDAY AND MONDAY ALONG WITH FAIR WEATHER CONDITIONS. DAYTIME HIGHS SHOULD BE MAINLY IN THE 70S ON BOTH DAYS WITH OVERNIGHT LOWS IN THE 50S. THE AXIS OF A MID LEVEL TROUGH APPROACHING FROM THE WEST IS EXPECTED TO BE LOCATED OVER THE MISSISSIPPI RIVER VALLEY ON MONDAY NIGHT. THE FEATURE IS FORECAST TO FLATTEN AS IT MOVES OVER THE EASTERN STATES. THE GFS REMAINS MORE PROGRESS WITH THE TROUGH THAN THE ECMWF. A STRONG SURFACE COLD FRONT ASSOCIATED WITH THE MID LEVEL TROUGH SHOULD EXTEND FROM THE EASTERN GREAT LAKES TO THE LOWER MISSISSIPPI RIVER VALLEY ON MONDAY EVENING. THE FRONT WILL PROGRESS EASTWARD AND IT IS EXPECTED TO PASS THROUGH OUR REGION AROUND TUESDAY AFTERNOON. WE HAVE TAKEN A COMPROMISE IN THE TIMING OF THE PRECIPITATION WITH THE SYSTEM BETWEEN THE GFS AND THE ECMWF. BOTH MODELS ARE SUGGESTING RAINFALL AMOUNTS IN THE 0.75 TO 1.25 INCH RANGE AT THIS POINT. HOWEVER, THE MODELS HAVE BEEN RUNNING A LITTLE HIGH OF LATE. WE WILL CONTINUE TO MONITOR THE TRENDS FOR ANY FLOODING POTENTIAL. FOR NOW, WE WILL SIMPLY MENTION THAT THE RAIN COULD BECOME HEAVY AT TIMES. AS THE MAIN AREA OF PRECIPITATION MOVES OFF THE COAST ON TUESDAY NIGHT, COLD AIR WILL BEGIN TO BUILD INTO OUR REGION FROM THE NORTHWEST. IT CONTINUES TO SEEM QUITE POSSIBLE THAT THE EVENT COULD END WITH A LITTLE SNOW ACROSS OUR NORTHERN COUNTIES. BASED ON THE EXPECTED TIMING OF THE BACK EDGE OF THE PRECIPITATION AND THE ARRIVAL OF THE COLD AIR, WE ARE NOT ANTICIPATING ANY SIGNIFICANT SNOWFALL AMOUNTS AT THIS POINT. COOL HIGH PRESSURE IS FORECAST TO BUILD FROM THE EASTERN GREAT LAKES TO ATLANTIC CANADA DURING THE PERIOD FROM WEDNESDAY THROUGH FRIDAY WITH A SURFACE RIDGE AXIS DEVELOPING DOWN THE LEE OF THE APPALACHIANS. THE PATTERN WILL KEEP OUR REGION IN A COOL NORTH TO NORTHEAST SURFACE FLOW. TEMPERATURES WILL BE BELOW NORMAL. A PARTLY CLOUDY TO MOSTLY CLEAR SKY IS ANTICIPATED FOR WEDNESDAY NIGHT ALONG WITH A RELATIVELY LIGHT WIND. AS A RESULT, PATCHY FROST IS POSSIBLE FOR LATE WEDNESDAY NIGHT INTO EARLY THURSDAY MORNING. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TODAY...LOCALLY MVFR/IFR OR LOWER AT TIMES EARLY DUE TO FOG ESPECIALLY FROM KRDG AND KABE TO NEAR KTTN, OTHERWISE VFR. THE COVERAGE OF THE FOG EARLY THIS MORNING CARRIES SOME LOWER CONFIDENCE. LIGHT AND VARIABLE WINDS EARLY THIS MORNING BECOMING NORTHERLY AROUND 5 KNOTS, THEN SOUTHWEST AND SOUTH FROM ABOUT MIDDAY ON. THERE SHOULD BE A SEA/BAY BREEZE DEVELOPING THIS AFTERNOON GIVEN LIGHTER WINDS, AND THIS WILL AFFECT KACY, KMIV TO KILG. TONIGHT...VFR OVERALL. A STRONG LOW-LEVEL INVERSION THOUGH ESPECIALLY LATE MAY RESULT IN SOME LOW CLOUDS AND/OR FOG DEVELOPMENT UNDER A LIGHT SOUTH TO SOUTHEAST WIND. AS OF NOW OUR CONFIDENCE IS ON THE LOWER SIDE, THEREFORE WE WILL JUST HINT AT THIS POTENTIAL IN THE 12Z TAFS. OUTLOOK... SUNDAY THROUGH MONDAY...MAINLY VFR. PATCHY LATE NIGHT AND EARLY MORNING LOW CLOUDS AND FOG MAY LOWER CONDITIONS INTO THE MVFR AND IFR RANGES. MONDAY NIGHT...LOWERING CONDITIONS LATE AT NIGHT AS RAIN SHOWERS BEGIN TO MOVE INTO OUR REGION FROM THE WEST. TUESDAY...MVFR AND IFR CONDITIONS IN RAIN. THE RAIN MAY BECOME HEAVY AT TIMES. TUESDAY NIGHT...MVFR AND IFR CONDITIONS WITH RAIN TAPERING TO SHOWERS. WEDNESDAY...MAINLY VFR.
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&& .MARINE... HIGH PRESSURE WILL SLIDE ACROSS THE AREA TODAY HOWEVER BE SHIFTING TO OUR EAST BY EARLY THIS EVENING. THIS WILL RESULT IN A NORTHERLY WIND BECOMING SOUTHERLY THROUGH THE AFTERNOON. THIS MAY BE SOMEWHAT ENHANCED NEAR SHORE AND UP DELAWARE BAY AS A SEA/BAY BREEZE DEVELOPS. OVERALL THOUGH THE WINDS ARE EXPECTED TO REMAIN BELOW ADVISORY CRITERIA THROUGH TONIGHT. THE SEAS HAVE SUBSIDED AND DESPITE THE FLOW BECOMING SOUTHERLY, WE ARE ANTICIPATING THIS TO REMAIN LIGHT ENOUGH TO KEEP SEAS BELOW 5 FEET. AN INCREASE IN THE LOW-LEVEL MOISTURE AND WARMER AIR ABOVE A STRENGTHENING INVERSION COULD RESULT IN SOME FOG DEVELOPMENT LATER TONIGHT. AS OF NOW, THIS WAS NOT INCLUDED DUE TO SOME LOWER CONFIDENCE. OUTLOOK... SUNDAY...NO MARINE HEADLINES ARE ANTICIPATED. SUNDAY NIGHT AND MONDAY...WAVE HEIGHTS ON OUR OCEAN WATERS MAY BUILD TO 5 FEET OR GREATER IN THE PERSISTENT SOUTHERLY FLOW. MONDAY NIGHT AND TUESDAY...WIND GUSTS OF 25 KNOTS OR GREATER FROM THE SOUTH AND WAVE HEIGHTS OF 5 FEET OR GREATER ARE POSSIBLE ON OUR OCEAN WATERS. TUESDAY NIGHT...WAVE HEIGHTS ON OUR OCEAN WATERS MAY REMAIN AT 5 FEET OR GREATER AS A STRONG COLD FRONT MOVES OUT TO SEA. WEDNESDAY...NO MARINE HEADLINES ARE ANTICIPATED. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...IOVINO NEAR TERM...GORSE SHORT TERM...GORSE LONG TERM...IOVINO AVIATION...GORSE/IOVINO MARINE...GORSE/IOVINO

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