Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KPHI 120750 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 350 AM EDT SAT JUL 12 2014 .SYNOPSIS... HIGH PRESSURE WILL SHIFT OFFSHORE THROUGH TODAY. A WARM FRONT SHOULD LIFT NORTH OF THE REGION SUNDAY, THEN A COLD FRONT IS FORECAST TO ARRIVE TUESDAY INTO WEDNESDAY. THIS FRONT SHOULD BE SLOWLY SETTLING TO OUR SOUTH AND EAST WEDNESDAY INTO THURSDAY, THEN HIGH PRESSURE ARRIVES FROM THE WEST THURSDAY AND FRIDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... HIGH PRESSURE IS FORECAST TO SETTLE OVER THE WATERS OFF NEW ENGLAND AND THE MID ATLANTIC REGION FOR TODAY. THE WIND SHOULD BE LIGHT AND VARIABLE EARLY THIS MORNING AND IT IS EXPECTED FAVOR THE SOUTHEAST AND SOUTH AROUND 5 TO 10 MPH FOR LATE THIS MORNING AND THIS AFTERNOON. STRATUS OVER OUR COASTAL WATERS CONTINUED TO DRIFT WESTWARD EARLY THIS MORNING. THE LOW CLOUDS ARE EXPECTED TO AFFECT OUR COASTAL COUNTIES UNTIL ABOUT 7 OR 8 O`CLOCK. THE INCREASING SUNLIGHT IS FORECAST TO MIX OUT THE LOW CLOUDS AROUND THAT TIME. RELATIVELY STABLE AIR IS EXPECTED TO ACCOMPANY THE AREA OF HIGH PRESSURE SO WE ARE ANTICIPATING A MOSTLY SUNNY DAY. THE WESTERN AND NORTHWESTERN FRINGE OF OUR FORECAST AREA MAY BECOME MARGINALLY UNSTABLE DURING THE AFTERNOON. HOWEVER, IT APPEARS AS THOUGH THE MARGINAL INSTABILITY WILL RESULT IN AN INCREASE IN CUMULUS WITH A VERY LOW CHANCE OF ANY PRECIPITATION DEVELOPING. THE STATISTICAL GUIDANCE FROM THE 0000 UTC NAM AND THE 0000 UTC GFS FOR TODAY`S MAXIMUM TEMPERATURES WAS ALMOST IDENTICAL. HIGHS IN OUR REGION SHOULD RANGE MAINLY FROM 86 TO 88 WITH COOLER READINGS NEAR THE COAST DUE TO THE ONSHORE FLOW AND IN THE ELEVATED TERRAIN. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... WE ARE ANTICIPATING AN INCREASE IN HIGH AND MID LEVEL CLOUDS FROM THE WEST FOR TONIGHT, ALONG WITH SOME LINGERING CUMULUS AND STRATOCUMULUS OVER OUR REGION. A LIGHT SOUTHERLY SURFACE FLOW IS EXPECTED. WHILE AN ISOLATED SHOWER OR TWO IS POSSIBLE, ESPECIALLY IN OUR NORTHERN COUNTIES TOWARD MORNING, THE NIGHT SHOULD BE PRECIPITATION FREE AT MOST LOCATIONS. THE SOUTHERLY FLOW WILL LIKELY CAUSE THE HUMIDITY TO INCREASE SLIGHTLY. MINIMUM TEMPERATURES ARE FORECAST TO BE MAINLY IN THE 60S. && .LONG TERM /SUNDAY THROUGH FRIDAY/... THE OVERALL SYNOPTIC SETUP IS COMPRISED OF A POTENT UPPER-LEVEL TROUGH THAT CLOSES OFF AS IT DIGS ACROSS THE MIDWEST AND GREAT LAKES REGION SUNDAY AND MONDAY, THEN BEGINS TO SHIFT INTO PORTIONS OF THE NORTHEAST TUESDAY AND WEDNESDAY. THERE REMAINS SOME DIFFERENCES IN THE MODEL GUIDANCE REGARDING THE TIMING AND AMPLIFICATION OF THIS FEATURE. A SHORT WAVE IN THE NORTHWEST COULD BE ENOUGH TO ALLOW FOR MORE PROGRESSION, HOWEVER AN UPSTREAM RIDGE IN CANADA COULD ALLOW THE SYSTEM TO DIG FARTHER SOUTH. OVERALL, WE LEANED MORE TOWARD THE SLOWER GUIDANCE WHICH RESULTS IN A COLD FRONT MOVING ACROSS OUR AREA IN THE LATER TUESDAY INTO WEDNESDAY TIME FRAME. WE ARE ANTICIPATING CONVECTIVE EPISODES AHEAD OF IT. THERE IS THE POTENTIAL FOR STRONG TO SEVERE THUNDERSTORMS TO OCCUR MONDAY AND TUESDAY AS THE MAIN FEATURES ALOFT AND AT THE SURFACE MOVE THROUGH. THE CONVECTIVE EPISODES SUNDAY AND MONDAY ESPECIALLY TO OUR WEST COULD COMPLICATE RENEWED CONVECTION ON TUESDAY. WE USED A MODEL BLEND FOR SUNDAY INTO TUESDAY, THEN MOSTLY BLENDED THE 00Z WPC GUIDANCE INTO CONTINUITY THEREAFTER. FOR SUNDAY...SOME INCREASE IN THE WAA AHEAD OF AN AMPLIFYING UPPER-LEVEL TROUGH INTO THE GREAT LAKES REGION SHOULD SEND A NORTHBOUND WARM FRONT ACROSS OUR AREA. AS THE UPPER-LEVEL FLOW STARTS TO TURN MORE CYCLONIC, SOME SHOWERS AND THUNDERSTORMS SHOULD DEVELOP WELL INLAND IN THE AFTERNOON. WE MAY HAVE TO WAIT FOR ORGANIZED CONVECTION THOUGH THAT DEVELOPS NEAR THE EASTERN GREAT LAKES TO PROPAGATE EASTWARD AND ARRIVE ACROSS OUR WESTERN ZONES DURING THE AFTERNOON. THIS WOULD BE ASSOCIATED WITH A LOW-LEVEL JET BENEATH THE EXIT REGION OF AN UPPER-LEVEL JET WITHIN A WARM AND MOIST AIRMASS. THERE LOOKS TO BE A LEE SIDE TROUGH AS WELL, SO PERHAPS SOME CONVECTION DEVELOPS NEAR THAT HOWEVER WE ARE MORE FOCUSED ON WHAT DEVELOPS FARTHER TO OUR WEST. AS A RESULT, WE SLOWED DOWN THE POP INCREASE SOME FROM WEST TO EAST DURING THE DAY. IT APPEARS THAT ANY STRONGER /SEVERE?/ CONVECTION WOULD HAVE THE BEST CHC REACHING OUR FAR NORTHWESTERN ZONES BY LATE AFTERNOON. AS AN INITIAL BOUNDARY NEARS AT NIGHT, CONVECTION MAY BE ABLE TO MAINTAIN ITSELF FOR AWHILE WITHIN A MOISTENING AND WARM AIRMASS. IT IS LESS CERTAIN HOW MUCH OCCURS AT NIGHT, THEREFORE CARRIED THE HIGHEST POPS IN THE EVENING. FOR MONDAY THROUGH WEDNESDAY...A ROBUST UPPER-LEVEL TROUGH/CLOSED LOW FOR THIS TIME OF THE YEAR IS FORECAST TO SLIDE ACROSS THE GREAT LAKES REGION AND TOWARD THE NORTHEAST. LOW PRESSURE TRACKING TO OUR NORTHWEST AND NORTH WILL PULL A COLD FRONT INTO THE EAST LATER TUESDAY INTO WEDNESDAY. THE PRESENCE OF STRENGTHENING CYCLONIC FLOW IN COMBINATION WITH AN INCREASINGLY UNSTABLE AIRMASS WILL INITIATE SHOWERS AND THUNDERSTORMS. THIS MAY BE TIED TO AN INITIAL LEE SIDE TROUGH MONDAY OR RESIDUAL BOUNDARIES FROM EARLIER CONVECTION WITH MORE OF A CONVECTIVE ORGANIZATION NEAR AND NORTHWEST OF THE INTERSTATE 95 CORRIDOR. ASSUMING THE FRONT DOES NOT MOVE THROUGH FASTER, THEN A MORE FOCUSED CONVECTIVE EVENT LOOKS TO OCCUR ON TUESDAY. THIS IS WHEN THE STRONGER FLOW, COLD FRONT AND SOME COOLING ALOFT ARRIVES. THE INSTABILITY SHOULD BE ENHANCED SOME AS DEEPER MOISTURE ADVECTS NORTHEASTWARD IN ADVANCE OF THE SURFACE FRONT, HOWEVER CLOUD DEBRIS COULD LIMIT THIS AT LEAST SOME. IT WILL BE WARM AND HUMID AS WELL, AND MONDAY LOOKS TO BE THE WARMEST DAY AS THE LOW-LEVEL WAA SHOULD PEAK /PENDING A WEALTH OF CLOUDS ARE NOT AROUND. ON MONDAY AND TUESDAY, THERE IS THE POTENTIAL FOR SOME STRONG TO SEVERE STORMS. WHILE THERE IS LESS CERTAINTY WITH THE DETAILS, THE POTENTIAL IS THERE FOR SEVERE THUNDERSTORMS. BASED ON THE FORECAST SOUNDINGS, IT APPEARS THAT LINE SEGMENTS WITH EMBEDDED BOWING STRUCTURES WOULD BE THE MAIN STORM MODE GIVEN A MORE UNIDIRECTIONAL FLOW THROUGH THE COLUMN. THE CONVECTION THAT OCCURS ON MONDAY MAY HAVE AN IMPACT ON WHAT DEVELOPS ON TUESDAY. THE PW VALUES ARE FORECAST TO INCREASE TO AROUND 2 INCHES MONDAY AND TUESDAY, WHICH WILL ALLOW FOR LOCALLY TORRENTIAL DOWNPOURS TO OCCUR. THIS COULD ALSO INCREASE THE THREAT FOR WATER LOADED DOWNDRAFTS. WE WILL MAINTAIN A MENTION IN THE HAZARDOUS WEATHER OUTLOOK. ASSUMING A SLOW ENOUGH SYSTEM, SHOWERS AND THUNDERSTORMS LOOK TO MAINTAIN THEMSELVES DEEP INTO TUESDAY NIGHT GIVEN PLENTY OF FORCING. THE COLD FRONT SHOULD BE SLOWLY EASING TO OUR SOUTH AND EAST DURING WEDNESDAY INTO THURSDAY, WITH DRYING ARRIVING FROM THE NORTHWEST. THERE COULD BE SOME SHOWERS/THUNDER LINGERING FOR MOSTLY OUR EASTERN ZONES, AND THEREFORE SOME POPS WERE MAINTAINED. A DECENT AMOUNT OF CLOUDS MAY LINGER WEDNESDAY AS THE FLOW REMAINS SOUTHWESTERLY ON THE EAST SIDE OF THE TROUGH. A COOLER AND MUCH DRIER AIRMASS THEN FOLLOWS. FOR THURSDAY AND FRIDAY...THE PRONOUNCED UPPER-LEVEL TROUGH IS FORECAST TO GRADUALLY LIFT NORTHWARD AWAY FROM OUR AREA DURING THIS TIME FRAME, ALLOWING SURFACE HIGH PRESSURE TO BUILD IN. WE WILL PROBABLY STILL BE WITHIN THE CYCLONIC FLOW THURSDAY WITH A REFRESHING AIRMASS IN PLACE, THEN SOME RIDGING TRIES TO ARRIVE FOR FRIDAY. THIS SHOULD ALLOW SURFACE HIGH PRESSURE TO START OVER OUR AREA BUT THEN BEGIN TO SHIFT EASTWARD DURING FRIDAY. THE GFS APPEARS TO BE OVERDONE AS IT SHOWS MAINLY DAYTIME HEATING DRIVEN CONVECTION BOTH DAYS. NO MAJOR CHANGES WERE MADE TO THIS TIME FRAME. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. IFR CEILINGS ARE FORECAST TO DRIFT OFF THE OCEAN EARLY THIS MORNING, AFFECTING KACY AND KMIV. ALSO, THERE MAY BE SOME LIGHT FOG AT KRDG AND KABE EARLY THIS MORNING. OTHERWISE, VFR CONDITIONS ARE ANTICIPATED THROUGH THE TAF PERIOD FOR OUR EIGHT SITES. THERE IS A LOW POTENTIAL FOR PRECIPITATION IN OUR REGION FOR TODAY INTO TONIGHT WITH THE RAIN SHOWER AND THUNDERSTORM ACTIVITY EXPECTED TO REMAIN TO OUR WEST AND NORTHWEST. A LIGHT AND VARIABLE WIND EARLY THIS MORNING SHOULD SETTLE INTO THE SOUTHEAST AND SOUTH FOR LATE THIS MORNING AND THIS AFTERNOON. SPEEDS ARE FORECAST TO INCREASE INTO THE 6 TO 10 KNOT RANGE. A LIGHT SOUTHERLY WIND, GENERALLY 6 KNOTS OR LESS IS EXPECTED FOR TONIGHT. OUTLOOK... SUNDAY AND MONDAY...GENERALLY VFR WITH SOME SHOWERS AND THUNDERSTORMS. IT APPEARS MOSTLY NORTHWEST OF KPHL SUNDAY, THEN EVERYWHERE SUNDAY NIGHT AND MONDAY. LOCALLY MVFR/IFR CONDITIONS WITH SHOWERS AND THUNDERSTORMS. GUSTY WINDS AT TIMES, ESPECIALLY WITH THUNDERSTORMS. TUESDAY...SHOWERS AND THUNDERSTORMS ARE EXPECTED WITH MVFR/IFR CONDITIONS EXPECTED AT TIMES. GUSTY WINDS IN THE AFTERNOON AROUND 20 KNOTS, WITH STRONGER GUSTS POSSIBLE WITH THUNDERSTORMS. WEDNESDAY...SHOWERS AND A THUNDERSTORM POSSIBLE MAINLY IN THE MORNING, OTHERWISE VFR. && .MARINE... HIGH PRESSURE IS EXPECTED TO REMAIN OVER OUR COASTAL WATERS FOR TODAY AND TONIGHT. A SOUTHEAST TO SOUTH WIND IS FORECAST TO BECOME ESTABLISHED. WIND SPEEDS SHOULD REMAIN LESS THAN 15 KNOTS. WAVE HEIGHTS ON OUR OCEAN WATERS ARE FORECAST TO BE AROUND 2 FEET. WAVE ON DELAWARE BAY ARE ANTICIPATED TO BE 1 FOOT OR LESS. OUTLOOK... SUNDAY THROUGH TUESDAY...THE FLOW BECOMES MORE SOUTHWESTERLY ON SUNDAY. THESE WINDS STRENGTHEN MONDAY AND TUESDAY AHEAD OF A COLD FRONT, HOWEVER THEY SHOULD MOSTLY REMAIN BELOW 25 KNOTS /SMALL CRAFT ADVISORY CRITERIA/. IF ENOUGH MIXING OCCURS ESPECIALLY DURING THE DAYTIME HOURS, SOME MARGINAL ADVISORY GUSTS CAN OCCUR ESPECIALLY NEARSHORE. THE SOUTHERLY FLOW WILL BUILD THE SEAS AND AN ADVISORY MAY BE NEEDED MONDAY AND TUESDAY FOR THE COASTAL WATER ZONES. THE GUIDANCE HOWEVER TENDS TO OVERDO THE SEAS WITHIN A SOUTHERLY FLOW/WAA REGIME. SOME SHOWERS AND THUNDERSTORMS ARE ANTICIPATED MONDAY AND TUESDAY, SOME WITH POTENTIALLY GUSTY WINDS. WEDNESDAY...THE CONDITIONS LOOK TO BE BELOW ADVISORY CRITERIA AS A COLD FRONT SETTLES SOUTH AND EASTWARD AND THE FLOW TURNS WESTERLY. && .TIDES/COASTAL FLOODING... THE HIGH TIDES TONIGHT AND SUNDAY NIGHT MAY APPROACH THE MINOR FLOOD LEVEL ALONG THE ATLANTIC COASTAL AREAS, BUT ARE NOT EXPECTED TO REACH HIGH ENOUGH LEVELS TO REQUIRE A COASTAL FLOOD ADVISORY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GORSE NEAR TERM...IOVINO SHORT TERM...IOVINO LONG TERM...GORSE AVIATION...GORSE/IOVINO MARINE...GORSE/IOVINO TIDES/COASTAL FLOODING...ROBERTSON

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.