Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Text Only | 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
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KPHI 302006 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 406 PM EDT SAT AUG 30 2014 .SYNOPSIS...
-- Changed Discussion --
A WARM FRONT WILL LIFT NORTH THROUGH THE AREA TONIGHT. THIS WARM FRONT IS EXPECTED BECOME QUASI-STATIONARY NEAR THE CANADIAN BORDER SUNDAY THROUGH TUESDAY...WITH A TROUGH EXTENDING SOUTHWARD TO THE LEE OF THE APPALACHIANS...BETWEEN BERMUDA HIGH PRESSURE ANCHORED OFFSHORE AND A SLOW MOVING COLD FRONT IN THE MISSISSIPPI VALLEY. THIS VERY WEAK COLD FRONT IS PROJECTED MOVE THROUGH THE REGION LATE TUESDAY INTO EARLY WEDNESDAY...FOLLOWED BY BERMUDA HIGH PRESSURE RETURNING TO DOMINATE LATER IN THE WEEK. ANOTHER COLD FRONT MAY APPROACH THE REGION EARLY NEXT WEEKEND.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --
EXPANSIVE AREA OF STRATOCU ACROSS THE REGION SHOULD BEGIN TO THIN OUT SOME BY THIS EVENING AS BOUNDARY LAYER HEATING CONTINUES. SOMETHING RESEMBLING A WARM FRONT, STILL TO OUR SOUTH AND WEST, WILL GRADUALLY LIFT THROUGH LATER TONIGHT, IF IT DOESN`T WASH OUT ENTIRELY. NONE-THE-LESS THE AIRMASS MODIFICATION WILL CONTINUE AS PLANNED AS DEWPOINTS WILL JUMP INTO THE MID TO UPPER-60S IN A LOT OF SPOTS TONIGHT. STRONGER WARM AIR ADVECTION WILL ALSO TAKE PLACE ALLOWING A LOW-LEVEL INVERSION TO SET UP. WINDS WILL GRADUALLY DECREASE TONIGHT, LIGHTENING UP FROM THE SOUTH, TO ALLOW FOR FOG AND A DECK OF STRATUS TO FORM. GUIDANCE IS SHOWING SOME ISOLATED SHOWERS TRYING TO WORK THERE WAY INTO THE REGION LATE TONIGHT ON THE NOSE OF THE BETTER WAA SHOT. WE DO CARRY SLIGHT CHANCE POPS FOR OUR WESTERN ZONES, BUT THE MODELS MAY BE PICKING UP ON THE MOISTENING BOUNDARY LAYER AND POTENTIAL FOG FORMATION WITH LITTLE IN THE WAY OF QPF. OVERNIGHT LOWS WILL BE SEVERAL DEGREES WARMER THAN THE PAST FEW MORNINGS. A BLEND OF THE MET/MAV SEEMS REASONABLE AT THIS TIME GIVING US ABOVE NORMAL LOWS.
-- End Changed Discussion --
&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
-- Changed Discussion --
CONTINUED AIRMASS MODIFICATION OCCURS A PWATS CLIMB CLOSER TO THE 2 INCH MARK. DEWPOINTS JUMP INTO THE UPPER-60S, POSSIBLY LOW-70S DURING THE DAY MAKING FOR MUGGY CONDITIONS. TEMPERATURES, UNDER STRONGER WAA, SHOULD BE ABLE TO WARM INTO THE MID TO UPPER-80S THOUGH NOT QUITE SURE HOW MUCH THE CLOUD COVER WILL PLAY A FACTOR. WE EXPECT THE MORNING STRATUS TO LIFT AND BURN OFF WITH A STRONGER LOW-LEVEL JET MOVING IN OVERHEAD ALLOWING FOR DEEPER MIXING. HIGHER BASED DECKS ARE EXPECTED IN ADVANCE OF AN APPROACHING MID-LEVEL SHORTWAVE AND SURFACE TROUGH. THESE TWO FEATURES WILL MORE THAN LIKELY BE THE CATALYST FOR AFTERNOON AND EVENING CONVECTIVE INITIATION. DECENT AMOUNT SHEAR AND BOUNDARY LAYER INSTABILITY WILL BE PRESENT AND WHEN COMBINED WITH THE ABOVE NORMAL PWATS HEAVY RAIN IS A POSSIBILITY. THE GOOD THING ABOUT TOMORROW IS THAT THE FLOW SHOULD BE STRONG ENOUGH TO KEEP THE STORMS MOVING, THE BAD THING IS THAT WITH THE AVAILABLE INSTABILITY WE COULD SEE NUMEROUS TOWERS SHOOT UP TO GIVE US SOME STRONG WET-MICROBURSTS LATER IN THE EVENING. MOST OF THE MESOSCALE MODELS PAINT THIS SCENARIO ACROSS OUR NORTHWESTERN ZONES, CLOSER TO THE SHORTWAVE PASSAGE. WE WILL CONTINUE TO WATCH THE DEVELOPMENT FOR ANY LOCALIZED FLOOD AND SEVERE ISSUES.
-- End Changed Discussion --
&& .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
-- Changed Discussion --
SUNDAY NIGHT....BIG CONCERN THROUGH THIS PERIOD WILL BE THE CONVECTION. THE UPPER LEVEL TROUGH OVER THE UPPER MID WEST NOW WILL BE LIFTING OVER THE NORTHEAST U.S. BY TOMORROW NIGHT. HOWEVER, ALL MODELS SHOW THE TROUGH FILLING AS IT LIFTS, WHICH IS CONSISTENT WITH WHAT WAS OBSERVED WITH THE 12Z SOUNDINGS THIS MORNING, WHICH SHOWED VERY MARGINAL HEIGHT FALLS AHEAD OF THE TROUGH AXIS. AS MENTIONED BY THE PREVIOUS SHIFT, PWAT VALUES ARE EXPECTED TO BE ABOVE NORMAL, NEAR 2 INCHES. HOWEVER, AS MENTIONED PREVIOUSLY WITH MEAN FLOW OF NEAR OR ABOVE 30 KT...STORM MOTIONS SHOULD BE RELATIVELY FAST AND AS MENTIONED IN THE PREVIOUS DISCUSSION, WE STILL HAVE RELATIVELY DRY ANTECEDENT CONDITIONS. THUS DON`T ANTICIPATE WIDESPREAD ISSUES OUTSIDE OF SOME POOR DRAINAGE/URBAN NUISANCE FLOODING AT THIS TIME. AS FOR THE SEVERE THREAT, CAPE VALUES (BOTH SURFACE BASED OR ELEVATED - WHICH MAY BE MORE REALISTIC FOR THE NIGHT TIME HOURS) COULD BE NEAR OR ABOVE 500 J/KG. AT THE SAME TIME, BULK SHEAR (MOSTLY SPEED SHEAR) COULD BE NEAR 30KT. THIS COULD BE ENOUGH FOR STRONG OR EVEN MARGINALLY SEVERE STORMS FOR WINDS, AND POSSIBLY ENOUGH FOR SOME SMALL HAIL. LABOR DAY...THERE MAY BE A BRIEF BREAK IN THE CONVECTION (OR AT LEAST MORE LIMITED COVERAGE) AS THE 500MB SHORT WAVE RIDGE AXIS MOVES OVER. AS IT DOES SO, MEAN FLOW WILL DECREASE, HOWEVER PWAT VALUES WILL LIKELY ALSO DECREASE AS THE FLOW TURNS MORE WESTERLY. THUS, THINK THE FLOODING THREAT WILL REMAIN MORE OF A URBAN AND POOR DRAINAGE THREAT. TUESDAY INTO WEDNESDAY...EXPECT A LULL IN THE PRECIPITATION CHANCES BEFORE THE NEXT UPPER LEVEL TROUGH (AT THIS TIME OVER THE GREAT BASIN REGION) SLIDES EAST, AS DOES THE ASSOCIATED SURFACE COLD FRONT. GFS AND ECMWF SPED UP THE TIMING OF THE COLD FRONT WITH THE LATEST RUNS...NOW ARRIVING AS EARLY AS TUESDAY EVENING. IN THE WAKE OF THE FRONT, EXPECT DRIER AND COOLER WEATHER, THOUGH TEMPERATURES WILL LIKELY STILL BE SLIGHTLY ABOVE NORMAL. THURSDAY THROUGH SATURDAY...UPPER LEVEL FLOW TRANSITIONS TO MOSTLY ZONAL FLOW BY THURSDAY WITH A SURFACE HIGH SETTLING IN THROUGH FRIDAY. BY SATURDAY THE NEXT UPPER LEVEL TROUGH PROPAGATES EAST ACROSS SOUTHERN CANADA. THERE IS UNCERTAINTY HOWEVER, GIVEN THE MOSTLY ZONAL FLOW IF THE ASSOCIATED COLD FRONT WILL DIG AS FAR SOUTH AS OUR REGION BEFORE FRONTOLYSIS OCCURS. FOR NOW, HAVE A SLIGHT CHANCE FOR THUNDERSTORMS THROUGH THE WEEKEND GIVEN THE UNCERTAINTY.
-- End Changed Discussion --
&& .AVIATION /19Z SATURDAY THROUGH THURSDAY/...
-- Changed Discussion --
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THROUGH LATE EVENING...VFR. STRATOCU BASES WILL REMAIN BETWEEN 3500 TO 5000 FEET. WINDS CONTINUE OUT OF THE SOUTH AND COULD BACK MORE TOWARDS THE SOUTH-SOUTHWEST AROUND 10 KNOTS. TONIGHT...VFR TO MVFR, POSSIBLY IFR. WINDS LIGHTEN UP BUT REMAIN MOSTLY SOUTHERLY. MORE MOISTURE MOVES IN ALLOWING AT LEAST AN MVFR DECK WITH PATCHY FOG TO DEVELOP. SOME LOCATIONS MAY DROP TO IFR, HAD SLIGHTLY HIGHER CONFIDENCE AT ILG AND TTN BASED ON SURFACE FLOW AND CLIMATOLOGY. TOMORROW...VFR. STRATUS MIXES OUT BY LATE MORNING LEAVING MOSTLY ALTOCU IN PLACE. MOST SHOWERS AND POTENTIAL THUNDER SHOULD HOLD OFF UNTIL LATE IN THE PERIOD. OUTLOOK... SUNDAY NIGHT INTO MONDAY NIGHT...IFR CONDITIONS EXPECTED WITH SHOWERS AND THUNDERSTORMS. COVERAGE OF PRECIPITATION DECREASING BY MONDAY NIGHT. TUESDAY AND TUESDAY NIGHT...CONDITIONS IMPROVING TO VFR EARLY IN THE DAY. STILL A SMALL THREAT OF SHOWERS AND THUNDERSTORMS. WEDNESDAY THROUGH THURSDAY...GENERALLY VFR CONDITIONS EXPECTED.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
SUB-SCA CONDITIONS EXPECTED TONIGHT AND A MAJORITY OF TOMORROW. SEAS WILL CONTINUE TO BUILD THROUGH SUNDAY UNDER A STRENGTHENING SOUTHERLY FLOW THAT BEGINS TO BACK TOWARDS THE SOUTHWEST LATER TOMORROW. THIS COULD POSE SOME ISSUES AROUND THE INLETS WHERE LARGER SWELLS, CLOSE TO 5 FEET, AND GUSTS AROUND 25 KNOTS MAY OCCUR...MOSTLY NEARSHORE FOR THE GUSTS. DECIDED THE SETUP WAS TOO MARGINAL TO WARRANT A SMALL CRAFT AT THIS TIME. OUTLOOK... MONDAY NIGHT...WINDS AND SEAS SHOULD REMAIN JUST BELOW SMALL CRAFT ADVISORY CRITERIA. GUSTIER WINDS POSSIBLE IN THE VICINITY OF THUNDERSTORMS. TUESDAY THROUGH THURSDAY...WINDS AND SEAS EXPECTED TO REMAIN WELL BELOW SCA CRITERIA. HOWEVER, SOME GUSTY WINDS ARE POSSIBLE WITH THUNDERSTORMS ON TUESDAY.
-- End Changed Discussion --
&& .RIP CURRENTS...
-- Changed Discussion --
THERE IS A MODERATE RISK OF DANGEROUS RIP CURRENTS THROUGH THIS EVENING, AS ENOUGH OF A SWELL COMPONENT IS STILL PRESENT TO ENHANCE THE FORMATION OF RIP CURRENTS.
-- End Changed Discussion --
&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...FRANCK NEAR TERM...HEAVENER SHORT TERM...HEAVENER LONG TERM...JOHNSON AVIATION...HEAVENER/JOHNSON MARINE...HEAVENER/JOHNSON RIP CURRENTS...

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