Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 011816 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 216 PM EDT FRI AUG 1 2014 .SYNOPSIS... SEVERAL WEAK SURFACE TROUGHS WILL MOVE INTO THE AREA TODAY, BEFORE HIGH PRESSURE OVER THE WESTERN ATLANTIC PUSHES AN OFFSHORE WARM FRONT NORTHWESTWARD ACROSS THE EAST COAST THIS WEEKEND. SEVERAL DISTURBANCES WILL MOVE NORTHEAST ALONG THIS BOUNDARY THROUGH THE WEEKEND. ANOTHER COLD FRONT WILL THEN MOVE ACROSS THE AREA LATE TUESDAY INTO WEDNESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... WITH THE UPDATE, WE RAISED DEWPOINTS ACROSS THE REGION BY TWO TO THREE DEGREES USING THE LAV/LAMP GUIDANCE TO REFLECT CURRENT OBS AND TRENDS THROUGH LATE MORNING AND INTO THE AFTERNOON. NOT MUCH ADJUSTMENT WAS NEEDED TO HOURLY TEMPS, AND TODAYS MAXIMUM TEMPS LOOK ON TRACK, ESPECIALLY WITH THE INCOMING MID AND HIGH CLOUDS. WE DID ADJUST POPS DOWN A BIT THROUGH THE REMAINDER OF THE MORNING, BASED ON CURRENT RADAR TRENDS AND HRRR GUIDANCE AS SHOWERS ARE HAVING A DIFFICULT TIME MAKING IT INTO OUR SOUTHERN DELMARVA ZONES, WITH SOMEWHAT DRIER MID/UPPER LEVEL AIR. WE ALSO CONFINED ANY ISOLATED TO SCATTERED TSTORM CHANCES TO THE AFTERNOON. OTHERWISE, AN ACTIVE WEATHER PATTERN WILL BE RAMPING UP IN THE NEAR AND SHORT TERM. FIRST...A SHORT WAVE TROUGH CURRENTLY OVER VIRGINIA WILL MOVE OVER THE REGION BY 18Z. THERE IS CURRENTLY AN AREA OF MOSTLY STRATIFORM PRECIPITATION ASSOCIATED WITH THIS TROUGH. HOWEVER...AS THIS TROUGH PROPAGATES NORTHEAST...IT WILL ENCOUNTER DRIER AIR ESPECIALLY IN THE MID AND UPPER LEVELS. THUS...EXPECT CLOUDS, BUT NOT NECESSARILY WIDESPREAD PRECIP TO MOVE INTO THE REGION EARLY IN THE DAY. WHAT SHOWERS AND STORMS DO MOVE INTO THE REGION SHOULD BE LIMITED IN COVERAGE, AT LEAST AT FIRST. IT DOES APPEAR THAT THERE WILL BE ENOUGH INSTABILITY TO SUPPORT THUNDERSTORMS. THE NAM EVEN SHOWS ML CAPE VALUES NEAR 1000 J/KG. HOWEVER, IT SEEMS THAT THE NAM IS OVERLY AGGRESSIVE WITH LOW LEVEL MOISTURE RETURN, AND THUS TOO HIGH ON THE INSTABILITY. ALSO, THE PERSISTENT CLOUD COVER SHOULD HELP TO KEEP SURFACE TEMPERATURES DOWN SLIGHTLY, FURTHER LIMITING INSTABILITY. THUS, THE GFS SEEMS TO HAVE A BETTER HANDLE ON THIS ASPECT, WITH ML CAPE VALUES GENERALLY LESS THAN 500 J/KG. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... RIGHT ON THE HEALS OF THE FIRST SHORT WAVE TROUGH TODAY, A SECOND UPPER LEVEL SHORT WAVE TROUGH APPROACHES THE REGION. THIS, COUPLED WITH THE MOIST SOUTHERLY AND SOUTHWESTERLY FLOW, AND A SLOW MOVING WARM FRONT WHICH APPROACHES THE REGION LATE TONIGHT, WILL MEAN INCREASED PRECIP CHANCES FOR MUCH OF THE REGION. THIS IS ESPECIALLY TRUE FOR THE EASTERN HALF OF THE REGION WHICH SHOULD HAVE SLIGHTLY BETTER LIFT, AND SEE PRECIPITABLE WATER VALUES CLIMB TO NEAR 2 INCHES BY LATE IN THE PERIOD. && .LONG TERM /SATURDAY THROUGH THURSDAY/... OVERALL THE MEDIUM RANGE IS ON PAR WITH ONE ANOTHER WITH THE SYNOPTIC FEATURES THROUGH EARLY NEXT WEEK. THE EARLY PART OF THE LONGTERM PERIOD, THIS WEEKEND, IS STILL VIEWED AS AN AVERAGE TO SLIGHTLY BELOW AVERAGE CONFIDENCE, INLAND, AS THE TIMING AND PLACEMENT OF SEVERAL SMALLER IMPULSES AND COASTAL BAROCLINIC ZONE INTERACTION OCCURS. SATURDAY...STARTING TO SEE SOME BETTER CONSENSUS, THOUGH STILL NOT GREAT, AND ACCORDING TO THE 01/00Z DATA THE NON-NCEP MEMBERS HAVE JUMPED MORE TOWARDS THE NCEP GUIDANCE IN KEEPING THE BAROCLINIC ZONE AND ITS SUBSEQUENT SURFACE WAVES MORE OFFSHORE...EC INCLUDED. THE GEFS HAS BEEN PRETTY CONSISTENT THE PAST FEW NIGHTS WHILE THE EC ENSEMBLES HAVE BEEN TRENDING LESS CONFIDENT IN THE MID-LEVELS AND AT MORESO AT THE SURFACE. PWATS INCREASE UPWARDS 1.5 TO 1.75 INCHES BY SATURDAY EVENING WITH GREATER AMOUNTS EAST OF THE DELAWARE RIVER. UPPER LEVEL JET DYNAMICS WITH THE RIGHT ENTRANCE REGION SITTING ACROSS THE MID-ATLANTIC AND AMPLE SUB-TROPICAL MOISTURE AVAILABLE FOR THE PASSING WAVES TO TAP INTO, WE COULD BE LOOKING AT A HEAVY RAIN POTENTIAL...GREATER CHANCES EAST OF THE RIVER CLOSER TO THE COAST AND FRONTAL BOUNDARY. TEMPERATURES WILL STRUGGLE TO GET OUT OF THE 70S IN A LOT OF PLACES WITH LOTS OF CLOUD COVER, RAIN, AND EASTERLY FLOW. THE METMOS SEEMED TOO LOW, AS IT USUALLY GOES CRAZY WITH STRATUS WHEN RAIN IS FORECASTED. ANY BREAKS IN THE CLOUDS FOR AN HOUR OR TWO COULD EASILY BOOST SOME LOCATIONS INTO THE LOW-80S. SUNDAY...THERE LOOKS TO BE A DRIER PERIOD, AT LEAST THE FIRST HALF OF THE DAY BEFORE A STRONGER MID-LEVEL WAVE NEARS FROM THE WEST DURING THE AFTERNOON HOURS...THIS IS THE KICKER VORT LOBE. COLD POOL INTERACTION ALOFT AND MINIMAL SURFACE HEATING SHOULD BE ENOUGH FOR SCATTERED SHOWERS WITH VERY ISOLATED CONVECTION. AGAIN, FRONTAL BOUNDARY STILL CLOSE TO THE REGION SO WE HAVE LIKELY POPS ACROSS SOUTHERN DELMARVA AND ALONG THE NJ COAST. TEMPERATURES MAY END UP BEING A DEGREE OR TWO WARMER THAN SATURDAY WITH POSSIBLY MORE BREAKS IN THE CLOUDS. MONDAY...DEPENDING ON THE TIMING OF MORE MID-LEVEL SHORTWAVES, OR LACK THEREOF, MONDAY COULD END UP BEING A MOSTLY DRY DAY. EC DOES NOT SHOW MUCH FORCING WHILE THE GFS KEEPS A FEW IMPULSES SHEARING THROUGH. GEFS PAINTS A PRETTY BROAD AREA OF AT LEAST CHANCE POPS AND GIVEN THE UNCERTAINTY AT THIS POINT DID NOT WANT TO CHANGE TOO MUCH DURING THE TIMEFRAME...CONTINUE CHANCE POPS WITH MODERATING TEMPERATURES. TUESDAY - THURSDAY...CONTINUING CYCLONIC FLOW ALOFT MAY BE ENOUGH FOR ISOLATED SHOWER ACTIVITY EACH AFTERNOON, OTHERWISE A MOSTLY DRY FORECAST IS EXPECTED THIS TIMEFRAME. WEAK FRONT MAY CROSS ON WEDNESDAY WITH OUR BEST CHANCES AT SCATTERED ACTIVITY. TEMPERATURES MODERATE EVEN MORE AND SHOULD END UP BEING NORMAL. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. WITH THE 18Z TAFS, WE HAVE INCLUDED A TEMPO GROUP FOR EITHER SHRA OR TSRA COVERING THE AFTERNOON TO EARLY EVENING TIMEFRAME TO BEST REFLECT THE POSSIBLE TIMING OF ISOLATED TO SCATTERED SHWRS/TSTORMS ACROSS THE REGION. OVERALL, MOST CIGS/VSBYS WILL REMAIN VFR, BUT AN ISOLATED SHWR/TSTORM COULD CAUSE LOCALLY REDUCED CIGS/VSBYS. THEREAFTER, WE EXPECT A BIT OF A LULL IN ACTIVITY LATER IN THE EVENING AS ISOLATED/SCATTERED CONVECTION WANES. ANOTHER DISTURBANCE AND OFFSHORE FRONTAL BOUNDARY IS THEN EXPECTED TO BRING ANOTHER ROUND OF RAIN/SHOWERS TO THE AREA DURING THE OVERNIGHT AND INTO SATURDAY, GRADUALLY SPREADING FROM SOUTHEAST TO NORTHWEST AND MAINLY IN THE 06Z TO 18Z SATURDAY TIMEFRAME. WITH THIS BATCH OF PRECIP, WE DO EXPECT CONDITIONS TO LOWER TO MVFR, ESPECIALLY FOR KACY/KMIV AND THE DELAWARE VALLEY TAF SITES, WITH SOMEWHAT LESS OF A CHANCE FOR KABE/KRDG. WITH REGARDS TO WINDS, SPEEDS ARE EXPECTED TO BE MAINLY UNDER 10 KNOTS THROUGH THE TAF PERIOD, WITH WINDS TURNING MORE FROM THE SOUTHWEST TO THE SOUTHEAST WITH TIME THROUGH THIS EVENING. THE WINDS WILL CONTINUE TO BACK MORE TOWARD AN EASTERLY TO NORTHEAST DIRECTION DURING THE OVERNIGHT AND THROUGH SATURDAY, REMAINING MOSTLY UNDER 10 KNOTS. OUTLOOK... SUNDAY...MOSTLY VFR WITH SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS POSSIBLE IN THE AFTERNOON. HEAVY RAIN MAY OCCUR CLOSER TO THE COAST. MVFR/IFR CONDITIONS LIKELY IN SHOWERY ACTIVITY. EASTERLY FLOW IN PLACE. MEDIUM CONFIDENCE. MONDAY - TUESDAY...VFR. ISOLATED SHOWERS POSSIBLE ON EACH AFTERNOON. MEDIUM CONFIDENCE. && .MARINE... EXPECT WINDS AND SEAS TO REMAIN BELOW SMALL CRAFT ADVISORY TODAY AND TONIGHT WITH WINDS STAYING NEAR OR BELOW 20 KT AND SEAS BETWEEN 2 AND 3 FEET. OUTLOOK... FRIDAY - TUESDAY...SUB-SCA CONDITIONS ARE EXPECTED ACROSS OUR WATERS THIS PERIOD. && .RIP CURRENTS... THE RISK OF RIP CURRENTS WILL INCREASE TO MODERATE TODAY AS THE WINDS SHIFT TO SOUTHEASTERLY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...HEAVENER NEAR TERM...JOHNSON/KLINE SHORT TERM...JOHNSON LONG TERM...HEAVENER AVIATION...HEAVENER/KLINE MARINE...HEAVENER/JOHNSON RIP CURRENTS...JOHNSON

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