Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 260453 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1253 AM EDT SUN JUL 26 2015 .SYNOPSIS... HIGH PRESSURE WILL CONTINUE MOVING EASTWARD OFF THE MID-ATLANTIC COAST TONIGHT GIVING WAY TO AN APPROACHING COLD FRONT ON SUNDAY. BY MONDAY, THIS FRONT WILL DISSIPATE TO OUR SOUTH. HIGH PRESSURE WILL BUILD EASTWARD INTO THE REGION FOR THE MIDDLE OF THE WEEK BEFORE ANOTHER COLD FRONT COMES THROUGH THE REGION ON FRIDAY. THE FRONTAL BOUNDARY LOOKS TO STALL ALONG OR JUST OFF THE EAST COAST NEXT WEEKEND WITH SEVERAL WAVES OF LOW PRESSURE FORMING ALONG IT. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... LATEST ESTF UPDATE, NOT TOO MANY CHANGES. TEMPERATURES AND DEW POINTS ARE CLOSE TO EXPECTATIONS. NOT AS PLEASANT OVERNIGHT AS DEW POINTS ARE HIGHER AND SOME CLOUD DEBRIS IS AROUND. BASED ON LATEST RADAR TRENDS AND COSPA, WE MADE A SLIGHT TWEAK TO POPS, ADJUSTING THEM UPWARD IN NORTHWEST NJ. LOOKS LIKE THUNDER SHOULD REMAIN NORTH OF OUR CWA, SO FOR NOW, SHOWERS. PREVIOUS UPDATE DISCUSSION...NO MAJOR CHANGES IN THE NEAR TERM. ADJUSTED TEMPS AND DEW POINTS TO REFLECT CURRENT TRENDS. AGREE WITH THE PREVIOUS SHIFT THAT ANY PRECIP TONIGHT WILL PROBABLY NOT BE UNTIL AFTER MIDNIGHT IN OUR AREA, IF EVEN THEN. PREVIOUS NEAR TERM DISCUSSION...HIGH PRESSURE WILL CONTINUE TO SLIDE OFF THE COAST TONIGHT PROVIDING A DECENT AMOUNT OF SUBSIDENCE KEEPING A TIGHT LID ON THE REGION THROUGH AT LEAST A BETTER PORTION OF THE OVERNIGHT HOURS. OF QUESTION IS WHEN THE NEXT SHOT OF OVER-RUNNING SHOWERS OCCURS LATE TONIGHT, MOSTLY ACROSS OUR NORTHERN ZONES WITH A PASSING MID- LEVEL WAVE. HAVE TRIMMED THE POPS BACK BY SEVERAL HOURS AND DROPPED THEM A CATEGORY AS THE ELEVATED WARM FRONT REMAINS PRETTY FAR TO OUR NORTH...MORE OF A STATIONARY BOUNDARY...SO NOT EXPECTING MUCH RAINFALL TONIGHT AS THE ATMOSPHERE IS STILL RATHER DRY. WILL NOT BE QUITE AS COOL AS THE PAST FEW MORNINGS WITH THE LOWER DEWPOINTS...AIRMASS MODIFICATION WILL COMMENCE LATE TONIGHT. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/... COLD FRONT ACROSS THE UPPER GREAT LAKES SLIDES INTO THE WESTERN PART OF PENNSYLVANIA BY SUNDAY AFTERNOON BUT IT LOOKS RATHER DIFFUSE/WASHED OUT. WHAT WE DO SEE AHEAD OF THE WIND SHIFT IS AN INCREASE IN LOW-LEVEL MOISTURE/INSTABILITY AS PROGGED BY OUR CAMS AND BETTER/DEEPER SHEAR ASSOCIATED WITH THE NORTHWESTERLY FLOW ALOFT. EXPECTING AN INCREASE IN SCATTERED COVERAGE FOR AFTERNOON SHOWERS AND THUNDERSTORMS WITH MORE MUGGY CONDITIONS IN PLACE. WE KEEP THE SAME TIMING WITH THE HIGHER CHANCES FOR SHOWERS IN PLACE THOUGH WE TRIED TO BETTER DEFINE THE SOUTHERN EDGE THROUGHOUT THE DAY. IT IS POSSIBLE THAT SEABREEZE CIRCULATIONS WILL ALSO ALLOW FOR ISOLATED SHOWERS WELL AHEAD OF ANY SYNOPTIC FORCING. HIGHS WILL AGAIN BE ABOVE NORMAL. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... SUNDAY NIGHT AND MONDAY: A WEAK COLD FRONT IS LIKELY TO DECAY INTO A TROUGH OF LOW PRESSURE BY MONDAY. AHEAD OF THIS FEATURE, TEMPERATURES AND HUMIDITY WILL CONTINUE TO BE ON THE RISE MAKING IT A MUGGIER NIGHT COMPARED TO THE PREVIOUS FEW NIGHTS. ENOUGH INSTABILITY MAY BE PRESENT IN CONJUNCTION WITH THE FRONT TO TRIGGER A FEW TYPICAL SUMMERTIME SCATTERED SHOWERS AND THUNDERSTORMS WITH DOWNPOURS AND LIGHTNING. SHEAR LOOKS ALMOST NON-EXISTENT FOR SEVERE CONSIDERATIONS. STILL AN ISOLATED STRONG WIND GUST CAN`T BE RULED OUT SUNDAY NIGHT OR MONDAY. TEMPERATURES LOOK TO BE AT OR A HAIR ABOVE MET/MAV/ECMWF MOS WITH HIGHS GETTING CLOSER TO 90. RFC GUIDANCE APPEARS TO HAVE A GOOD HANDLE ON QPF ACROSS THE REGION. AS USUAL, SOMEONE WILL SEE LOCALLY HEAVIER RAINFALL WITH THE THUNDERSTORMS. MONDAY NIGHT THROUGH THURSDAY: A GRADUAL CONTINUED UPTICK IN HEAT AND HUMIDITY WITH A STRONG RIDGE ACROSS THE SOUTHERN PLAINS MAKING ANOTHER CHARGE ACROSS THE REGION WITH RISING HEIGHTS. THIS WILL RESULT IN A MAINLY DRY PERIOD. FOR ACTUAL HIGH TEMPERATURES, MODELED 925 MB TEMPERATURES RISE FROM AROUND 22C ON TUESDAY TO 25C FOR WEDNESDAY AND THURSDAY. THIS EQUATES TO HIGH TEMPERATURES STARTING OFF AROUND 90 ON TUESDAY THEN RISING INTO THE MID 90`S FOR WEDNESDAY AND THURSDAY. THIS IS ANOTHER POTENTIAL MODELED HEAT WAVE FOR MOST OF THE REGION. OVERALL, IN THE MODELING WORLD THE GFS CONTINUES TO RUN SEVERAL DEGREES WARMER THAN THE ECMWF. THE FORECAST SPLITS THE DIFFERENCE BETWEEN THE TWO AND TAKES INTO ACCOUNT SOMEWHAT HIGHER CLOUD COVER ON THURSDAY. A COLD FRONTAL BOUNDARY MAY BE ENOUGH OF A TRIGGER FOR SOME SCATTERED SHOWERS AND THUNDERSTORMS TO DEVELOP LATE THURSDAY AFTERNOON AS THE 12Z MODEL GUIDANCE IS A BIT FASTER COMPARED TO THE 00Z RUNS. THURSDAY NIGHT THROUGH SATURDAY: THE COLD FRONTAL BOUNDARY APPROACHING THE REGION TO START THIS PERIOD WILL LIKELY SLOW DOWN OR STALL BY FRIDAY. THIS IS DUE TO MODELED HEIGHT RISES/INCREASED RIDGING OFF THE EAST COAST. SOME COOLER AIR IS LIKELY TO END THE POTENTIAL HEAT WAVE BEHIND THE FRONT AS A TROUGH MOVES ACROSS NEW ENGLAND. WITH THE FRONT NEARBY, SHOWER AND THUNDERSTORM CHANCES ( SLIGHT TO LOW) WILL CONTINUE THROUGHOUT THIS TIMEFRAME. THE POTENTIAL FOR WAVES OF LOW PRESSURE OR EVEN SOMETHING TROPICAL/ SUB-TROPICAL IN NATURE TO DEVELOP IS ALSO PRESENT ALONG THE FRONT AT THE END OR JUST BEYOND THE FORECAST PERIOD. HOWEVER, CONSIDERABLE UNCERTAINTY IS PRESENT THIS FAR OUT IN THE FORECAST. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. 06Z TAFS VFR INTO EARLY AFTERNOON, THEN SOME UNCERTAINTY AS TO EXTENT OF SHOWERS AND THUNDERSTORMS DURING THE LATE AFTERNOON AND EVENING. REST OF THE NIGHT...VFR. LIGHT WINDS, SOME CIRRUS CLOUDS AROUND. NOT EXPECTING FOG AT TERMINALS AS THERE IS STILL A FAIRLY LARGE TEMPERATURE AND DEW POINT SPREAD. ALTHOUGH SOME OF THE MORE SMALLER RURAL AIRPORTS MIGHT HAVE PATCHY GROUND FOG. THIS MORNING...VFR. LIGHT SOUTH TO SOUTHWEST WINDS DEVELOPING. THIS AFTERNOON...VFR WITH STRONGER SOUTH TO SOUTHWEST WINDS AVERAGING CLOSER TO 10 KNOTS. IF THERE IS A SEA BREEZE FRONT, ITS TOUGH TO DECIPHER IT AS THE GENERAL FLOW WILL BE EITHER SOUTH OR SOUTHWEST. SCATTERED SHOWERS AND THUNDERSTORMS SHOULD START FORMING IN THE NORTHWEST PART OF OUR AREA. BECAUSE OF THUNDERSTORM EXTENT UNCERTAINTY, THE TEMPO GROUP AT KABE AND KRDG IS CARRYING MVFR CONDITIONS IN SHOWERS, MIGHT UPGRADE TO THUNDER WITH 12Z TAFS. THIS EVENING...VFR CIG EXPECTED. SOUTH WINDS WILL BECOME LIGHTER. SHOWERS AND THUNDERSTORMS SHOULD SPREAD FARTHER TO THE SOUTHEAST. BECAUSE INSTABILITY WILL BE DECREASING, TERMINALS EITHER HAVE SHOWERS OR VCSH. WE KEPT KACY AND KMIV PCPN FREE AS ANY PRECIPITATION THAT WOULD MAKE IT THERE SHOULD BE AFTER 06Z. OUTLOOK... SUNDAY OVERNIGHT THROUGH MONDAY NIGHT: VFR, ISOLATED TO SCATTERED SHOWERS THUNDERSTORMS, PARTICULARLY MONDAY MAY BRIEFLY REDUCE VISIBILITIES AND CEILINGS. WINDS AT OR UNDER UNDER 10 KNOTS OUTSIDE OF THUNDERSTORMS. TUESDAY THROUGH THURSDAY: VFR, ISOLATED TO SCATTERED THUNDERSTORMS POSSIBLE THURSDAY AFTERNOON. WINDS AT OR UNDER 10 KNOTS OUTSIDE OF THUNDERSTORMS.
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&& .MARINE... SUB-SCA CONDITIONS EXPECTED TONIGHT AND TOMORROW WITH HIGH PRESSURE CONTINUING TO SLIDE OFF THE COAST TONIGHT. EAST-SOUTHEAST WINDS VEER MORE TOWARDS THE SOUTH-SOUTHWEST BY SUNDAY AFTERNOON AS A WARM FRONT LIFTS THROUGH. WINDS INCREASE BEHIND THE FRONT AND SEAS INCREASE A TAD BUT SHOULD REMAIN LESS THAN 4 FEET WITH SOME GUSTS UPWARDS OF 20 KNOTS.OUTLOOK... OUTLOOK: SEAS AND WINDS LOOK TO REMAIN BELOW SCA CRITERIA THROUGH THURSDAY. ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE SUNDAY EVENING THEN AGAIN MONDAY AFTERNOON/NIGHT AND THURSDAY AFTERNOON/EVENING WITH THE POTENTIAL FOR LIGHTNING A STRONG WIND GUST OR TWO. SEAS OVERALL FOUR FEET OR LESS WITH WIND GUSTS 20 KNOTS OR LESS OUTSIDE OF THUNDERSTORMS. BUOY 44009... WATER TEMPERATURE HAS NOT BEEN REPORTED BY BUOY 44009 SINCE JULY 22ND. WE`VE BEEN INFORMED BY THE NDBC THAT THE FAILED SENSOR WILL UNFORTUNATELY REMAIN OUT OF SERVICE UNTIL IT IS REPAIRED OR REPLACED SOMETIME NEXT YEAR. && .RIP CURRENTS... WITH THE LONG PERIOD (11-12 SECOND) 1 TO 2 FOOT EASTERLY SWELL CONTINUING INTO TOMORROW...EXPECT THE MODERATE RISK OF DANGEROUS RIP CURRENTS TO ALSO CONTINUE TOMORROW. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GAINES NEAR TERM...GIGI/HEAVENER/JOHNSON SHORT TERM...HEAVENER LONG TERM...GAINES AVIATION...GAINES/HEAVENER/JOHNSON/O`HARA MARINE...GAINES/HEAVENER/O`HARA RIP CURRENTS...

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