Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 071034 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 634 AM EDT TUE JUL 7 2015 .SYNOPSIS... A TROUGH OF LOW PRESSURE LOCATED TO OUR SOUTH TODAY WILL MERGE WITH A COLD FRONTAL BOUNDARY APPROACHING THE REGION TONIGHT. THIS FRONTAL BOUNDARY WILL VERY SLOWLY MOVE THROUGH THE REGION BY FRIDAY, BECOMING NEARLY STATIONARY. SEVERAL WAVES OF LOW PRESSURE WILL ALSO TRAVEL EASTWARD ALONG THE BOUNDARY. A WARM FRONTAL BOUNDARY WILL THEN LIFT NORTHEASTWARD THROUGH THE REGION NEXT WEEKEND GIVING WAY TO ANOTHER COLD FRONTAL BOUNDARY BY THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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EARLY TODAY...STRATUS AND A COUPLE OF DYING ISOLATED LEFTOVER SHOWERS FROM THIS PAST EVENINGS REMNANT HEAVY SHOWERS/TSTMS ON THE DELMARVA/E PA. PWAT RIGHT NOW STILL NEAR 1.9 INCHES BUT SLOWLY LOWERS FROM SW TO NE DURING THE DAY, DOWN TO NEAR 1.6 INCHES LATE AFTN. LAST OF THE SHOWERS SEEM TO HAVE ENDED PHL AREA. .04 AT KPNE IN 1 HR ENDING 10Z AFTER 8 AM...BECOMING PARTLY SUNNY, HOT AND HUMID. UNSTABLE THIS AFTN IN THE WARM SECTOR AND MODELS CONTINUE DEVELOPING CLUSTERS OF HEAVY SHOWERS AND ISOLATED GULLY WASHING THUNDERSTORMS AS THE WEAKENING CLOSED LOW SHORT WAVE LIFTS NEWD OVERHEAD THIS AFTERNOON. BULK SHEAR IS MINIMAL TODAY SO ANY TSTORM GUSTS SHOULD NOT EXCEED 40 KT. BLENDED 00Z/7 GFS/NAM POPS WERE USED WITH SOME SREF/HRRR DIURNAL DRIER MORNING MODIFICATION OF THE POPS. IN ESSENCE THE SHOWERS TODAY, MAINLY ALONG AND NW OF I-95, ESP E PA AND NORTHERN NJ (N OF I-78). OTHERWISE...THE STRATUS BURNS OFF RAPIDLY FROM SW TO NE DURING MID MORNING WITH A BKN DECK NEAR 5000 FT EARLY THIS AFTN AND THAT TOO DRYING OUT FROM SW TO NE DURING MID-LATE AFTN. HEAT FOLLOWS THIS AFTN WITH 90-92F EXPECTED TO BE WIDESPREAD ON A GUSTY SW WIND TO 20 MPH. THE HEAT INDEX WITH DEWPOINTS DIPPING BACK TO THE UPPER 60S SHOULD BE IN THE 95-99 CATEGORY FOR A FEW HOURS BUT NO HEAT ADVISORY. BLENDED THE 00Z/7 GFS/NAM MOS GUIDANCE AND MODIFIED IT UP A DEGREE FOR THE 16-17C 850 TEMPS. THE PRIMARY HAZARD TODAY WILL LIKELY BE POOR DRAINAGE ROAD FLASH FLOOD OPPORTUNITIES WHERE CONVECTION TRAINS FOR AN HOUR OR SO. HOURLY FFG IN MORRIS COUNTY IS OUR MOST VULNERABLE AREA WITH ONLY 1 INCH NEEDED IN AN HOUR IN PARTS OF MORRIS COUNTY. SUSPECT WE`LL SEE SOME CONVECTIVE NARROW SWATH FFW`S THIS AFTN ALONG AND N OF I-78. THE IDEA: IF WARNINGS ARE ISSUED FOR YOUR AREA, NO WORKING IN CULVERTS OR PLAYING ALONG SIDE SMALL STREAMS. IF HEAVY SHOWERS HAVEN`T DEVELOPED BY MID AFTERNOON, ITS UNLIKELY THEREAFTER IN OUR AREA AS THE BACK EDGE OF THE DEEPER INSTABILITY (KI=30) IS DEPARTING NEWD FROM NE NJ BY 5P. THEREFORE, LOWERED POPS TO NO MENTION AT 6 PM.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... RAINFREE THIS EVENING AND QUITE WARM! THEN A BAND OF CONVECTION AHEAD OF THE EWD MOVING COLD FRONT MAY ARRIVE AND CROSS NE PA AND NW NJ NEAR AND AFTER MIDNIGHT WITH ISOLATED EMBEDDED THUNDER. PWAT IN THE EARLY EVENING BRIEFLY DRIES TO 1.4 INCHES BUT WITH THE CONVECTIVE BAND, INCREASES TO 1.85 INCHES BY WEDNESDAY MORNING. OTHERWISE...I CALL IT SUMMERTIME FAIR-A TYPICAL WARM SUMMER NIGHT! USED THE WARMER OF THE AVAILABLE MOS GUIDANCE FOR TONIGHT. LIGHT SW WIND. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... WEDNESDAY AND WEDNESDAY NIGHT: A COLD FRONTAL BOUNDARY BEGINS TO ENTER THE PICTURE WEDNESDAY AFTERNOON AND EVENING GIVING US THE TRIGGER MISSING TODAY FOR A MORE WIDESPREAD SHOWER AND THUNDERSTORM CHANCE. WITH THE HIGHER CHANCES OF RAIN, HIGH TEMPERATURES MAY NOT REACH THE FULL POTENTIAL DUE TO THE PRESENCE OF MORE CLOUDS. DID KNOCK DOWN THE HIGHS BUT NOT AS MUCH AS MET/ MAT ECMWF MOS DO, GIVEN THE MAJORITY OF PRECIPITATION HOLDS OFF TILL AFTER 18Z. PLENTY OF WINDOW FOR WARMING AHEAD OF THE FRONT. ANOTHER RESULT OF THE PROSPECTS FOR INCREASED CLOUD COVER IS THAT MODELED INSTABILITY HAS DECREASED TO UNDER 1000 J/KG OF CAPE IN SOME PARTS OF THE REGION COUPLED WITH LESS IN THE WAY OF MODELED STEEP LAPSE RATES. SHEAR CONTINUES TO LOOK TO BE MINIMAL AS WELL IN THE REGION. THIS POINTS TO ANY STRONG/SEVERE STORM TO BE ISOLATED. HEAVY RAIN LOOKS TO BE THE PRIMARY CONCERN WITH PW VALUES NEAR 2 INCHES. STORM MOTIONS LOOK FASTER AS WELL, SO EVEN WITH THE INCREASED CONVERGE ANY OCCURRENCES OF FLASH FLOODING MAY NOT BE WIDESPREAD. THIS WOULD LEAD TO MORE TYPICAL POOR DRAINAGE FLOODING ISSUES. A WARM, MUGGY NIGHT IS LIKELY WEDNESDAY NIGHT AS WELL WITH PLENTY OF CLOUDCOVER TO KEEP TEMPERATURES UP. THURSDAY THROUGH FRIDAY NIGHT: THE FRONTAL BOUNDARY WILL LIKELY SLOWLY SAG TO OUR SOUTH IN THIS TIMEFRAME WITH THE POTENTIAL FOR A WAVE OF LOW PRESSURE LATE THURSDAY TO BUCKLE IT BACK NORTH FOR A SHORT PERIOD. THIS KEEPS A SHOWER/STORM CHANCE GOING AS WELL INTO FRIDAY. AFTER THE PASSAGE OF THE FRONT, A COOLER AIRMASS WILL ADVECT INTO THE REGION. MODELING DOES DIFFER ON HOW FAST THE FRONT COMES THROUGH THE REGION. THE 00Z 7/7 NAM AND ECMWF ARE SLOWER AND TAKE A LOW PRESSURE SYSTEM INTO THE EASTERN LAKES/ NORTH OF OUR REGION, BRINGING RENEWED WARM AND INSTABILITY ADVECTION INTO THE REGION LATE THURSDAY (WARM FRONT) BEFORE SENDING THE FRONT BACK SOUTH ON FRIDAY. THESE POSSIBILITIES PLACE A HIGHER SHEAR ENVIRONMENT IN THE REGION COUPLED WITH THE INCREASING INSTABILITY LATE THURSDAY, MORE OF A SEVERE THREAT. THE MORE PROGRESSIVE SOLUTIONS AKA THE GFS AND CMC WEAKEN THE LOW PRESSURE TO OUR SOUTH. OUR FORECAST RAISES POPS AND SETS UP A QPF MAX AREA ACROSS NORTHERN PARTS OF THE FORECAST AREA THURSDAY AND THURSDAY NIGHT. THE NAM DOES HAVE A BIAS OF TRACKING LOWS TO FAR NORTH IN THE LAST 24-36 HOURS OF MODEL RUNS. SO THIS FORECAST DID NOT FULLY JUMP ON THE BOARD WITH THE SLOWER MOVING FURTHER NORTH FRONTAL IDEA. IT WILL BE COOLER AS WELL WITH A SOMEWHAT MORE REFRESHING AIRMASS COMING IN BEHIND THE FRONT. RAIN CHANCES MAY LINGER ON FRIDAY IN THE DELMARVA. SATURDAY THROUGH MONDAY NIGHT: ANOTHER WARM FRONT WILL PUSH NORTHWARD INTO THE REGION LATER IN THE WEEKEND. SO THE SOMEWHAT COOLER AND LESS HUMID AIRMASS WILL GET REPLACED BY ANOTHER ROUND OF HOT AND HUMID WEATHER EARLY NEXT WEEK. DID TREND TEMPERATURES THAN THE ENSEMBLE GUIDANCE BY EARLY NEXT WEEK. THE ENSEMBLE GUIDANCE POPS WERE ALSO LOWERED IN THIS FORECAST GIVEN NORMAL 5-7 DAY FORECAST UNCERTAINTIES. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. AMD NOT SKED AT KACY DUE TO LACK OF TIMELY AUTOMATED TRANSMISSION OF METAR INFORMATION WHICH WITH IFR CONDITIONS. THROUGH ABOUT 12Z...WIDESPREAD CIGS AOB 1200 FEET WITH AREAS IFR STRATUS, ESPECIALLY VCNTY KABE/KTTN. SPOTTY 3-5 MILE FOG. SOUTHEAST WIND 5-10 KT BECOMES SOUTH SOUTHWEST BY 12Z. SCATTERED SHOWERS AT 10Z NOW RACING NEWD FROM KTTN-KMPO AND THAT MAY BE IT FOR AWHILE. AFTER 12Z...AS THE WIND SHIFTS MORE SOUTHWESTERLY, CONDITIONS IMPROVE TO VFR SCT-BKN AOA 3500 FEET BETWEEN 12Z AND 14Z. CIGS RISE FURTHER TO AOA 5000 FT EARLY THIS AFTERNOON THEN CLEAR FROM SW TO NE LATER IN THE DAY AS THE PWAT DROPS. SCATTERED IFR SHOWERS AND ISOLATED TSTMS IN THE 16Z-21Z TIME FRAME, MAINLY ALONG AND NW OF I-95. A COUPLE OF THESE STORMS MAY PRODUCE A GUST TO 35 KT. GRADIENT SOUTHWEST WIND GUSTS 15-20 KT AT ALL SITES DURING THE AFTN. TONIGHT...VFR CLEAR THIS EVENING THEN A DECK OF BKN CIGS AOA 5000 FT ARRIVES N OF I-78 (NEAR KABE AND KRDG) AFTER 04Z/8 ASSOCIATED WITH A DECAYING BAND OF CONVECTION AHEAD OF THE EWD MOVING COLD FRONT. OUTLOOK... WEDNESDAY THROUGH THURSDAY NIGHT: POTENTIAL MVFR AND IFR RESTRICTIONS IN SHOWERS AND THUNDERSTORMS, HIGHEST CHANCES EACH AFTERNOON AND EVENING. WEST-SOUTHWEST WIND GUSTS AT OR UNDER 20 KNOTS. FRIDAY THROUGH SATURDAY NIGHT: VFR. WINDS AT OR UNDER 10 KNOTS, MAINLY NORTHERLY.
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&& .MARINE... SUB-SCA CONDITIONS EXPECTED THROUGH THIS EVENING. ATLC SEAS MAY INCREASE TO THE HAZARDOUS 5 FT THRESHOLD LATE TONIGHT BUT NO SCA ATTM SINCE DURING WARM AIR ADVECTION, GUIDANCE TENDS TO HAVE A HIGH BIAS ON THE SEAS. WINDS WILL BECOME SW TODAY AND INCREASE TO 15 TO 20 KT LATE TODAY AND TONIGHT. OUTLOOK... SUB-SCA WINDS AND SEAS EXPECTED. ANY WIND GUSTS LOOK TO REMAIN BELOW 20 KNOTS, MORE SOUTHWESTERLY THROUGH WEDNESDAY NIGHT THEN MORE NORTHERLY THROUGH SATURDAY NIGHT. SEAS AROUND FOUR FEET ON WEDNESDAY AND THURSDAY. THE HIGHEST CHANCE OF THUNDERSTORMS IS WEDNESDAY AFTERNOON AND EVENING THEN AGAIN LATER THURSDAY. && .RIP CURRENTS...
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FORECASTING A LOW RISK TODAY USING A 3 FT 5 SECOND SOUTHERLY SWELL THIS AFTERNOON OR EARLY THIS MORNINGS 2 FT 9 SECOND. COMBINE THAT WITH A SOUTHERLY WIND THAT INCREASES TO 12-13 KT THIS AFTERNOON AND WE GET A LOW RISK ALONG OUR WATERS. WE CANNOT OVEREMPHASIZE...LOW RISK DOES NOT MEAN NO RISK. TRANSITORY AND RECURRENT RIP CURRENTS OCCUR EVERY DAY. PLAY IT SMART AND SWIM SAFELY IN THE PRESENCE OF A LIFEGUARD WHO KNOWS WHAT THEY`RE DOING IF A RESCUE IS NEEDED. THEY ARE THERE INSTANTLY TO SAVE LIVES INSTEAD OF BE NOTIFIED TO LATER RECOVER. TIDE GOING OUT THIS AFTERNOON FOSTERS A POSSIBLE ENHANCED LOW RISK FOR THE FORMATION OF DANGEROUS RIP CURRENTS, ESPECIALLY COMBINED WITH AN INCREASING SOUTH WIND. MEDIA COMMUNICATION OF THE INCREASED RIP CURRENT DANGER SWIMMING AWAY (OUTSIDE) FROM THE WATCHFUL EYES OF LIFEGUARDS IS VERY IMPORTANT. RAISING AWARENESS CAN BE A LIFESAVER, FOR ALL AGES BUT EVEN MORE SO FOR THE VULNERABLE 10-29 AGE MALES THAT COMPRISE THE PREPONDERANCE OF RIP CURRENT RELATED FATALITIES. INTERVIEWS CAN BE CONDUCTED. JUST CONTACT US.
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&& .EQUIPMENT... KACY DATA MAY NOT BE TRANSMITTING THOUGH WE SEE IT INTERNALLY IN THE OFFICE. NO NOTAM. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GAINES NEAR TERM...DRAG 634 SHORT TERM...DRAG LONG TERM...GAINES AVIATION...DRAG/GAINES 634 MARINE...DRAG/GAINES RIP CURRENTS...634 EQUIPMENT...

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