Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 280133 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 933 PM EDT MON JUL 27 2015 .SYNOPSIS... A NEARLY STALLED FRONTAL BOUNDARY WILL CONTINUE TO DISSIPATE IN OUR REGION TONIGHT. WEAK HIGH PRESSURE BUILDING EASTWARD FROM THE GREAT LAKES IS FORECAST TO INFLUENCE OUR WEATHER FOR TUESDAY AND WEDNESDAY. A FRONTAL BOUNDARY FROM THE NORTHWEST IS EXPECTED TO ARRIVE ON THURSDAY NIGHT FOLLOWED BY HIGH PRESSURE FOR FRIDAY AND THE WEEKEND. ANOTHER FRONT MAY APPROACH FROM THE NORTHWEST ON MONDAY. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... A WEAK RIDGE OF HIGH PRESSURE WILL CONTINUE ITS HOLD ON THE MID- ATLANTIC REGION TONIGHT. AS OF 9 PM, THERE WERE ONLY A HANDFUL OF SHOWERS LEFT ON RADAR AS CONVECTION CONTINUES TO WANE WITH THE LOSS OF DAYTIME INSTABILITY. WITHOUT AN ORGANIZED LIFTING MECHANISM IN PLACE, POPS WERE LOWERED TO 20 PERCENT OR LESS IN AN UPDATE EARLIER THIS EVENING. BASED ON RADAR/SATELLITE TRENDS AND THE LATEST HRRR REFLECTIVITY SIMULATIONS, TRIED TO CONFINE ISOLATED SHOWERS AND STORMS TO THE NEXT COUPLE OF HOURS AND FROM ABOUT I-76/I-195 NORTHWARD UP TO I-78. THERE COULD ALSO BE A SHOWER OR TWO THIS EVENING IN THE LOWER DELMARVA (WHERE THE AIRMASS IS SLIGHTLY MORE UNSTABLE AND MOIST). FOR THE OVERNIGHT, THERE STILL MAY BE AN ISOLATED POP UP SHOWER OR STORM, BUT COVERAGE WILL BE 10 PERCENT OR LESS. CLOUD COVER WILL BE VARIABLE THIS EVENING OWING TO DEBRIS LEFTOVER FROM THE CONVECTION. THESE CLOUDS SHOULD GENERALLY DIMINISH TOWARD MIDNIGHT. FOG AND STRATUS MAY DEVELOP TOWARD MORNING. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... ONCE WE BURN OFF ANY FOG AND STRATUS THAT MAY FORM DURING THE EARLY MORNING HOURS WE SHOULD BE LEFT WITH CLEARING SKIES, ALBEIT SELF DESTRUCTING. A RAPID CU-FIELD SHOULD DEVELOP BY EARLY AFTERNOON AS CONVECTIVE TEMPERATURES ARE REACHED WITH TEMPERATURES CLIMBING INTO THE LOW-90S. WINDS WILL REMAIN RELATIVELY LIGHT SO NO RELIEF IN TERMS OF THE HUMIDITY. SEA AND BAY BREEZES SHOULD DEVELOP BY EARLY AFTERNOON AND GIVEN THE SOUPINESS OF THE AIR MASS, THEY MIGHT PROVIDE ENOUGH LIFT TO INITIATE ISOLATED SHOWERS. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... A MID LEVEL RIDGE AXIS IS FORECAST TO EXTEND ACROSS THE GREAT LAKES ON TUESDAY NIGHT. THE RIDGE IS EXPECTED TO PROGRESS EASTWARD AND ITS AXIS SHOULD PASS OVER OUR REGION ON WEDNESDAY NIGHT. A MID LEVEL LOW IS ANTICIPATED TO MOVE FROM SOUTHERN MANITOBA ON TUESDAY NIGHT TO HUDSON BAY ON WEDNESDAY NIGHT. THE LOW IS FORECAST TO MEANDER OVER THE HUDSON BAY REGION FROM WEDNESDAY NIGHT THROUGH MONDAY. MID LEVEL TROUGHING IS EXPECTED OVER THE NORTHEASTERN STATES FOR THURSDAY NIGHT THROUGH MONDAY WITH A RIDGE BUILDING OVER THE WESTERN STATES. THE HEAT IS FORECAST TO BE ON THE INCREASE FOR WEDNESDAY AND THURSDAY. WE ARE ANTICIPATING MAXIMUM TEMPERATURES MAINLY IN THE LOWER AND MIDDLE 90S ON BOTH DAYS WITH HEAT INDEX VALUES APPROACHING 100 EXCEPT IN THE ELEVATED TERRAIN AND IN THE COMMUNITIES ALONG THE COAST. DEW POINT READINGS ARE EXPECTED TO BE MAINLY IN THE MID TO UPPER 60S ON WEDNESDAY AFTERNOON AND IN THE UPPER 60S AND LOWER 70S ON THURSDAY AFTERNOON. THE MAXIMUM HEAT INDEX VALUES IN OUR HIGHLY URBANIZED AREAS ALONG THE INTERSTATE 95 CORRIDOR ARE EXPECTED TO BE IN THE UPPER 90S ON WEDNESDAY AND THURSDAY BASED ON THE LATEST GUIDANCE. AS A RESULT, WE WILL NOT ISSUE AN EXCESSIVE HEAT WATCH AT THIS TIME. THE GUIDELINE CRITERION IS 100. HOWEVER, WE WILL KEEP A CLOSE WATCH TO SEE IF THE GUIDANCE BEGINS TO CREEP UPWARD WITH EITHER THE TEMPERATURE OR DEW POINT FORECAST. WE ARE NOT ANTICIPATING ANY PRECIPITATION FOR TUESDAY NIGHT, WEDNESDAY AND WEDNESDAY NIGHT DUE TO THE LACK OF ANY SUBSTANTIAL TRIGGERING MECHANISMS. WE WILL MENTION A CHANCE OF SHOWERS AND THUNDERSTORMS FOR THURSDAY AFTERNOON INTO THURSDAY NIGHT AS A FRONTAL BOUNDARY IS EXPECTED TO APPROACH AND PASS THROUGH OUR REGION DURING THAT PERIOD OF TIME. A WEAK WAVE OF LOW PRESSURE MAY DEVELOP ALONG THE FRONT CAUSING PRECIPITATION TO LINGER INTO EARLY FRIDAY MORNING IN OUR SOUTHEASTERN COUNTIES. HIGH PRESSURE IS EXPECTED TO FOLLOW THURSDAY NIGHT`S FRONTAL PASSAGE. THE HIGH IS ANTICIPATED TO INFLUENCE OUR WEATHER FOR FRIDAY AND THE WEEKEND. WE WILL CARRY A PRECIPITATION-FREE FORECAST ALONG WITH SLIGHTLY ABOVE NORMAL DAYTIME TEMPERATURES. EVEN WITH THE MID LEVEL TROUGHING, IT APPEARS AS THOUGH OUR WEATHER WILL REMAIN QUITE WARM. HOWEVER, HUMIDITY LEVEL SHOULD DROP A BIT FROM THOSE EXPECTED DURING THE MID WEEK PERIOD. ANOTHER FRONTAL BOUNDARY MAY APPROACH FROM THE NORTHWEST ON MONDAY AND WE WILL MENTION A CHANCE OF SHOWERS AND THUNDERSTORMS FOR THAT PERIOD OF TIME. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. A FEW SHOWERS REMAIN STATIONARY IN VC OF TTN/ABE AT 01Z. THIS ACTIVITY SHOULD DIMINISH IN THE NEXT HOUR OR SO. DRY FOR ALL TERMINALS TNGT. VFR AT LEAST THRU 06Z. THERE IS A POTENTIAL FOR FOG AND STRATUS TO DEVELOP LATE TONIGHT AND EARLY TUESDAY MORNING. THE LATEST LAMP, HRRR, AND TIME-LAGGED SREF GUIDANCE PROVIDED MORE SUPPORT FOR LOW CLOUDS THAN RADIATIONAL FOG. THIS SEEMS PLAUSIBLE GIVEN THE 15 KT SWLY FLOW AIDING IN MODEST MOISTURE/WARM AIR ADVECTION AT THE TOP OF THE NOCTURNAL BOUNDARY LAYER. THIS WOULD MOST LIKELY RESULT IN A FEW HOURS OF MVFR CIGS BETWEEN 1500-3000 FT AFTER 06Z AND BEFORE 14Z. LOW CONFIDENCE IN IFR TONIGHT, THOUGH SOME OUTLIER GUIDANCE IS INDICATING JUST THAT. TUESDAY...MOSTLY VFR. WE SHOULD LOSE ANY LOWER CLOUDS AND FOG BY MID MORNING LEAVING US WITH A SCATTERED 3-5 KFT CU FIELD. SHOWER CHANCES WILL BE LOWER THAN THE PAST COUPLE OF DAYS WITH MIV/ACY HAVING BETTER CHANCES, BUT STILL TOO LOW TO MENTION IN THE TAFS. LOCAL SEA/BAY BREEZES MAY OCCUR AT ACY/MIV/ILG BY THE EARLY AFTERNOON WITH WINDS BACKING MORE TOWARDS THE SOUTHEAST. OUTLOOK... TUESDAY NIGHT THROUGH THURSDAY MORNING...MAINLY VFR. HOWEVER, THE HIGH HUMIDITY LEVELS MAY RESULT IN SOME LATE NIGHT AND EARLY MORNING LOW CLOUDS, HAZE AND FOG. THURSDAY AFTERNOON AND THURSDAY NIGHT...A CHANCE OF SHOWERS AND THUNDERSTORMS THAT MAY RESULT IN MVFR OR IFR CONDITIONS AT TIMES. FRIDAY THROUGH SATURDAY...MAINLY VFR. && .MARINE... SUB-SCA CONDITIONS TONIGHT AND TUESDAY UNDER PROLONGED SOUTHERLY FLOW. WINDS WILL CONTINUE TO DECREASE TONIGHT AND TOMORROW AS THE PRESSURE GRADIENT SLACKENS. SEAS WILL ALSO BE ON THE DOWNWARD TREND RUNNING CLOSER TO 2-3 FEET THROUGH TUESDAY. OUTLOOK... TUESDAY NIGHT THROUGH SATURDAY...NO MARINE HEADLINES ARE ANTICIPATED. && .RIP CURRENTS... A MEDIUM TO LONG PERIOD (AROUND 10 SECONDS) SWELL OUT OF THE E-SE WILL CONTINUE INTO TUESDAY. SLY WINDS WILL BE AROUND 10 KT AND 2-3 FT WAVES ARE FORECAST IN THE SURFACE ZONE. GIVEN SIMILARCONDITIONS TO TODAY`S MODERATE RISK AND THE INFLUENCE OF AN APPROACHING FULL MOON LATER IN THE WEEK, TOOK A CAUTIOUS APPROACH AND WENT WITH A MODERATE RISK OF DANGEROUS RIP CURRENTS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...IOVINO NEAR TERM...KLEIN SHORT TERM...HEAVENER LONG TERM...IOVINO AVIATION...IOVINO/HEAVENER/KLEIN MARINE...IOVINO/HEAVENER/KLEIN RIP CURRENTS...KLEIN

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