Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 280726 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 326 AM EDT TUE JUL 28 2015 .SYNOPSIS... WEAK HIGH PRESSURE BUILDING EASTWARD FROM THE GREAT LAKES IS FORECAST TO INFLUENCE OUR WEATHER TODAY THROUGH WEDNESDAY. A FRONTAL BOUNDARY FROM THE NORTHWEST IS EXPECTED TO ARRIVE THURSDAY NIGHT, FOLLOWED BY HIGH PRESSURE FOR FRIDAY AND THE WEEKEND. ANOTHER FRONT MAY APPROACH FROM THE NORTHWEST ON MONDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL TROUGH AXIS NOW TO OUR EAST WITH A RIDGE BUILDING TO OUR WEST. THIS ALLOWS A NORTHWESTERLY FLOW ALOFT REGIME TO BE MAINTAINED ACROSS THE NORTHEAST AND MID ATLANTIC. AT THE SURFACE, WEAK HIGH PRESSURE IS FORECAST TO SETTLE INTO OUR AREA TODAY. AS THE RIDGE TO OUR WEST GRADUALLY BUILDS NORTH AND EASTWARD SOME THROUGH TODAY, THERE DOES NOT APPEAR TO BE MUCH IN THE WAY OF SHORT WAVE ENERGY /AT LEAST ORGANIZED/ SLIDING SOUTHEASTWARD. AS A RESULT, NO ORGANIZED AREAS OF LIFT IS FORECAST TO OCCUR TODAY WITHIN A VERY WARM TO HOT AND HUMID AIR MASS. THE FORECAST SOUNDINGS DO SHOW DECENT INSTABILITY DEVELOPING THROUGH THE AFTERNOON, HOWEVER ABOVE ABOUT THE 850 MB LEVEL IT IS DRY. THE WATER VAPOR IMAGERY EARLY THIS MORNING SHOWS A LOT OF MID LEVEL DRY AIR FROM AROUND THE EASTERN GREAT LAKES TO THE MID ATLANTIC. AS A RESULT, ANY CONVECTION THAT CAN DEVELOP SHOULD BE ISOLATED AND ALSO PULSE DRIVEN GIVEN LITTLE FLOW IN THE LOWER TO MID LEVELS. IT APPEARS THAT SEA AND BAY BREEZE BOUNDARIES ESPECIALLY THIS AFTERNOON COULD FOCUS SOME CONVECTIVE DEVELOPMENT AND WE CONTINUED WITH SLIGHT CHC POPS FOR THE EASTERN ZONES AND PORTIONS OF THE DELMARVA. ELSEWHERE, WE OPTED TO CARRY A DRY FORECAST ATTM AS THERE IS NOT MUCH TO LATCH ONTO FOR CONVECTIVE INITIATION OTHER THAN TERRAIN. SOME WARMING AROUND THE 925 MB LEVEL MAY ALSO TEMPER CONVECTIVE DEVELOPMENT. A POCKET OF NEAR +25C AIR AT 925 MB IS FORECAST TO ADVECT INTO OUR AREA THROUGH THE AFTERNOON. DESPITE SOME CUMULUS DEVELOPMENT, PLENTY OF HEATING IS EXPECTED /ALTHOUGH A LACK OF MIXING DUE TO THE WEAK FLOW/ AND THEREFORE SOME AREAS ARE ANTICIPATED TO REACH 90 DEGREES THIS AFTERNOON. THE STRONG WARMING OF THE BOUNDARY LAYER MAY ALLOW THE SURFACE DEW POINTS TO DECREASE AT LEAST SOME ESPECIALLY FARTHER NORTH ACROSS THE CWA, AND WITH WEAK FLOW SEA AND BAY BREEZES ARE EXPECTED. THIS WILL PROVIDE SOME COOLING ALONG THE COAST. AS FOR THE HIGH TEMPERATURES, WE USED AN EVEN BLEND OF THE NAM/GFS MOS THEN MADE SOME LOCAL TWEAKS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... A WEAK SURFACE HIGH IS FORECAST TO BE OVER OUR AREA TONIGHT AS AN UPPER-LEVEL RIDGE AXIS SLIDES ACROSS THE EASTERN GREAT LAKES AND OHIO VALLEY. THIS STILL MAINTAINS NORTHWESTERLY FLOW ALOFT, BUT LIGHT AND VARIABLE FLOW AT THE SURFACE. DUE TO A LACK OF ORGANIZED SHORT WAVES TO PROVIDE ENOUGH LIFT, AN ISOLATED SHOWER OR THUNDERSTORM INITIATED PROBABLY BY ANY LOW-LEVEL CONVERGENCE /I.E. SEA AND BAY BREEZES/ ARE EXPECTED TO DISSIPATE EARLY IN THE EVENING. IN ADDITION, ANY CUMULUS FIELD IS EXPECTED TO FLATTEN AND DISSIPATE WITH PERHAPS SOME HIGH CLOUDINESS OCCURRING AT TIMES. IT WILL BE A WARM AND MUGGY NIGHT FOR MUCH OF THE CWA AS THE SURFACE DEW POINTS SHOULD RECOVER FROM ANY DAYTIME HEATING INFLUENCE. THE COMBINATION OF LIGHT TO CALM WINDS, A MOIST BOUNDARY LAYER AND NOT A LOT OF CLOUDINESS COULD RESULT IN PATCHY LOW CLOUDS/FOG DEVELOPMENT LATE. AS FOR THE LOW TEMPERATURES, A MOS BLEND WAS GENERALLY USED. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... A MID LEVEL 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 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 /08Z TUESDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TODAY...LOCAL LOW CLOUDS/FOG DISSIPATE BY MID MORNING, OTHERWISE VFR WITH A CLOUD BASE MOSTLY BETWEEN 3500-5000 FEET. AN ISOLATED SHOWER OR THUNDERSTORM MAY DEVELOP THROUGH THE DAY ESPECIALLY SOUTH AND EAST OF KPHL. SEA/BAY BREEZES ARE EXPECTED TO DEVELOP BY MID AFTERNOON AND AFFECT KACY, KMIV AND KILG WITH WINDS TURNING MORE FROM THE SOUTHEAST. TONIGHT...MAINLY VFR. HOWEVER DUE TO THE MOIST AIR MASS IN PLACE, SOME LATE NIGHT LOW CLOUDS/FOG MAY DEVELOP, AND OUR CONFIDENCE IS ON THE LOWER SIDE AT THIS TIME. LIGHT SOUTHERLY TO CALM WINDS. OUTLOOK... WEDNESDAY 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... THE CONDITIONS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA THROUGH TONIGHT. A SOUTHERLY FLOW WILL CONTINUE WITH SOME ENHANCEMENT OCCURRING THIS AFTERNOON AND EARLY EVENING AS A SEA AND BAY BREEZE DEVELOPS. THE SEAS SHOULD RUN IN THE 1-3 FEET RANGE THROUGH TONIGHT. OUTLOOK... WEDNESDAY THROUGH SATURDAY...NO MARINE HEADLINES ARE ANTICIPATED. && .RIP CURRENTS... A LONG PERIOD /AROUND 10 SECONDS/ SWELL FROM THE EAST-SOUTHEAST WILL CONTINUE TODAY. A SOUTHERLY WIND AT 10-15 MPH WITH SOME AFTERNOON SEA BREEZE ENHANCEMENT ALONG WITH WAVES OF AROUND 2 FEET IN THE SURF ZONE ARE FORECAST TODAY. THE SETUP IS SIMILAR TO YESTERDAY AND THEREFORE WE WILL MAINTAIN A MODERATE RISK OF DANGEROUS RIP CURRENTS FOR BOTH THE NEW JERSEY AND DELAWARE COASTS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...IOVINO NEAR TERM...GORSE SHORT TERM...GORSE LONG TERM...IOVINO AVIATION...GORSE/IOVINO MARINE...GORSE/IOVINO RIP CURRENTS...GORSE

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