Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 111418 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1018 AM EDT FRI JUL 11 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD ACROSS THE NORTHEAST STATES TODAY, THEN SHIFT OFFSHORE LATER TONIGHT AND SATURDAY. A WARM FRONT SHOULD LIFT NORTH OF THE REGION SUNDAY, THEN A COLD FRONT IS FORECAST TO ARRIVE LATE MONDAY NIGHT AND ESPECIALLY TUESDAY. THIS FRONT SHOULD BE SETTLING TO OUR SOUTH AND EAST WEDNESDAY, AS HIGH PRESSURE GRADUALLY ARRIVES FROM THE WEST DURING THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE SFC FRONTAL BOUNDARY THAT STALLED OVER THE DELMARVA YESTERDAY HAS FINALLY MOVED SOUTH AND EAST OF THE REGION THIS MORNING. A BROAD SFC HIPRES OVER UPSTATE NY WILL BUILD EWD INTO NEW ENGLAND TODAY. LIGHT NELY FLOW AROUND THE HIGH THIS MORNING HAS BEEN ASSOCIATED WITH MARINE STRATUS ALONG THE SRN NJ COAST/DELMARVA. STRATUS IS ALREADY MIXING OUT QUICKLY DURING THE MID MORNING IN SRN NJ AND NRN DELAWARE BUT FARTHER SOUTH, WHERE THE 925 MB COLD FRONT HAS LAGGED BEHIND THE SFC BOUNDARY AND LLVL MOISTURE HAS POOLED, LOW CLOUDS WILL TAKE LONGER TO ERODE FROM NORTH TO SOUTH. SEVERAL HIRES MODELS SHOW POP UP SHOWERS AND STORMS DEVELOPING IN EXTREME SERN PA AND OVER THE DELMARVA THIS AFTN DURING THE PEAK HEATING HRS. THIS APPEARS TO BE WHERE THE HIGHER MOISTURE RESIDES WITH SFC DEWPOINTS IN THE UPPER 60S VS UPPER 50S/LOWER 60S FARTHER NORTH). LIFT WOULD BE ATTRIBUTED TO AN APPROACHING SHORTWAVE TROUGH AXIS AND EVEN THE RUC SHOWS SFC CONVERGENCE DEVELOPING NEAR THE ERN SHORE OF THE CHSPK BAY AROUND 18Z. THE FORCING WILL BE WEAK THOUGH, FAVORING MINIMAL CONVECTIVE COVERAGE. INSTABILITY/SHEAR PROFILES NOT INDICATIVE OF A SEVERE THREAT, BUT CANNOT RULE OUT AN ISO STRONG STORM DEVELOP OVER THE DELMARVA. MAX TEMPS TODAY IN THE LOW TO MID 80S EXCEPT 5-10F COOLER ALONG THE COAST AND IN THE POCONOS. MAY NEED TO LOWER TEMPS A COUPLE OF DEGREES IN THE CENTRAL DELMARVA IF LOW CLOUDS HOLD ON A BIT LONGER. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... THE MID LEVEL TROUGH IS FORECAST TO MOVE TO OUR EAST TONIGHT. ANY ISOLATED PRECIPITATION EARLY THIS EVENING SHOULD DISSIPATE QUICKLY AS THE ATMOSPHERE CONTINUES TO TO STABILIZE AND AS HIGH PRESSURE BUILDS INTO OUR REGION FROM THE NORTH. THE SKY IS EXPECTED TO BE MOSTLY CLEAR FOR TONIGHT AND THE WIND SHOULD BECOME LIGHT AND VARIABLE. THE COMBINATION IS ANTICIPATED TO ALLOW TEMPERATURES TO FALL INTO THE UPPER 50S TO MIDDLE 60S IN MUCH OF OUR REGION. && .LONG TERM /SATURDAY THROUGH THURSDAY/... THE OVERALL SYNOPTIC SETUP IS COMPRISED OF A POTENT UPPER-LEVEL TROUGH THAT CLOSES OFF AS IT DIGS ACROSS THE MIDWEST AND GREAT LAKES REGION SUNDAY AND MONDAY, THEN BEGINS TO SHIFT INTO PORTIONS OF THE NORTHEAST TUESDAY AND WEDNESDAY. THIS FEATURE WILL DRIVE A COLD FRONT ACROSS OUR AREA IN THE TUESDAY INTO WEDNESDAY TIME FRAME WITH CONVECTIVE EPISODES AHEAD OF IT. THERE IS THE POTENTIAL FOR STRONG TO SEVERE THUNDERSTORMS TO OCCUR ESPECIALLY TUESDAY AS THE MAIN FEATURES ALOFT MOVE THROUGH. WE USED A MODEL BLEND FOR SATURDAY INTO MONDAY, THEN MOSTLY BLENDED THE 00Z WPC GUIDANCE INTO CONTINUITY THEREAFTER. FOR SATURDAY AND SUNDAY...AS THE CENTER OF HIGH PRESSURE SHIFTS FARTHER OFFSHORE SATURDAY, THE FLOW WILL TURN FROM EAST-SOUTHEAST TO MORE SOUTHERLY. AS THIS OCCURS, SOME INCREASE IN THE WAA AHEAD OF AN AMPLIFYING UPPER-LEVEL TROUGH INTO THE GREAT LAKES REGION SHOULD ORGANIZE A WARM FRONT TO OUR SOUTHWEST. THIS FRONT SHOULD THEN START MIGRATING NORTHWARD SUNDAY. OVERALL SATURDAY LOOKS TO BE DRY WITH HIGH PRESSURE CLOSE ENOUGH TO START AND THEN OVERALL A LACK OF ORGANIZED LIFT. IF ISOLATED CONVECTION WHERE TO FORM IN THE AFTERNOON, IT SHOULD BE TO OUR WEST ON THE PERIPHERY OF THE SURFACE HIGH AND CLOSER TO THE TERRAIN INFLUENCES. AS THE UPPER-LEVEL FLOW STARTS TO TURN MORE CYCLONIC SUNDAY, SOME SHOWERS AND THUNDERSTORMS SHOULD DEVELOP MAINLY INLAND IN THE AFTERNOON PERHAPS FOCUSED NEAR A LEE SIDE TROUGH. THIS WOULD BREAK OUR STRING OF NICE WEATHER ON THE WEEKENDS AT LEAST FOR A PORTION OF OUR CWA. FOR MONDAY THROUGH WEDNESDAY...A ROBUST UPPER-LEVEL TROUGH/CLOSED LOW FOR THIS TIME OF THE YEAR IS FORECAST TO SLIDE ACROSS THE GREAT LAKES REGION AND TOWARD THE NORTHEAST. LOW PRESSURE TRACKING ACROSS CANADA WILL PULL A COLD FRONT INTO THE EAST LATER TUESDAY INTO WEDNESDAY. THE PRESENCE OF STRENGTHENING CYCLONIC FLOW IN COMBINATION WITH AN INCREASINGLY UNSTABLE AIRMASS WILL INITIATE SHOWERS AND THUNDERSTORMS. THIS MAY BE TIED TO AN INITIAL LEE SIDE TROUGH MONDAY WITH MORE OF A CONVECTIVE ORGANIZATION ACROSS OUR WESTERN ZONES, THEN MORE FOCUSED TUESDAY WITH THE COLD FRONT /ALSO A PRE-FRONTAL TROUGH/ ALONG WITH SOME COOLING ALOFT AND STRONGER FLOW. THE INSTABILITY SHOULD BE ENHANCED SOME AS DEEPER MOISTURE ADVECTS NORTHEASTWARD IN ADVANCE OF THE SURFACE FRONT. IT WILL BE WARM AND HUMID AS WELL, AND MONDAY LOOKS TO BE THE HOTTEST DAY AS THE LOW-LEVEL WAA SHOULD PEAK. AS OF NOW, WE ARE NOT ANTICIPATING ANY HEAT RELATED HAZARDS ACROSS THE CWA. THE LARGE SCALE LIFT IS FORECAST TO INCREASE SUBSTANTIALLY TUESDAY WITH THE PRESENCE OF A STRONG SHORT WAVE SLIDING ACROSS THE REGION. THIS COULD RESULT IN SOME STRONG TO SEVERE CONVECTIVE EPISODES MONDAY AND PARTICULARLY ON TUESDAY. WHILE THERE IS LESS CERTAINTY WITH THE DETAILS, THE POTENTIAL IS THERE FOR SEVERE THUNDERSTORMS. BASED ON THE FORECAST SOUNDINGS, IT APPEARS THAT LINE SEGMENTS WITH EMBEDDED BOWING STRUCTURES WOULD BE THE MAIN STORM MODE GIVEN A MORE UNIDIRECTIONAL FLOW THROUGH THE COLUMN. THE CONVECTION THAT OCCURS ON MONDAY MAY HAVE AN IMPACT ON WHAT DEVELOPS ON TUESDAY. THE PW VALUES ARE FORECAST TO INCREASE TO AROUND 2 INCHES MONDAY AND TUESDAY, WHICH WILL ALLOW FOR LOCALLY HEAVY RAIN TO OCCUR. THIS COULD ALSO INCREASE THE THREAT FOR WATER LOADED DOWNDRAFTS. WE WILL MAINTAIN A MENTION IN THE HAZARDOUS WEATHER OUTLOOK. THE COLD FRONT SHOULD BE EASING TO OUR SOUTH AND EAST DURING WEDNESDAY, WITH DRYING ARRIVING FROM THE NORTHWEST. THERE COULD BE SOME CONVECTION LINGERING TO START ACROSS OUR EASTERN ZONES, AND THEREFORE MUCH OF THE REGION WAS KEPT DRY. FOR THURSDAY...A LARGE UPPER-LEVEL TROUGH IS FORECAST TO BE IN PLACE, HOWEVER THE CENTER OF IT LOOKS TO BE NORTH OF THE GREAT LAKES. THIS WILL MAINTAIN CYCLONIC FLOW ACROSS OUR AREA AS SURFACE HIGH PRESSURE GRADUALLY BUILDS IN FROM THE WEST. WE ARE ANTICIPATING A COOLER AIRMASS TO BE IN PLACE ALONG WITH LOWER DEW POINTS. NO MAJOR CHANGES WERE MADE TO THIS TIME FRAME. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. EARLIER LOW CLOUDS AT MIV/ACY DISSIPATED BETWEEN 12-13Z THIS MRNG. VFR TODAY, BUT AN ISO POP UP SHRA/TSRA POSSIBLE IN SOUTHWESTERN AREA TERMINALS. THE BEST CHANCE TO SEE THIS ACTIVITY WOULD BE ILG, BUT COVERAGE TOO LOW TO INCLUDE IN 12Z TAFS. NE WINDS 5-10 KT TDA WILL BECOME SELY THIS EVE AROUND 5 KT. OUTLOOK... SATURDAY...PERHAPS LOCAL MVFR/IFR STRATUS OR FOG TO START, OTHERWISE VFR. SOUTHERLY WINDS MAINLY 5-10 KNOTS. SUNDAY AND MONDAY...TIMES OF SUB-VFR WITH SOME SHOWERS AND THUNDERSTORMS AROUND. THE BEST CHANCE APPEARS TO BE FOR THE FARTHER INLAND TERMINALS EACH AFTERNOON AND EVENING. TUESDAY...A BETTER CHANCE FOR ORGANIZED SHOWERS AND THUNDERSTORMS AS A COLD FRONT ARRIVES. SOME STORMS MAY PRODUCE GUSTY SURFACE WINDS. && .MARINE... THE FRONTAL BOUNDARY WILL CONTINUE TO SINK TO OUR SOUTH TODAY, ALLOWING HIGH PRESSURE FROM THE NORTH TO BUILD ACROSS THE COASTAL WATERS OF NEW JERSEY AND DELAWARE FOR TONIGHT. NE WINDS AROUND 10-15 KT ARE OCCURRING OVER THE COASTAL ATLANTIC WATERS THIS MRNG. THESE WINDS WILL DECREASE BY LATE AFTN. LIGHT AND VARIABLE WINDS TNGT. WIND SPEEDS AND WAVE HEIGHTS ARE ANTICIPATED TO REMAIN BELOW THE SMALL CRAFT ADVISORY CRITERIA FOR TODAY AND TONIGHT. OUTLOOK... SATURDAY...HIGH PRESSURE NEAR THE NEW ENGLAND COAST WILL SHIFT FARTHER OFFSHORE. THIS WILL RESULT IN THE FLOW TURNING MORE SOUTHERLY WITH TIME, HOWEVER IT IS ANTICIPATED TO BE LIGHT. SUNDAY THROUGH TUESDAY...THE FLOW BECOMES MORE SOUTHWESTERLY ON SUNDAY. THESE WINDS STRENGTHEN MONDAY AND TUESDAY AHEAD OF A COLD FRONT, HOWEVER THEY SHOULD REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA. IF ENOUGH MIXING OCCURS ON TUESDAY, SOME MARGINAL ADVISORY GUSTS CAN OCCUR ESPECIALLY NEARSHORE. THE SOUTHERLY FLOW WILL BUILD THE SEAS AND AN ADVISORY MAY BE NEEDED MONDAY AND TUESDAY FOR THE COASTAL WATER ZONES. THE WAVEWATCH GUIDANCE HOWEVER COULD BE OVERDONE GIVEN THE SOUTHERLY FLOW WITHIN A WAA REGIME. SOME SHOWERS AND THUNDERSTORMS ARE ANTICIPATED MONDAY AND TUESDAY, SOME WITH POTENTIALLY GUSTY WINDS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GORSE NEAR TERM...KLEIN SHORT TERM...IOVINO LONG TERM...GORSE AVIATION...GORSE/IOVINO/KLEIN MARINE...GORSE/IOVINO/KLEIN

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