Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 271510 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1110 AM EDT SAT JUN 27 2015 .SYNOPSIS... LOW PRESSURE WILL TRACK ACROSS OHIO TO WESTERN PENNSYLVANIA TODAY INTO TONIGHT, THEN INTO NEW ENGLAND BY LATE SUNDAY. A WEAK AREA OF HIGH PRESSURE WILL BUILD IN FOR MONDAY, THEN A COLD FRONT SETTLES ACROSS OUR REGION LATER TUESDAY AND WEDNESDAY BEFORE STALLING TO OUR SOUTH THURSDAY. THIS FRONT MAY THEN LIFT NORTHWARD ACROSS OUR AREA FRIDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... WE HAVE NOT NEEDED MAY CHANGES DURING THE MID-MORNING UPDATE. THERE WERE SOME MINOR POP CHANGES FOR THE ONSET OF THE STEADIER RAINS. A COUPLE OF MAX TEMPS CHANGES WERE ALSO MADE ACROSS THE NORTH. THE PREVIOUS DESCRIPTION OF THE OVERALL SITUATION REMAINS VALID AND IS COPED BELOW. A MID LEVEL LOW IS FORECAST TO DRIFT ACROSS SOUTHERN MICHIGAN TODAY. MEANWHILE, A SURFACE REFLECTION OF THE LOW IS EXPECTED TO PASS ACROSS OHIO. THE SURFACE LOW IS ANTICIPATED TO LIFT A WARM FRONT TOWARD OUR REGION TODAY. AN EAST TO SOUTHEAST SURFACE FLOW IS EXPECTED AND THAT FLOW WILL DRAW ATLANTIC MOISTURE INTO OUR REGION. A LARGE AREA OF RAIN ASSOCIATED WITH THE LOW TO OUR WEST WILL SPREAD INTO OUR REGION THIS MORNING. RAINFALL RATES WILL BECOME ENHANCED THIS AFTERNOON DUE TO THE INCREASING ISENTROPIC LIFT, A DEVELOPING SOUTHEAST TO SOUTH LOW LEVEL JET AND INCREASING MOISTURE. WE WILL LEAVE THE FLOOD WATCH IN PLACE FOR SOUTHEASTERN PENNSYLVANIA (INCLUDING BERKS COUNTY AND THE LEHIGH VALLEY) AND FOR CECIL COUNTY IN MARYLAND AND NEW CASTLE COUNTY IN DELAWARE. A FAIR AMOUNT OF WIND SHEAR ALONG WITH MARGINAL INSTABILITY WILL CREATE THE POTENTIAL FOR LOW TOPPED SEVERE THUNDERSTORMS MAINLY IN AREAS NEAR THE APPROACHING WARM FRONT. THE AREA OF GREATEST CONCERN INCLUDES NORTHEASTERN MARYLAND, DELAWARE AND THE ADJACENT COUNTIES OF SOUTHEASTERN PENNSYLVANIA AND SOUTHERN NEW JERSEY. THE GREATEST THREAT IS FROM THIS AFTERNOON INTO THIS EVENING. HIGH TEMPERATURES ARE FORECAST TO RANGE FROM THE 60S TODAY IN OUR NORTHERN COUNTIES TO THE LOWER 80S IN THE SOUTH. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... THE MID LEVEL LOW IS FORECAST TO MOVE ALONG LAKE ERIE TONIGHT WITH THE SURFACE LOW EXPECTED TO BE IN THAT VICINITY, AS WELL. A SECONDARY LOW IS ANTICIPATED TO DEVELOP AT THE TRIPLE POINT AROUND THE WASHINGTON AND BALTIMORE AREA THIS EVENING BEFORE LIFTING NORTHEASTWARD AND INTO OUR FORECAST AREA OVERNIGHT. A SOUTHERLY LOW LEVEL JET WILL CONTINUE TO DRAW MOISTURE INTO OUR REGION TONIGHT. PRECIPITABLE WATER VALUES SHOULD EXCEED 2 INCHES IN MUCH OF OUR REGION. RAIN IS ANTICIPATED FOR MUCH OF THE NIGHT AND IT SHOULD TAPER TO SHOWERS WITH THE ARRIVAL OF THE LOW. RAINFALL TOTALS FOR THE EVENT ARE EXPECTED TO RANGE MAINLY FROM 1.5 TO 2.5 INCHES FROM THE INTERSTATE 95 CORRIDOR NORTHWESTWARD. LOCALLY HIGHER AMOUNTS ARE LIKELY. RAINFALL AMOUNTS NEAR THE COAST SHOULD RANGE FROM ABOUT AN INCH TO AN INCH AND A QUARTER. THE EAST TO SOUTHEAST SURFACE FLOW IS FORECAST TO LESSEN TONIGHT BEFORE BECOMING SOUTHWEST AFTER THE LOW PASSES. MINIMUM TEMPERATURES SHOULD BE MAINLY IN THE 60S. && .LONG TERM /SUNDAY THROUGH FRIDAY/... THE SYNOPTIC SETUP IS COMPRISED OF A RIDGE ACROSS THE WEST WITH A TROUGH ACROSS THE EAST. THIS WILL RESULT IN SOME UNSETTLED WEATHER AT TIMES ESPECIALLY AS IT AMPLIFIES AND TOSSES SOME FRONTAL BOUNDARIES OUR WAY, HOWEVER EVEN A SURGE IN WARMTH IS ANTICIPATED FOR A TIME. WE USED A MODEL BLEND FOR SUNDAY THROUGH TUESDAY, THEN BLENDED IN THE 00Z WPC GUIDANCE WITH CONTINUITY. SOME ADJUSTMENTS WERE THEN MADE FOLLOWING ADDITIONAL COLLABORATION WITH OUR NEIGHBORING OFFICES. FOR SUNDAY...SHOWERS ARE EXPECTED TO QUICKLY END EARLY IN THE MORNING FROM SOUTHWEST TO NORTHEAST AS LOW PRESSURE HEADS TOWARD NEW ENGLAND. THERE THEN SHOULD BE A FEW LINGERING WRAPAROUND SHOWERS THROUGH THE DAY MAINLY UP NORTH. OTHERWISE, SOME SUNSHINE SHOULD DEVELOP DURING THE DAY ESPECIALLY SOUTH AS LOW PRESSURE MOVES TO OUR NORTH AND NORTHEAST AND WINDS SHIFT TO SOUTHWEST AND WEST. THE PRESSURE GRADIENT TIGHTENS AND WITH BOUNDARY LAYER HEATING AND DEEPER MIXING BREEZY CONDITIONS SHOULD OCCUR DURING THE DAY FOR MUCH OF THE CWA, THEN THE WINDS START TO DIMINISH AT NIGHT. FOR MONDAY AND TUESDAY...AN UPPER-LEVEL TROUGH IS FORECAST TO REMAIN IN PLACE DURING THIS TIME FRAME, WITH EVEN SOME AMPLIFICATION TAKING PLACE TUESDAY. A WEAK AREA OF HIGH PRESSURE SHOULD BUILD IN FOR MONDAY, HOWEVER THE NEXT SHORT WAVE TO AMPLIFY THE TROUGH SWINGS ACROSS THE LOWER GREAT LAKES MONDAY NIGHT AND TUESDAY. THIS MAY ALLOW FOR A WEAK WARM FRONT TO LIFT NORTHWARD TUESDAY WITH POTENTIALLY SOME SURGE IN WARMTH. AN INCREASE IN WAA AND LIFT SHOULD RESULT IN SOME CONVECTION ESPECIALLY INLAND TUESDAY. FOR WEDNESDAY THROUGH FRIDAY...A STRONGER PUSH OF THE UPPER- LEVEL TROUGH IS FORECAST TO OCCUR DURING THIS TIME FRAME. THIS SHOULD FORCE A COLD FRONT ACROSS OUR AREA WEDNESDAY BEFORE STALLING TO OUR SOUTH THURSDAY. THIS COULD RESULT IN SOME SHOWERS AND THUNDERSTORMS ON WEDNESDAY. THERE IS THE POTENTIAL FOR SHORT WAVE ENERGY TO RIDE THE TAIL END OF THE FRONT, AND THEREFORE SLOWING THE FRONT DOWN AS IT CROSSES OUR AREA. AS OF NOW, WE STALL THE FRONT TO OUR SOUTH THURSDAY THEN AS ANOTHER TROUGH AMPLIFIES FROM THE WEST THE FRONT SHOULD LIFT NORTHWARD FRIDAY. AT LEAST SOME OF THE MODEL GUIDANCE MAY HAVE CONVECTIVE FEEDBACK ISSUES, HOWEVER THE PATTERN LOOKS ACTIVE WITH POTENTIAL ENERGY SLIDING EAST WITH A FRONT LIFTING NORTH. OVERALL, THE POPS ARE IN THE CHC RANGE OR LESS. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY, AND SURROUNDING AREAS. VFR CONDITIONS CONTINUE AT THE TAF SITES THIS MORNING...BUT A TREND TOWARD MVFR CONDITIONS WILL CONTINUE...BEGINNING N/W DURING THE EARLY AFTERNOON. CONDITIONS WILL CONTINUE TO DETERIORATE GRADUALLY...AND WE ARE ANTICIPATING MVFR AND IFR CONDITIONS FOR MUCH OF THE LATE AFTERNOON INTO TONIGHT. THE RAIN WILL BECOME MODERATE TO HEAVY AT TIMES AND SCATTERED THUNDERSTORMS ARE ANTICIPATED. AN EAST TO SOUTHEAST WIND IS FORECAST TO INCREASE TO 10 TO 15 KNOTS FOR TODAY WITH GUSTS IN THE 20 TO 25 KNOT RANGE. THE EAST TO SOUTHEAST WIND WILL CONTINUE INTO THIS EVENING BEFORE DECREASING AND GRADUALLY BECOMING SOUTHWEST LATE TONIGHT. OUTLOOK... SUNDAY...WIDESPREAD SHOWERS SHIFTING TO OUR NORTHEAST EARLY, THEN A FEW SHOWERS DURING THE DAY MAINLY NORTH AND WEST OF KPHL. THE CONDITIONS ARE EXPECTED TO BE VFR OVERALL. SOUTHWEST TO WEST WINDS 12 TO 15 KNOTS WITH GUSTS TO 25 KNOTS, DIMINISHING SOME AT NIGHT. MONDAY...VFR. WESTERLY WINDS 5 TO 10 KNOTS. TUESDAY...MAINLY VFR, HOWEVER SUB-VFR POSSIBLE IN ANY SHOWERS OR THUNDERSTORMS THAT MAY DEVELOP. SOUTHERLY WINDS 10 TO 15 KNOTS. WEDNESDAY...SUB-VFR POSSIBLE IN SHOWERS OR THUNDERSTORMS. WESTERLY WINDS 5 TO 10 KNOTS. && .MARINE... LOW PRESSURE WILL CONTINUE TO APPROACH FROM THE WEST DURING TODAY AND TONIGHT. AN EAST TO SOUTHEAST WIND IS FORECAST TO INCREASE TO 15 TO 25 KNOTS FOR TODAY INTO THIS EVENING. GUSTS AROUND 30 KNOTS ARE ANTICIPATED. WAVE HEIGHTS ON OUR OCEAN WATERS ARE EXPECTED TO BUILD TO 6 TO 8 FEET. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR OUR OCEAN WATERS FOR TODAY AND TONIGHT. THE ADVISORY IS IN EFFECT ONLY UNTIL 1100 PM FOR DELAWARE BAY. WIND SPEEDS ARE ANTICIPATED TO DECREASE GRADUALLY TONIGHT BUT WAVE HEIGHTS SHOULD REMAIN ABOVE 5 FEET ON OUR OCEAN WATERS. OUTLOOK... SUNDAY...THE SMALL CRAFT ADVISORY IN EFFECT DURING THE DAY BUT MAY NEED TO BE EXTENDED INTO THE EVENING. IN ADDITION, WINDS MAY GUST TO 25 KNOTS ON DELAWARE BAY AND THEREFORE AN ADVISORY MAY NEED TO BE ADDED. SEAS REMAINING ELEVATED BUT GRADUALLY SUBSIDING THROUGH THE EVENING. MONDAY...THE WINDS AND SEAS ARE ANTICIPATED TO SUBSIDE BELOW ADVISORY CRITERIA. TUESDAY...AN INCREASE IN A SOUTHERLY FLOW MAY BUILD THE SEAS ON THE OCEAN TO ADVISORY CRITERIA. WEDNESDAY...SUBSIDING SEAS WITH SUB-ADVISORY CONDITIONS ANTICIPATED. && .HYDROLOGY... A FLOOD WATCH IS IN EFFECT FOR BERKS COUNTY, THE LEHIGH VALLEY AND SOUTHEASTERN PENNSYLVANIA FROM NOON TODAY UNTIL 500 AM SUNDAY. ALSO, THE FLOOD WATCH INCLUDES CECIL COUNTY IN MARYLAND AND NEW CASTLE COUNTY IN DELAWARE. WE ARE ANTICIPATING WIDESPREAD RAINFALL AMOUNTS OF 1.5 TO 2.5 INCHES IN THE WATCH AREA. LOCALLY HIGHER AMOUNTS ARE LIKELY. THE LOWER SCHUYLKILL RIVER VALLEY IS PARTICULARLY VULNERABLE TO NEW FLOODING DUE TO THE SATURATED CONDITIONS THERE. RADAR INDICATED LOCALIZED RAINFALL AMOUNTS OF GREATER THAN 4 INCHES FROM AROUND PHOENIXVILLE AND COLLEGEVILLE DOWN TO CONSHOHOCKEN DURING THE HOURS AROUND MIDNIGHT. GENERALLY, SMALL STREAMS AND CREEKS WILL BE MOST VULNERABLE DURING THIS EVENT ALONG WITH AREAS OF POOR DRAINAGE. THE MAIN RIVERS SUCH AS THE LEHIGH, THE SCHUYLKILL AND THE DELAWARE ARE NOT EXPECTED TO FLOOD. && .TIDES/COASTAL FLOODING... THE EAST TO SOUTHEAST FLOW WILL PUSH WATER UP ALONG THE COAST AND INTO DELAWARE BAY. WE ARE NOT ANTICIPATING ANY PROBLEMS ON THE OCEANFRONT OR ALONG THE DELAWARE BAY SHORE. HOWEVER, WE ARE A BIT CONCERNED THAT MINOR TIDAL FLOODING MAY OCCUR EARLY TONIGHT ON THE LOWER DELAWARE RIVER AS THE SURGE WORKS ITS WAY INTO THAT AREA. HIGH TIDE AT REEDY POINT, DELAWARE IS AT 838 PM AND HIGH TIDE AT PHILADELPHIA OCCURS AT 1113 PM. WE WILL RE-EXAMINE THE LATEST GUIDANCE AND A COASTAL FLOOD ADVISORY MAY BE NEEDED FOR THE LOWER DELAWARE RIVER FOR EARLY TONIGHT. && .RIP CURRENTS... THE STRENGTHENING EAST TO SOUTHEAST FLOW WILL RESULT IN THE DEVELOPMENT OF A HIGH RISK OF RIP CURRENTS TODAY ALONG THE NEW JERSEY SHORE. WE WILL KEEP THE RISK AT MODERATE FOR THE DELAWARE BEACHES BASED ON OUTPUT FROM OUR LOCAL PROGRAM. THE SURF IS EXPECTED TO BECOME DANGEROUS TODAY. BE SAFE AND STAY OUT OF THE WATER. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...FLOOD WATCH THROUGH LATE TONIGHT FOR PAZ060>062-070-071- 101>106. NJ...HIGH RIP CURRENT RISK UNTIL 10 PM EDT THIS EVENING FOR NJZ014- 024>026. DE...FLOOD WATCH THROUGH LATE TONIGHT FOR DEZ001. MD...FLOOD WATCH THROUGH LATE TONIGHT FOR MDZ008. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT SUNDAY FOR ANZ450>455. SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR ANZ430- 431. && $$ SYNOPSIS...GORSE NEAR TERM...IOVINO/PO SHORT TERM...IOVINO LONG TERM...GORSE AVIATION...GORSE/IOVINO/MEOLA/PO MARINE...GORSE/IOVINO/MEOLA HYDROLOGY... TIDES/COASTAL FLOODING... RIP CURRENTS...

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