Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 191032 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 632 AM EDT SUN APR 19 2015 .SYNOPSIS... HIGH PRESSURE CENTERED TO OUR NORTH THIS MORNING WILL GRADUALLY SHIFT OFF THE NEW ENGLAND COAST LATE TODAY AND TONIGHT. LOW PRESSURE ORGANIZING IN THE GREAT LAKES REGION TONIGHT WILL LIFT INTO CANADA MONDAY AND TUESDAY. AN ASSOCIATED WARM FRONT WILL LIFT INTO A PORTION OF OUR REGION MONDAY, FOLLOWED BY A COLD FRONT MONDAY NIGHT. AS LOW PRESSURE SLOWLY MOVES EASTWARD ACROSS NEW ENGLAND, A COLD FRONT WILL CROSS OUR REGION LATE WEDNESDAY INTO THURSDAY WITH ANOTHER ONE LATE THURSDAY INTO FRIDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A MID LEVEL RIDGE EXTENDED FROM THE WATERS OFF THE SOUTHEAST COAST TO THE GREAT LAKES EARLY THIS MORNING. THE RIDGE WILL PROGRESS TO THE EAST AND ITS AXIS IS FORECAST TO PASS OVERHEAD THIS AFTERNOON. MEANWHILE, SURFACE HIGH PRESSURE WILL NOSE DOWN FROM QUEBEC FOR TODAY. WE ARE ANTICIPATING A MOSTLY SUNNY DAY EVEN WITH A FAIR AMOUNT OF CIRRUS OVERHEAD. THE WIND IS EXPECTED TO SETTLE INTO THE EAST FOR TODAY DUE TO THE CIRCULATION AROUND THE HIGH TO OUR NORTH AND NORTHEAST. WIND SPEEDS ARE EXPECTED TO INCREASE TO 10 TO 15 MPH IN MUCH OF OUR REGION. THE ONSHORE FLOW WILL RESULT IN OUR HIGHEST TEMPERATURES BEING IN EASTERN PENNSYLVANIA AND NORTHERN NEW JERSEY WHERE READINGS SHOULD GET INTO THE MIDDLE 60S THIS AFTERNOON EXCEPT IN THE ELEVATED TERRAIN WHERE HIGHS SHOULD BE AROUND 60. MAXIMUM TEMPERATURES ARE ANTICIPATED TO FAVOR THE LOWER 60S ON THE COASTAL PLAIN WITH HIGHS ONLY IN THE MIDDLE AND UPPER 50S NEAR THE COAST. SOME LOW CLOUDS MAY BEGIN TO DRIFT OFF THE OCEAN AND OVER PARTS OF OUR COASTAL COUNTIES TOWARD EVENING. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... MID LEVEL CLOUDS WILL APPROACH FROM THE WEST AND SOUTHWEST THIS EVENING. MEANWHILE, LOW CLOUDS WILL MOVE INLAND OFF THE OCEAN AS THE EASTERLY SURFACE FLOW CONTINUES THROUGH THE NIGHT. WIND SPEEDS ARE FORECAST TO FAVOR THE 10 TO 20 MPH RANGE WITH THE STRONGEST WINDS ON THE COASTAL PLAIN. RAIN WILL BEGIN TO ARRIVE FROM THE SOUTHWEST TOWARD MIDNIGHT. THE LEADING EDGE OF THE RAIN IS FORECAST TO REACH A LINE FROM THE POCONOS TO PHILADELPHIA TO CAPE MAY AROUND 200 AM WITH THE PRECIPITATION EXPECTED TO OVERSPREAD THE REMAINDER OF NEW JERSEY BY ABOUT 400 AM. THE MODEL GUIDANCE IS INDICATING A SOUTHEASTERLY LOW LEVEL JET OF 50 KNOTS OR GREATER OVER OUR REGION LATE TONIGHT. THE LOW LEVEL JET WILL DRAW MOISTURE OFF THE OCEAN. THE ENHANCED LIFT WILL LIKELY INCREASE RAINFALL RATES AT THAT TIME. PRECIPITABLE WATER VALUES ARE FORECAST TO INCREASE TO ABOUT 1.5 INCHES. WE ARE EXPECTING RAINFALL AMOUNTS OF A THIRD TO THREE QUARTERS OF AN INCH BY DAYBREAK ON MONDAY WITH LOCALLY HIGHER AMOUNTS, CLOSE TO AN INCH POSSIBLE. WE SHOULD BE ABLE TO HANDLE THOSE TOTALS BASED ON THE RELATIVELY DRY ANTECEDENT CONDITIONS. HOWEVER, PONDING OF WATER ON ROADWAYS AND IN AREAS OF POOR DRAINAGE IS LIKELY. && .LONG TERM /MONDAY THROUGH SATURDAY/... THE SYNOPTIC SETUP IS COMPRISED OF AN AMPLIFYING UPPER-LEVEL TROUGH FROM THE MIDWEST TO THE LOWER MISSISSIPPI VALLEY MONDAY, WHICH THEN CLOSES OFF AND STRENGTHENS ACROSS THE GREAT LAKES REGION THROUGH TUESDAY. THIS FEATURE MAY ELONGATE INTO NEW ENGLAND WEDNESDAY AS SHORT WAVES ROTATE AROUND IT, HOWEVER IT SHOULD THEN BECOME CENTERED OVER NEW ENGLAND FRIDAY AND SATURDAY. THE MOST NOTABLE PRECIPITATION EVENT DURING THIS TIME FRAME IS ON MONDAY AS THE PATTERN CHANGES INTO A HIGHLY AMPLIFIED ONE. GIVEN THE SURGE IN MOISTURE, THE RAIN COULD BE HEAVY AT TIMES MONDAY MORNING. THE PATTERN THEREAFTER RESULTS IN CYCLONIC FLOW ACROSS THE EAST ALONG WITH COOLER TEMPERATURES AS A COUPLE OF COLD FRONTS MOVE THROUGH. WE USED A MODEL BLEND FOR MONDAY INTO WEDNESDAY, THEN BLENDED IN THE 00Z WPC GUIDANCE. SOME ADJUSTMENTS WERE THEN MADE FOLLOWING ADDITIONAL COLLABORATION WITH OUR NEIGHBORING OFFICES. FOR MONDAY AND TUESDAY...A DEEPENING AND INCREASINGLY CLOSING OFF LOW RESULTS IN SURFACE LOW PRESSURE IN THE GREAT LAKES REGION TO START WHICH THEN LIFTS INTO CANADA. A ROBUST LOW-LEVEL JET DURING MONDAY MORNING COMBINED WITH WAA, DEEP MOISTURE, LARGE SCALE ASCENT AND STRONG FRONTOGENETIC FORCING RESULTS IN AN AREA OF RAIN LIFTING NORTHEASTWARD. THERE COULD BE A LITTLE ELEVATED INSTABILITY WITHIN THIS, HOWEVER WE ARE NOT ANTICIPATING THUNDER ATTM. THE PW VALUES OF ABOUT 1.5 INCHES WILL RESULT IN SOME HEAVIER RAIN. OTHER THAN SOME TYPICAL PONDING OF WATER ON THE ROADWAYS AND POOR DRAINAGE FLOODING DURING HEAVIER RAIN, NO OTHER FLOODING IS ANTICIPATED ATTM. THE WARM SECTOR MAY NOT BE CLEAN AND MAY NOT CLEAR OUR ENTIRE CWA BUT IT SHOULD GET INTO AT LEAST THE SOUTHERN HALF OF THE CWA. THIS WILL HAVE AN IMPACT ON HIGH TEMPERATURES MONDAY. IT APPEARS AN AREA OF MID LEVEL DRYING OVERSPREADS THE REGION AS THE STRONG LIFT AND LOW-LEVEL JET CLEARS OUR CWA BY ABOUT THE EARLY AFTERNOON. THIS MAY RESULT IN A LULL, THEN INCOMING LIFT WITH THE COLD/OCCLUDING FRONT ALONG WITH COOLING ALOFT SHOULD TRIGGER ADDITIONAL SHOWERS. IT IS AT THIS TIME WHEN SOME THUNDERSTORMS MAY ALSO OCCUR. THERE MAY BE TWO TARGET AREAS DURING MONDAY AFTERNOON AND EVENING, ONE BEING ACROSS THE WESTERN ZONES /INCOMING SHORT WAVE AND FRONT/ AND THE OTHER ACROSS THE DELMARVA /SHORT WAVE AND PRE- FRONTAL TROUGH/. THE SOUTHERN AREAS MAY HAVE BETTER INSTABILITY AS THE WARM SECTOR SHOULD ARRIVE SOONER. IF WE CAN DESTABILIZE ENOUGH, SHEAR PROFILES SUGGEST SOME LINE SEGMENTS OR MULTICELL/CLUSTERS MOVING ACROSS PORTIONS OF THE AREA. DEPENDING ON THE ORGANIZATION OF THE CONVECTION, LOCALLY STRONG WIND GUSTS AND SOME HAIL CANNOT BE RULED OUT. THE THUNDER MENTION WAS EXPANDED NORTH A BIT MORE IN THE AFTERNOON AND EARLY EVENING. THE AFOREMENTIONED MONDAY MORNING ROBUST LOW-LEVEL JET SHOULD ALLOW FOR GUSTY ONSHORE SURFACE WINDS, WITH THE STRONGEST GUSTS CLOSER TO THE COAST AND THE HIGHER ELEVATIONS. A WEAK LOW LOOKS TO DEVELOP NEAR THE TRIPLE POINT, AND THIS ALONG WITH THE COLD/OCCLUDING FRONT SHOULD BE EXITING TO OUR EAST LATE MONDAY NIGHT INTO TUESDAY MORNING WITH ANY SHOWERS ENDING. A CLOSED LOW OVER THE GREAT LAKES THOUGH WILL PROVIDE CYCLONIC FLOW INTO THE AREA, AND WITH SOME SHORT WAVE ENERGY NEARBY A FEW SHOWERS IN THE AFTERNOON CANNOT BE RULED OUT MAINLY ACROSS THE NORTHWESTERN ZONES. FOR WEDNESDAY THROUGH SATURDAY...A CLOSED LOW CENTERED NEAR THE GREAT LAKES WEDNESDAY SHOULD SHIFT TO NEW ENGLAND FRIDAY AND SATURDAY. THERE LOOKS TO BE SEVERAL SHORT WAVES EMBEDDED IN THE CYCLONIC FLOW AND THESE WILL ROTATE THROUGH OUR AREA, PULLING A COLD FRONT THROUGH LATE WEDNESDAY INTO THURSDAY. SOME SHOWERS WILL BE POSSIBLE, ESPECIALLY ACROSS THE NORTHERN AND WESTERN AREAS. ANOTHER COLD FRONT SHOULD PUSH THROUGH LATE THURSDAY INTO FRIDAY, WITH ADDITIONAL COOLING BEHIND IT. THE CLOSED LOW LOOKS TO BE CLOSEST TO OUR AREA LATE FRIDAY INTO SATURDAY, AND THE CYCLONIC FLOW WILL RESULT IN EVEN COOLER TEMPERATURES. THERE COULD BE SOME FROST IN PARTS OF THE AREA FRIDAY AND SATURDAY MORNINGS, HOWEVER THIS WILL BE DEPENDENT ON CLOUD COVER AND WINDS. THE DETAILS ARE OF LOWER CONFIDENCE DURING THIS TIME FRAME AS IT WILL DEPEND ON THE TIMING OF THE CLOSED LOW AS WELL AS THE EMBEDDED SHORT WAVES. WE MAINLY BLENDED IN THE 00Z WPC GUIDANCE WITH CONTINUITY DURING THIS TIME FRAME. && .AVIATION /10Z SUNDAY THROUGH THURSDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY, AND SURROUNDING AREAS. VFR CONDITIONS ARE EXPECTED FOR TODAY WITH HIGH CLOUDS OVERHEAD. THE WIND WILL FAVOR THE EAST THROUGH THE DAY AT SPEEDS AROUND 8 TO 12 KNOTS. LOW CLOUDS ARE FORECAST TO MOVE INTO OUR REGION FROM THE OCEAN THIS EVENING, LOWERING CONDITIONS INTO THE IFR CATEGORY. RAIN WILL OVERSPREAD OUR TAF SITES FROM THE SOUTHWEST AFTER MIDNIGHT RESULTING IN A FURTHER DETERIORATION OF CONDITIONS. THE SURFACE WIND WILL REMAIN FROM THE EAST AROUND 10 TO 15 KNOTS WITH GUSTS AROUND 20 KNOTS, ESPECIALLY FROM KPHL EAST AND SOUTHWARD. A 50 PLUS KNOT LOW LEVEL SOUTHEASTERLY JET IS FORECAST TO BE LOCATED OVER OUR REGION LATE TONIGHT. AS A RESULT, WE WILL MENTION THE POTENTIAL FOR LOW LEVEL WIND SHEAR. OUTLOOK... MONDAY...MVFR/IFR WITH RAIN IN THE MORNING, THEN SOME SHOWERS WITH POTENTIALLY IMPROVEMENT TO VFR FROM SOUTH TO NORTH IN THE AFTERNOON AND EVENING. A FEW THUNDERSTORMS ARE POSSIBLE IN THE AFTERNOON AND EVENING. LOW-LEVEL WIND SHEAR SHOULD OCCUR IN THE MORNING AS A LOW- LEVEL JET MOVES THROUGH WITH A WARM FRONT. SOUTHEAST SURFACE WINDS 10 TO 15 KNOTS AND GUSTY EARLY IN THE MORNING ESPECIALLY CLOSER TO THE COAST, THEN TURNING SOUTHERLY 5-10 KNOTS IN THE AFTERNOON AND EVENING. TUESDAY...VFR OVERALL. SOME SHOWERS ARE STILL POSSIBLE MAINLY NEAR AND NORTH/WEST OF KABE AND KRDG. WESTERLY WINDS 10-15 KNOTS, DIMINISHING AT NIGHT. WEDNESDAY AND THURSDAY...MAINLY VFR. SOME SHOWERS ARE POSSIBLE, ESPECIALLY FROM KTTN TO KPHL METRO AND KILG TO THE NORTH AND WEST DURING EACH AFTERNOON AND EVENING. WEST-SOUTHWEST WINDS MAINLY NEAR 10 KNOTS. && .MARINE... HIGH PRESSURE LOCATED OVER QUEBEC THIS MORNING WILL SLIDE TO THE EAST. A WARM FRONT IS FORECAST TO APPROACH OUR REGION FROM THE SOUTHWEST TONIGHT. THE SURFACE FLOW WILL FAVOR THE EAST THROUGH THE PERIOD. WE WILL BEGIN A SMALL CRAFT ADVISORY FOR OUR OCEAN WATERS FROM LITTLE EGG INLET, NEW JERSEY SOUTHWARD TO FENWICK ISLAND, DELAWARE AND FOR THE LOWER PART OF DELAWARE BAY AT NOON TODAY. THE EASTERLY FLOW SHOULD CAUSE WAVE HEIGHTS ON THE ABOVE MENTIONED OCEAN WATERS TO BUILD TO 5 FEET THIS AFTERNOON AND WIND GUSTS IN THE ADVISORY AREA WILL APPROACH 25 KNOTS AT THAT TIME. THE SMALL CRAFT ADVISORY CONDITIONS ARE ANTICIPATED TO EXPAND ACROSS OUR OCEAN WATERS NORTH OF LITTLE EGG INLET AND TO THE WATERS OF UPPER DELAWARE BAY THIS EVENING. AS A RESULT, A SMALL CRAFT ADVISORY WILL BEGIN FOR THOSE AREAS AT 600 PM. OUTLOOK... MONDAY AND TUESDAY...A POTENT LOW-LEVEL JET WILL MOVE THROUGH MONDAY MORNING. THE FORECAST SOUNDINGS CONTINUE TO SHOW A STRONG LOW-LEVEL INVERSION IN PLACE AND THEREFORE MORE STABILITY. HOWEVER, RATHER STRONG WINDS ARE FORECAST TO BE NOT TO FAR ABOVE THE SURFACE. THE GFS DOES APPEAR TO BE STRONGER, AND THIS WOULD INTRODUCE A PERIOD OF GALES ESPECIALLY ACROSS THE FAR NORTHERN WATERS AS THERE IS A LONGER PERIOD OF EASTERLY INFLOW. THIS COULD BE OVERDONE AND SINCE OUR CONFIDENCE IS LOW ON THE MAGNITUDE AND DURATION, WE HELD OFF ON A GALE WATCH AND MAINTAINED A STRONG SMALL CRAFT ADVISORY. THE WINDS SHOULD SETTLE DURING THE COURSE OF MONDAY AND TURN MORE SOUTHERLY AS THE LOW-LEVEL JET EXITS, THEN TURN WESTERLY TUESDAY. SEAS WILL BUILD TO THE 5-9 FOOT RANGE ON THE OCEAN AND THEN GRADUALLY SUBSIDE MONDAY NIGHT AND TUESDAY. THE SMALL CRAFT ADVISORY ON THE BAY ENDS AT 14Z MONDAY, AND ON THE OCEAN WE EXTENDED IT TO 10Z TUESDAY FOR ELEVATED SEAS. IT MAY NEED TO BE EXTENDED MORE DEPENDING ON HOW THE SEAS BEHAVE /WE DID GO A FOOT BELOW WAVE WATCH AS THE GFS MAY BE TO STRONG WITH THE SURFACE WINDS MONDAY/. WEDNESDAY AND THURSDAY...THE CONDITIONS SHOULD BE BELOW SMALL CRAFT ADVISORY CRITERIA. SOME INCREASE IN THE WINDS SHOULD OCCUR OUT OF THE SOUTHWEST WEDNESDAY, THEN SHIFT TO THE WEST FOR THURSDAY. && .FIRE WEATHER... RELATIVE HUMIDITY VALUES ARE FORECAST TO LOWER INTO THE 20S DURING THE LATE MORNING AND AFTERNOON IN MUCH OF EASTERN PENNSYLVANIA AND NEW JERSEY. MINIMUM RELATIVE HUMIDITY VALUES SHOULD BE IN THE 30S IN MUCH OF DELAWARE AND NORTHEASTERN MARYLAND. FINE FUELS WILL CONTINUE TO DRY TODAY. IT APPEARS AS THOUGH MAXIMUM WIND GUSTS WILL BE IN THE 15 TO 20 MPH RANGE IN MUCH OF OUR REGION TODAY. CONDITIONS ARE ANTICIPATED TO REMAIN JUST BELOW THE RED FLAG WARNING CRITERIA IN EASTERN PENNSYLVANIA AND NEW JERSEY. WE WILL KEEP AN EYE ON THE SITUATION AS THE MORNING PROGRESSES. MEANWHILE, THE FORECAST RELATIVE HUMIDITY VALUES WILL LIMIT THE CONCERN FOR WILDFIRE SPREAD IN DELAWARE AND IN NORTHEASTERN MARYLAND. && .TIDES/COASTAL FLOODING... A MODERATE EASTERLY SURFACE FLOW IS EXPECTED FOR TODAY AND TONIGHT. THE LATEST GUIDANCE IS BRINGING TIDE LEVELS CLOSE TO THE MINOR FLOODING THRESHOLD IN NEW JERSEY AND DELAWARE FOR THIS EVENING`S HIGH TIDE. WE ARE CONCERNED THAT THE GUIDANCE IS A BIT LOW CONSIDERING THE LONG EASTERLY FETCH THAT IS DEVELOPING. WE WILL CONTINUE TO MONITOR THE SITUATION FOR A POSSIBLE COASTAL FLOOD ADVISORY. A WARM FRONT IS FORECAST TO LIFT THROUGH OUR REGION ON MONDAY CAUSING THE WIND TO SHIFT TO THE SOUTH. HOWEVER, THE EASTERLY WIND MAY PERSIST THROUGH MUCH OF THE DAY ALONG THE NORTHERN PART OF THE NEW JERSEY COAST. THERE IS THE CONTINUING POTENTIAL FOR MINOR TIDAL FLOODING ON MONDAY MORNING, ESPECIALLY FROM ATLANTIC CITY NORTHWARD TO SANDY HOOK. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 AM EDT TUESDAY FOR ANZ452>455. SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM EDT TUESDAY FOR ANZ450-451. SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 10 AM EDT MONDAY FOR ANZ430. SMALL CRAFT ADVISORY FROM NOON TODAY TO 10 AM EDT MONDAY FOR ANZ431. && $$ SYNOPSIS...GORSE NEAR TERM...IOVINO SHORT TERM...IOVINO LONG TERM...GORSE AVIATION...GORSE/IOVINO MARINE...GORSE/IOVINO FIRE WEATHER...IOVINO TIDES/COASTAL FLOODING...IOVINO

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