Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 190740
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
340 AM EDT SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE CENTERED TO OUR NORTH THIS MORNING WILL THEN GRADUALLY
SHIFT OFF THE NEW ENGLAND COAST LATER 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 /08Z 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 WAVEWATCH
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 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.

&&

.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



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