Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 270438
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1238 AM EDT SAT JUN 27 2015

.SYNOPSIS...
HIGH PRESSURE WILL MOVE ACROSS TO THE NORTH OF OUR AREA AND OFF
THE NEW ENGLAND COAST SATURDAY. LOW PRESSURE WILL TRACK ALONG A
FRONTAL BOUNDARY SATURDAY, LIFTING TO THE OUR NORTH AND EAST
SUNDAY. WEAK HIGH PRESSURE WILL ARRIVE FOR MONDAY. A COLD FRONT
WILL CROSS THE AREA TUESDAY INTO WEDNESDAY. A SECOND COLD FRONT
WILL SLOWLY MOVE THROUGH THE REGION LATER THIS WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
THE RAINFALL RATES ALONG THE LOWER SCHUYLKILL RIVER VALLEY WERE
DECREASING GRADUALLY AROUND 1230 AM. THE SHOWERS WERE CONTINUING
TO REDEVELOP ALONG REMNANT BOUNDARIES. BASICALLY, THE
PRECIPITATION HAS BEEN REGENERATING ITSELF BUT IT SHOULD
DISSIPATE SLOWLY OVER THE NEXT FEW HOURS. RADAR BASED RAINFALL
AMOUNTS OF 4 INCHES OR MORE WERE INDICATED, ESPECIALLY IN
MONTGOMERY COUNTY FROM AROUND COLLEGEVILLE TO CONSHOHOCKEN. WE
HAVE RECEIVED REPORTS OF ROAD CLOSURES. DUE TO THE LATE HOUR, WE
ANTICIPATE GETTING ADDITIONAL REPORTS FROM THOSE AREAS COVERED BY
FLASH FLOOD WARNINGS IN THE MORNING.

ADDITIONAL LIGHT TO MODERATE SHOWERS WERE INDICATED ALONG ANOTHER
REMNANT BOUNDARY ACROSS THE POCONOS AND NORTHERN NEW JERSEY.
RAINFALL AMOUNTS THERE HAVE BEEN GENERALLY LESS THAN A HALF INCH.

WHILE THE SHOWER ACTIVITY IS ANTICIPATED TO LESSEN, A LARGE AREA
OF RAIN ASSOCIATED WITH THE WARM ADVECTION IN ADVANCE OF LOW
PRESSURE IN THE OHIO RIVER VALLEY SHOULD REACH OUR FORECAST AREA
LATE TONIGHT. WE ARE EXPECTING THE RAIN TO AFFECT MAINLY EASTERN
PENNSYLVANIA AT THAT TIME BEFORE SPREADING FARTHER EAST.

AN EAST TO SOUTHEAST WIND IS FORECAST OVERNIGHT AND TEMPERATURES
ARE EXPECTED TO DROP ONLY A FEW DEGREES FROM THEIR MIDNIGHT
READINGS.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 AM SUNDAY/...
WE HAVE ISSUED A FLOOD WATCH FOR MOST OF OUR WESTERN ZONES AND
INCLUDING SOME OF THE PHILLY METRO AREA FROM SATURDAY AFTERNOON
THROUGH EARLY SUNDAY MORNING...WHEN WE EXPECT THE HEAVIEST OF THE
RAIN TO FALL. DID NOT THINK A FLASH FLOOD WAS PRUDENT GIVEN OUR
GUIDANCE REMAINS ON THE HIGHER SIDE, EVEN WITH THE RECENT
CONVECTIVE RAINS. THAT BEING SAID WE DO NOT EXPECT ANY MAIN STEM
RIVER FLOODING TO BE AN ISSUE, THIS WATCH IS MOSTLY FOR THE
SMALLER STREAMS AND CREEKS, LOW-LYING AREAS AND THE URBAN CORRIDOR
WHERE OUR HEADWATER GUIDANCE REMAINS RATHER LOW...SMALL BASIN
STREAMS/CREEKS THAT USUALLY RESPOND QUICKLY TO HEAVIER
RAIN....AGAIN NOT FLASH FLOODING.

THERE ARE SOME THINGS THAT WE QUESTIONED WITH THE POTENTIAL FOR
FLOODING ON SATURDAY. FOR STARTERS, JET STREAK POSITIONING DOES
NOT SEEM IDEAL FOR ENHANCED LIFT PLACING US IN THE RIGHT EXIT
REGION. ITS VERY POSSIBLE THAT THE SURFACE WARM FRONT WILL ONLY BE
ABLE TO PROGRESS AS FAR NORTH AS NORTHERN DELMARVA BEFORE STALLING
AGAIN WITH RAIN FALLING TOWARDS THE NORTH AS THE LOW-LEVEL FRONT
MOVES THROUGH...NOT A TRUE WARM SECTOR SETUP. GUIDANCE SHOWS
STRONGER THETA-E SURGE ACROSS THE SOUTHERN ZONES... WITHIN WARM
SECTOR, BUT COULD SEE MORE DRYING AS THE WINDS VEER SOUTHWEST
LATER IN THE DAY. THERE IS SOME WEAK INSTABILITY LATE IN THE DAY,
ALL ELEVATED, BUT EVEN THE SHOWALTER INDICES ARE NOT THAT
EXCITING.

WHAT WE ARE FOCUSING ON MAINLY IS THE LONG EASTERLY FETCH OFF THE
ATLANTIC THAT WILL USE THE OUR WESTERN ZONE UPSLOPE COMPONENT TO
HELP LOCALLY ENHANCE RAINFALL. PWATS ARE EXPECTED TO CLIMB UP
TOWARDS THE 2 INCH MARK WITH A SECONDARY LOW PRESSURE FORMING
RIGHT AROUND THE CITY LATE TONIGHT...TRIPLE POINT ENHANCEMENT.
LASTLY, A 45-50 KNOTS 850MB JET PUMPING INTO THE AREA WITH A VERY
STRONG ISENTROPIC LIFT WILL FURTHER HELP THE HEAVY RAIN POTENTIAL.

OUTSIDE OF OUR FLOOD WATCH, A WIDESPREAD 1 TO 2 INCHES OF RAIN IS
EXPECTED BUT GIVEN THE LONG DURATION OF THE EVENT, NOT EXPECTING
MUCH IN THE WAY OF FLOODING ISSUES. THERE IS ALSO THE CHANCE FOR
AFTERNOON/LATE EVENING CONVECTION ACROSS OUR DELMARVA ZONES...IN
THE WARM SECTOR, AS MUCAPE CLIMBS UPWARDS OF 750J/KG AND WITH A
DECENT AMOUNT OF SHEAR IN PLACE. GOOD LOW-LEVEL VEERING PROFILES
MAY ALLOW FOR A FEW SPINNING STORMS SHOULD ANY FORM DURING THIS
TIME FRAME.

&&

.LONG TERM /SUNDAY THROUGH SATURDAY/...
SUNDAY...THINGS START TO WIND DOWN ON SUNDAY AS THE LOW LIFTS TO
THE NORTHEAST. SHOWERS WILL GRADUALLY TAPER OFF WITH HIGHEST
CHANCES REMAINING ACROSS THE NORTHERN AREAS WHERE SOME WRAPAROUND
MOISTURE LINGERS. CLOUDY SKIES WILL CONTINUE AND AREAS ALONG THE
COAST SHOULD SEE SOME SUN BY THE AFTERNOON.

MONDAY...A WEAK AREA OF HIGH PRESSURE WILL CROSS THE REGION,
KEEPING US DRY WITH MOSTLY SUNNY SKIES. WINDS WILL START TO BECOME
MORE SOUTHWESTERLY AND THIS WILL BE THE START OF DECENT WARM AIR
ADVECTION INTO OUR AREA.

TUESDAY THROUGH FRIDAY...WARM AIR ADVECTION WILL CONTINUE ACROSS
THE REGION AND WE SHOULD BE ABLE TO SEE TEMPERATURES REACH INTO
THE MID 80S BY THE AFTERNOON. AS WE GO THROUGH THE DAY, WE WILL
SEE AN INCREASE IN CLOUDINESS AS A COLD FRONT STARTS TO PUSH
TOWARD THE AREA FROM THE GREAT LAKES REGION. THE COLD FRONT
DOESN`T LOOK LIKE IT WILL REACH THE AREA UNTIL LATE TUESDAY
CLEARING THE COAST EARLY WEDNESDAY MORNING. A SECOND COLD FRONT
WILL MOVE TOWARDS OUR AREA REACHING OUR WESTERN ZONES LATE
WEDNESDAY. THE FRONT WILL SLOWLY SAG THROUGH THE REGION THE MODELS
DIFFER AT THE SPEED AND LOCATION OF THIS FRONT WITH IT POSSIBLY
STALLING IN OR NEAR OUR FORECAST AREA. WHILE SHOWERS AND
THUNDERSTORMS LOOK POSSIBLE THROUGH MUCH OF THE PERIOD, IT DOES
NOT LOOK LIKE IT WILL BE A TOTAL WASHOUT. TEMPERATURES THROUGH
THIS PERIOD LOOK TO REMAIN NEAR NORMAL.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY, AND SURROUNDING AREAS.

00Z TAFS BRING IFR/WINDY CONDITIONS DURING THE DAY ON SATURDAY.

OVERNIGHT...LOWERING VFR CIG. SOME MVFR VSBYS DUE TO FOG POSSIBLE
TOWARD MORNING AT MORE RURAL AIRPORTS AND TERMINALS. SLIGHTLY
STRONGER EAST WIND. SCATTERED SHOWERS WILL CONTINUE BUT MAY NOT
AFFECT OUR TAF SITES.

SATURDAY MORNING...CIGS LOWERING FURTHER. CONFIDENCE ABOUT THEM
REMAINING VFR IS DECREASING. RAIN SHOULD ARRIVE AT NORTHWEST
TERMINALS AND OTHER WESTERN AIRPORTS IN PA. MVFR CONDITIONS ONCE
RAIN ARRIVES. EAST WINDS AVERAGING AROUND 10 KNOTS WITH GUSTINESS
STARTING FROM KPHL METRO AIRPORTS EAST AND SOUTHEAST.

SATURDAY AFTERNOON...ALL TERMINALS PREDICTED TO DROP TO IFR IN
RAIN AND FOG. RAIN SHOULD BE HEAVY, ESPECIALLY NORTHWEST
TERMINALS. EAST TO SOUTHEAST WINDS SUSTAINED SPEEDS INCREASING TO
CLOSE TO 15 KNOTS WITH GUSTS AVERAGING CLOSE TO 25 KNOTS.

OUTLOOK...
SATURDAY NIGHT...IFR CONDITIONS CONTINUING. GUSTY EAST WINDS
SHIFTING TO THE WEST.

SUNDAY...SHOWERS CONTINUE THROUGH SUNDAY, TAPERING OFF BY THE
LATE AFTERNOON. WEST SOUTHWEST WINDS AROUND 10 TO 15 KNOTS WITH
GUSTS AROUND 20 KNOTS.

MONDAY...VFR CONDITIONS EXPECTED. WESTERLY WINDS AROUND 5 TO 10
KNOTS.

TUESDAY...MAINLY VFR CONDITIONS EXPECTED. SUB-VFR CONDITIONS
POSSIBLE IN ANY SHOWERS OR THUNDERSTORMS THAT MAY DEVELOP.
SOUTHERLY WINDS AROUND 10 KNOTS.

WEDNESDAY...MAINLY VFR CONDITIONS EXPECTED. SUB-VFR CONDITIONS
POSSIBLE IN SHOWERS OR THUNDERSTORMS WITH CLEARING TOWARD LATE
AFTERNOON/EVENING. WESTERLY WINDS AROUND 5 TO 10 KNOTS.

&&

.MARINE...
WE HAVE ISSUED A SCA FOR ALL OUR COASTAL WATERS STARTING FIRST
ACROSS THE SOUTH AND THEN NORTH AS A WARM FRONT LIFTS THROUGH THE
REGION. SEAS WILL ALSO INCREASE BEHIND THE FRONT UPWARDS OF 5-7
FEET AS STRONGER EASTERLY FLOW OCCURS JUST AHEAD OF THE WARM
FRONT...WINDS VEER TOWARDS THE SOUTH LATE SATURDAY. GUSTS UPWARDS
OF 30 KNOTS ARE EXPECTED THOUGH A VERY BRIEF PERIOD OF GALE FORCE
GUSTS MAY OCCUR, MOSTLY ACROSS OUR NORTHERN WATERS WHERE THE
TIGHTEST PRESSURE GRADIENT EXISTS.

OUTLOOK...
SUNDAY...THE SMALL CRAFT ADVISORY REMAINS UP THROUGH SUNDAY WITH
LINGERING ADVISORY CONDITIONS IN A WEST- SOUTHWEST FLOW, WITH SEAS
REMAINING ELEVATED BUT GRADUALLY SUBSIDING THROUGH THE EVENING.

MONDAY...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 EXPECTED
ACROSS THE AREA WATERS.

&&

.HYDROLOGY...
WE`VE ISSUED A FLOOD WATCH FOR 8 COUNTIES ACROSS THE HSA...6
COUNTIES IN SOUTHEAST PA, CECIL COUNTY IN MD, AND NEW CASTLE
COUNTY IN NORTHERN DE.

LIGHT RAIN WILL MOVE INTO THE REGION SATURDAY MORNING.
INTENSITIES WILL INCREASE IN THE AFTERNOON AS A CONVECTIVE
CONTRIBUTION IS ADDED INTO THE MIX. THIS IS A STRONG SYSTEM TO
BEGIN WITH EVEN WITHOUT THE SAID CONVECTIVE CONTRIBUTION. PER THE
NAEFS, THE STRENGTH OF THE PARENT SURFACE LOW (SUB 1000 MB) ONLY
OCCURS ONCE EVERY 5 TO 10 YEARS FOR THIS TIME OF YEAR (3 STANDARD
DEVIATIONS).

TWO TO TWO AND A QUARTER INCHES OF RAINFALL ARE EXPECTED. THE
RAINFALL COMES TO AN END LATE SATURDAY NIGHT.

SMALL CREEKS AND STREAMS WILL BE MOST VULNERABLE DURING THIS
EVENT ALONG WITH POOR DRAINAGE AND URBAN AREAS.

MAINSTEM RIVERS SUCH AS THE SCHUYLKILL AND DELAWARE ARE NOT
EXPECTED TO FLOOD.

&&

.TIDES/COASTAL FLOODING...
A FEW SPOTS ALONG THE DELAWARE BAY AND DELAWARE RIVER MIGHT
EXPERIENCE MINOR TIDAL FLOODING SATURDAY EVENING AND NIGHT.

A SOUTHEAST FLOW WILL DEVELOP TONIGHT AND INCREASE OVERNIGHT INTO
SATURDAY. THE ONSHORE FLOW WILL PERSIST INTO SATURDAY NIGHT. WINDS
LOOK TO BE IN THE 10-20 MPH RANGE WITH HIGHER GUSTS. THE STRONGEST
WINDS SHOULD OCCUR SATURDAY EVENING AND COINCIDE WITH RUNOFF AND
THE HIGH TIDES.

&&

.RIP CURRENTS...
THE INITIAL FORECAST FOR RIP CURRENT FOR SATURDAY IS MODERATE.
BUT OUR IN HOUSE PROCEDURE NEARLY GAVE US A HIGH RISK WITH THE
SHORT PERIOD BEING THE LIMITING FACTOR. NOT EXACTLY A GREAT BEACH
DAY WITH STRONG ONSHORE WINDS AND RAIN ON THE WAY. WE WILL
REACCESS OVERNIGHT.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...FLOOD WATCH FROM NOON EDT TODAY THROUGH LATE TONIGHT FOR
     PAZ060-061-070-071-101>104.
NJ...NONE.
DE...FLOOD WATCH FROM NOON EDT TODAY THROUGH LATE TONIGHT FOR
     DEZ001.
MD...FLOOD WATCH FROM NOON EDT TODAY THROUGH LATE TONIGHT FOR
     MDZ008.
MARINE...SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 6 PM EDT SUNDAY
     FOR ANZ452>455.
     SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 6 PM EDT
     SUNDAY FOR ANZ450-451.
     SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 11 PM EDT THIS
     EVENING FOR ANZ430-431.

&&

$$

SYNOPSIS...MEOLA
NEAR TERM...IOVINO
SHORT TERM...HEAVENER
LONG TERM...MEOLA
AVIATION...GIGI/MEOLA
MARINE...GORSE/HEAVENER/MEOLA
HYDROLOGY...KRUZDLO
TIDES/COASTAL FLOODING...KRUZDLO
RIP CURRENTS...GIGI


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