Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 260218
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1018 PM EDT MON AUG 25 2014

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OVERHEAD THROUGH TUESDAY. THE CENTER OF
THE HIGH SHIFTS TO OUR SOUTH BY WEDNESDAY AS A COLD FRONT MOVES
THROUGH THE REGION. HIGH PRESSURE RETURNS THURSDAY AND FRIDAY. A
WARM FRONT IS EXPECTED TO LIFT NORTHWARD THROUGH THE MID ATLANTIC
THIS WEEKEND ONCE THE HIGH MOVE OFF THE NEW ENGLAND COAST. A COLD
FRONT MAY APPROACH FROM THE GREAT LAKES CLOSER TO LABOR DAY.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
THE FORECAST FOR TONIGHT IS WELL ON TRACK AS THE DAYTIME CU HAVE
DISSIPATED AND ALL THAT REMAINS CLOUD-WISE ARE SOME PATCHY AND
DECREASING CI MOVING AROUND THE UPPER RIDGE. SFC WINDS HAVE BECOME
VERY LIGHT OR CALM UNDER THE RIDGE OF HIGH PRESSURE NOW OVER THE
MID-ATLANTIC REGION. WITH SFC DEWPTS A COUPLE OF DEGREES HIGHER
NOW THAN YDA EVENING...PATCHY GROUND FOG IS LIKELY AGAIN OVERNIGHT
TONIGHT.

PREVIOUS DISCUSSION BELOW...
OUR WEATHER WILL BE DRIVEN BY AN UPPER-LEVEL RIDGE THAT WILL
CONTINUE TO BUILD ACROSS THE MID ATLANTIC REGION THROUGH TONIGHT.
AS THIS OCCURS, SURFACE HIGH PRESSURE WILL CONTINUE TO SET UP SHOP
OVER OUR CWA. THIS IS PROVIDING LESS AND LESS WIND, HOWEVER THERE
IS STILL AN ONSHORE COMPONENT TO THE LOW- LEVEL FLOW GIVEN THE
SURFACE HIGH IS WEDGED DOWN INTO THE CAROLINAS.

DUE TO THE DRIER AIR AND ADDITIONAL SUBSIDENCE, ANY FLAT CUMULUS
IS EXPECTED TO DISSIPATE EARLY THIS EVENING. OTHER THAN A BIT OF
HIGH LEVEL CLOUDS AT TIMES THROUGH TONIGHT, THE SKY SHOULD BE
CLEAR TO MOSTLY CLEAR. THIS COMBINED WITH LIGHT TO CALM WINDS AND
A COOLING BOUNDARY LAYER MAY SET UP CONDITIONS RIGHT FOR SOME
PATCHY FOG AGAIN. THIS MAY END UP BEING A SHALLOW GROUND FOG AND
MOSTLY OVER FIELDS AND OTHER OPEN AREAS, WHICH HAS LESS IMPACT.

AS FOR LOW TEMPERATURES, WE USED A NAM/GFS MOS BLEND THEN MADE
SOME TWEAKS FOR SOME OF THE TYPICALLY COOLER SPOTS. THE HOURLY
GRIDS WERE ADJUSTED BASED ON THE LATEST OBSERVATIONS, THEN THE
LAMP/LAV GUIDANCE WAS BLENDED IN TO ASSIST ESPECIALLY WITH
TEMPERATURE AND DEW POINT TRENDS THROUGH THIS EVENING.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
WHILE WE WILL REMAIN UNDERNEATH A STRONG UPPER-LEVEL RIDGE, IT IS
FORECAST TO FLATTEN SOME THROUGH TUESDAY. THIS IS DUE TO A SHORT
WAVE TROUGH SLIDING FROM NEAR THE UPPER GREAT LAKES REGION ON
NORTHWARD. AS THIS OCCURS, THE FLOW ALOFT WILL TEND TO BECOME MORE
ZONAL. AT THE SURFACE, HIGH PRESSURE OVER THE REGION TO START
SHOULD BEGIN TO SHIFT EAST AND NORTHEASTWARD. THIS WILL RESULT IN
A LIGHT FLOW REGIME, WITH THE SURFACE FLOW TENDING TO BE FROM THE
SOUTHWEST. AMPLE HEATING OF THE SURFACE THOUGH COMBINED WITH THE
WEAKER WINDS SHOULD RESULT IN SEA/BAY BREEZE DEVELOPMENT DURING
THE AFTERNOON. THIS WILL MAINTAIN AN ONSHORE FLOW COMPONENT AT THE
COAST AND ACROSS PORTIONS OF THE DELMARVA ESPECIALLY.

GIVEN THE PRESENCE OF HIGH PRESSURE AT THE SURFACE AND ALOFT
ALONG WITH THE AIR MASS MODIFYING SOME MORE, A GOOD AMOUNT OF
SUNSHINE IS FORECAST. THERE COULD BE A BIT OF CUMULUS THEN ALSO A
TOUCH OF HIGH LEVEL CLOUDS AT TIMES, BUT OTHERWISE PLENTY OF
SUNSHINE IS ANTICIPATED. AS FOR HIGH TEMPERATURES, AN EVEN BLEND
OF THE GFS/NAM MOS WAS USED BUT THEN SOME DOWNWARD ADJUSTMENTS
WERE MADE ESPECIALLY ALONG THE COAST AND ACROSS PORTIONS OF THE
DELMARVA GIVEN THE ONSHORE FLOW. WE MAY HAVE A QUICK JUMP IN
TEMPERATURES DURING THE MORNING HOURS, WHICH MAY ALLOW FOR EVEN
WARMER THAN CURRENTLY FORECAST AFTERNOON TEMPERATURES INLAND.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
A LARGE UPPER RIDGE IS FORECAST TO REMAIN CENTERED OVER THE
SOUTHERN APPALACHIANS TUESDAY NIGHT. THE NORTHEASTERN PERIPHERY OF
THE RIDGE WILL START TO BREAK DOWN AS A COLD FRONT MOVES ATOP THE
RIDGE INTO THE GREAT LAKES/UPSTATE NY TUESDAY NIGHT AND NEW
ENGLAND/NORTHERN MID-ATLANTIC STATES WEDNESDAY AND WEDNESDAY
NIGHT. HIGH PRESSURE REFLECTED AT THE SURFACE IS ALSO FORECAST TO
RETREAT SOUTH OF OUR REGION DURING THIS TIME. KEPT POPS WITH FROPA
WEDNESDAY AFTERNOON/ EVENING VERY LOW ACROSS THE MOUNTAINS SINCE A
DIRECT FETCH OF GULF OF MEXICO OR ATLANTIC MOISTURE AROUND THE
RIDGE TO OUR SOUTHEAST WILL BE ABSENT. REMOVED ANY MENTION OF
PRECIP EAST OF THE DIVIDE AS DOWNSLOPING FLOW OFF THE HIGHER
TERRAIN SHOULD HELP TO DRY OUT THE BOUNDARY LAYER. TRENDED WARMER
FOR MAX TEMPS WEDNESDAY WITH THE SETUP ALLOWING FOR STRONG SOLAR
HEATING TO OCCUR IN PRE- FRONTAL WARM SECTOR. MAX TEMPS IN THE
UPPER 80S TO LOWER 90S WILL BE COMMON (COOLER ALONG THE COAST AND
IN THE MOUNTAINS). IF PHL REACHES 90F, IT WOULD ONLY BE THE SECOND
90-DEGREE DAY THIS AUGUST (LAST AUGUST, THERE WERE ZERO 90-DEGREE
DAYS DURING THE ENTIRE MONTH).

THE COLD FRONT IS EXPECTED TO MOVE SOUTH OF THE AREA OVERNIGHT
WEDNESDAY NIGHT BEFORE STALLING NEAR THE VA-NC BORDER THURSDAY.
HIGH PRESSURE BUILDS BACK INTO THE AREA DURING THIS TIME. THE HIGH
WILL SHIFT INTO NEW ENGLAND ON FRIDAY. SLIGHTLY COOLER AND DRIER
CONDITIONS CAN BE EXPECTED DURING THIS TIME.

THE CENTER OF HIGH EVENTUALLY SHIFTS OFF THE NEW ENGLAND COAST
FRIDAY NIGHT AND THIS WEEKEND. RETURN FLOW AROUND THE OFFSHORE
HIGH WILL DEVELOP DURING THIS TIME, ALLOWING THE OLD FRONTAL
BOUNDARY TO OUR SOUTHWEST TO LIFT BACK NORTHWARD. THE TREND WILL
BE FOR INCREASING TEMPERATURES AND HUMIDITY THROUGHOUT THE HOLIDAY
WEEKEND, ALTHOUGH THERE IS UNCERTAINTY CONCERNING HOW QUICKLY THE
FRONT MAKES IT INTO THE FORECAST AREA. SHOWERS AND STORMS RETURN
TO THE FORECAST FOR THE HOLIDAY WEEKEND, PARTICULARLY ON SUNDAY
AND MONDAY WHEN AN AREA OF LOPRES AND ATTENDANT COLD FRONT
APPROACH FROM THE GREAT LAKES. THERE ARE STILL SIGNIFICANT MODEL
SPREAD WITH THE STRENGTH OF THE UPPER RIDGE AND THE TIMING OF THE
COLD FRONT.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

TONIGHT...VFR OVERALL. LOCALIZED FOG MAY OCCUR TOWARD MORNING,
HOWEVER IT MAY BE SHALLOW GROUND FOG. OUR CONFIDENCE IS LOW THAT
IT WOULD HAVE AN IMPACT ON ANY TERMINALS, THEREFORE IT WAS NOT
INCLUDED AT THIS TIME. SOUTH-SOUTHEAST WINDS AROUND 5 KNOTS,
BECOMING LIGHT AND VARIABLE OR CALM.

TUESDAY...VFR. LIGHT AND VARIABLE WINDS TO START, BECOMING
SOUTHWESTERLY AT 5-8 KNOTS. A SEA/BAY BREEZE IN THE AFTERNOON
SHOULD AFFECT KACY, KMIV AND KILG WITH WINDS MORE FROM THE
SOUTHEAST.

OUTLOOK...
TUESDAY NIGHT...VFR CONDITIONS AND LIGHT WINDS.

WEDNESDAY AND WEDNESDAY NIGHT...PREDOMINATELY VFR. A STRAY SHRA
OR TSRA CANNOT BE RULED OUT, MAINLY IN VC OF ABE/RDG DURING THE
AFTN AND EARLY EVE.

THURSDAY THROUGH FRIDAY NIGHT...VFR AND DRY EXPECTED.

SATURDAY...MAINLY VFR BUT ISOLATED SHRA/TSRA POSSIBLE AS A WARM
FRONT MOVES THRU.

&&

.MARINE...
AS OF 900 PM...SEAS AT BUOY 44009 HAVE SUBSIDED TO BETWEEN 4.0
AND 4.5 FEET. THIS SLOW DOWNWARD TREND IS EXPECTED TO CONTINUE AND
THE SCA FOR DELAWARE COASTAL WATERS WILL LIKELY EXPIRE AT MIDNIGHT
AS CURRENTLY PROJECTED.

PREVIOUS DISCUSSION BELOW...
HIGH PRESSURE WILL REMAIN IN CONTROL OF OUR WEATHER THROUGH
TUESDAY. THE CIRCULATION AROUND THIS HIGH THOUGH IS RESULTING IN
AN ONSHORE FLOW, ALTHOUGH IT IS LIGHTER. THIS WILL ALSO BE
ENHANCED SOME WITH SEA AND BAY BREEZE DEVELOPMENT THROUGH TUESDAY
AFTERNOON. THE SEAS AT BUOY 44009 HAVE BEEN SUBSIDING SOME THIS
AFTERNOON, BUT HAVE TRENDED NEARLY STEADY STATE AT 5 FEET. THIS
MAY CONTINUE FOR AWHILE AS THE ONSHORE FLOW COMPONENT CONTINUES
DESPITE THE WINDS LESSENING SOME. WHILE IT MAY BECOME MORE
MARGINAL, WE WILL GO AHEAD AND EXTEND THE SMALL CRAFT ADVISORY
THROUGH MIDNIGHT FOR NOW AS WE HAVE LOWER CONFIDENCE BEYOND THIS.
WE WILL ALSO GO AHEAD AND CANCEL THE TWO NORTHERN ZONES FROM THE
CURRENT ADVISORY, AS SEAS SHOULD BE JUST UP TO 4 FEET. IT APPEARS
THE MAIN 5 FOOTERS ARE OFF THE DELAWARE COAST NOW. ELSEWHERE, THE
CONDITIONS ARE EXPECTED TO BE BELOW ADVISORY CRITERIA THROUGH
TUESDAY.

OUTLOOK...

TUESDAY...WINDS AND SEAS BELOW SCA CRITERIA

WEDNESDAY THROUGH THURSDAY NIGHT...SWLY WINDS WILL STRENGTHEN
AHEAD OF A COLD FRONT LATE WEDNESDAY. NW WINDS BEHIND THE FRONT
MAY APPROACH SCA CRITERIA WEDNESDAY NIGHT AND THURSDAY, BUT THE
MAIN THREAT WILL BE SEAS. LONG-PERIOD SWELLS ASSOCIATED WITH
CRISTOBAL MAY START TO REACH THE NEAR-SHORE WATERS AS EARLY AS
WEDNESDAY AND CONTINUE. SEAS COULD REACH SCA CRITERIA DURING THIS
PERIOD. HOWEVER, TIMING AS WELL AS WAVE HEIGHTS ASSOCIATED WITH
THESE SWELLS IS STILL VERY UNCERTAIN AT THIS TIME.

FRIDAY THROUGH SATURDAY...WINDS WILL BE LIGHT. LATEST MODEL
PROJECTIONS SHOW SEAS GRADUALLY SUBSIDING DURING THIS PERIOD AS
CRISTOBAL MOVES FARTHER OUT TO SEA.

&&

.RIP CURRENTS...
THE PRELIMINARY RIP FORECAST FOR TUESDAY IS MODERATE FOR BOTH NJ
AND DE BEACHES. WINDS AND WAVES ARE SLOWLY DECREASING AS THE
SURFACE HIGH PRES RIDGE SHIFTS SOUTHWARD. HWVR RIP-PRODUCING CONDS
STILL MAY BE SOMEWHAT ENHANCED...IN CONTINUITY FROM MONDAYS HIGH
LEVELS. THIS FCST WILL BE RE-EVALUATED EARLY TUESDAY MORNING.

PREVIOUS DISCUSSION BELOW...
THE THREAT OF DANGEROUS RIP CURRENTS WILL BE ENHANCED HEADING
INTO WEDNESDAY AND THURSDAY AS CRISTOBAL TRACKS WELL EAST OF THE
MID ATLANTIC COAST. LATEST PROJECTIONS SHOW THE POTENTIAL FOR A
HIGH RIP CURRENT RISK, BUT THERE IS STILL UNCERTAINTY THIS FAR OUT
SO STAY TUNED AS WE REFINE THE FORECAST.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ454-455.

&&

$$

SYNOPSIS...KLEIN
NEAR TERM...AMC
SHORT TERM...GORSE
LONG TERM...KLEIN
AVIATION...GORSE/KLEIN
MARINE...GORSE/KLEIN
RIP CURRENTS...GORSE/KLEIN/AMC





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