Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 242226
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
626 PM EDT THU APR 24 2014

.SYNOPSIS...
A NARROW AREA OF HIGH PRESSURE WILL SLIDE ACROSS OUR REGION
THROUGH TONIGHT, THEN WEAKEN AND SHIFT OFFSHORE FRIDAY. LOW
PRESSURE IS FORECAST TO TRACK ACROSS THE OHIO VALLEY AND MID
ATLANTIC REGION FRIDAY INTO SATURDAY MORNING. HIGH PRESSURE WILL
THEN FOLLOW FOR LATE SATURDAY INTO MONDAY. LOW PRESSURE,
DEVELOPING OVER THE MIDDLE OF THE NATION MONDAY AND TUESDAY, WILL
BE A SLOW MOVER AND IT SHOULD RESULT IN AN EXTENDED PERIOD OF
UNSETTLED WEATHER FOR OUR REGION STARTING TUESDAY AND LASTING
THROUGH THURSDAY.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
FOR TONIGHT...THE FCST AREA WILL COME UNDER THE INFLUENCE OF A
SFC HIGH PRES RIDGE WHICH WILL EXTEND FROM HUDSON BAY SWD ACROSS
THE MID-ATLANTIC REGION TO OFF THE SE US COAST. AS A RESULT THE
GUSTY WINDS WILL DIMINISH BY SUNSET THIS EVENING AND THEN BECOME
LIGHT AND VARIABLE OVERNIGHT. GENERALLY GOOD RADIATIONAL CONDS
WILL ALLOW MIN TEMPS TO REACH NEAR OR BELOW FREEZING AT MANY
PLACES N OF PHL AND POSSIBLY ALSO IN THE SRN NJ PINE BARRENS. A
FREEZE WARNING HAS BEEN ISSUED FOR PARTS OF NJ GENLY N OF TTN
WHERE SUB-FREEZING TEMPS ARE EXPECTED TO LAST FOR THREE OR MORE
HOURS. BECAUSE OF THE DRY AIR... LITTLE FROST IS EXPECTED EVEN IN
COLDER AREAS. ALSO, AS THE UPPER RIDGE AXIS NOW OVER THE MIDWEST
MOVE EAST...SOME HI LVL CLOUDINESS SHOULD BEGIN TO SPILL OVER AND
MAY LIMIT COOLING OVER ERN PA.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
FOR FRIDAY...THE SFC RIDGE AXIS WILL BE OVER THE AREA IN THE
MORNING BUT WILL MOVE OFFSHORE IN THE AFTN. WINDS WILL PICK UP
FROM THE SE TO S BY MID DAY. HI AND MID LVL CLOUDS WILL BE
INCREASING AHEAD OF AN UPPER SHRTWV TROF APPROACHING FROM THE OHIO
VLY. EVEN SO SUNSHINE THROUGH THE CLOUDINESS AND LOW LVL WARM
ADVECTION SHOULD RESULT IN MAX TEMPS A FEW DEGS WARMER THAN TODAY.

NO PRECIP IS FCST FOR FRI MORN BUT BY AFTN POPS BEGIN TO INCREASE
FROM WEST TO EAST ACROSS THE FCST AREA. SCT SHRA ARE EXPECTED BY
LATE AFTN WEST OF PHL BUT ANY RAINFALL AMOUNTS SHOULD BE JUST A
FEW HUNDREDTHS AT MOST.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF AN INITIALLY
PROGRESSIVE FLOW WITH A SHORT WAVE TROUGH SLIDING ACROSS THE AREA
FRIDAY NIGHT AND SATURDAY. THE FLOW THEN LOOKS TO UNDERGO
SIGNIFICANT AMPLIFICATION AS BLOCKING DEVELOPS. THIS ALLOWS FOR A
CLOSED LOW TO DEVELOP SOUTHEAST OF NEW ENGLAND SUNDAY, WITH
ANOTHER ONE EJECTING OUT INTO THE PLAINS. AN INITIAL SHARP/NARROW
RIDGE BETWEEN THESE TWO SYSTEMS SHOULD GET KNOCKED DOWN AS ENERGY
ROTATES ACROSS THE GREAT LAKES BEFORE BEING ABSORBED BY THE CLOSED
SYSTEM FROM THE PLAINS. DUE TO BLOCKING DOWNSTREAM, A LARGE CLOSED
LOW SHOULD RESULT DURING NEXT WEEK FROM THE GREAT LAKES TO THE
TENNESSEE VALLEY. THIS PLACES OUR AREA ON THE EAST SIDE OF THE
CLOSED LOW, WHICH IS TYPICALLY A FAVORABLE AREA FOR MOISTURE TO
SURGE NORTHWARD. IF THIS PANS OUT LIKE THIS, A PERIOD OF UNSETTLED
AND COOLER WEATHER WILL OCCUR ACROSS OUR AREA. WE USED A GENERAL
MODEL BLEND FROM FRIDAY NIGHT INTO SUNDAY, THEN FAVORED WPC
GUIDANCE THEREAFTER. SOME ADJUSTMENTS WERE THEN MADE FOLLOWING
ADDITIONAL COLLABORATION WITH OUR NEIGHBORING OFFICES.

FRIDAY NIGHT AND SATURDAY...A SHORT WAVE TROUGH IS FORECAST TO
MOVE THROUGH DURING AT LEAST A PORTION OF THIS TIME FRAME. THE
AXIS OF THE TROUGH LOOKS TO START TAKING ON A NEGATIVE TILT FOR A
TIME BEFORE IT WEAKENS AND GIVES WAY TO INCREASING HEIGHT FALLS
WITH THE CLOSED LOW NEAR THE UPPER GREAT LAKES. THIS WILL PROVIDE
A RIBBON OF ENHANCED LIFT ACROSS THE AREA, WHICH SHOULD RESULT IN
A DECENT AMOUNT OF SHOWERS DURING AT LEAST FRIDAY EVENING. THERE
MAY BE ENOUGH INSTABILITY FRIDAY EVENING COMBINED WITH THE FORCING
FOR SOME THUNDER ESPECIALLY ACROSS PORTIONS OF THE SOUTHERN ZONES.
AS LOW PRESSURE SLIDES ACROSS THE AREA LATER FRIDAY EVENING THEN
SHIFTS TO OUR NORTHEAST SATURDAY MORNING, THE SHOWERS ARE EXPECTED
TO CLEAR OUR CWA. HOWEVER, THE MAIN UPPER-LEVEL TROUGH/CLOSED LOW
IS THEN FORECAST TO DROP DOWN ACROSS THE NORTHEAST AND NORTHERN
MID ATLANTIC REGION. THIS ALONG WITH COLDER AIR ALOFT AND A
SECONDARY FRONTAL BOUNDARY SHOULD TRIGGER SOME ADDITIONAL SHOWERS.
WHILE THERE COULD BE SOME INSTABILITY TO ALLOW FOR THUNDER, WE MAY
HAVE JUST SOME LOW-TOPPED CONVECTIVE CELLS DURING SATURDAY
AFTERNOON AND THUS NO THUNDER WAS ADDED FOR SATURDAY ATTM. WE WENT
WITH LIKELY POPS FOR A PORTION OF FRIDAY NIGHT, THEN LOWERED TO
THE CHC/SLIGHT CHC RANGE THROUGH SATURDAY. THE SHOWER THREAT
SHOULD END VERY EARLY SATURDAY EVENING AS THE SYSTEM SHIFTS TO THE
EAST AND THE AIR MASS STABILIZES.

SUNDAY AND MONDAY...IT APPEARS THAT THIS TIME FRAME WILL FEATURE
OUR AREA BEING BETWEEN WEATHER SYSTEMS. A CLOSED LOW TO OUR
NORTHEAST IS FORECAST TO SHIFT FARTHER OUT TO SEA, HOWEVER THIS
FEATURE MAY ALSO HELP IN THE MAIN FLOW BECOMING SLOWER. A NARROW
AREA OF HIGH PRESSURE LOOKS TO WEDGE DOWN INTO THE MID ATLANTIC
DURING SUNDAY INTO MONDAY. THE MAIN SURFACE HIGH IS FORECAST TO BE
CENTERED WELL TO OUR NORTH AS A SYSTEM CLOSES OFF ACROSS THE
CENTRAL PARTS OF THE NATION. AS DOWNSTREAM BLOCKING LOOKS TO GET
GOING, THE SYSTEMS AS A WHOLE SHOULD MOVE RATHER SLOWLY EASTWARD.
THIS WOULD INITIALLY PLACE OUR REGION WITHIN AN AREA OF GENERAL
SUBSIDENCE, HOWEVER THE FLOW TURNING ONSHORE ESPECIALLY LATER
MONDAY SHOULD ALLOW FOR MORE CLOUDS TO START DEVELOPING. THIS TIME
FRAME IS DRY, WITH THE EXCEPTION OF SOME SLIGHT CHC TO LOW CHC
POPS LATE MONDAY NIGHT AS THE ONSHORE FLOW BECOMES BETTER
ESTABLISHED ALONG WITH THE DEVELOPMENT OF A WARM FRONT TO OUR
SOUTH AND GRADUAL ISENTROPIC LIFT.

TUESDAY THROUGH THURSDAY...A SIGNIFICANT CLOSED LOW DRIFTING
EASTWARD FROM THE MID MISSISSIPPI VALLEY TUESDAY WILL SPELL AN
UNSETTLED PERIOD OF WEATHER FOR OUR ENTIRE REGION. THIS WILL DRIVE
A SURFACE LOW THAT WILL PROBABLY OCCLUDE INTO THE MID ATLANTIC
LATER WEDNESDAY AND THURSDAY. THERE MAY BE A LINGERING SURFACE
WEDGE OF HIGH PRESSURE DOWN INTO THE MID ATLANTIC INITIALLY,
ALLOWING FOR A BETTER OVERRUNNING SURFACE TO BE PRESENT. THE
INITIAL WAA AND ASSOCIATED ISENTROPIC LIFT COUPLED WITH MOISTURE
ADVECTION SHOULD ALLOW FOR RAIN TO DEVELOP ESPECIALLY LATER
TUESDAY. THIS LOOKS TO CONTINUE RIGHT THROUGH THURSDAY, HOWEVER
THE RAIN MAY MOVE THROUGH IN STAGES AND BE HEAVY AT TIMES
ESPECIALLY WHEN TIED TO THE ARRIVAL OF EMBEDDED SHORT WAVE ENERGY
EJECTING AHEAD OF THE CLOSED LOW. THE INITIAL SURGE IN MOISTURE
THOUGH MAY HAVE A TOUGHER TIME GETTING TO OUR NORTHERN ZONES FOR A
TIME AS SOME DRIER AIR MAY HANG ON. WE THEREFORE WENT WITH HIGH
CHC TO LIKELY POPS THROUGH MUCH OF THIS TIME FRAME. THE LOW-LEVEL
FLOW LOOKS TO BE ONSHORE WHICH TENDS TO LIMIT OR SUBDUE THE
INSTABILITY /ESPECIALLY SURFACE-BASED/, HOWEVER SOME ELEVATED
INSTABILITY IS POSSIBLE WHICH COULD LEAD TO SOME EMBEDDED THUNDER.
GIVEN IT BEING THIS FAR OUR IN TIME AND LOWER CONFIDENCE REGARDING
THE THERMAL PROFILES AND THEREFORE ASSOCIATED INSTABILITY, THUNDER
WAS NOT INCLUDED ATTM.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

VFR CONDS ARE EXPECTED FOR THE NEXT 24 HOURS OR SO. THE GUSTY NW
WINDS WILL DIMINISH THIS EVENING AND BECOMING LIGHT AND VARIABLE
OVERNIGHT AS A SFC HIGH PRES RIDGE MOVES OVERHEAD. LIGHT WINDS
WILL CONTINUE TOMORROW MORNING BUT WILL START TO PICK UP FROM THE
SE TO S BY MIDDAY. HIGH TO MID-LVL CLOUDS WILL BE INCREASING
DURING THE DAY BUT CIGS WILL REMAIN WELL ABOVE MVFR LIMITS UNTIL
LATE IN THE DAY.

OUTLOOK...
FRIDAY NIGHT AND SATURDAY...MVFR TO AT TIMES IFR WITH SHOWERS
/SOME THUNDER CANNOT BE RULED OUT ESPECIALLY SOUTH OF KPHL FRIDAY
EVENING/, THEN CONDITIONS IMPROVING TO VFR EARLY SATURDAY MORNING.
SOME ADDITIONAL SHOWERS ARE ANTICIPATED FOR SATURDAY AFTERNOON.
SOUTHERLY WINDS GENERALLY 5-10 KNOTS, BECOMING WEST AND NORTHWEST
10-15 KNOTS SATURDAY.

SUNDAY AND MONDAY...OVERALL VFR. NORTHERLY WINDS 10-15 KNOTS
SUNDAY, BECOMING LIGHT AND VARIABLE SUNDAY NIGHT AND MONDAY.
CLOUDS INCREASE MONDAY NIGHT WITH A CHANCE OF SOME MVFR CEILINGS
TOWARD DAYBREAK TUESDAY.

TUESDAY...MVFR CEILINGS SHOULD DEVELOP WITH AN ONSHORE FLOW
ESPECIALLY LATER IN THE DAY. SOME RAIN SHOULD OVERSPREAD THE AREA
FROM SOUTH TO NORTH LATE IN THE DAY AND AT NIGHT WITH SUB-VFR
CONDITIONS ANTICIPATED.

&&

.MARINE...
WINDS WILL CONTINUE TO DIMINISH AS LOW PRES WELL EAST OF NEW
ENGLAND MOVES FARTHER OUT TO SEA AND THE PRES GRADIENT RELAXES.
SEAS SHOULD ALSO SUBSIDE. THE SCA HAS BEEN DROPPED. WINDS SHOULD
BE RATHER LIGHT OVERNIGHT AND FRIDAY MORNING BUT WILL BEGIN TO
INCREASE FROM THE SE TO S DURG THE AFTN TMRW.

OUTLOOK...
FRIDAY NIGHT AND SATURDAY...SOUTHERLY WINDS AHEAD OF A COLD FRONT
WILL SHIFT TO THE NORTHWEST LATER FRIDAY NIGHT AND SATURDAY. THE
FLOW MAY BE STRONG ENOUGH TO ALLOW FOR ADVISORY LEVEL GUSTS TO
OCCUR. THE SEAS WILL BUILD IN THE SOUTHERLY FLOW, HOWEVER THE
SOUTHERLY DIRECTION IS NOT ANTICIPATED TO BE PROLONGED. THE
CONDITIONS SHOULD THEN BE MAINLY SUB-ADVISORY SATURDAY NIGHT.

SUNDAY AND MONDAY...GENERALLY SUB-ADVISORY NORTHWESTERLY FLOW
SUNDAY, THEN WINDS DIMINISH AND START TO TURN ONSHORE MONDAY.

TUESDAY...EASTERLY WINDS INCREASE, HOWEVER PROBABLY REMAINING
BELOW ADVISORY CRITERIA. THE SEAS HOWEVER SHOULD BUILD TO NEAR 5
FEET DURING THIS TIME FRAME.

&&

.FIRE WEATHER...
THE RED FLAG WARNING REMAINS IN EFFECT THROUGH EARLY THIS
EVENING, AS GUSTY WINDS CONTINUE ALONG WITH RATHER LOW RELATIVE
HUMIDITY VALUES. THE FUELS HAVE DRIED OUT MORE TODAY AS WELL, AND
SOME BRUSH FIRES HAVE BEEN REPORTED. RADAR SHOWED A LARGE SMOKE
PLUME EARLIER FROM A FIRE IN OCEAN COUNTY. THE WINDS ARE EXPECTED
TO DIMINISH THIS EVENING. FOR FRIDAY, THERE MAY BE AN ENHANCED
RISK OF FIRE WEATHER /SPS ISSUANCE POSSIBLE/ ESPECIALLY FOR
EASTERN PENNSYLVANIA AND NEW JERSEY, HOWEVER THE WINDS ARE
ANTICIPATED TO BE MUCH LESS COMPARED TO THE LAST FEW DAYS.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR PAZ054-055-
     060>062-070-071-101>106.
NJ...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR NJZ001-
     007>010-012>027.
     FREEZE WARNING FROM 2 AM TO 8 AM EDT FRIDAY FOR NJZ001-007>010.
DE...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR DEZ001>004.
MD...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR MDZ008-012-
     015-019-020.
MARINE...NONE.

&&

$$

SYNOPSIS...GORSE
NEAR TERM...AMC
SHORT TERM...AMC
LONG TERM...GORSE
AVIATION...AMC/GORSE
MARINE...AMC/GORSE
FIRE WEATHER...GORSE






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