Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 291953
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
353 PM EDT FRI AUG 29 2014

.SYNOPSIS...
HIGH PRESSURE SITUATED OVER THE NORTHEAST WILL MOVE OFFSHORE
TONIGHT...MAKING WAY FOR A WARM FRONTAL PASSAGE SATURDAY NIGHT.
THIS WARM FRONT WILL BECOME A QUASI-STATIONARY BOUNDARY NEAR THE
CANADIAN BORDER DURING THE SUNDAY THROUGH TUESDAY TIMEFRAME...A
TROUGH OF LOW PRESSURE WILL EXTEND SOUTHWARD FROM THIS BOUNDARY
TO THE EAST OF THE APPALACHIANS...BETWEEN A BERMUDA HIGH PRESSURE
ANCHORED TO THE EAST AND SLOW MOVING COLD FRONT IN THE MISSISSIPPI
VALLEY. THIS COLD FRONT IS PROJECTED MOVE THROUGH THE REGION LATE
TUESDAY INTO EARLY WEDNESDAY...FOLLOWED BY HIGH PRESSURE ON THURSDAY.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
UPPER LEVEL TROUGH SLIDES OVER THE REGION TONIGHT, LEAVING THE
REGION UNDER CLEARING SKIES. THE COMBINATION OF MID AND UPPER LEVEL
SUBSIDENCE, WEAK ON SHORE/UPSLOPE FLOW, AND CLEARING SKIES COULD
SUPPORT PATCHY FOG DEVELOPMENT ACROSS THE REGION. ONE LIMITING
FACTOR HOWEVER, IS THAT DEW POINTS REMAIN RELATIVELY LOW (IN THE 40S
AND LOW 50S). THUS, NOT ANTICIPATING ANYTHING WIDESPREAD OR
PARTICULARLY DENSE AT THIS TIME.

LOWS COULD BE A BIT TRICKY DEPENDING ON HOW MUCH AND HOW QUICKLY
MOISTURE ADVECTION TAKES PLACE TONIGHT. GIVEN HOW WEAK THE FLOW IS,
THINK WE WILL BE ABLE TO HAVE AT LEAST A FEW HOURS OF PRIME
RADIATIONAL COOLING CONDITIONS THROUGH LATE THIS EVENING, BEFORE
INCREASING MOISTURE HELPS TO LEVEL OFF THE TEMPERATURE TRENDS.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
WINDS WILL SHIFT TO SOUTHERLY AND INCREASE BY AT LEAST MID MORNING.
THIS WARM AIR ADVECTION WILL RESULT IN MAX TEMPS A FEW DEGREES
HIGHER THAN TODAY, EVEN IN SPITE OF ANY PATCHY FOG THAT MAY LINGER
INTO THE MID MORNING HOURS.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
HEMISPHERIC MODEL ANALYSIS SHOWS SOUTHEAST U.S. RIDGING WITH WEAK
TROUGHING NORTH OF THE GREAT LAKES AND MID-WEST AT THE START OF THE
LONGTERM. BETTER TROUGHING ACROSS THE WESTERN U.S. MOVES EASTWARD
EVENTUALLY CARVING INTO THE TOP OF THE SOUTHEAST RIDGE BY EARLY NEXT
WEEK. THE PREVAILING SOUTHWEST FLOW ALOFT DECREASES, ULTIMATELY
BECOMING MORE ZONAL, AS THE NORTHERN STREAM OF THE JET MOVES TO THE
NORTH OF OUR REGION LATE IN THE PERIOD.

SUNDAY - TUESDAY...SLOW SAGGING BOUNDARY TO THE NORTHWEST OF THE REGION
SLOWS EVEN FURTHER AND MORE THAN LIKELY BECOMES PSEUDO-STATIONARY
WITH STRONG RIDGING TO OUR SOUTHEAST. MID AND UPPER LEVEL FLOW,
BEING SOUTHWESTERLY, KEEP THIS BOUNDARY DRAPED JUST TO OUR NORTHWEST
AS WARM AND MOIST GOMEX AIR IS PUMPED INTO THE REGION. MULTIPLE
MID-LEVELS WAVES, WITH WEAK SURFACE TROUGHS, TRAVERSE THE REGION
EACH DAY PROVIDING CHANCES OF SHOWERS AND THUNDERSTORMS. THE BEST
CHANCES FOR CONVECTION CONTINUES TO HONE IN ON THE SUNDAY NIGHT INTO
MONDAY TIMEFRAME AS THE STRONGEST OF THE MID-LEVEL WAVES MOVES
THROUGH. AFTERWARDS, HIGHER THAN NORMAL PWAT AIRMASS, POSSIBLY
EXCEEDING 2 INCHES, AND AMPLE INSTABILITY EACH AFTERNOON SHOULD
ALLOW FOR DIURNALLY DRIVEN CONVECTION. TEMPERATURES AND
UNFORTUNATELY THE DEWPOINTS WILL BE ON THE INCREASE THIS TIMEFRAME
MAKING CONDITIONS FEEL TRULY LIKE AN EARLY AUGUST DAY, IN EARLY
SEPTEMBER.

WEDNESDAY...LOW PRESSURE SYSTEM WELL TO THE NORTH OF THE REGION
SENDS A SOMEWHAT STRONGER COLD FRONT TOWARDS OUR AREA. RIDGING TO
OUR SOUTH SHOULD PREVENT A QUICK PASSAGE, BUT NONE-THE-LESS WE
CURRENTLY EXPECT THE FRONT TO CLEAR OR BECOME WASHED OUT LATER IN
THE DAY. STILL HAVE SOME LOW-END CHANCES, MOSTLY NORTH, WITH THIS
FRONT THOUGH IT CONTINUES TO LOSE STEAM RUNNING INTO THE BUILDING
RIDGE TO OUR SOUTH. WE SHOULD BE DRYING OUT NORTH TO SOUTH BY THE
AFTERNOON HOURS WITH LOWERING OF THE DEWPOINTS...TEMPERATURES SHOULD
STILL BE IN THE UPPER-80S.

THURSDAY - FRIDAY...HIGH PRESSURE CONTINUES TO BUILD BACK INTO OUR
REGION WITH ZONAL FLOW ALOFT. THERE DOES NOT LOOK TO BE MUCH IN THE
WAY OF MID-LEVEL FORCING FROM ANY OF THE PASSING SHORTWAVES, MOST OF
THE ENERGY STAYS WELL TO OUR NORTH...WE SHOULD BE DRY BOTH DAYS.
TEMPERATURES WILL VENTURE BACK DOWN INTO THE NORMAL RANGE WITH
CONTINUED DEWPOINT LOWERING.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

VFR CONDITIONS SHOULD CONTINUE THROUGH AT LEAST 06Z, WITH ONLY HIGH
CIRRUS CLOUDS FOR MOST OF THE REGION, WHILE SCT TO BKN MID LEVEL
CLOUDS (050) PERSIST NEAR THE JERSEY SHORE THROUGH 00Z (INCLUDING
KACY AND KMIV).

AFTER 06Z...THERE IS A CHANCE THAT PATCHY FOG COULD DEVELOP. VERY
WEAK ON SHORE FLOW, SUBSIDENCE IN THE MID AND UPPER LEVELS, AND
CLEARING SKIES WILL PROMOTE FOG DEVELOPMENT. ON THE OTHER HAND
HOWEVER, DEWPOINTS ACROSS THE REGION REMAIN RELATIVELY LOW (IN THE
40S AND LOW 50S) DESPITE SOME MODEST MOISTURE ADVECTION. AS WEAK AS
THE LOW LEVEL FLOW IS, IT IS DOUBTFUL ENOUGH MOISTURE WILL ADVECT
INTO THE REGION BY TONIGHT TO SUPPORT WIDESPREAD FOG. FOR NOW,
EXPECT THE HIGHEST THREAT OF FOG TO BE NEAR THE COAST (KACY AND
KMIV) AND AT KABE AND KRDG WHICH ARE STARTING OUT WITH SLIGHTLY
HIGHER DEW POINTS THAN THE REST OF THE REGION. ALSO, IF THE WINDS
CONSISTENTLY STAY SOUTHEASTERLY, THE THREAT AT KILG WOULD INCREASE
THANKS TO THE MOIST FETCH ALONG THE BAY. GIVEN THE UNCERTAINTIES
WITH THE MOISTURE ADVECTION, HAVE INCLUDED VISIBILITIES ONLY AS LOW
AS MVFR. AT THIS TIME, FOG OR BR DEVELOPMENT APPEARS VERY UNLIKELY
AT KPHL, KPNE, AND KTTN.

CONDITIONS SHOULD RETURN TO VFR BY MID MORNING AS SOUTHERLY WINDS
INCREASE.

OUTLOOK...
SUNDAY...VFR. SCATTERED SHOWERS AND THUNDERSTORMS NORTH AND WEST OF
PHL. MDT CONFIDENCE.

MONDAY - WEDNESDAY...VFR. SCATTERED SHOWERS AND THUNDERSTORMS POSSIBLE
EVERYWHERE. LOW TO MDT CONFIDENCE ON PRECIP COVERAGE.

&&

.MARINE...
WAVE HEIGHTS SHOULD REMAIN 2 TO 4 FEET, AND WINDS LESS THAN 20KT,
THUS CONDITIONS SHOULD REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA.
PATCHY FOG MAY DEVELOP SATURDAY MORNING ON THE DELAWARE BAY,
ESPECIALLY THE UPPER BAY, BUT SHOULD DISSIPATE BY LATE MORNING AS
WINDS INCREASE.

OUTLOOK...
SUNDAY - WEDNESDAY...SUB-SCA CONDITIONS EXPECTED ACROSS OUR WATERS
WITH HIGH PRESSURE OFFSHORE. COLD FRONT WILL APPROACH MONDAY AND
TUESDAY EVENTUALLY CROSSING ON WEDNESDAY. WINDS WILL BACK TOWARDS THE
SOUTHWEST ON SUNDAY AND REMAIN THAT WAY THROUGH TUESDAY. SEAS WILL
INCREASE BUT REMAIN BELOW SCA AT THIS TIME.

&&

.RIP CURRENTS...
RESIDUAL SWELLS FROM CRISTOBAL WILL CONTINUE TO AFFECT THE COASTS OF
DELAWARE AND NEW JERSEY INTO THIS EVENING. THUS, THE MODERATE RISK
FOR RIP CURRENTS CONTINUES.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...FRANCK
NEAR TERM...JOHNSON
SHORT TERM...JOHNSON
LONG TERM...HEAVENER
AVIATION...HEAVENER/JOHNSON
MARINE...HEAVENER/JOHNSON
RIP CURRENTS...JOHNSON





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