Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 212322
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
622 PM EST FRI NOV 21 2014

.SYNOPSIS...
STRONG HIGH PRESSURE WILL BUILD ACROSS THE MID ATLANTIC STATES
TONIGHT AND SATURDAY, BEFORE MOVING OFFSHORE LATER SATURDAY NIGHT. A
WARM FRONT WILL LIFT NORTH ACROSS THE REGION SUNDAY NIGHT INTO
MONDAY AS STRONG LOW PRESSURE ADVANCES INTO THE GREAT LAKES. THIS
LOW PRESSURE WILL TRACK INTO EASTERN CANADA AS ITS COLD FRONT
CROSSES OUR REGION MONDAY NIGHT TO EARLY TUESDAY. HIGH PRESSURE WILL
BUILD TO OUR SOUTH LATER TUESDAY THROUGH WEDNESDAY, FOLLOWED BY
POSSIBLE LOW PRESSURE DEVELOPING AROUND THE GREAT LAKES THURSDAY.
HIGH PRESSURE FROM THE MIDWEST SHOULD BUILD INTO THE AREA FRIDAY.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...

WINDS HAVE BECOME LIGHTER THIS EVENING AS WE HAVE LOST DAYTIME
HEATING THAT PROMOTES MIXING. THE LIGHT OR NEAR CALM WINDS PLUS A
DRY ATMOS WILL ALLOW FOR PLENTY OF RADIATIONAL COOLING OVERNIGHT.
WARMER AIR WILL BE MOVING IN ALOFT FROM THE WEST BUT THIS WILL
ONLY ENHANCE THE LOW LEVEL INVERSION AND FURTHER DE- COUPLING OF
THE SURFACE LAYER. DECIDED TO UNDERCUT MOS GUIDANCE BY A DEGREE OR
TWO. THE OVERNIGHT MIN TEMPS MAY APPROACH RECORDS FOR THE DATE FOR
SOME LOCATIONS. HWVR URBAN AND COASTAL AREAS SHOULD NOT BE QUITE
AS COLD. WITH THE 6:30 PM UPDATE IT APPEARS THE LOCATIONS WHERE
THE WINDS HAVE DIED DOWN QUICKER ARE RUNNING A DEGREE OR TWO
COOLER AND THOSE STILL SOMEWHAT WINDY ARE A DEGREE OR TWO WARMER.
ADJUSTED TEMPERATURES SOME OVER THE NEXT FEW HOURS TO ACCOUNT FOR
THIS BUT DID MAKE ANY CHANGES TO THE OVERALL LOW TEMPERATURES
REFERENCED IN THE CLIMATE SECTION.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
HIGH PRES WILL CONT TO SHIFT EWD OR SEWD AND SHOULD BE CENTERED OFF
OF CAPE HAT BY LATE IN THE DAY. THIS WILL RESULT IN SWLY FLOW AND
SMWHT OF A MODERATING TREND IN TEMPS. WITH WARM ADVECTION CONTINUING
ALOFT...AFTN MAXS SHOULD BE 5 TO 10 DEGREES WARMER THAN TODAY BUT
STILL BELOW NORMAL. INCREASING HI CLOUDS WILL TEND TO HOLD TEMPS
BACK ESPECIALLY N/W OF PHL. NO PRECIP IS EXPECTED BEFORE 00Z SUNDAY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
A CHANGING PATTERN AND NOTICEABLY MILDER AIRMASS ARE IN STORE AT THE
BEGINNING OF THE LONG TERM PERIOD, BUT A RETURN TO COOLER AND BELOW
AVERAGE TEMPERATURES LOOKS TO FOLLOW FOR THE MIDDLE OF NEXT WEEK.
AFTER A FAIRLY QUIET DAYTIME SATURDAY, THE DEVELOPING RETURN FLOW
AROUND HIGH PRESSURE AS IT GRADUALLY MOVES OFFSHORE INTO SATURDAY
NIGHT WILL ALLOW FOR SOME LOWER LEVEL MOISTURE TO RETURN BACK IN
ACROSS THE REGION. LOOKING AT FORECAST SOUNDINGS ALOFT THROUGH ABOUT
850MB, SOME WARM AIR ADVECTION WILL BE TAKING PLACE THROUGH THE 0Z
TO 12Z SUNDAY TIMEFRAME. THESE SIGNALS LOOK TO INITIATE SOME LIGHT
PRECIP OFF OF THE GREAT LAKES, ESPECIALLY TO OUR NORTHWEST, FROM
LATE-DAY SATURDAY AND INTO SATURDAY NIGHT. FOR OUR REGION, THERE
LOOKS TO BE ENOUGH LIFT ALOFT TO PERHAPS SUPPORT SOME LIGHT PRECIP
REACHING OUR FAR NORTHERN ZONES, AND IF THIS WERE TO OCCUR INTO
SATURDAY NIGHT, IT MAY RESULT IN SOME LIGHT FREEZING RAIN AS SURFACE
TEMPS WILL BE BELOW FREEZING AS THE WARMING ALOFT OCCURS. THIS STILL
LOOKS TO BE A LOW PROBABILITY EVENT, WITH PERHAPS THE SHELTERED
VALLEYS HAVING THE BEST CHANCE FOR A LITTLE FREEZING RAIN AS THE
COLD SURFACE AIR REMAINS TRAPPED. NONETHELESS, WITH OUR CONFIDENCE
IN THIS OCCURRENCE BELOW AVERAGE, WE HAVE KEPT POPS AT 30 PERCENT OR
LESS. WE WILL, HOWEVER, KEEP A MENTION OF THIS POSSIBILITY IN THE
HAZARDOUS WEATHER OUTLOOK PRODUCT.

GOING INTO SUNDAY AND SUNDAY NIGHT, WAA AND MOISTURE ADVECTION WILL
BE TAKING SHAPE IN EARNEST ACROSS OUR REGION BEHIND THE OFFSHORE
HIGH PRESSURE. AT THE SURFACE, A WARM FRONT WILL BE APPROACHING OUR
REGION FROM THE SOUTHWEST AS STRONG SURFACE LOW PRESSURE TRACKS INTO
THE GREAT LAKES. HIGHEST POPS FOR RAIN ARE KEPT THROUGH THE SUNDAY
NIGHT TO EARLY MONDAY TIMEFRAME, WITH THE BEST LIFT OCCURRING AND
THE WARM FRONT PROGRESSING NORTH THROUGH THE REGION. HOWEVER, SOME
HIGH CHANCE POPS ARE IN PLACE FOR LATE-DAY SUNDAY FOR OUR SOUTHERN
AND WESTERN ZONES. INTO MONDAY, WITH THE WARM FRONT NORTH OF OUR
AREA, WE TRIM BACK POPS FOR ONLY SOME SCATTERED SHOWERS. MONDAY
LOOKS TO BE THE WARMEST DAY OF THE LONG TERM AS WAA AND A
SOUTH-SOUTHWEST FLOW CONTINUE ACROSS THE REGION. DEPENDING ON CLOUD
COVER, ANY SHOWER ACTIVITY, AND DECENT MIXING, MAXIMUM TEMPERATURES
ARE EXPECTED TO EASILY REACH INTO THE MIDDLE AND UPPER 60S FOR MUCH
OF THE FORECAST AREA, WITH SOME AREAS HAVING A CHANCE AT REACHING
AROUND 70 DEGREES. THIS WOULD BE NEARING RECORD HIGH TERRITORY.

LATER MONDAY NIGHT INTO EARLY TUESDAY, THE GFS AND ECMWF SHOW STRONG
SURFACE LOW PRESSURE TRACKING INTO EASTERN CANADA, WITH ITS
ASSOCIATED COLD FRONT CROSSING OUR REGION. THIS COLD FRONT MAY TAKE
ITS TIME MOVING FARTHER OFFSHORE AND AWAY FROM THE EASTERN SEABOARD
THROUGH TUESDAY AND WEDNESDAY AS THE GFS AND ECMWF SHOW THE UPPER
TROUGH REMAINING OFF TO OUR WEST. IN FACT, THE GUIDANCE CONTINUES TO
SHOW POTENTIAL LOW PRESSURE DEVELOPMENT ALONG THIS LINGERING
BOUNDARY OFF OF THE SOUTHEAST UNITED STATES COAST AS SOME ENERGY
EMERGES THROUGH THE BASE OF THE UPPER TROUGH. WHILE ANY PRECIP
CHANCES SHOULD BE FAIRLY LIMITED TUESDAY INTO WEDNESDAY, IT WILL
DEPEND ON THE PROXIMITY OF THIS LOW PRESSURE TO THE EASTERN SEABOARD
AS IT ADVANCES NORTHEAST ALONG THE LINGERING BOUNDARY. FOR NOW, WE
HAVE KEPT SOME CHANCE POPS FOR RAIN/SHWRS INTO WEDNESDAY, ESPECIALLY
FOR OUR EASTERN ZONES. IN ADDITION TO ANY POSSIBLE PRECIP CHANCES,
COLD AIR ADVECTION WILL BE TAKING SHAPE THROUGH MIDWEEK, WITH A
RETURN TO BELOW AVERAGE TEMPERATURES BY WEDNESDAY.

WHILE THERE IS A LITTLE MORE UNCERTAINTY TOWARD THE END OF THE LONG
TERM PERIOD, THERE ARE MORE SIMILARITIES WITH THE GFS AND ECMWF RUNS
AS COMPARED TO PREVIOUS RUNS WITH REGARDS TO A MUCH STRONGER
MID/UPPER TROUGH DIGGING DOWN FROM THE GREAT LAKES AND TOWARD OUR
REGION THURSDAY. AT THIS TIME, WE WENT PRIMARILY WITH A
WPC/CONTINUITY BLEND WITH REGARDS TO TEMPS AND POPS THURSDAY. AS
THIS TROUGH MOVES OFFSHORE INTO FRIDAY MORNING, SURFACE HIGH
PRESSURE FROM THE MIDWEST LOOKS TO TAKE ITS PLACE AND BUILD EAST
TOWARD OUR REGION.

&&

.AVIATION /23Z FRIDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

VFR CONDS ARE EXPECTED TO CONTINUE FOR AT LEAST THE NEXT 24 HOURS
FOR ALL TAF SITES WITH PERHAPS SOME MID TO HIGH LEVEL CLOUDS BY
THE AFTERNOON ON SATURDAY. LIGHT WESTERLY OR VARIABLE WINDS SHOULD PREVAIL
OVERNIGHT. AS HIGH PRES MOVES OFFSHORE ON SATURDAY...SWLY WINDS
WILL DEVELOP BY MID/LATE MORNING BUT SHOULD GENLY REMAIN BELOW 10
KT DURG THE DAY.

OUTLOOK...
SATURDAY NIGHT THROUGH SUNDAY...VFR CONDITIONS; ALTHOUGH, INCREASING
CLOUDINESS IS EXPECTED SUNDAY.

SUNDAY NIGHT THROUGH MONDAY NIGHT...CEILING AND VSBY RESTRICTIONS
ARE EXPECTED IN AREAS OF RAIN.

TUESDAY...MAINLY VFR CONDITIONS.

WEDNESDAY...POSSIBLE SUB-VFR DEPENDING ON THE TRACK OF OFFSHORE LOW
PRESSURE. LOW CONFIDENCE.

&&

.MARINE...
WITH WINDS DECREASING THIS EVENING WE ALLOWED THE SCA TO EXPIRE AT
6PM. WINDS OVERNIGHT AND SATURDAY WILL BACK AROUND TO THE WEST
AND THEN SW BUT SHOULD REMAIN BELOW SCA LEVEL. SEAS WILL BE ALSO
BELOW SCA CRITERIA.

OUTLOOK...
SATURDAY NIGHT...CONDITIONS MAY BE CLOSE TO SCA CRITERIA FOR OUR
COASTAL WATERS, WITH SOME WIND GUSTS BETWEEN 20 TO 25 KNOTS.

SUNDAY...SUB-ADVISORY CONDITIONS ARE EXPECTED, WITH WIND GUSTS TO
AROUND 20 KNOTS OR LESS FOR THE COASTAL WATERS.

SUNDAY NIGHT THROUGH MONDAY NIGHT...SCA CONDITIONS ARE EXPECTED AT
THIS TIME FOR THE COASTAL WATERS AND INTO DELAWARE BAY, WITH WIND
GUSTS AS HIGH AS 30 KNOTS PLUS AT TIMES ALONG WITH ELEVATED SEAS.

TUESDAY...SOME LINGERING SCA CONDITIONS ON THE COASTAL WATERS DUE TO
ELEVATED SEAS.

WEDNESDAY...SUB-ADVISORY CONDITIONS ARE EXPECTED.

&&

.CLIMATE...
HERE ARE SOME RECORD LOWS FOR OVERNIGHT TONIGHT FOR
11/22.

ATLANTIC CITY 12 BACK IN 1879
PHILADELPHIA 14 BACK IN 1880
WILMINGTON 17 BACK IN 1964
ALLENTOWN 17 BACK IN 1969 AND 1964
TRENTON 15 BACK IN 1880
GEORGETOWN 16 BACK IN 1987
READING 16 BACK IN 1969
MOUNT POCONO 5 BACK IN 1969

HERE ARE THE FORECASTED LOWS FOR TONIGHT.

ATLANTIC CITY 18
PHILADELPHIA 23
WILMINGTON 20
ALLENTOWN 16
TRENTON 21
GEORGETOWN 18
READING 16
MOUNT POCONO 13

&&

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

&&

$$
SYNOPSIS...KLINE
NEAR TERM...AMC/GAINES
SHORT TERM...AMC
LONG TERM...KLINE
AVIATION...AMC/GAINES/KLINE
MARINE...AMC/KLINE
CLIMATE...DRAG/GAINES






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