Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 221958
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
358 PM EDT SUN MAR 22 2015

.SYNOPSIS...
STRONG COLD HIGH PRESSURE CENTERED NEAR THE UPPER GREAT LAKES
WILL GRADUALLY BUILD SOUTHEASTWARD AND OVER OUR AREA THROUGH
TUESDAY. A WARM FRONT ARRIVES ON WEDNESDAY, FOLLOWED BY A COLD
FRONT THURSDAY NIGHT. NORTHEASTWARD MOVING LOW PRESSURE MAY FORM
ON THAT FRONT ALONG THE SOUTH ATLANTIC COAST FRIDAY WITH A COLDER
NORTHERLY FLOW TO FOLLOW NEXT WEEKEND.


&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
THE SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL TROUGH OVER
EASTERN CANADA AND THE NORTHEASTERN U.S. THIS FEATURE WILL CONTINUE
TO DOMINATE THE FLOW ACROSS OUR AREA THROUGH TONIGHT. MEANWHILE,
HIGH PRESSURE AT THE SURFACE CENTERED NEAR THE UPPER GREAT LAKES
WILL BUILD SOUTHEASTWARD.

AS THE SURFACE HIGH EDGES CLOSER TONIGHT, THE PRESSURE GRADIENT WILL
RELAX. WE WILL SHRINK THE MIXING THIS EVENING THEREFORE THE WINDS
ARE EXPECTED TO DIMINISH QUICKLY. THERE DOES APPEAR TO BE A LITTLE
WIND THOUGH THAT IS MAINTAINED FOR SEVERAL AREAS DURING THE NIGHT.
THE COMBINATION OF LESS WIND THOUGH AND LOW DEW POINTS WILL RESULT
IN A COLD NIGHT.

OUR AREA IS VERY NEAR A 850 MB THERMAL BOUNDARY. THIS SEPARATES THE
MUCH COLDER AIR TO OUR NORTH/NORTHEAST WITH WARMER AIR TO THE
SOUTHWEST. GIVEN THE NORTHWESTERLY FLOW, THIS WILL MAINTAIN A COLD
AIRMASS OVER OUR REGION. THE PRESENCE OF THE THERMAL GRADIENT MAY
SUSTAIN AT LEAST SOME HIGH CLOUDINESS AT TIMES THROUGH THE NIGHT.
SOME MID LEVEL CLOUDS ARE WORKING THEIR WAY ACROSS OHIO AND
SOUTHWESTERN PENNSYLVANIA THIS AFTERNOON, AND SOME OF THIS MAY
ARRIVE ACROSS MAINLY OUR SOUTHERN ZONES SOMETIME THIS EVENING.

AS FOR THE LOW TEMPERATURES, WE USED A NAM/GFS MOS BLEND THEN
ADJUSTED THESE DOWN SOME MAINLY FOR THE USUALLY COLDER LOCALES.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
THE CYCLONIC FLOW ALOFT IS MAINTAINED DURING MONDAY, ALLOWING FOR A
CHILLY DAY. AT THE SURFACE, HIGH PRESSURE IS FORECAST TO BE SETTLING
INTO OUR AREA ALTHOUGH ITS CENTER SLIDES ACROSS THE LOWER GREAT
LAKES REGION. THIS WILL ALLOW FOR LESS OF A PRESSURE GRADIENT AND
THEREFORE LESS WIND. A THERMAL GRADIENT ALOFT THOUGH ACROSS OUR AREA
WILL PROBABLY RESULT IN SOME HIGH LEVEL CLOUDS AT TIMES, ESPECIALLY
WITH SOME SHEARING ENERGY TO OUR SOUTH. SOME BOUTS OF WAA INTO THE
OHIO VALLEY MAY ALSO AIDE IN SOME MID TO HIGH LEVEL CLOUD
DEVELOPMENT. THE FORECAST SOUNDINGS OVERALL INDICATE THE CONVECTIVE
TEMPERATURES BEING REACHED, HOWEVER THE LOW-LEVEL AIRMASS IS RATHER
DRY. THERE MAY STILL BE ENOUGH THOUGH FOR LIMITED FLAT STRATOCUMULUS
DEVELOPMENT.

AS FOR THE HIGH TEMPERATURES, WE STARTED WITH A BLEND OF THE NAM/GFS
MOS HOWEVER THE NAM MOS ESPECIALLY LOOKS TO CONTINUE WITH A COLD
BIAS. THEREFORE WE BUMPED THEM UP SOME AND ARE CLOSER TO THE GFS
MOS.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
500 MB: A TROUGH IN THE NE USA MONDAY NIGHT AND TUESDAY GIVES WAY TO
RIDGING WEDNESDAY INTO THURSDAY. THEREAFTER A HIGH AMPLITUDE TROUGH
EVOLVES ALONG THE EAST COAST BY NEXT WEEKEND.

TEMPERATURES: 10 TO 15 DEGREES BELOW NORMAL TUESDAY,  5 TO 10
DEGREES BELOW NORMAL WEDNESDAY,  5 TO 10 DEGREES ABOVE NORMAL
THURSDAY, NEAR NORMAL FRIDAY AND 5 TO 10 DEGREES BELOW NORMAL
NEXT WEEKEND.

FORECAST BASIS: UNLESS OTHERWISE NOTED, A 50 50 BLEND 12Z/22 GFS/NAM
MOS GUIDANCE MONDAY NIGHT-TUESDAY NIGHT, 12Z/22 MEX MOS WEDNESDAY
AND WEDNESDAY NIGHT, THEN THE 16Z/22 WPC GRIDDED ELEMENTS OF MAX/MIN
TEMP, 12 HOUR POP, 6 HOUR DEWPOINT-SKY-WIND FROM THURSDAY
THROUGH NEXT SUNDAY.

THE DAILIES...

MONDAY NIGHT AND TUESDAY...POLAR HIGH CONTINUES TO BUILD OVER THE
REGION RESULTING IN TUESDAY`S HIGH TEMPS ALMOST 15 DEGREES BELOW
NORMAL. WITH THE HIGH NEARER THE REGION, AND A MINIMAL PRESSURE
GRADIENT ACROSS THE REGION, WINDS WILL BE RATHER LIGHT - GUSTS AT
OR BELOW (AOB) 15 MPH. THROUGH THIS PERIOD.

CIGS AOA 5000 FT WILL BECOME PREDOMINANT ACROSS AT LEAST SE PA
AND S NJ SOUTHWARD LATER MONDAY NIGHT THROUGH MIDDAY TUESDAY AS A
WARM AIR ADVECTION PATTERN INTO THE DELMARVA ATTEMPTS TO SEND A
PERIOD OF LIGHT SNOW OUR WAY. THIS IN ASSOCIATION WITH FAIRLY
STRONG SHORT WAVE PASSING SEWD THROUGH THE MID ATLANTIC STATES.

CONFIDENCE: ABOVE AVERAGE EXCEPT NOT ABSOLUTELY SURE THERE WONT BE
A FEW FLURRIES OR PERIOD OF LIGHT SNOW OVER MD`S EASTERN SHORE
TUESDAY MORNING (DRYING OUT FURTHER EAST).


TUESDAY NIGHT...LOOKS LIKE A GOOD RADIATING NIGHT. LIGHT WIND AND
CLEAR SKIES FOR THE MOST PART.  CONFIDENCE: ABOVE AVERAGE.


WEDNESDAY INTO THURSDAY...WARM FRONT-COLD FRONT SCENARIO. IT COULD
BE RATHER COOL DURING THE DAY WEDNESDAY, ESPECIALLY I78 NORTH AND
ALONG THE COAST WHERE WINDS WILL BE OFF THE WATER. THE 330 PM FCST
TEMPS ON THE IMMEDIATE NJ COAST MAY BE SEVERAL DEGREES TOO WARM.
A PERIOD OF LIGHT RAIN OR DRIZZLE APPEARS PROBABLE FOR PORTIONS OF
THE AREA, ESPECIALLY I-78 NORTH LATER WED OR WED NIGHT. FOG SHOULD
DEVELOP LATE WED NIGHT, AGAIN ESPECIALLY NORTH AND HIGHER TERRAIN.
FOR NOW BLANKETED THE FCST WITH PATCHY FOG LATE WED NIGHT/EARLY
THU.

THEN THE 12Z/22 ECMWF HAS CAUGHT UP WITH THE GFS AND IT LOOKS
LIKE WE SHOULD TRANSITION TO A WINDY WARM THURSDAY AFTN (60S MUCH
OF THE COASTAL PLAIN) WITH A CHANCE OF SHOWERS AND EVEN A STRONG
GUSTY TSTM AHEAD OF THE APPROACHING COLD FRONT. PLENTY OF 0-6KM
BULK SHEAR AND APPEARS TO BE SOME INSTABILITY THOUGH A BIT
LIMITED WITH MLCAPE LESS THAN 400J.

SCENARIO CONFIDENCE: ABOVE AVERAGE.

THURSDAY NIGHT-SATURDAY...UNCERTAINTY EXISTS REGARDING THE EVOLUTION
OF THE AMPLIFYING TROUGH ALOFT. ENSEMBLES ARE TOTALLY SPAGHETTI
THOUGH THE 12Z OP RUNS ARE ALL STARTING TO INDICATE IT BEING
WORTHY TO KEEP AN EYE ON THE SOUTHERN STREAM AND A POTENTIAL WET
WEATHER MAKER FOR FRIDAY OR SATURDAY. IF THIS TRANSPIRES, WINTRY
WEATHER WOULD BE POSSIBLE. THE GGEM BEING THE INSIDE RUNNER WARM
FCST. SO WHILE THE DETAILS ARE TO BE DETERMINED OUR FCST HAS
INDICATIONS OF THIS EVENT AND FROM MY OWN PERSPECTIVE IT IS
CONSERVATIVE ON POPS (REFERENCE THE NAEFS).

LATER IN THE WEEKEND...A RATHER COLD FOR THE SEASON NORTHERLY
FLOW SHOULD FOLLOW WHATEVER DEPARTS FROM THE MID ATLANTIC COAST.
PARTLY CLOUDY. CONFIDENCE: ABOVE AVERAGE

&&

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

REST OF THIS AFTERNOON...VFR WITH SOME HIGH LEVEL CLOUDS. NORTHWEST
WINDS 10-15 KNOTS WITH GUSTS TO AROUND 20 KNOTS.

TONIGHT...VFR. NORTHWEST TO NORTH WINDS QUICKLY DIMINISHING TO 10
KNOTS OR LESS.

MONDAY...VFR. NORTH TO NORTHWEST WINDS AROUND 10 KNOTS.

OUTLOOK...
MONDAY NIGHT AND TUESDAY...VFR CIGS AOA 5000 FT. IT SHOULD CLEAR
TUESDAY AFTERNOON. MOSTLY NW WIND...GUSTS UNDER 15 KT.
CONFIDENCE: ABOVE AVERAGE.

TUESDAY NIGHT...VFR CLEAR.  LIGHT WIND. CONFIDENCE: ABOVE AVERAGE.

WEDNESDAY AND THURSDAY...VFR CIGS DEVELOP WEDNESDAY LOWERING TO IFR
RAIN/DRIZZLE/FOG WEDNESDAY NIGHT AND IMPROVING TO VFR CIGS THU
AFTN WITH A CHANCE OF MVFR CONDS IN AFTERNOON/EVENING SHOWERS/ISO
TSTMS. SMALL CHANCE LLWS THURSDAY MORNING. PRESSURE GRADIENT DRIVEN
SW WIND GUSTS OF 25-30 KT THU AFTN. CONFIDENCE: ABOVE AVERAGE ON
THE SCENARIO BUT BELOW AVERAGE ON THE TIMING.

FRIDAY...VFR CIGS KEEPING AN EYE ON POSSIBLE LOW PRESSURE DEVELOPMENT
JUST TO OUR SOUTH. CONFIDENCE: BELOW AVERAGE ON WHAT WILL OCCUR.

&&
&&

.MARINE...
HIGH PRESSURE AT THE SURFACE WILL GRADUALLY BUILD INTO THE AREA
THROUGH MONDAY. THIS WILL RESULT IN LESS WIND AS THE PRESSURE
GRADIENT RELAXES. THERE IS ENOUGH MIXING THOUGH TO MAINTAIN SOME
WIND, HOWEVER THE TRENDS HAVE BEEN RATHER MARGINAL FOR AN ADVISORY
UP NORTH AND THEREFORE WE WILL GO AHEAD AND CANCEL IT EARLY.
OTHERWISE, NO HEADLINES ANTICIPATED THROUGH MONDAY AS THE FLOW TURNS
MORE NORTHERLY.

OUTLOOK...
MONDAY NIGHT THROUGH WEDNESDAY...WINDS AND SEAS SHOULD REMAIN BELOW
SCA CRITERIA.  CONFIDENCE: ABOVE AVERAGE.

WEDNESDAY NIGHT INTO THURSDAY...WINDS AND SEAS WILL INCREASE ABOVE
SCA THRESHOLDS WEDNESDAY NIGHT. GUSTS ABOVE 30 KT WILL BE POSSIBLE
ON THURSDAY AHEAD OF A COLD FRONTAL PASSAGE. CONFIDENCE: AVERAGE.

FRIDAY...LINGERING SCA HAZARDOUS 5 FOOT SEAS POSSIBLE ON THE ATLANTIC
WATERS, MAINLY DURING THE MORNING. OTHERWISE NO MARINE HAZARDS YET
THOUGH CONFIDENCE IS BELOW AVERAGE FOR THIS DAY SINCE A SECOND LOW
PRESSURE SYSTEM MAY DEVELOP NEARBY ON FRIDAY.

&&

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

&&

$$
SYNOPSIS...DRAG/GORSE 358
NEAR TERM...GORSE
SHORT TERM...GORSE
LONG TERM...DRAG 358
AVIATION...DRAG/GORSE 358
MARINE...DRAG/GORSE 358



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