Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 230243
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
943 PM EST MON DEC 22 2014

.SYNOPSIS...
A FRONTAL BOUNDARY WILL STALL NEAR THE SOUTHEAST COAST THROUGH
TUESDAY. THIS STALLED BOUNDARY WILL EVENTUALLY LIFT NORTHWARD INTO
THE AREA AS A WARM FRONT BY WEDNESDAY. MEANWHILE, LOW PRESSURE
DEVELOPING NEAR THE NORTHERN GULF COAST LATE TUESDAY IS EXPECTED TO
STRENGTHEN AS IT TRACKS NORTHWARD INTO THE MIDWEST WEDNESDAY AND
GREAT LAKES WEDNESDAY NIGHT. A COLD FRONT WILL MOVE THROUGH EARLY
THURSDAY. HIGH PRESSURE BUILDS OVER THE EASTERN UNITED STATES FOR
THURSDAY AND FRIDAY. ANOTHER COLD FRONT IS FORECAST TO ARRIVE LATE
SATURDAY INTO SUNDAY.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
LATEST RAP GUIDANCE SHOWS A COUPLE LOW-LEVEL FEATURES PUSHING
ACROSS THE REGION FROM THE SOUTHWEST, NOTED BY THE DISTINCT RAIN
BANDS. WE MAINTAIN THE CURRENT POP FORECAST, CATEGORICAL ACROSS
THE NORTH WITH SLIGHTLY LESS ACROSS EXTREME SOUTHERN DELMARVA.
HAVE ALSO DROPPED THE FREEZING RAIN ADVISORY WITH THIS UPDATE AS
TEMPERATURES ARE ABOVE FREEZING IN MOST LOCATIONS. THERE COULD BE
SOME LINGERING AT OR BELOW FREEZING TEMPERATURES IN THE HIGHEST
ELEVATIONS IN CARBON/MONROE, BUT THIS CAN BE HANDLED BY AN SPS.

OTHERWISE, AS THE AIRMASS MOISTENS AND THE LOW-LEVEL INVERSION
STRENGTHENS, SOME DRIZZLE MAY OCCUR ALONG WITH SOME FOG. GIVEN THE WAA
FORECAST, DESPITE THE LIGHT FLOW, THE TEMPERATURES WERE SHOWN TO
MAINLY BE STEADY OR EVEN SLOWLY RISE DURING THE NIGHT. LOW
TEMPERATURES WERE MOSTLY A BLEND OF THE NAM/GFS MOS. THE LAMP/LAV
GUIDANCE WAS USED TO ASSIST WITH THE HOURLY TEMPERATURES AND DEW
POINTS.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
THE SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL TROUGH TO OUR
WEST. THIS WILL DRIVE LOW PRESSURE TOWARD THE GREAT LAKES WITH
CONTINUED LOW-LEVEL WAA ACROSS OUR AREA. A WEAK SURFACE LOW SLIDING
NORTHWARD OFF OF THE MID ATLANTIC COAST SHOULD TEND TO WEAKEN
FURTHER DURING THE COURSE OF THE DAY AS SOME RIDGING BUILDS. THE
COMBINATION OF THIS WEAKENING FEATURE, A LOW-LEVEL INVERSION AND
PLENTY OF MOISTURE BENEATH IT SPELLS UNSETTLED WEATHER.

THE FORECAST SOUNDINGS OVERALL SHOW AS THE LARGE SCALE LIFT WANES,
SOME DRYING OCCURS ALOFT. THIS WOULD TEND TO LEAD TO SOME DRIZZLE
AND FOG ACROSS MUCH OF THE AREA, ASSUMING THE LOW CLOUDS DO INDEED
LOCK IN. THE MORE FOCUSED RAIN MAY BE ACROSS OUR NORTHERN ZONES
BEFORE LIFTING NORTH OF OUR CWA, THEN LEFTOVER DRIZZLE AROUND. WE
TRENDED THE POPS TO REFLECT THIS IDEA AS MUCH OF THE QPF SHOULD BE
ON THE LIGHT SIDE.

AS FOR THE HIGH TEMPERATURES, WE USED AN EVEN GFS/NAM MOS BLEND BUT
THEN ADJUSTED THESE DOWN SOME DUE TO THE EXPECTED LOW CLOUDS AND
LIGHT RAIN/DRIZZLE.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
THE LARGE SCALE PATTERN DURING MIDWEEK WILL FEATURE A HIGH AMPLITUDE
TROUGH OVER THE CENTRAL CONUS AND DOWNSTREAM RIDGE OVER THE WESTERN
ATLANTIC. CYCLOGENESIS IS FORECAST TO OCCUR ALONG THE NORTHERN GULF
COAST LATE TUESDAY. THE SURFACE LOW IS THEN FORECAST TO TRACK
NORTHWARD THROUGH THE DEEP SOUTH TUESDAY NIGHT AND MIDWEST ON
WEDNESDAY. THIS TRACK MEANS THE WARM SECTOR WILL BECOME ESTABLISHED
UP THE EASTERN SEABOARD OWING TO A DEEP SOUTHERLY FETCH ON THE EAST
SIDE OF THE STORM SYSTEM. FORECAST SOUNDINGS ARE ONLY SUPPORTIVE ON
ONE PTYPE WITH THIS EVENT: RAIN. THERE IS AN OPPORTUNITY FOR A
BRIEF LULL IN THE RAIN TUESDAY EVENING WHEN THE INITIAL BAND OF
ISENTROPIC LIFT PASSES TO OUR NORTH. A LARGE PRECIP SHIELD OVER THE
SOUTHEAST STATES IS EXPECTED TO EXPAND NORTHWARD INTO THE NORTHERN
MID ATLANTIC LATE TUESDAY NIGHT AND WEDNESDAY MORNING. RAIN SHOULD
BECOME WIDESPREAD AND MODERATE AT TIMES ON CHRISTMAS EVE BOTH DURING
THE DAY AND AT NIGHT. ADDED A SLIGHT CHANCE OF THUNDERSTORMS NEAR
THE DE AND SOUTHERN NJ COAST AS WELL. NOT EXPECTING A LOT OF HYDRO
ISSUES WITH QPF BETWEEN 0.75 AND 1.50 INCHES FOR THIS EVENT.

MODELS HAVE TRENDED SLIGHTLY SLOWER WITH THE COLD FRONT, INDICATING
A LATE WEDNESDAY NIGHT/EARLY THURSDAY MORNING FROPA WITH TODAY`S 12Z
GUIDANCE COMPARED TO A WEDNESDAY EVENING PASSAGE FROM YESTERDAY`S
RUNS. WE FAVORED A MORE PROGRESSIVE SOLUTION WHERE THE PRECIP ENDS
BY CHRISTMAS MORNING SINCE THE UPPER TROUGH IS EXPECTED TO
DE-AMPLIFY, ALLOWING FOR MORE OF AN EASTWARD PUSH WITH THE FRONTAL
BOUNDARY.

WESTERLY WINDS BEHIND THE FRONT WILL ADVECT COLDER AND DRIER AIR
INTO THE REGION ON THURSDAY. SKIES MAY CLEAR IN THE MORNING BEFORE
POST-FRONTAL STRATOCU IS EXPECTED TO DEVELOP BY THE AFTERNOON. IT
WILL BE BREEZY DURING THE DAY AS BUFKIT MOMENTUM TRANSFER FROM THE
12Z GFS SHOWS THE POTENTIAL FOR 30 TO 40 MPH GUSTS. MAX TEMPS IN THE
UPPER 40S AND LOWER 50S MAY OCCUR IN THE EARLY MORNING JUST PRIOR TO
FROPA BEFORE DROPPING THRUOUT THE DAY. A FEW FLURRIES MAY REACH THE
POCONOS DURING THE AFTERNOON.

BROAD AREA OF HIGH PRESSURE BUILDS ALONG THE EASTERN SEABOARD
THURSDAY NIGHT AND FRIDAY. QUIET CONDITIONS AND SLIGHTLY ABOVE
NORMAL TEMPS ARE IN STORE TO END THE WEEK.

THERE IS STILL A LARGE FORECAST SPREAD WITH THE LATEST 12Z MODELS
FOR THIS WEEKEND. THE ECMWF REMAINS THE MOST BULLISH WITH LOW
PRESSURE DEVELOPING OVER THE GULF COAST STATES THIS WEEKEND AS A
RESULT OF A STRONG SHORTWAVE TROUGH TRACKING ACROSS THE SOUTHERN
STATES. THIS MODEL THEN SIMULATES THE LOW STRENGTHENING AS IT MOVES
NORTHEASTWARD TOWARD THE MID-ATLANTIC STATES AND STARTS TO PHASE
WITH NORTHERN STREAM ENERGY SUNDAY AND SUNDAY NIGHT. MEANWHILE, THE
GFS SHOWS A MUCH MORE PROGRESSIVE PATTERN WITH THE ABOVE MENTIONED
SHORTWAVE TROUGH PUSHING A WEAK COLD FRONT THRU THE MID ATLANTIC
EARLIER IN THE WEEKEND. SIDED CLOSELY WITH WPC FOR THE WEEKEND
FORECAST, WHICH WAS WEIGHTED MORE TOWARD THE NAEFS/ECMWF ENSEMBLE
MEAN. LOW CHANCE POPS FOR RAIN NEAR THE COAST AND RAIN/SNOW INLAND
WERE INCLUDED FOR LATE IN THE WEEKEND.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

TONIGHT...MVFR CEILINGS ARE ANTICIPATED TO LOWER TO IFR/LIFR WITH
LIGHT RAIN AND DRIZZLE. SOME FOG WILL OCCUR AS THE CEILINGS LOWER,
WHICH WILL BRING THE VISIBILITIES DOWN. NORTHEAST WINDS GENERALLY
AROUND 5 KNOTS.

TUESDAY...THE CEILINGS SHOULD REMAIN AROUND IFR AS THE LOW-LEVEL
MOISTURE BECOMES TRAPPED. THIS WILL ALSO COMBINE WITH SOME LIGHT
RAIN OR DRIZZLE. NORTHEAST WINDS 5 KNOTS OR LESS, POSSIBLY TURNING
LOCALLY SOUTHEAST IN THE AFTERNOON.

OUTLOOK...
TUESDAY NIGHT...MAY BE A LULL IN PRECIP TUESDAY EVENING BEFORE
MORE RAIN MOVES BACK INTO THE AREA OVERNIGHT. STILL EXPECTING MVFR
AND IFR CONDITIONS.

WEDNESDAY AND WEDNESDAY NIGHT...MAINLY IFR CONDITIONS IN LOW CLOUDS
AND RAIN. THE RAIN WILL BE STEADY AND MODERATE AT TIMES. SOUTHERLY
WINDS ARE FORECAST TO INCREASE TO NEAR 50 KT LESS THAN 1000 FT AGL
WEDNESDAY AFTERNOON AND EVENING. MAY SEE LLWS DURING THIS TIME
ESPECIALLY IF WEDGE OF COLDER AIR NEAR THE SURFACE IS MORE STUBBORN
TO ERODE THAN MODELS INDICATE, MAKING THE THERMAL INVERSION STRONGER.

THURSDAY...MVFR LINGERING EARLY, IMPROVING TO VFR DURING THE DAY.
BREEZY WEST WINDS GUSTING 30-25 KT.

THURSDAY NIGHT THROUGH SATURDAY...VFR AND LIGHT WINDS.

&&

.MARINE...
WE ARE STARTING TO SEE AN UPTICK IN THE SEAS ACROSS OUR WATERS
WITH THE MOST NOTICEABLE INCREASE ACROSS THE SOUTH. WE EXPECT,
WITH A STRENGTHENING NORTHEASTRLY FLOW, TO SEE SEAS ACROSS THE
SOUTH CLIMB CLOSE TO 6 FEET LATER TONIGHT. WE HAVE THEREFORE
ISSUED A SCA WITH WINDS AND SEAS THROUGH TOMORROW LATE MORNING
WHEN THE PRESSURE GRADIENT SHOULD RELAX ENOUGH TO ALLOW THE
ELEVATED SEA CONDITIONS SUBSIDE A BIT. ELSEWHERE, THE TRAJECTORY
AND THE AMOUNT OF FETCH DO NOT APPEAR CONDUCIVE FOR SCA SEAS AND
GUSTS. THE WINDS SHOULD LESSEN TUESDAY AS THE SURFACE LOW WEAKENS.

OUTLOOK...
TUESDAY NIGHT...SOUTH WINDS BELOW SCA CRITERIA. WAVES FORECAST TO
BUILD TO 4 FT OFF THE DE COAST.

WEDNESDAY AND WEDNESDAY NIGHT...WIDESPREAD SCA CONDITIONS EXPECTED
WITH SEAS BUILDING TO 5-8 FT AND SOUTHERLY WINDS SUSTAINED 20-25 KT.
STABLE LAPSE RATES WILL LIMIT MIXING POTENTIAL SO NOT EXPECTING MUCH
HIGHER GUSTS, EXCEPT IF CONVECTION IS ABLE TO DEVELOP OVER THE OCEAN.

THURSDAY...WEST WIND GUSTING IN EXCESS OF 25 KNOTS EXPECTED. GALES
ARE EVEN POSSIBLE DURING FOR A PERIOD. 5 TO 8 FEET SEAS FORECAST FOR
THE OCEAN.

THURSDAY NIGHT THROUGH SATURDAY...NO MARINE HEADLINES EXPECTED AT
THIS TIME.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EST TUESDAY FOR ANZ453>455.

&&

$$
SYNOPSIS...KLEIN
NEAR TERM...GORSE/HEAVENER
SHORT TERM...GORSE
LONG TERM...KLEIN
AVIATION...GORSE/HEAVENER/KLEIN
MARINE...GORSE/IOVINO/HEAVENER/KLEIN






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