NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Dec 29, 3:31 PM EST, 1 hour 39 minutes earlier.
Area forecast discussion, Dec 29, 3:31 PM EST, 1 hour 39 minutes before
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
331 PM EST SUN DEC 29 2013
.SYNOPSIS...
LOW PRESSURE OVER SOUTHERN NEW ENGLAND WILL CONTINUE MOVING
NORTHEAST TONIGHT BEFORE A COLD FRONT CROSSES THE AREA MONDAY
MORNING. LIGHT SNOW ASSOCIATED WITH A CLIPPER SYSTEM MOVING EAST
ACROSS UPPER NEW YORK STATE ON TUESDAY SHOULD REMAIN JUST TO OUR
NORTH. HIGH PRESSURE WILL BRIEFLY BUILD ACROSS THE NORTHEAST TUESDAY
NIGHT AND WEDNESDAY BEFORE ANOTHER STORM SYSTEM AFFECTS THE MID
ATLANTIC AREA THURSDAY INTO THURSDAY NIGHT. HIGH PRESSURE IS THEN
EXPECTED TO BUILD ACROSS THE REGION BEGINNING LATE FRIDAY NIGHT,
PROVIDING TRANQUIL BUT COLD WEATHER NEXT WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
THE MODEL 500MB INITIALIZATION WHILE NOT SHOWING GLARING ERRORS,
SHOWED SOME TENDENCY ERRORS. THIS INCLUDED THE GFS, WRF AND ECMWF.
IN THE EAST, THE SOUTHEAST RIDGE WAS STRONGER. IN THE WEST (FOR THE
NEXT SYSTEM), THE MODELS INITIALIZED TOO MUCH HANG BACK ENERGY IN
THE BAJA AND NOT ENOUGH RIDGING ALONG THE WEST COAST. AT THE LEAST
ITS A ZERO SUM GAIN (THE RIDGING WILL SLOW THE BAJA PROGRESSION DOWN
THE ROAD). AT THE MOST, ITS JUST AN OVERALL FASTER PROGRESSION. HAVE
TO SEE HOW THE 00Z INITIALIZATION RESPONDS. THE DIGGING NORTHERN
STREAM SHORT WAVE IS SOUTH OF THE ALEUTIANS, STILL SHOULD GET INTO
THE DENSER RAOB NETWORK FOR THE 00Z/31 OR 12Z/31 MODEL RUNS. 850MB
AND 925MB, MODEL ERRORS WERE GENERALLY 1C OR LESS, AND THE ERRORS
WERE IN BOTH DIRECTION, GFS SLIGHTLY BETTER.
GETTING BACK TO THE NEAR TERM, THIS PCPN EVENT IS STARTING TO WIND
DOWN AND WE KEPT SIMILAR ENDING TIMING TO THE PREVIOUS UPDATE, MOST
PLACES DONE BY 00Z. WITH THE STRONG SHORT WAVE MOVING THROUGH BY
00Z, AGREE WITH THE MODELING THAT THE COMMA HEAD PCPN IN WESTERN PA
IS GOING TO HAVE ITS MOISTURE FEED CUT OFF AND START DISSIPATING.
THIS LEAVES REMNANT PCPN NEAR THE NORTHWESTERN EDGE OF OUR CWA INTO
THIS EVENING. WE DID KEEP POPS GOING FOR A LITTLE WHILE. THERMALLY
IT DOES GET COLDER ALOFT FOR SNOW (WRF DYNAMICALLY COOLS IT AND THEN
WARMS AGAIN OVERNIGHT AFTER INTENSITY LESSENS AT 925MB). UPSTREAM
SFC TEMPS ARE FAIRLY WARM. SO IF PCPN DOES CHANGE TO SNOW, ITS
LIKELY TO BE AT 32-34F. COUPLED WITH OVERALL EXPECTED LIGHT PCPN, WE
KEPT ACCUMS AT LESS THAN HALF AN INCH IN THE POCONOS.
THE WRF-NMMB WAS SLIGHTLY TOO SLOW, BUT DID IN REALITY VERIFY CLOSE
WITH THE LLJ AT KDOV. ITS FORECAST TO SHIFT OFFSHORE AND THE
STRONGEST WINDS FOR THIS EVENT ARE ALSO ABOUT DONE ON LAND. THE WEST
WIND MIXING THIS EVENING BECAUSE THE JET IS FORECAST TO MOVE
OFFSHORE QUICKER IS LESS THAN YDA OFF THE BUFKIT SOUNDINGS. THIS
CAPS THE WIND GUSTS FAR SERN CWA UNDER 40 MPH. SOME WIND GUSTS
DID EXCEED 40 MPH IN SUSSEX COUNTY, DE THIS AFTERNOON.
GIVEN THE WARM UPWIND TEMPS, WE SIDED WITH THE HIGHER STAT GUIDANCE
FOR THE DOWNWARD PROGRESSION OF TEMPS TONIGHT AND THE MINS IN
GENERAL.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
A DRY DAY FOR OUR CWA ON MONDAY. THERE ARE A COUPLE OF CHANNELIZED
SHORT WAVE TRAINS FORECAST TO MOVE THROUGH. IN THE NORTHWEST PART OF
OUR CWA, WHERE THE STRONGEST ONE IS PREDICTED, THE FCST SUBSIDENCE
INVERSION IS PRETTY LOW AND WOULD NOT BE ABLE TO GENERATE MORE THAN
FLURRIES IF WE ARE WRONG. ELSEWHERE, WITH THE 250MB JET OVERHEAD,
THE EXTENT OF THE IMPACT IS FOR MID TO HIGH LEVEL CLOUDS TO DEVELOP.
WINDS INITIALLY ABOVE THE BOUNDARY LEVEL WILL BE BRISK, BUT ARE
PREDICTED TO DECREASE AS WE GET DEEPER INTO THE AFTERNOON, A QUICKER
DROP-OFF THAN TYPICAL FOR OUR AREA. GOING WITH THE WARMER TEMP THEME
AND BASED ON A BUMP UP OF PREDICTED 850MB AND 925MB TEMPS FROM
YESTERDAY'S 12Z RUN, WE ARE SIDING WITH THE HIER STAT GUIDANCE FOR
MAX TEMPS.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
A PROGRESSIVE MID-LEVEL PATTERN WILL MAINTAIN AN ACTIVE WEATHER
REGIME FOR THE REGION THROUGH THE LONG-TERM PERIOD...AND POSSIBLY
BEYOND.
HIGH PRESSURE CENTERED OVER NORTHERN NEW ENGLAND MONDAY NIGHT WILL
PROVIDE DRY WEATHER TO THE REGION BEFORE RETREATING NORTHWARD,
ALLOWING A CLIPPER SYSTEM TO MOVE EAST FROM THE GREAT LAKES REGION
ON TUESDAY. LATEST MODEL GUIDANCE (GFS, ECMWF) KEEP PRECIPITATION
ASSOCIATES WITH THIS CLIPPER SYSTEM JUST TO OUR NORTH, SO THE
FORECAST FOR THIS TIME PERIOD WILL REMAIN DRY. THEN HIGH PRESSURE
FROM THE TENNESSEE RIVER VALLEY BUILDS EAST, AGAIN KEEPING THE
WEATHER DRY FOR TUESDAY NIGHT AND WEDNESDAY. THIS MEANS THE
WEATHER SHOULD BE FINE FOR OUTDOOR NEW YEAR/S EVE CELEBRATIONS,
WITH SEASONABLY COLD TEMPERATURES.
THEN THINGS GO DOWNHILL. LOW PRESSURE FROM THE MIDWEST, AND ITS
ATTENDANT COLD FRONT, IS PROGGED TO MOVE EAST TOWARD THE NEW JERSEY
COAST ON THURSDAY. MEANWHILE...LOW PRESSURE FROM THE GULF OF MEXICO IS
EXPECTED TO MOVE NORTHEAST NEAR OR ALONG THIS FRONT, WITH THE TWO
LOW PRESSURE SYSTEMS EVENTUALLY MERGING OFF THE NEW JERSEY COAST
THURSDAY NIGHT. THIS MERGED LOW WILL THEN CONTINUE TO DEEPEN AS IT
MOVES AWAY, CREATING VERY WINDY CONDITIONS IN ITS WAKE LATE
THURSDAY NIGHT AND FRIDAY. THE ATMOSPHERE SHOULD BE COLD ENOUGH
FOR ALL SNOW NORTH AND WEST OF PHILADELPHIA, WITH A MIXED BAG OF
PRECIPITATION SOUTH. THERE COULD EVEN BE A COMPLETE CHANGEOVER TO
ALL RAIN NEAR THE COAST, BUT AS COLDER AIR MOVES IN BEHIND THIS
SYSTEM THURSDAY EVENING, LIGHT SNOW IS EXPECTED EVERYWHERE. SINCE
MOST OF THE ENERGY WITH THIS SYSTEM WILL BE CONCENTRATED OFFSHORE,
SNOWFALL ACCUMULATIONS ARE EXPECTED TO BE ONLY IN THE ADVISORY
RANGE EVEN UP NORTH. HOWEVER, A LOT CAN CHANGE BETWEEN NOW AND
THEN SO STAY TUNED.
HIGH PRESSURE IS EXPECTED TO MOVE IN BEHIND THIS DEPARTING LOW LATE
FRIDAY OR EARLY SATURDAY WHICH SHOULD PROVIDE TRANQUIL BUT COLD
WEATHER FOR THE REGION THROUGH MOST OF THE WEEKEND. IN FACT, LOW
TEMPERATURES SATURDAY MORNING COULD DIP DOWN TO NEAR ZERO IN THE
SOUTHERN POCONOS AND NORTHWEST NEW JERSEY...WITH SINGLE DIGITS
POSSIBLE IN THE PHILADELPHIA METRO AREA. WIND CHILL VALUES COULD BE
EVEN LOWER.
ANOTHER STORM SYSTEM MAY AFFECT THE AREA EARLY INTO THE NEXT WEEK.
&&
.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
LATE-DAY AND TONIGHT...IFR CONDITIONS WITH SOME MODERATE RAIN AT
LATE-DAY WILL CONTINUE AS AN AREA OF LOW PRESSURE MOVES
NORTHEASTWARD ALONG THE EAST COAST AND NEAR THE MID ATLANTIC REGION.
AS THE CENTER OF LOW PRESSURE BEGINS TO TRACK AWAY FROM THE AREA,
THE STEADIER RAIN WILL CONTINUE TO PULL AWAY TO THE NORTHEAST, WITH
SOME LIGHTER RAIN EXPECTED EARLY THIS EVENING, BEFORE PRECIP ENDS BY
AROUND 0Z FOR THE REGION. THROUGH EARLY EVENING WITH LIGHT RAIN
ACROSS THE AREA, CONDITIONS ARE EXPECTED TO IMPROVE BACK TO MVFR
FROM SOUTHWEST TO NORTHEAST, WITH CONTINUED IMPROVEMENT BACK TO VFR
ANTICIPATED PRIOR TO MIDNIGHT AS LOW PRESSURE QUICKLY TRACKS AWAY.
WITH REGARDS TO WINDS, EASTERLY WINDS AROUND 10 KNOTS ARE EXPECTED
TO CONTINUE THROUGH LATE-DAY BEFORE TURNING AND BECOMING
NORTHWESTERLY AND INCREASING TO BETWEEN 10 TO 15 KNOTS THIS EVENING
AS LOW PRESSURE TRACKS AWAY FROM THE REGION. SKIES ARE EXPECTED TO
SCATTER OUT DURING THE OVERNIGHT WITH WEST-NORTHWEST WINDS DROPPING
UNDER 10 KNOTS.
MONDAY...VFR CONDITIONS ARE ANTICIPATED THROUGH THE DAY WITH GUSTY
NORTHWEST WINDS. GUSTS FROM MID-MORNING THROUGH THE AFTERNOON IN THE
20 TO 25 KNOT RANGE ARE EXPECTED.
OUTLOOK...
WEDNESDAY NIGHT-THURSDAY...MVFR DEVELOPING WITH IFR CONDITIONS
POSSIBLE WITH SNOW NORTH AND MIXED PRECIPITATION SOUTH.
THURSDAY NIGHT-FRIDAY...VFR WITH GUSTY NORTHWEST WINDS.
&&
.MARINE...
THE MARINE HEADLINES REMAIN AS IS. LOWEST CONFIDENCE ABOUT GALE
WARNINGS BEING REACHED NORTHERN COASTAL WATERS. SOUTHERN OCEAN
WATERS HAVE ALREADY HAD SOME GALE FORCE GUSTS. WE KEPT THE ENDING
TIME OF THE GALES AS IS AT 03Z. THIS WILL LIKELY BE REPLACED BY A
SMALL CRAFT ADVISORY FOR THE OCEAN WATERS LATER THIS EVENING AND
SMALL CRAFT CONDITIONS ARE EXPECTED TO CONTINUE THROUGH MONDAY.
ON DELAWARE BAY...THERE SHOULD BE A LULL IN SMALL CRAFT ADVISORY
CONDITIONS AS THE SFC LOW PASSES THROUGH, THEN A PAIR OF BUMP UPS
FROM THE STRONGER WESTERLY FLOW THIS EVENING AND THE NORTHWESTERLY
FLOW ON MONDAY SHOULD BRING THEM BACK TO SMALL CRAFT ADVISORY
CRITERIA. THE ENDING TIME ON THE BAY MAY BE TOO LONG. PRETTY
CONFIDENT SCA CONDITIONS WILL BE DONE BY 23Z. WILL MAKE MENTION IN
THE MWW.
OUTLOOK...
MONDAY NIGHT THROUGH WEDNESDAY...MOSTLY SUB ADVISORY CONDITIONS...EXCEPT
POSSIBLE ADVISORY LEVEL ON LATE TUESDAY INTO EARLY TUESDAY NIGHT.
THURSDAY...A RETURN TO ADVISORY CONDITIONS POSSIBLE WITH A STORM
STRENGTHENING ACROSS THE AREA.
THURSDAY NIGHT AND FRIDAY...GALE CONDITIONS POSSIBLE.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...GALE WARNING UNTIL 10 PM EST THIS EVENING FOR ANZ450>455.
SMALL CRAFT ADVISORY UNTIL 6 PM EST MONDAY FOR ANZ430-431.
&&
SYNOPSIS...MIKETTA
NEAR TERM...GIGI
SHORT TERM...GIGI
LONG TERM...MIKETTA
AVIATION...KLINE/MIKETTA
MARINE...GIGI/MIKETTA