-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 291441
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
941 AM EST THU JAN 29 2015

.SYNOPSIS...
HIGH PRESSURE OVERHEAD THIS MORNING WILL MOVE OFFSHORE LATE IN THE
AFTERNOON. LOW PRESSURE WILL MOVE ACROSS NEW YORK TONIGHT AND THEN
ACROSS THE NEW ENGLAND WATERS FRIDAY NIGHT. IT WILL SEND AN ARCTIC
FRONT ACROSS OUR AREA EARLY FRIDAY. HIGH PRESSURE WILL BUILD IN FOR
MOST OF THE WEEKEND. A LOW PRESSURE SYSTEM IS EXPECTED TO MOVE JUST
SOUTH OF THE AREA SUNDAY NIGHT THROUGH MONDAY NIGHT. HIGH PRESSURE
WILL BUILD BACK IN FOR THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
NO BIG CHANGES WITH THIS ESTF UPDATE. THE MESOSCALE MODELS REMAIN
PRETTY TIGHTLY CLUSTERED AS TO THE ONSET OF PRECIPITATION PRETTY
CLOSE TO 00Z ALG THE DE VLY. THERE IS A SOUTHWARD DP/DT TREND WITH
THE HRRR. WE HAVE NOT ARRIVED WITHIN THE HOURS OF CONCERN AND THE
LATEST 12Z NAM REMAINS DRY IN THE SRN PART OF OUR CWA. WE WILL SEE
IF THE TREND CONTINUES TO UP POPS WITH THE NEXT UPDATE. MORNING
12Z SOUNDINGS SHOWING PLENTY OF DRY AIR BELOW 700MB. THIS IS A
GOOD THING BECAUSE PRECIPITATION WOULD EVAP COOL TO SNOW. BASED ON
FCST SOUNDINGS (NO TEMPS ALF GET >2C) IN OUR CWA CONTINUES
PREVIOUS SHIFT`S THINKING IN THE SRN PART OF OUR CWA OF EITHER
SNOW OR SLEET AS A NON LIQUID PTYPE AND NOT FREEZING RAIN. THE
12Z SOUNDINGS MAXT MACROS GIVE AROUND 40F FOR MAX TEMPS, BUT WITH
CLOUDS ARRIVING AND SNOW COVER, WE JUST DID A SLIGHT UPWARD NUDGE.
MUCH CLOSER TO CONTINUITY THAN THE SOUNDING SUGGESTIONS.

SURFACE HIGH PRESSURE WAS CENTERED BETWEEN THE EAST COAST AND THE
APPALACHIANS. THERE HAS BEEN A FAIRLY LARGE TEMP SPREAD ACROSS THE
AREA. TEMPS HAVE DROPPED INTO THE SINGLE DIGITS IN THE SHELTERED
VALLEYS OF NE PA AND NW NJ WHERE THE HIGH IS DIRECTLY OVERHEAD AND
WINDS WERE CALM. THERE IS ENOUGH OF A PRESSURE GRADIENT FARTHER
SOUTH AND EAST FOR A LIGHT NW WIND TO KEEP TEMPS STEADY IN THE UPPER
TEENS/LOWER 20S ACROSS THE DELMARVA, FAR SE PA AND S NJ. HOWEVER,
THESE AREAS HAVE A CHANCE TO COOL SEVERAL MORE DEGREES THRU DAYBREAK
AS THE HIGH BUILDS TOWARD THE COAST.

THE HIGH WILL MOVE OFFSHORE IN THE AFTERNOON WHILE AN AREA OF LOW
PRESSURE THAT IS CURRENTLY OVER THE MIDWEST TRACKS EASTWARD TOWARD
THE MID-ATLANTIC STATES LATE IN THE DAY. AFTER A SUNNY START TO THE
MORNING, HIGH AND MID CLOUDS AHEAD OF THIS SYSTEM WILL OVERSPREAD
OUR AREA LATER THIS MORNING AND LOWER/THICKEN DURING THE AFTERNOON.

THERE IS GOOD MODEL AGREEMENT REGARDING THE TIME OF ARRIVAL FOR THE
PRECIP LATE THIS AFTERNOON IN OUR FAR WESTERN ZONES (MPO-RDG-MQS-ESN
ROUGHLY BETWEEN 4 PM AND 6 PM). NOTE THAT WE DID SPEED UP THE ONSET
AN HOUR OR TWO EARLIER AS MODELS OFTEN ARE TOO SLOW WITH THE LEADING
WAA BAND. THERMAL PROFILES SUPPORT PTYPE STARTING OUT AS SNOW IN PA,
SN/IP IN NE MD/FAR N DELMARVA AND RA/IP TOWARD QUEEN ANNE`S AND
TALBOT.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
LOW PRESSURE WILL MOVE THROUGH THE EASTERN GREAT LAKES THIS EVENING.
THE INITIAL SHIELD OF PRECIP THAT IS EXPECTED TO BE ENTERING OUR FAR
WESTERN ZONES BY THE START OF THE PERIOD WILL SPREAD EASTWARD DURING
THE EARLY AND MID EVENING AS A LEADING SHORTWAVE TROUGH ALOFT SWINGS
THRU. PTYPE FROM PHILLY AND POINTS NORTHWARD WILL BE ALL SNOW. A
WARM NOSE ALOFT IS FORECAST TO CAUSE SNOW TO MIX WITH SLEET IN THE
NORTHERN DELMARVA AND THE SOUTHERN MOST LOCATIONS IN NJ. WARMER SFC
TEMPS WILL LIKELY RESULT IN MAINLY RAIN ACROSS SOUTHERN DE AND
ADJACENT MD ZONES.

POPS AND SNOWFALL AMOUNTS ARE HIGHEST ALONG AND NORTH OF THE I-78
CORRIDOR, WHERE SYNOPTIC LIFT WILL BE GREATEST AND LESS TRANSITORY
CLOSER TO THE SURFACE LOW. FORECAST SNOWFALL AMOUNTS WITH THIS EVENT
ARE AROUND 1-2 FOR THESE AREAS. THERE IS CERTAINLY A POSSIBILITY FOR
LOCALLY HIGHER AMOUNTS UP TO 3 INCHES MAINLY ACROSS THE HIGHER
ELEVATIONS IN NORTHEAST PA AND NORTHWEST NJ BUT NOT EXPECTING IT TO
BE WIDESPREAD ENOUGH TO WARRANT A WINTER WX ADVISORY.

THE MAJORITY OF THE SNOW IS EXPECTED TO MOVE OUT OF THE AREA BY
MIDNIGHT. HOWEVER, SOME LIGHT SNOW MAY LINGER OVERNIGHT IN NORTHEAST
PA AND NORTHERN NJ.

WE ARE NOT ANTICIPATING TEMPS TO FALL MUCH DURING THE OVERNIGHT WITH
CLOUD COVER BLANKETING THE AREA AND A SOUTHWEST WIND AHEAD OF A COLD
FRONT.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
FRIDAY...THE ARCTIC FRONT AND LOW PRESSURE NORTH OF THE REGION WILL
BE MOVING AWAY. SCT SNOWS ACROSS THE NORTHERN AREAS JUST AFTER 12Z
WILL REMAIN INTO THE MORNING BEFORE DIMINISHING. COLD AND WINDY
CONDITIONS DEVELOPING WITH TEMPS NOT CHANGING MUCH...REMAINING IN
THE LOW 30S NORTH AND MID 30S SOUTH. TEMPS MAY BEGIN TO FALL DURING
THE AFTERNOON AS THE COLD AIR ADVECTION INCREASES. WINDS GUSTING TO
25 TO 35 MPH AT TIMES. WIND CHILLS IN THE SINGLE DIGITS OVER THE SRN
POCONOS...TEENS ACROSS THE NRN THIRD OF THE AREA AND LOW 20S
ELSEWHERE.

FRI NIGHT THRU SUN MORNING...HIGH PRESSURE REMAINS ACROSS THE AREA.
A DRY FCST BUT BITTER COLD TEMPS CONTINUE SAT WITH SOME MODERATION
SUNDAY. HIGHS SAT MOSTLY TEENS (NORTH) AND LOW 20S (SOUTH) WIND
CHILLS MOSTLY SINGLE DIGITS EARLY WITH SUB ZERO FAR NORTH. A WIND
CHILL FLAG MAY BE NEEDED. WIND CHILLS IN THE TEENS ACROSS THE
DELMARVA AND SRN NJ.

SUN AFTERNOON THRU MONDAY...ANOTHER LOW PRESSURE SYSTEM WILL AFFECT
MUCH OF THE AREA. AFTER MORE DISORGANIZED SOLUTIONS FOR THE SYSTEM
WITH THE 12Z WED MODELS...THE 00Z THU OP MODELS HAVE AGAIN SWUNG
BACK TO WETTER SOLUTIONS FOR OUR AREA. GFS...MOVES LOW PRESSURE FROM
THE CAROLINAS UP OFF THE DELMARVA THEN JUST EAST OF 40/70 MONDAY. A
DECENT SWATH OF MODERATE QPF (MOSTLY SNOW) TO MUCH OF THE FORECAST
AREA. EC...WEAKER LOW PRESSURE MOVES FROM THE CAROLINAS UP WELL EAST
OF THE 40/70 MARK WITH SLOWER DEEPENING. STILL SOME SNOW TO THE
AREA...BUT MUCH LIGHTER AND THE HIGHER TOTALS ARE ACROSS THE
DELMARVA AND SRN NJ. CMC...MUCH CLOSER...STRONGER AND VERY WET.
AREAS S/E OF I-95 WOULD CHANGE TO RAIN MON WITH THE CMC SOLUTION.

THERE CAN BE A TENDENCY FOR A NORTHWARD TRACK BIAS WITH SYSTEMS WHEN
A STRONG HIGH IS NORTH/NORTHWEST OF THE SYSTEM. THE GFS/CMC MODELS
MAY BE DISPLAYING THIS...SO WE HAVE GONE WITH THE WPC NUMBERS FOR
NOW AND OFFERED THE HIGH CHC/LOW LIKELY POPS FOR THESE PERIOD. NOT
MUCH OF A CHANGE FROM PREVIOUS FCST. WITH THIS WRITTEN...AN
INCREASING CHC FOR AN ACCUMULATING SNOW FOR SUN NIGHT MONDAY FOR THE
SRN/ERN PARTS OF THE CWA. WE WILL MAKE MENTION OF THIS IN THE HWO
AND ASK USERS TO CONTINUE TO FOLLOW THIS SYSTEM OVER THE NEXT FEW
DAYS. MODELS HAVE YET TO LOCK ON TO A SOLUTION...BUT MAY BE
BEGINNING TO SETTLE...WITH AT LEAST MORE AGREEMENT THAN THIS TIME
LAST NIGHT.

MON NIGHT THRU WED...MORE HIGH PRESSURE WITH COLD TEMPS TUE AND A
BIT WARMER WED. A MOSTLY DRY FCST FOR THIS PERIOD.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

VFR THIS MRNG AND FIRST PART OF THE AFTN. EXPECT A BAND OF SNOW TO
REACH THE WRN TERMINALS LATE IN THE DAY (RDG AROUND 22Z AND ABE
23Z). VSBYS WILL LIKELY LOWER TO IFR QUICKLY AFTER ONSET OF SNOW.
SNOW MOVES EWD TOWARD THE I-95 TERMINALS BETWEEN 00Z-02Z. THIS
WILL BE A QUICK MOVING SYSTEM, SO ONLY EXPECTING A BRIEF, 3-6 HOUR,
PERIOD OF SNOW. SLEET MAY MIX IN AT ILG/MIV/ACY BUT CONFIDENCE IN
PRECIP MAKING IT TO ACY IS RELATIVELY LOW FOR THIS CLOSE TO THE
EVENT. SNOW MAY LINGER OUT TOWARD ABE-RDG AFTER MIDNIGHT.

WINDS WILL BE LIGHT THIS MORNING, BECOMING SLY THIS AFTN/EVE AND
SWLY OVERNIGHT 5-10 KT.

OUTLOOK...
FRIDAY THRU SUN MORNING...VFR EXPECTED. GUSTY WINDS FRIDAY.
SUN AFTERNOON THRU MONDAY...LOWERING CIGS. SNOW WITH MVFR/IFR POSSIBLE.

&&

.MARINE...
LIGHT WINDS TODAY WITH HIGH PRESSURE OVERHEAD. THE HIGH SHIFTS
OFFSHORE TONIGHT AND SOUTHWEST WINDS INCREASE. SCA WAS ISSUED FOR
THE COASTAL ZONES, WHICH STARTS AT 11 PM AND CONTINUES THRU THE
OVERNIGHT. WAVES WILL BUILD TO NEAR 5 FT DURING THE OVERNIGHT.

OUTLOOK...
SAT THRU SUN...GALE WARNINGS ISSUED. WINDS AND SEAS SUBSIDE BACK
  TO SCA CONDITIONS SUNDAY. FREEZING SPRAY EXPECTED.
SUN NIGHT...SUB-SCA CONDITIONS.
MON THRU TUE...SCA CONDITIONS. WINDS/SEAS SUBSIDE TUE AFTERNOON.
TUE NIGHT THRU WED...SCA SEAS POSSIBLE.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 11 PM THIS EVENING TO 6 AM EST
     FRIDAY FOR ANZ450>455.
     GALE WARNING FROM 6 AM FRIDAY TO 6 AM EST SATURDAY FOR ANZ430-
     431-450>455.

&&

$$
SYNOPSIS...O`HARA
NEAR TERM...GIGI/KLEIN
SHORT TERM...KLEIN
LONG TERM...O`HARA
AVIATION...KLEIN/O`HARA
MARINE...KLEIN/O`HARA