February 8, 2013 Pre Storm Forecast Discussion Binghamton

000
FXUS61 KBGM 080754
AFDBGM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BINGHAMTON NY
254 AM EST FRI FEB 8 2013

.SYNOPSIS…
A COMPLEX SYSTEM…WITH TWO LOW PRESSURE CENTERS THAT WILL MERGE
IN OUR VICINITY…WILL BRING SIGNIFICANT WINTER WEATHER TO THE
REGION. WHILE SOME SPOTTY LIGHT SNOW MAY GET STARTED THIS
MORNING…HEAVIER SNOWFALL RATES WILL DEVELOP THIS AFTERNOON
THROUGH EVENING. THE SNOW WILL THEN DIMINISH INTO SATURDAY
MORNING…BUT THE WIND WILL ALSO PICK UP FROM THE NORTHWEST WHICH
MAY CAUSE SOME BLOWING AND DRIFTING SNOW SATURDAY.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/…
8 PM UPDATE…
1037 MB SFC HIGH CONTS TO SIT ACRS QUEBEC PROVIDING NERN U.S. WITH
PLENTY OF CLD AIR. POTENT UL TROF SWINGING THRU THE MIDWEST ATTM
WITH WIDESPREAD SWATH OF PCPN EXTNDG FM MI DOWN TO SRN PLAINS.
SFC TROF EXTENDS FM SFC LOW NWRD ALONG THE GREAT LKS LEADING TO
SNOW NOW FALLING IN SRN ONTARIO. EXPECT THIS TROF WL LIFT TO THE
NORTH AS LL WINDS INCRS OUT OF THE SOUTH. AIRMASS WL SLOWLY
SATURATE OVRNGT TONIGHT AND AS TROF LIFTS THRU THE NRN ZONES VRY
LIGHT SNOW IS EXPECTED TO REACH THE GROUND OCCASIONALLY. THUS HV
DROPPED POPS TO LOCHC CATEGORY EVERYWHERE THRU 10Z AS SNOW WL LKLY
HV A HARD TIME OVERCOMING DRY ATMOS.

LOOKING AHD, WRN WV WL MV PCPN EASTWARD WHILE H5 WV LIFTS INTO THE
CAROLINAS BY 12Z. 18Z GFS IS IN LOCK-STEP WITH 12Z RUN WITH ENERGY
TRANSFER OCCURRING FRI EVNG. 24-HR QPF AMNTS THRU 12Z SATURDAY
CONT TO INDICATE TWO DISTINCT AREAS OF ARND 1.00 INCH AMNTS, GNRLY
IN THE FINGER LKS AND ALSO TWD THE WRN CATSKILLS. AVG QPF AMNTS
FOR RMNDR OF THE AREA RANGES FM 0.5 TO 0.7 INCHES. 18Z GFS
INDICATES MAX SNOWFALL RATES EXPECTED TO OCCUR SOMETIME LATE FRI
AFTN AND THRU 06Z SATURDAY. AT THIS TIME, SNOW RATIO VALUES
EXPECTED TO RANGE FM 10-15:1.

NO CHGS NEEDED TO WARNING PRODUCTS AT THIS TIME AS THINGS RMN
STATUS QUO.

PREV DISCO BLO…

345 PM UPDATE… THE LEADING EDGE OF THE -SN IS STREAKING ACRS SRN
ONT AND INTO THE IAG FRONTIER OF WRN NY LATE THIS AFTN. AS ISEN
LIFT GRADUALLY INCREASES OVER OUR NRN ZNS TNT…WITH DEEPENING
MOISTURE…FLRYS SHOULD FIRST DVLP THIS EVE…WITH A STEADIER -SN
AFTER 06Z…PARTICULARLY OVER NRN ONEIDA. AMTS BY 12Z SHOULD
MAINLY BE 1" OR LESS.

ELSEWHERE…CLDS WILL SLOWLY LWR AND THICKEN…BUT ONLY A FEW FLRYS
ARE ANTICIPATED…AT WORST.

PREV DISC… UPDATED AT 1020 AM…MID LEVEL CLOUDS CONTINUE TO
THICKEN ACROSS THE AREA LATE THIS MORNING IN ADVANCE OF THE NEXT
STORM SYSTEM. SKIES WILL END UP CLOUDY ACROSS THE ENTIRE AREA THIS
AFTERNOON. MADE MINOR ADJUSTMENTS TO TEMPERATURES TO ACCOUNT FOR
LATEST TRENDS.

QUICK LOOK AT LATEST 12Z NAM INDICATES PERHAPS THE POTENTIAL FOR A
LITTLE MORE SNOW IN OUR AREA AS THE 500 MB LOW CLOSES OFF A LITTLE
FARTHER WEST… NOW OVER SOUTHEAST PA BY 06Z SATURDAY. THE SURFACE
LOW TRACK ALSO IS FORECAST SLIGHTLY FARTHER WEST THAN PREVIOUS
RUNS. NAM QPF HAS ALSO SLIGHTLY INCREASED TO THE WEST WITH
SIGNIFICANT SNOW FORECAST TO LINGER THROUGH MUCH OF FRIDAY NIGHT.
HOWEVER WILL WAIT FOR THE 12Z GFS BEFORE MAKING ANY CHANGES.
EXPECT WOBBLES IN THE MODEL FORECASTS WILL CONTINUE WITH THIS
COMPLEX SYSTEM INVOLVING TRANSFER OF ENERGY FROM MIDWEST SYSTEM TO
SYSTEM DEVELOPING OFF THE MID ATLANTIC COAST. THESE TYPES OF
SYSTEMS ARE NOTORIOUSLY DIFFICULT TO FORECAST FOR OUR AREA.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY/…
4 PM UPDATE… COMPLICATED FCST SCENARIO STILL IN PLAY FOR FRI/FRI
NGT.

THE TRICKIEST ASPECT REMAINS INTERACTION BETWEEN A STRENGTHENING
NRN STREAM WV…COMING IN FROM THE W…AND A NEG TILT TROUGH
COMING UP THE E COAST. THE NAM/EC/GEM HAVE PHASING BETWEEN THESE
SYSTEMS OCCURRING CLOSEST TO OUR FA BY ARND 00Z SAT (NEAR THE NJ
COAST/S OF LONG ISLAND)…WHILE THE GFS IS A BIT FARTHER N AND E.
CONSEQUENTLY…THE GFS HAS SOMEWHAT LESS QPF…SPCLY FOR SWRN PTNS
OF THE CWA. OVERALL…THOUGH…A BLEND OF THESE MODELS…ALG WITH
HPC OUTPUT…YIELDS FAIRLY SIMILAR SNOW ACCUMS TO OUR PREV
UPDATE…MAYBE JUST A TOUCH HIGHER FOR PTNS OF THE SRN TIER AND NE
PA. AS A RESULT…WE`VE DECIDED TO HOIST WS WRNGS AREA-WIDE (A
GENERAL 6-12" FOR OUR NRN ZNS…8-12" AND LOCALLY HIGHER IN THE
WRN CATSKILLS AND POCONOS…AND 5-8" FOR MUCH OF THE SRN
TIER…AND THE REST OF NE PA). THIS ALSO MATCHES WELL WITH OUR
NEIGHBORING WFO`S.

EXCEPT IN OUR FAR NRN ZNS…WHERE -SN WILL BE ONGOING…MUCH OF
THE AM…AND EVEN EARLY AFTN HRS…LOOK TO FEATURE LGT AND SPOTTY
PCPN. THE "MAIN EVENT" SHOULD TAKE SHAPE IN OUR NRN/WRN ZNS FROM
ABT 18-21Z…SPREADING EWD THEREAFTER. THE BEST SNOW RATES
(LOCALLY 1-2" PER HOUR) WILL LIKELY CONCENTRATE FROM 21-04Z…WHEN
THE MORE NRN UPR WV AMPLIFIES A BIT…AND ATTEMPTS TO PULL SOME
COASTAL MOISTURE NWWD INTO CNY/NE PA. ONCE THE TWO SYSTEMS BEGIN
TO FULLY MERGE LTR FRI NGT…THE COASTAL LOW SHOULD "BOMB
OUT"…WITH SNOW INTENSITY WANING BACK INLAND OVER OUR CWA
BY/AFTER 06Z.

SAT LOOKS MUCH QUIETER…ALBEIT BLUSTERY…AS A TIGHT PRES
GRADIENT RESIDES OVER CNY/NE PA. -SHSN/FLRYS SHOULD DIMINISH BY
THE AFTN…AS DRIER AIR COMES IN FROM THE W AND NW.
MEANWHILE…BLIZZARD CONDS ALG THE NEW ENG COAST…MAY FINALLY
START TO LET UP BY LTR IN THE DAY/SAT EVE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/…
FORECAST TWEAKED FOR LATEST HPC GUIDANCE/MODEL INFORMATION WHERE
NEEDED…OVERALL NO BIG CHANGES. CONFIDENCE CONTINUES TO INCREASE
FOR A DASH OF FREEZING RAIN LATE SUNDAY NIGHT INTO MONDAY
MORNING…SINCE SURGE OF ABOVE FREEZING AIR ALOFT WILL FAR OUTPACE
TEMPERATURES AT THE SURFACE WHICH WILL INITIALLY STILL BE BELOW
FREEZING. POPS WERE INCREASED TO CARRY A SPOKE OF LIKELY RANGE
THROUGH THE REGION DURING THAT TIME…WITH RAIN/FREEZING RAIN AS
WEATHER TYPE. ICE ACCUMULATIONS LOOK LIKE THEY WILL BE LIGHT…YET
ALSO A GOOD CHANCE OF IMPACTING MONDAY MORNING SCHOOL AND WORK
COMMUTES. AS IS ALREADY THE CASE…THIS FREEZING RAIN POTENTIAL
WILL STAY MENTIONED IN THE HAZARDOUS WEATHER OUTLOOK.

PREVIOUS DISCUSSION…
LTL CHG TO THE MED RNG FCST WITH A FAIRLY QUIET PD IN STORE. WE
COULD SEE A MIXED PCPN EVENT LATE SUN NGT/MON MRNG AS SFC FNT…
ASSCD WITH A SFC CYCLONE LIFTING INTO THE GTLAKES…PASSES THE
RGN. PROFILES SHOW POTNL FOR -FZRA OR -IP AND HAVE RETAINED IN THE
FCST. THIS FNT PASSES ON MONDAY WITH PCPN LIKELY DCRSNG IN THE
AFTN. CONFIDENCE DECREASES AFTER THIS TIME WITH SUBTLE TIMING
DIFFS IN MINOR S/WV`S…ANOTHER MORE SIG SRN STREAM SYSTEM MAY
APRCH LATE IN THE WEEK IF GFS PANS OUT. SOME MINOR LES ALSO LIKELY
FOR FVRD AREAS. FOR THE MOST PART WE USED WITH HPC GDNC WITH ONLY
MINOR TWEEKS.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/…
SOUTHEASTERLY WINDS AHEAD OF COMPLEX DOUBLE-LOW PRESSURE SYSTEM IS
ALREADY BRINGING IN SHALLOW MOISTURE IN THE FORM OF DEVELOPING
MVFR CIGS. HOWEVER…WITH CONTINUED DRY LAYER BETWEEN ABOUT 4KFT
AND 10 KFT AGL…NOT YET EXPECTING PRECIPITATION TO CONNECT
THROUGH PRIOR TO 12Z EXCEPT PERHAPS KRME WHERE CONDITIONS ARE A
BIT MORE FAVORABLE /THOUGH STILL MVFR/. BETWEEN 12Z-
18Z…SOME SPOTTY -SN MAY START BUT STILL MVFR CONDITIONS/CIGS.
HOWEVER…THE MERGING OF STRONG COASTAL LOW PRESSURE TO OUR
SOUTHEAST…AND GREAT LAKES LOW MOVING IN FROM THE WEST…WILL CAUSE
RAPIDLY DETERIORATING CONDITIONS AFTER 18Z…AND ESPECIALLY DURING
22Z FRI-04Z SAT TIME FRAME WHEN PEAK OF THE SYSTEM WILL CAUSE
AIRPORT OPERATING MINS TO BE APPROACHED AND PERHAPS REACHED AT
TIMES DUE TO HEAVY SNOW…SEE TAFS FOR SPECIFICS ON TIMING. EAST
TO SOUTHEAST WINDS THROUGH ABOUT 18Z…WILL BACK NORTHEASTERLY AS
THE SYSTEM EVOLVES 18Z FRI- 06Z SAT…BUT EVEN GUSTS SHOULD
GENERALLY STAY UNDER 20 KTS.

.OUTLOOK…

LATE FRI NGT…IFR TO MVFR IN SNOW…POSSIBLY WORSE THAN IFR IN
SPOTS EARLY.

SAT…MVFR/POSSIBLE IFR AT CNTRL NY TERMINALS MAINLY EARLY MORNING
AS -SN AS DEPARTING SYSTEM WINDS DOWN.

SAT NGT/SUN…VFR.

SUN NGT/MON…MVFR/IFR POSSIBLE IN A WINTRY MIX /INCLUDING
FREEZING RAIN/…CHANGING TO ALL RAIN ON MON.

TUE…SCT MVFR CNTRL NY IN -SHSN…VFR ELSEWHERE.

&&

.BGM WATCHES/WARNINGS/ADVISORIES…
PA…WINTER STORM WARNING FROM 10 AM THIS MORNING TO 7 AM EST
SATURDAY FOR PAZ038>040-043-044-047-048-072.
NY…WINTER STORM WARNING FROM 10 AM THIS MORNING TO 7 AM EST
SATURDAY FOR NYZ022>025-044>046-055>057-062.
WINTER STORM WARNING UNTIL 7 AM EST SATURDAY FOR NYZ009-
015>018-036-037.

&&

$$
SYNOPSIS…MDP/RRM
NEAR TERM…MLJ/PVN
SHORT TERM…MLJ
LONG TERM…MDP
AVIATION…MDP

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