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000
FXUS61 KBUF 132031
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
331 PM EST FRI DEC 13 2013

.SYNOPSIS...
AN ARCTIC COLD FRONT WILL DROP SOUTH ACROSS OUR REGION THROUGH THIS
EVENING WITH SNOW SHOWERS AND LAKE EFFECT SNOW GRADUALLY
DIMINISHING. AN AREA OF LOW PRESSURE WILL THEN MOVE ACROSS THE
REGION OVER THE WEEKEND WITH WIDESPREAD ACCUMULATING SNOW SATURDAY
AND SATURDAY NIGHT. SOME LAKE EFFECT SNOW WILL LINGER SOUTHEAST OF
THE LAKES SUNDAY BEFORE DIMINISHING MONDAY. ANOTHER SYSTEM MAY BRING
THE NEXT ROUND OF SNOW ON TUESDAY WITH SOME LIMITED LAKE EFFECT SNOW
POSSIBLE THROUGH MIDWEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
THE LAKE ENHANCED SNOW OFF LAKE ERIE CONTINUES ACROSS PORTIONS OF
SOUTHERN ERIE AND WYOMING COUNTIES AND THE NORTHERN PORTION OF THE
SOUTHERN TIER...EVEN EXTENDING INTO THE WESTERN FINGER LAKES. THERE
IS SOME LAKE MOISTURE INVOLVED FOR SURE...BUT MUCH OF THE FORCING IS
NOW COMING FROM A RIBBON OF MID LEVEL FRONTOGENESIS AND SOME LOW
LEVEL CONVERGENCE FROM AN ADVANCING ARCTIC COLD FRONT. THIS MAY DROP
A FEW MORE INCHES ACROSS THE HIGHER TERRAIN OF THE SOUTHERN TIER
THROUGH EARLY EVENING. THE LAKE EFFECT SNOW WARNING WILL REMAIN IN
PLACE THROUGH 7PM TO COVER THIS NEW ACCUMULATION.

FARTHER NORTH...THE BAND OF FRONTAL SNOW AND LAKE ONTARIO REMNANTS
WHICH WAS OVER THE NIAGARA FRONTIER HAS WEAKENED CONSIDERABLY...
WITH JUST SOME LIGHT SNOW LEFT. THIS SHOULD CONTINUE TO SLOWLY
DIMINISH THROUGH EARLY EVENING. EAST OF ROCHESTER THERE IS NOTHING
ON RADAR...BUT SUSPECT THERE IS STILL SOME LIGHT MULTIPLE BANDS OF
LAKE EFFECT SNOW ACROSS MUCH OF WAYNE/N.CAYUGA/OSWEGO COUNTIES WITH
COLD NORTHERLY FLOW. ANY ADDITIONAL ACCUMS SHOULD BE VERY LIGHT
HOWEVER...SO ALL LAKE EFFECT ADVISORIES AND WARNINGS HAVE BEEN
DROPPED.

THROUGH THE EVENING HOURS LAKE EFFECT SNOW SOUTHEAST OF LAKE ERIE
SHOULD STEADILY DIMINISH AS FLOW BECOMES NORTHEAST. OFF LAKE
ONTARIO...MESOSCALE MODEL GUIDANCE SUGGESTS LAKE EFFECT MAY TRY TO
MAKE A RESURGENCE TO SOME EXTENT ON COLD NORTHEAST FLOW. THE BAND
SHOULD GET ORGANIZED BY MID TO LATE EVENING FROM WESTERN OSWEGO
COUNTY INTO WAYNE COUNTY ON NORTHEAST FLOW...THEN MOVE STEADILY WEST
ALONG THE SHORELINE PAST MONROE COUNTY AND INTO ORLEANS/NIAGARA
COUNTY RIGHT ALONG THE IMMEDIATE LAKESHORE BY DAYBREAK SATURDAY.
EQUILIBRIUM LEVELS REMAIN SHALLOW AT 6-7K FEET...BUT WITH A VERY
COLD LOW LEVEL AIRMASS AND THE POTENTIAL FOR SOME LAND BREEZE
CONVERGENCE...THIS MAY ALLOW FOR SOME DECENT SNOWFALL RATES OF VERY
FLUFFY SNOW. THE BAND SHOULD REMAIN MOBILE...SO FOR NOW HAVE KEPT
AMOUNTS SUB-ADVISORY IN THE 2-4 INCH RANGE...WITH THE MAJORITY OF
THAT IN A NARROW ZONE RIGHT ALONG THE LAKESHORE.

OUR ATTENTION THEN TURNS BACK TO THE SYNOPTIC SCALE AS A SYSTEM
APPROACHES THE OHIO VALLEY. AN INITIAL SOMEWHAT UNRELATED WING OF
WARM ADVECTION WILL DEVELOP LATER TONIGHT ACROSS THE WESTERN
SOUTHERN TIER. INCREASING ISENTROPIC UPGLIDE WILL PRODUCE AN AREA OF
LIGHT SNOW LATE TONIGHT ACROSS THE WESTERN SOUTHERN TIER. THIS MAY
PRODUCE AN INCH OR TWO OF ADDITIONAL SNOW FROM MIDNIGHT TO DAYBREAK
ACROSS THE SOUTHERN TIER.

ON SATURDAY LOW PRESSURE WILL MOVE INTO THE OHIO VALLEY...AND BY THE
END OF THE DAY SECONDARY COASTAL CYCLOGENESIS WILL BE STARTING ALONG
THE MID ATLANTIC COAST. LOW/MID LEVEL WARM ADVECTION WILL SUPPORT
INCREASING ISENTROPIC UPGLIDE...AND A LEAD SHORTWAVE WILL PROVIDE
SOME LARGE SCALE ASCENT. PERHAPS MOST IMPORTANT...A COUPLED UPPER
LEVEL JET STRUCTURE WILL DEVELOP ACROSS THE LOWER LAKES AND PROVIDE
ORGANIZED UPPER LEVEL DIVERGENCE.

THIS SHOULD ALL SUPPORT A WIDESPREAD STEADY SNOW...WHICH WILL
ALREADY BE ONGOING BY 7AM AS FAR NORTH AS THE THRUWAY FROM THE
FINGER LAKES WESTWARD. THIS WILL VERY SLOWLY SPREAD NORTHEAST...NOT
REACHING THE NORTH COUNTRY UNTIL LATE IN THE DAY OR EARLY EVENING.
EXPECT 2-3 INCHES OF SNOW FROM THE FINGER LAKES AND GENESEE VALLEY
WESTWARD WITH 3-4 INCHES CLOSER TO THE PA STATE LINE.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
MID WINTER WILL NOT RELENT AT ALL THIS TIME PERIOD WITH SEVERAL
EVENTS OF SNOWFALL WORTH WATCHING. THE FIRST EVENT WILL BE ONGOING
SATURDAY NIGHT.

ALOFT A BROAD RIDGE OF HIGH PRESSURE WILL BE FOUND OVER THE WESTERN
US...WHILE A LONG WAVE TROUGH OF LOW PRESSURE WILL BE FOUND OVER THE
EASTERN US. SEVERAL SHORTWAVES...A SOUTHERN STREAM AND A NORTHERN
STREAM WAVE WITHIN THIS DEEP TROUGH WILL SPAWN A PRIMARY LOW THAT
WILL TRACK THROUGH THE OHIO VALLEY...WHILE THE SOUTHERN STREAM
SHORTWAVE AIDS IN THE FORMATION OF A LEE LOW TO THE EAST OF THE
SOUTHERN APPALACHIANS...WITH THE SOUTHERN SHORTWAVE RAPIDLY
DEEPENING A COASTAL LOW ALONG THE ATLANTIC SEABOARD.

IN THE MID LEVELS A LLJ AT 925 HPA WILL BE ORIENTED FROM THE
VIRGINIAS NORTHWARD INTO CENTRAL AND EASTERN NEW YORK. ALOFT AT 250
HPA A 150 KNOT JET STREAK WILL BE ACROSS SOUTHERN QUEBEC/MAINE WITH THE
RIGHT ENTRANCE REGION OF THE JET OVER NORTHERN NEW YORK AND NEW
ENGLAND. ANOTHER JET STREAK OF 140 KNOTS WILL BE ADVANCE NORTHWARD
UP THE ATLANTIC COASTLINE. THE FAVORABLE LEFT EXIT OF THIS JET...ONE
THAT WILL PROMOTE UPWARD LIFT WILL BE ACROSS EASTERN NEW YORK AND
NEW ENGLAND.

ALOFT WARMING IN MID LEVELS AHEAD OF THE OHIO VALLEY LOW PRESSURE
WILL ALLOW FOR ISENTROPIC UPGLIDE AND WILL CONTINUE TO SPREAD A
SWATH OF FAIRLY STEADY LIGHT SNOW ACROSS NEW YORK STATE. THEN AS THE
INITIAL LOW ENTERS INTO EASTERN OHIO AND WESTERN PENNSYLVANIA
IT WILL TRANSFERS ITS ENERGY TO THE SECONDARY COASTAL LOW SATURDAY
NIGHT. FAVORABLE LIFT WILL CONTINUE A LIGHT SNOW ACROSS THE REGION
OVERNIGHT. THE COMBINATION OF FAVORABLE UPPER LEVEL DYNAMICS WITH A
COUPLED JET PROVIDING FOR UPPER LEVEL DIVERGENCE...AND LOW LEVEL
SUPPLYING LOW LEVEL CONVERGENCE...DEEP UPWARD MOTION SHOULD ALLOW
FOR SOME ENHANCEMENT TO THE SNOW SATURDAY NIGHT AND INTO EARLY
SUNDAY MORNING FROM THE GENESEE VALLEY EASTWARD. MAXIMUM VERTICAL
MOTION SHOULD BE FOUND ACROSS FAR EASTERN SECTIONS OF THE CWA...THE
EASTERN LAKE ONTARIO REGION WHERE SNOWFALL TOTALS COULD EXCEED A
HALF A FOOT. BELIEVE THE MODELS CONTINUE TO OVER DUE THE QPF AND
WILL MAINTAIN ADVISORIES...THOUGH WILL HAVE TO MONITOR FOR POSSIBLE
UPGRADE TO WARNINGS.

AS THE COASTAL LOW DEEPENS AND LIFTS NORTHEASTWARD...A TROUGH OF LOW
PRESSURE WILL LINGER BACK ACROSS THE CWA SUNDAY MORNING. CONVERGENCE
ALONG THIS FOCUS POINT WILL LIKELY PRODUCE LIGHT SNOW
SHOWERS...THOUGH WITH THE MOISTURE DIMINISHING EXPECT JUST LIGHT
SNOW SHOWERS SUNDAY MORNING TO BECOME MORE SCATTERED THROUGH THE MID
DAY HOURS.

THROUGH THE DAY SUNDAY A NORTHWEST FLOW WILL DEEPEN THE COLD AIR TO
-12C TO -14C OVER THE EASTERN GREAT LAKES. THIS COLD AIR WILL AGAIN
MAKE CONDITIONS PRIME FOR LAKE EFFECT SNOW WITH PARAMETERS OF
MODERATE LAKE INSTABILITY...LAKE INDUCED EQUILIBRIUM LEVELS RISING
TO AROUND 10K FEET...AND LITTLE DIRECTIONAL WIND SHEAR. A WEAK WAVE
OF LOW PRESSURE WILL RIDE SOUTHEASTWARD ALONG A LAKE AGGREGATED
TROUGH WITH ADDED CONVERGENCE ALONG THE LOW BRINGING AGAIN
CATEGORICAL POPS TO MUCH OF THE REGION SOUTH OF LAKE ONTARIO...AND
LIKELY EAST OF LAKE ONTARIO. WILL HAVE THE GREATEST POPS SOUTHEAST
OF THE LAKES WHERE LAKE EFFECT AND TERRAIN INFLUENCES WILL BRING
THE GREATEST THREAT FOR ACCUMULATING SNOWFALL.

THESE LAKE EFFECT SNOW SHOWERS WILL DECREASE IN COVERAGE AREA LATER
SUNDAY NIGHT AND MONDAY WITH THE PASSAGE OF THE WEAK SURFACE LOW.
HIGH PRESSURE COUPLED WITH DRIER AIR WILL BEGIN TO SNEAK NORTHWARD
INTO OUR REGION LATER THROUGH THE DAY ON MONDAY. WINDS WILL ALSO
BACK SOME WITH THIS HIGH PRESSURE AND WEAKENING LAKE SNOWS ACROSS
AREAS SOUTHEAST OF THE GREAT LAKES MAY LIFT NORTHWARD TOWARDS
BUFFALO/WATERTOWN BEFORE ENDING. THE AREA OF HIGH PRESSURE WILL ALSO
AID IN THE WEAKENING OF THE LAKE SNOWS...AND MAY ALLOW FOR SOME
SUNSHINE OUTSIDE OF THE WEAKENING SNOW BANDS.

TEMPERATURES THIS TIME PERIOD WILL CONTINUE TO RUN BELOW NORMAL.
HIGHS WILL RANGE FROM THE UPPER TEENS TO MID 20S...WITH OVERNIGHT
LOWS IN THE TEENS...WITH AROUND ZERO ACROSS THE INLAND NORTH
COUNTRY.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
THE MAIN FEATURE THIS TIME PERIOD WILL BE A CLIPPER LOW THAT WILL
CROSS THE EASTERN GREAT LAKES REGION TUESDAY OR TUESDAY NIGHT.
MODELS STILL HAVE SOME DISAGREEMENT ON THE TIMING WITH THE 12Z ECMWF
SUGGESTING A WAVE OF SNOW COMES ACROSS THE CWA...WHILE THE GFS
SUGGESTS A LIGHTER SNOW AND DELAYED MORE TOWARDS TUESDAY NIGHT. WE
WILL LIKELY SEE SOME SNOW THIS TIME PERIOD...THOUGH TIMING IS STILL
UNCERTAIN.

NORTHWEST FLOW WILL MAINTAIN SOME LAKE SNOWS SOUTHEAST OF THE LAKES
THROUGH THURSDAY...THEN FRIDAY IN RESPONSE TO A POTENT UPPER LEVEL
TROUGH DIVING DOWN INTO THE WEST COAST DOWNSTREAM RIDGING WILL BRING
INCREASING HEIGHTS AND WARMER TEMPERATURES TO THE REGION. FRIDAY
WILL LIKELY BE THE WARMEST DAY THIS FORECAST PERIOD AS 850S CLIMBING
TO 5 TO 8C ALONG WITH WARMING SOUTHERLY WINDS WILL BRING LOW 40S
ACROSS THE REGION. THERE WILL BE A SMALL CHANCE FOR A RAIN SHOWER
FRIDAY AHEAD OF THE NEXT STORM SYSTEM...THOUGH THE BETTER LIFT AND
MOISTURE WILL LIKELY HOLD OFF TO THE WEEKEND.

&&

.AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
AN ARCTIC COLD FRONT WILL SLOWLY SAG SOUTH ACROSS THE AREA WITH LAKE
ENHANCEMENT SOUTHEAST OF THE LAKES THROUGH LATE AFTERNOON OR EARLY
EVENING. FAIRLY WIDESPREAD IFR VSBY TO THE SOUTH OF LAKE ONTARIO
WILL GRADUALLY SHRINK IN COVERAGE...AND BY THIS EVENING MOST OF THE
IFR SHOULD BE CONFINED TO THE WESTERN SOUTHERN TIER AND A FEW LOCAL
SPOTS OF LAKE EFFECT BETWEEN KROC AND KFZY.

LOW PRESSURE MOVING INTO THE OHIO VALLEY WILL THEN ALLOW A GENERAL
SNOWFALL TO OVERSPREAD THE REGION LATE TONIGHT THROUGH SATURDAY WITH
VSBY DETERIORATING TO IFR FROM SOUTHWEST TO NORTHEAST. WIDESPREAD
IFR VSBY WILL CONTINUE THROUGH SATURDAY NIGHT IN SNOW.

OUTLOOK...
SUNDAY...MVFR/IFR WITH SNOW SHOWERS LIKELY AND AREAS OF LAKE SNOW
SOUTHEAST OF THE LAKES.
MONDAY...LAKE EFFECT SNOW SHOWERS WITH LOCAL IFR SOUTHEAST OF THE
LAKES DIMINISHING.
TUESDAY...POSSIBLE MVFR/IFR WITH A CHANCE OF SNOW SHOWERS.
WEDNESDAY...MAINLY VFR WITH A CHANCE OF SNOW SHOWERS.

&&

.MARINE...
NORTHERLY WINDS WILL CONTINUE TO PRODUCE MARGINAL SMALL CRAFT
CONDITIONS ON THE SOUTH SHORE OF LAKE ONTARIO THROUGH EARLY EVENING
BEFORE DIMINISHING AS HIGH PRESSURE BUILDS ACROSS SOUTHEAST CANADA.
LATER TONIGHT AND SATURDAY LOW PRESSURE WILL APPROACH FROM THE OHIO
VALLEY. THE PRESSURE GRADIENT BETWEEN THE HIGH OVER SOUTHEAST CANADA
AND THE APPROACHING LOW WILL ALLOW EAST TO NORTHEAST WINDS TO
INCREASE ON THE LOWER LAKES. THIS WILL BRING SMALL CRAFT ADVISORY
CONDITIONS AGAIN TO THE WEST HALF OF LAKE ONTARIO.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...WINTER WEATHER ADVISORY FROM 2 PM SATURDAY TO 10 AM EST SUNDAY
     FOR NYZ006>008.
     WINTER WEATHER ADVISORY FROM 6 AM SATURDAY TO 6 AM EST SUNDAY
     FOR NYZ001>005-010>014-085.
     WINTER WEATHER ADVISORY FROM 2 AM SATURDAY TO 6 AM EST SUNDAY
     FOR NYZ019>021.
     LAKE EFFECT SNOW WARNING UNTIL 7 PM EST THIS EVENING FOR
     NYZ012-019-020-085.
MARINE...SMALL CRAFT ADVISORY UNTIL 9 AM EST SUNDAY FOR LOZ042-043.
         SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR
         LOZ044-045.

&&

$$

SYNOPSIS...HITCHCOCK
NEAR TERM...HITCHCOCK
SHORT TERM...THOMAS
LONG TERM...THOMAS
AVIATION...HITCHCOCK
MARINE...HITCHCOCK