Lake Effect Snow Advisory 33, NWS Buffalo, NY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
332 AM EST MON DEC 30 2013

.SYNOPSIS...
MUCH COLDER AIR BEHIND A DEPARTING COLD FRONT WILL DEEPEN ACROSS OUR
AREA TODAY AND GENERATE WEAK LAKE EFFECT SNOW SOUTHEAST OF THE
LAKES. THE SNOW WILL TAPER OFF THIS AFTERNOON AS HIGH PRESSURE
BUILDS ACROSS NEW YORK STATE. LOW PRESSURE MOVING EAST FROM THE
CENTRAL GREAT LAKES WILL BRING A GENERAL SNOWFALL AND SOME LAKE
ENHANCED SNOW ON TUESDAY. VERY COLD AIR THAT FOLLOWS THIS LOW WILL
LAST THROUGH THE END OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
THE LATEST SURFACE MAP SHOWS THE COLD FRONT FRONT ADVANCING INTO
EASTERN NEW YORK STATE EARLY THIS MORNING. COLDER AIR ADVECTING
BEHIND THE FRONT DOES NOT HAVE A LOT OF LOW LEVEL MOISTURE TO
INTERACT WITH. CONSEQUENTLY...REGIONAL RADARS SHOW RATHER WEAK
RETURNS WITH MULTIPLE BANDS OF SNOW FORMING OVER WESTERN LAKE
ONTARIO AND SOUTHEAST OF LAKE ERIE. CONDITIONS FOR LAKE EFFECT SNOW
SHOWERS WILL IMPROVE AS COLDER AIR ADVECTS INTO WESTERN NEW YORK
WHILE THE LOW LEVEL MOISTURE INCREASES (SEE 00Z KDTX  SOUNDING).
HIGHEST SNOW ACCUMULATIONS ARE EXPECTED ALONG THE CHAUTAUQUA RIDGE
WHERE ONE TO TWO INCHES MAY ACCUMULATE BEFORE DAYBREAK. ELSEWHERE
ACROSS THE AREA...EXPECT LESS THAN AN INCH OF SNOW.

MEANWHILE...HIGH PRESSURE CENTERED OVER THE MIDWEST WILL MOVE TO THE
EAST AND CREST OVER NEW YORK STATE THIS AFTERNOON. MUCH DRIER AIR
AND STRONG SUBSIDENCE IN THE VICINITY OF THE HIGH WILL CAUSE ANY
LINGER LAKE SNOWS TO WEAKEN AND DIE OUT BEFORE THE END OF THE DAY.
BEFORE THE SNOW DOES END...AN ADDITIONAL INCH MAY ACCUMULATE ALONG
THE CHAUTAUQUA RIDGE...WHILE ANOTHER INCH OR TWO IS POSSIBLE
SOUTHEAST OF LAKE ONTARIO. AREAS OUTSIDE OF THE LAKE EFFECT...WILL
SEE A GRADUAL INCREASE IN SUNSHINE.

TEMPERATURES EARLY THIS MORNING RANGE FROM THE LOWER 30S EAST OF
LAKE ONTARIO TO THE LOWER 20S AND MID 20S ACROSS THE FAR WEST. THIS
WILL BE THE WARMEST PART OF THE DAY AS TEMPERATURES DIP INTO THE
TEENS AFTER DAYBREAK.

AS THE SURFACE RIDGE SHIFTS EAST INTO NEW ENGLAND TONIGHT...OUR
FOCUS WILL TURN TO THE NEXT CLIPPER THAT WILL BE HEADING EAST TOWARD
WESTERN NEW YORK. WARM AIR ADVECTION AND INCREASING MOISTURE AHEAD
OF THIS SYSTEM WILL CAUSE SOME LIGHT SNOW TO DEVELOP ACROSS WESTERN
NEW YORK AND THE GENESEE VALLEY BEFORE DAYBREAK TUESDAY.
SUPER-IMPOSED ON THIS GENERAL AREA OF LIGHT SNOW...EXPECT A NARROW
BAND OF LAKE ENHANCED SNOW TO SET UP NORTHEAST OF LAKE ERIE AS THE
BOUNDARY LAYER WINDS LINE UP FROM SOUTHWEST. ONE TO THREE INCHES OF
SNOW MAY ACCUMULATE OVER WESTERN NIAGARA COUNTY...WITH LOWER
ACCUMULATIONS THE FARTHER EAST YOU GO.

THE ANTICIPATED INCREASE IN CLOUD COVER AND SOUTHERLY WINDS WILL
ALLOW TEMPERATURES TO WARM UP A FEW DEGREES TONIGHT...ESPECIALLY
NORTHEAST OF LAKE ERIE.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
ON TUESDAY A FAST MOVING CLIPPER WILL PASS BY JUST NORTH OF LAKE
ONTARIO. THIS FEATURE WILL PRODUCE A LITTLE LIGHT SNOW ACROSS MOST
OF THE AREA WITH WEAK WARM ADVECTION AND ISENTROPIC UPGLIDE
INITIALLY ON THE FRONT SIDE OF THE SYSTEM...THEN A PERIOD OF DPVA
AND LOW LEVEL CONVERGENCE WITH THE MID LEVEL SHORTWAVE AND SURFACE
COLD FRONT. OUTSIDE OF LAKE ENHANCED AREAS ANY ACCUMULATIONS SHOULD
BE AN INCH OR LESS.

THE AIRMASS IS PLENTY COLD ENOUGH TO SUPPORT A RESPONSE FROM THE
LAKES HOWEVER...WITH A COMPLEX LAKE ENHANCED SNOW SCENARIO APPEARING
LIKELY. LAKE INDUCED EQUILIBRIUM LEVELS RISE TO AROUND 10K FEET NEAR
THE TIME OF THE COLD FRONTAL PASSAGE...FOLLOWED BY A PERIOD OF
MODERATE INSTABILITY AND EQUILIBRIUM LEVELS AROUND 9K FEET TUESDAY
AFTERNOON AND EVENING. THE BETTER INSTABILITY WILL FADE TUESDAY
NIGHT OFF LAKE ERIE AS SURFACE HIGH PRESSURE BUILDS NEAR THE LAKE...
BUT WILL LINGER INTO WEDNESDAY MORNING OFF LAKE ONTARIO.

OFF LAKE ERIE...
LATEST MESOSCALE MODEL GUIDANCE CONTINUES TO SUGGEST A BAND OF
MODERATE TO HEAVY LAKE ENHANCED SNOW WILL DEVELOP ACROSS THE NIAGARA
FRONTIER EARLY IN THE MORNING...THEN SWING SOUTH ACROSS THE BUFFALO
METRO AREA DURING THE MID MORNING BEFORE SETTLING INTO SOUTHERN
ERIE/WYOMING COUNTIES AND EVENTUALLY THE SOUTHERN TIER DURING THE
AFTERNOON. THE SNOW WILL NOT LAST LONG ACROSS THE NIAGARA FRONTIER
OR IMMEDIATE BUFFALO AREA...BUT THE INSTABILITY AND STRONG
CONVERGENCE MAY SUPPORT HIGH SNOWFALL RATES FOR A BRIEF PERIOD OF
TIME AND DUMP A QUICK 2-4 OR 3-5 INCH ACCUMULATION.

BY AFTERNOON WITH THE CLIPPER PULLING AWAY THE LAKE ENHANCEMENT WILL
TRANSITION INTO MORE PURE LAKE EFFECT ON WESTERLY FLOW ACROSS THE
SOUTHERN TIER. THE BOUNDARY LAYER FLOW WILL CONTINUE TO VEER MORE
WNW BY TUESDAY EVENING. THE CONSTANT CHANGE IN WIND DIRECTION WILL
LIMIT THE RESIDENCE TIME OF THE BAND OVER ANY ONE LOCATION...SO THIS
SHOULD KEEP AMOUNTS IN THE ADVISORY RANGE ACROSS THE WESTERN
SOUTHERN TIER. THE MOST PERSISTENT BANDS MAY PRODUCE 4-8 INCHES IN
SOME SPOTS TUESDAY AND TUESDAY EVENING.

LATER TUESDAY NIGHT AND WEDNESDAY THE LAKE EFFECT SHOULD SLOWLY
DIMINISH TO SCATTERED LIGHT SNOW SHOWERS ACROSS THE SOUTHERN TIER AS
INVERSION HEIGHTS LOWER TO AROUND 5K FEET.

WITH THE ABOVE IN MIND...WE WILL GO WITH AN ADVISORY FOR NORTHERN
ERIE AND GENESEE COUNTIES FOR A BRIEF HEAVY BAND OF SNOW TUESDAY
MORNING. ADVISORIES WILL ALSO BE POSTED FROM SOUTHERN ERIE AND
WYOMING COUNTIES INTO THE SOUTHERN TIER TUESDAY AND TUESDAY EVENING.
FOR NOW HAVE LEFT ALLEGANY COUNTY OUT...BUT FAIRLY STRONG BOUNDARY
LAYER WINDS MAY BRING SOME DECENT SNOW WELL INLAND AND INTO PORTIONS
OF THAT COUNTY. IF CONFIDENCE GROWS IN THAT SCENARIO THEY CAN BE
ADDED TO THE ADVISORY.

OFF LAKE ONTARIO...
LATEST MESOSCALE MODEL GUIDANCE SUPPORTS AN AREA OF LAKE ENHANCED
SNOW DEVELOPING OVER JEFFERSON COUNTY BY EARLY AFTERNOON. THIS WILL
QUICKLY SHIFT SOUTH ACROSS THE TUG HILL REGION DURING THE AFTERNOON
AND TRANSITION INTO A MORE PURE LAKE EFFECT BAND BY LATE AFTERNOON
AS ANY CLIPPER SNOW PULLS AWAY. THE BAND SHOULD REMAIN MOBILE AND
QUICKLY DROP INTO OSWEGO COUNTY BY EARLY EVENING. SIMILAR TO LAKE
ERIE...SNOWFALL RATES COULD BECOME QUITE HIGH GIVEN THE INSTABILITY
AND STRONG CONVERGENCE...BUT WITH THE BAND MOVING STEADILY SOUTH
THIS SHOULD LIMIT ACCUMULATIONS TO THE ADVISORY RANGE THROUGH LATE
TUESDAY. THE TUG HILL MAY GET CLOSE TO WARNING CRITERIA WITH AN
ADDED BOOST OF UPSLOPE FLOW...BUT FOR NOW WILL KEEP AMOUNTS IN THE
4-8 INCH RANGE EAST OF THE LAKE TUESDAY.

TUESDAY NIGHT THE BAND WILL SETTLE FURTHER SOUTH AND END UP IN
SOUTHERN OSWEGO COUNTY AND ALSO PORTIONS OF NORTHERN CAYUGA/WAYNE
COUNTIES. LATEST NAM SUGGESTS A DYNAMIC UPSTREAM CONNECTION TO
GEORGIAN BAY MAY DEVELOP FOR A FEW HOURS. LATER TUESDAY NIGHT INTO
WEDNESDAY MORNING THE NAM OMEGA PLUME SIMULATION OF THE LAKE
EFFECT BAND TAKES ON ANTICYCLONIC CURVATURE...EXTENDING INTO THE
FAIR HAVEN/OSWEGO AREAS. PAST EXPERIENCE SHOWS THESE BANDS CAN
PRODUCE HIGH SNOWFALL RATES AS LOW LEVEL CONVERGENCE INCREASES FROM
LAND BREEZE CIRCULATIONS. CONVERGENCE IN GENERAL WILL ALSO FOCUS ON
THIS BAND OVERNIGHT AS AN ARCTIC BOUNDARY SITS OVER LAKE ONTARIO.
UNLIKE DURING THE DAY TUESDAY...IT APPEARS THE BAND MAY SIT IN ONE
PLACE LONG ENOUGH TO PRODUCE HIGHER ACCUMULATIONS TUESDAY NIGHT INTO
WEDNESDAY MORNING SOUTHEAST OF THE LAKE.

WITH THIS IN MIND...WILL COVER JEFFERSON AND LEWIS COUNTIES WITH AN
ADVISORY FOR A FAST MOVING YET STRONG BAND TUESDAY. HAVE THEN GONE
WITH A WATCH TUESDAY AFTERNOON THROUGH MIDDAY WEDNESDAY FOR OSWEGO
COUNTY AND TUESDAY EVENING THROUGH MIDDAY WEDNESDAY FOR WAYNE AND
NORTHERN CAYUGA COUNTIES WITH HIGHER AMOUNTS POSSIBLE.

OUTSIDE OF LAKE EFFECT AREAS ON WEDNESDAY...SOME LIGHT SNOW MAY
DEVELOP ACROSS WESTERN NY LATER IN THE DAY AS WARM ADVECTION
INCREASES AHEAD OF THE NEXT SYSTEM. AMOUNTS WILL BE LIGHT AT FIRST.
HIGHS ON WEDNESDAY WILL BE WELL BELOW AVERAGE WITH TEENS IN MOST
LOCATIONS AND SINGLE NUMBERS ACROSS THE NORTH COUNTRY.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
THE LATEST ECMWF CONTINUES ITS TREND OF BEING MUCH SLOWER AND MORE
AMPLIFIED WITH A TROUGH AND SURFACE LOW MOVING THROUGH THE OHIO
VALLEY AND NORTHEAST DURING THE THURSDAY/FRIDAY TIME FRAME. THE
GFS/GEM SOLUTIONS ARE NOTABLY FASTER AND LESS AMPLIFIED. WHILE BOTH
MODEL SOLUTIONS WOULD BRING ACCUMULATING SNOW TO THE REGION...THE
FASTER GFS SOLUTION WOULD BE A RELATIVELY MINOR ADVISORY EVENT WHILE
THE ECMWF WOULD BE A SIGNIFICANT SNOWSTORM. THIS WILL BE A COMPLEX
SCENARIO INVOLVING THE INTERACTION OF TWO SEPARATE SHORTWAVES AND
STREAM PHASING...SO IT MAY STILL TAKE ANOTHER DAY OR SO BEFORE MODEL
GUIDANCE COMES INTO BETTER AGREEMENT WITH THE DETAILS.

FOR NOW THERE IS ENOUGH CONFIDENCE TO INCREASE POPS TO HIGH LIKELY
FOR WEDNESDAY NIGHT THROUGH FRIDAY. TEMPERATURES WILL CONTINUE WELL
BELOW AVERAGE...ESPECIALLY ON FRIDAY IN THE WAKE OF THIS SYSTEM AS
HIGHS MAY STRUGGLE TO REACH 10F EVEN AT LOWER ELEVATIONS...AND MAY
NOT GET ABOVE ZERO EAST OF LAKE ONTARIO.

INTO THE WEEKEND THE FRIGID TEMPERATURES WILL RELAX AS THE DEEP
TROUGH SWINGS OUT THROUGH ATLANTIC CANADA...TO BE REPLACED BRIEFLY
BY A PUSH OF MILDER AIR. ECMWF/GFS ARE IN GENERAL AGREEMENT THAT
ANOTHER SURGE OF ARCTIC AIR IS LIKELY EARLY NEXT WEEK.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
A COLD FRONT HAS CROSSED WNY AS OF 0430Z AND WILL WORK ACROSS CNY
THROUGH 07Z. WINDS SHIFTING TO THE NW BEHIND THE FRONT HAVE BROUGHT
A MIX OF MVFR/IFR CIGS WITH SOME PATCHY DRIZZLE OR FREEZING DRIZZLE.
LAKE EFFECT SNOW SHOWERS WILL DEVELOP AFTER 08Z ONCE THE COLDER AIR
ALOFT BUILDS ACROSS NEW YORK IN THE WAKE OF THE FRONT. THE LAKE
EFFECT WILL BE MAINLY EAST OF THE LAKES OVERNIGHT BRINGING REDUCED
VISIBILITIES.

SNOW SHOWERS WILL BE MOST PERSISTENT AT JHW...WITH IFR CONDITIONS
LIKELY PERSISTING OVERNIGHT. A SECONDARY FRONTAL BOUNDARY WILL BRING
SNOW TO ART LATE TONIGHT...WHILE CONDITIONS GRADUALLY IMPROVE
ELSEWHERE. BY MONDAY...DRIER AIR SHOULD ALLOW ALL TAF SITES TO
IMPROVE TO VFR WITH LIFTING AND SCATTERING CIGS. A NARROW AREA OF
HIGH PRESSURE WILL KEEP DRY CONDITIONS THROUGH MONDAY EVENING BUT
CIGS WILL LOWER TO MVFR NEAR 06Z TUESDAY AHEAD OF A CLIPPER SHIFTING
ACROSS THE UPPER LAKES.

OUTLOOK...
MONDAY NIGHT...VFR/MVFR WITH A CHANCE OF SNOW SHOWERS.
TUESDAY...IFR/MVFR. SNOW SHOWERS LIKELY.
TUESDAY NIGHT AND WEDNESDAY...VFR/MVFR. A CHANCE OF SNOW SHOWERS.
WEDNESDAY NIGHT AND THURSDAY...MVFR. SNOW LIKELY.
FRIDAY...VFR/MVFR. A CHANCE OF SNOW SHOWERS.

&&

.MARINE...
A BRISK WEST TO NORTHWEST FLOW OF MUCH COLDER AIR HAS SET UP ACROSS
THE LOWER LAKES IN THE WAKE OF THE DEPARTING COLD FRONT. THIS WILL
RESULT IN SMALL CRAFT ADVISORY CONDITIONS ON BOTH LAKES THROUGH AT
LEAST THIS MORNING. AS HIGH PRESSURE BUILDS EAST ACROSS NEW YORK
STATE THIS AFTERNOON...WIND AND WAVES WILL GRADUALLY SUBSIDE FROM
WEST TO EAST.

A CLIPPER WILL APPROACH WESTERN NEW YORK TONIGHT...THEN PASS JUST
NORTH OF LAKE ONTARIO ON TUESDAY. INCREASING WEST WINDS ALONG THE
SOUTHERN FLANK OF THIS LOW MAY REACH GALE FORCE ON LAKE ONTARIO LATE
TUESDAY MORNING THROUGH THE FIRST HALF OF TUESDAY NIGHT.

ON LAKE ERIE...INCREASING SOUTHWEST TO WEST WINDS WILL LIKELY RESULT
IN SMALL CRAFT CONDITIONS LATE TONIGHT THROUGH TUESDAY NIGHT.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...LAKE EFFECT SNOW ADVISORY FROM 8 AM TO 7 PM EST TUESDAY FOR
     NYZ012-085.
     LAKE EFFECT SNOW ADVISORY FROM 11 AM TO 10 PM EST TUESDAY FOR
     NYZ007-008.
     LAKE EFFECT SNOW WATCH FROM TUESDAY AFTERNOON THROUGH
     WEDNESDAY AFTERNOON FOR NYZ006.
     LAKE EFFECT SNOW WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY
     AFTERNOON FOR NYZ004-005.
     LAKE EFFECT SNOW ADVISORY FROM 8 AM TUESDAY TO 1 AM EST
     WEDNESDAY FOR NYZ019-020.
     LAKE EFFECT SNOW ADVISORY FROM 6 AM TO 3 PM EST TUESDAY FOR
     NYZ010-011.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 AM EST THIS MORNING FOR LEZ020-
         040-041.
         SMALL CRAFT ADVISORY UNTIL 10 AM EST THIS MORNING FOR
         LOZ030.
         GALE WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING
         FOR LOZ042>045-062>065.
         SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR
         LOZ043>045.
         SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
         LOZ042.

&&

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

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BUFFALO NY
1237 AM EST MON DEC 30 2013

NYZ003-004-010>014-019>021-085-300745-
MONROE-WAYNE-NORTHERN ERIE-GENESEE-WYOMING-LIVINGSTON-ONTARIO-
CHAUTAUQUA-CATTARAUGUS-ALLEGANY-SOUTHERN ERIE-
INCLUDING THE CITIES OF...ROCHESTER...NEWARK...BUFFALO...
BATAVIA...WARSAW...GENESEO...CANANDAIGUA...JAMESTOWN...OLEAN...
WELLSVILLE...ORCHARD PARK...SPRINGVILLE
1237 AM EST MON DEC 30 2013

...BRIEF PERIOD OF FREEZING DRIZZLE EARLY THIS MORNING...

A BRIEF PERIOD OF PATCHY FREEZING DRIZZLE WILL OCCUR ACROSS
PORTIONS OF THE REGION THROUGH THE WEE HOURS OF THE MORNING. THIS
MAY RESULT IN A FEW PATCHES OF BLACK ICE AS TEMPERATURES QUICKLY
FALL THROUGH THE 20S. THE FREEZING DRIZZLE SHOULD CHANGE OVER TO
LIGHT SNOW AFTER A SHORT TIME.

HITCHCOCK

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BUFFALO NY
209 AM EST MON DEC 30 2013

NYZ003>006-008-010>014-019>021-085-300900-
MONROE-WAYNE-NORTHERN CAYUGA-OSWEGO-LEWIS-NORTHERN ERIE-GENESEE-
WYOMING-LIVINGSTON-ONTARIO-CHAUTAUQUA-CATTARAUGUS-ALLEGANY-
SOUTHERN ERIE-
INCLUDING THE CITIES OF...ROCHESTER...NEWARK...FAIR HAVEN...
OSWEGO...LOWVILLE...BUFFALO...BATAVIA...WARSAW...GENESEO...
CANANDAIGUA...JAMESTOWN...OLEAN...WELLSVILLE...ORCHARD PARK...
SPRINGVILLE
209 AM EST MON DEC 30 2013

...BRIEF PERIOD OF FREEZING DRIZZLE EARLY THIS MORNING...

A BRIEF PERIOD OF PATCHY FREEZING DRIZZLE WILL OCCUR ACROSS
PORTIONS OF THE REGION THROUGH THE WEE HOURS OF THE MORNING. THIS
MAY RESULT IN A FEW PATCHES OF BLACK ICE AS TEMPERATURES QUICKLY
FALL THROUGH THE 20S. THE FREEZING DRIZZLE SHOULD CHANGE OVER TO
LIGHT SNOW AFTER A SHORT TIME.

HITCHCOCK