173 
FXUS61 KBUF 190337
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
1137 PM EDT MON MAR 18 2013

.SYNOPSIS...
A WINTRY MIX OF PRECIPITATION WILL CONTINUE INTO THE OVERNIGHT
HOURS ACROSS WESTERN NEW YORK...WHILE SNOW CONTINUES ACROSS THE
NORTH COUNTY. LATE TONIGHT AND TOMORROW AN OCCLUDED FRONT WILL
CROSS THE REGION...WITH A REINFORCING SHOT OF COLD AIR AND BELOW
AVERAGE TEMPERATURES THEN FOLLOWING FOR TUESDAY ON THROUGH THE
REMAINDER OF THE WEEK. WITH THE ARRIVAL OF THE COLDER AIR...
FREQUENT SNOW SHOWERS AND AREAS OF LAKE EFFECT SNOW WILL DEVELOP
EAST OF THE LAKES.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 1130 PM...HAVE DROPPED THE WIND ADVISORY FOR CHAUTAUQUA AND
SOUTHERN ERIE COUNTIES...AS THE EXPECTED STRONGER WINDS IN THESE
AREAS HAVE NEVER REALLY MATERIALIZED...AND THE WINDOW FOR THESE IS
JUST ABOUT TO CLOSE AS WINDS ALOFT WILL BE STEADILY WEAKENING THE
NEXT FEW HOURS.

OTHERWISE...WIDESPREAD PRECIPITATION CONTINUES FROM THE GENESEE
VALLEY EASTWARD ACROSS THE NORTH COUNTRY...WITH MORE SPOTTY LIGHT
PRECIPITATION FOUND BACK ACROSS EXTREME FAR WESTERN NEW YORK. SURFACE
OBS SHOW THAT PTYPE IS STILL IN THE FORM OF SNOW ACROSS THE NORTH
COUNTRY ...WITH A VARIETY OF MIXED PRECIPITATION THEN COVERING
THE REMAINDER OF THE REGION...WITH THE IMMEDIATE LAKESHORE REGIONS
OF FAR WESTERN NEW YORK HAVING FINALLY GONE OVER TO PLAIN RAIN
THANKS TO THE EXPECTED SOUTHERLY/SOUTHEASTERLY DOWNSLOPE FLOW.

ALL OF THIS IS FOUND IN ADVANCE OF A SECONDARY SURFACE WAVE
OVER SOUTHERN LAKE HURON AND A TRAILING OCCLUDED FRONT THAT
EXTENDS SOUTHEASTWARD TO THE OHIO/PENNSYLVANIA BORDER...WHICH
CONTINUES TO GENERATE ANOTHER SWATH OF LIGHTER PRECIPITATION
IMMEDIATELY UPSTREAM OF OUR CWA.

THROUGH THE EARLY OVERNIGHT HOURS...EXPECT RELATIVELY HIGH 
PRECIPITATION CHANCES TO REMAIN IN PLACE ACROSS THE ENTIRE REGION
IN ADVANCE OF THE APPROACHING OCCLUDED FRONT...THOUGH OVER WESTERN
NEW YORK ANY PRECIP WILL TEND TO BE MUCH LIGHTER THAN THAT FALLING
FURTHER TO THE EAST ACROSS THE FINGER LAKES AND NORTH COUNTRY. AFTER
ABOUT 06Z-07Z...THE OCCLUDED FRONT WILL BEGIN PUSHING ACROSS THE
REGION...WITH PRECIP CHANCES FALLING OFF TO THE CHANCE RANGE
FOLLOWING ITS PASSAGE AS DRY SLOTTING WORKS IN ALOFT.

IN TERMS OF PTYPE...EXPECT MAINLY SNOW TO CONTINUE ACROSS THE
NORTH COUNTRY...WITH MIXED PRECIPITATION AND LIGHT RAIN/DRIZZLE
FOUND ACROSS THE REMAINDER OF THE AREA...WITH THE MAJORITY OF THE
LIGHT RAIN/DRIZZLE FOUND ALONG THE LAKE PLAINS AS TEMPS CONTINUE
TO WARM IN ADVANCE OF THE APPROACHING OCCLUDED FRONT. 

HAVE ADJUSTED THE FORECAST TO KEEP IT IN LINE WITH THE ABOVE
OBSERVATIONAL AND EXPECTED TRENDS. RELEVANT PORTIONS OF THE MID
AFTERNOON NEAR TERM DISCUSSION FOLLOW BELOW...

TOTAL SNOW AND SLEET ACCUMULATIONS FOR THE NIGHT WILL BE 2 TO 4
INCHES WHERE CURRENT ADVISORIES ARE IN EFFECT. MUCH OF THE NIAGARA
FRONTIER FROM BUFFALO EAST TO ROCHESTER WILL JUST SEE AN INCH OR
TWO OF SNOW. THE LARGER THREAT FOR AREAS SOUTH OF THE THRUWAY WILL
BE WITH ICE ACCUMULATIONS FROM FREEZING RAIN. ONE TO TWO TENTHS OF
ICE ALONG WITH THE GUSTY WINDS WOULD POSE A RISK FOR DOWNED TREES
AND POWERLINES.

THE FORECAST FOR THE NORTH COUNTY HAS CHANGES FROM EARLIER FORECAST 
PACKAGES. IT NOW APPEARS AS THE AIR MASS IN THIS REGION WILL REMAIN 
SUB-FREEZING. THERE FOR ALL OR THE MAJORITY OF PRECIPITATION WILL 
FALL IN THE FORM OF SNOW. A MIX OF WPC AND SREF QPF GUIDANCE YIELDS 
NEAR AND INCH OF LIQUID EQUIVALENT PRECIPITATION TONIGHT THROUGH 
TOMORROW. RESULTS FROM THE ROEBBER TECHNIQUE USED FOR ESTIMATING 
SNOW RATIOS SHOW MODEL ESTIMATES OF BETWEEN 8:1 AND 15:1. THIS WOULD 
YIELD 8 TO 15 INCHES OF SNOW ACROSS THE THE TUG HILL REGION WITH 
LOWER AMOUNTS FOUND AT LOWER ELEVATIONS DUE TO SOME DOWNSLOPING 
EFFECTS. SREF PLUME DIAGRAMS FOR KRME SHOW 8 TO 9 INCHES OF SNOW 
POSSIBLE THROUGH TOMORROW. UPGRADED NORTHERN TIER COUNTIES TO A 
WINTER STORM WARNING WITH 8 TO 12 INCHES OF SNOW EXPECTED TONIGHT 
AND TOMORROW FOCUSED ON THE TOP OF THE TUG HILL. THIS INCLUDES MUCH 
OF SOUTHERN LEWIS...NORTHEASTERN OSWEGO AND SOUTHEASTERN JEFFERSON 
COUNTIES. OUTSIDE OF THESE AREAS EXPECT MORE TOWARD ADVISORY LEVEL 
SNOW AMOUNTS AS LOW A 3 INCHES FOR WATERTOWN TO 6 TO 7 INCHES FOR 
OSWEGO AND FULTON AND PORTIONS OF NORTHERN JEFFERSON COUNTY. IN 
ADDITION TO TO THE SNOW FALL WIND GUSTS IN THE RANGE OF 30 TO 50 MPH 
WILL BRING BLOWING SNOW OVERNIGHT TO THE REGION. A WIND ADVISORY IS 
IN EFFECT THROUGH THE OVERNIGHT.

THROUGH TOMORROW WE WILL SEE THE NEGATIVITY TILTED UPPER TROUGH CUT 
OFF INTO A CLOSED UPPER LOW OVER THE UPPER GREAT LAKES. AT THE 
SURFACE WE WILL SEE THE SURFACE LOW OVER MINNESOTA TODAY SHIFT EAST 
TO EASTERN LAKE SUPERIOR WHILE THE OHIO VALLEY SURFACE LOW SHIFTS 
OFF THE SOUTHERN NEW ENGLAND COAST AND DEPENDS. DURING THIS 
TRANSITION OUR FORECAST AREA WILL SEE AN OCCLUDED SURFACE FRONT 
CROSS FROM WEST TO EAST THROUGH THE DAY. THIS WILL BRING A 
REINFORCING SHOT OF COLDER AIR WHICH WILL CHANGE ANY AREAS WHICH SAW 
PLAIN RAIN OVERNIGHT BACK TO SNOW. ONCE THIS FRONT PASSES EAST MUCH 
OF THE STEADIER SNOW WILL TAPER OFF TO JUST SCATTERED SNOW SHOWERS. 
THE WESTERLY COLD ADVECTION FLOW BEHIND THE OCCLUDED FRONT WILL KEEP 
TEMPS SLOWLY FALLING THROUGH THE DAY. BY LATE AFTERNOON TEMPERATURES 
AT 850MB WILL COOL TO -10 TO -13C WHICH SHOULD BE COLD ENOUGH FOR 
LAKE EFFECT SNOWS TO BEGIN TO GET ORGANIZED.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
DESPITE THE FACT THAT SPRING WILL OFFICIALLY START AT THE BEGINNING 
OF THIS PERIOD (7:02 AM EDT WED)...OLD MAN WINTER WILL PERSIST 
ACROSS THE REGION. TEMPERATURES WILL REMAIN 10...TO AT TIMES 15... 
DEGREES F BELOW NORMAL AS A HIGH LATITUDE BLOCKING PATTERN WILL 
STILL BE IN PLACE.  

THE BLOCKING PATTERN CONSISTS OF AN ANOMALOUSLY STRONG (+4 STD) H5 
RIDGE OVER GREENLAND THAT HAS BEEN HOLDING A POLAR VORTEX OVER 
EASTERN CANADA...THUS DELAYING ANY SIGNS OF SPRING. THIS PATTERN 
WILL BE IN PLACE ON WEDNESDAY...BUT AS WE TOWARDS THE END OF THE 
WORK WEEK...THE RIDGE WILL RETROGRADE BACK ACROSS EASTERN CANADA. 
THIS WILL CUT OFF THE SUPPLY OF ARCTIC AIR AND ALLOW OUR AIRMASS TO 
GRADUALLY MODIFY AS WE HEAD INTO THE LONG TERM PORTION OF THE 
FORECAST (SEE BELOW). THE DETAILS...

A STACKED POLAR VORTEX BASED OVER SOUTHERN ONTARIO TUESDAY NIGHT 
WILL SLOWLY WOBBLE TO THE EAST ACROSS TO NEW ENGLAND BY FRIDAY 
MORNING. SEVERAL SHORTWAVES DISPLAYING THE FUJIWHARA EFFECT WILL 
ROTATE ABOUT THE CORE OF THE VORTEX AND PERIODICALLY ENHANCE LAKE 
SNOWS PRODUCED BY -12C H85 AIR CIRCULATING ACROSS THE NEARLY ICE 
FREE WATERS OF BOTH LAKES ERIE AND ONTARIO. THIS WILL GENERATE LAKE 
INDUCED CAPES OF A FEW HUNDRED J/KG WHILE A CAP WILL RANGE FROM 
ABOUT 8K FT OVER LK ERIE TO 10K OVER LK ONTARIO. THESE ARE FAIRLY 
IMPRESSIVE VALUES GIVEN THE TIME OF YEAR. MEANWHILE...THE FLOW WILL 
GENERALLY BE FROM THE WEST WITH A WEALTH OF SYNOPTIC MOISTURE IN 
THE DENDRITIC GROWTH ZONE...SO LAKE SNOWS WILL BE CONCENTRATED 
ACROSS THE WESTERN SOUTHERN TIER AND TUG HILL REGIONS. A LIMITING 
FACTOR IN SNOW ACCUMULATIONS WILL BE THE STRONG DIURNAL EFFECTS THAT 
WILL HELP TO MAKE ANY ORGANIZED OVERNIGHT BANDS MORE CELLULAR BY 
DAY. 

SPEAKING OF ACCUMULATIONS...THERE WILL BE THE POTENTIAL FOR 12 HOUR 
SNOWFALL AMOUNTS TO EXCEED 6 INCHES EAST OF LAKE ONTARIO...WHILE 
SOMEWHAT LESSER AMOUNTS SHOULD BE FOUND AS A RESULT OF A SHORTER 
FETCH DOWNWIND OF LK ERIE. WILL KEEP THE LAKE SNOW WATCH IN EFFECT 
FOR THE TUG HILL REGION...WHILE UPSLOPE FROM THE CHAUTAUQUA RIDGE 
WILL LIKELY HELP TO PRODUCE ADVISORY CRITERIA SNOWFALL. 

ELSEWHERE...A COLD MOISTURE RICH CYCLONIC FLOW WILL KEEP SCATTERED 
LIGHT SNOW SHOWERS AND FLURRIES OVER THE REGION WITH TEMPERATURES 
MORE TYPICAL OF MID JANUARY THAN THE START OF SPRING. DURING THIS 
PERIOD LAST YEAR...OUR TEMPERATURES WERE AT RECORD HIGH LEVELS SOME 
30 TO 40 DEG ABOVE NORMAL...AND THIS YEAR THEY WILL BE 10 TO 15 DEG 
BELOW. SUCH IS SPRINGTIME IN THE GREAT LAKES REGION.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
A WEAK SHORT WAVE ROTATING WITHIN THE UPPER LEVEL TROUGH PARKED OVER 
SOUTHEAST CANADA AND THE LOWER GREAT LAKES IS FORECAST TO MOVE 
THROUGH THE AREA FRIDAY AND FRIDAY NIGHT. THIS SYSTEM WILL BRING A 
PERIOD OF SNOW SHOWERS AND LAKE ENHANCED SNOWS TO THE FAVORED AREAS 
SOUTHEAST OF LAKE ERIE AND ONTARIO. AFTER THIS SYSTEM MOVES THROUGH 
MID-LEVEL DRYING AND 850H TEMPERATURES START WARMING FROM -13C TO 
-9C BY LATE SATURDAY. SO ANY LINGERING LAKE EFFECT SNOWS DOWN WIND 
OF THE LAKES WILL LIKELY COME TO A SLOW END WITH MAINLY JUST SOME 
LEFT OVER FLURRIES. TEMPERATURES DURING THIS PERIOD WILL START OUT 
BELOW NORMAL BUT WILL GRADUALLY CLIMB TO NEAR NORMAL BY MONDAY AS 
THE TROUGH OVER THE REGION SLOWLY WEAKENS AND MODIFIES.

&&

.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
A MIXED BAG OF PRECIPITATION WILL CONTINUE ACROSS THE REGION TONIGHT 
AS LOW PRESSURE LIFTS THROUGH THE CENTRAL GREAT LAKES. ACROSS 
WESTERN NY...SNOW WILL CHANGE TO A MIX OF SLEET...RAIN AND FREEZING 
RAIN DEPENDING ON SURFACE TEMPERATURE. ALONG THE LOWER ELEVATIONS 
FROM KDKK TO KBUF TO KROC SURFACE TEMPS SHOULD WARM ENOUGH TO CHANGE 
PRECIPITATION TO JUST RAIN FOR A FEW HOURS BETWEEN ABOUT 03Z-06Z. 
AFTER THAT...THE AIRMASS GROWS COLDER AGAIN WITH ANY LINGERING 
PRECIPITATION CHANGING BACK TO SNOW. ACROSS THE INTERIOR SOUTHERN 
TIER INCLUDING KJHW...SURFACE TEMPS WILL REMAIN AT OR BELOW FREEZING 
WITH SLEET AND FREEZING RAIN CHANGING BACK TO SNOW LATER TONIGHT. 
FINALLY...EAST OF LAKE ONTARIO INCLUDING KART...TEMPERATURES ALOFT 
AND AT THE SURFACE WILL REMAIN COLD ENOUGH TO SUPPORT ALL SNOW.

VSBY WILL GENERALLY BE IFR IN AREAS OF SNOW...AND A MIX OF MVFR/VFR 
IN AREAS OF SLEET...FREEZING RAIN...AND RAIN. CIGS WILL BE A MIX OF 
MVFR AND VFR...KEPT UP SOME BY SOUTHEAST TO SOUTH DOWNSLOPE WINDS 
ACROSS LOWER ELEVATIONS. ACROSS THE HIGHER TERRAIN...AREAS OF IFR 
CIGS ARE MORE LIKELY WITHOUT THE BENEFIT OF DOWNSLOPE WINDS.

LATE TONIGHT AND INTO TUESDAY PRECIPITATION WILL END FROM WEST TO 
EAST AS AN OCCLUDED FRONT MOVES ACROSS THE REGION. THE DRY SLOT THAT 
FOLLOWS WILL ALLOW FOR A PERIOD OF MVFR TO VFR CONDITIONS. LATER ON 
TUESDAY WRAP AROUND MOISTURE AND COLD AIR ALOFT WILL 
ARRIVE...BRINGING INCREASING CHANCES OF SNOW SHOWERS AND A RETURN TO 
MVFR/IFR VSBY. WINDS WILL ALSO GET QUITE BLUSTERY ON TUESDAY...WITH 
GUSTS IN THE 30-35 KNOT RANGE ESPECIALLY NORTHEAST OF LAKE ERIE.

FINALLY...LOW LEVEL WIND SHEAR WILL CONTINUE THROUGH 06Z-08Z AS A 
STRONG LOW LEVEL JET CROSSES THE REGION. AFTER THAT...WINDS ALOFT 
WILL STILL REMAIN STRONG BUT WILL BE BETTER ALIGNED AND COUPLED WITH 
THE SURFACE WINDS...BRINGING LESS RISK OF SHEAR.

OUTLOOK...
WEDNESDAY AND THURSDAY...MVFR/IFR IN SNOW SHOWERS AND LAKE EFFECT 
SNOW. 
FRIDAY...MVFR WITH LIGHT SNOW SHOWERS.
SATURDAY...MAINLY VFR.

&&

.MARINE...
BRISK SOUTHEASTERLY AND SOUTHERLY WINDS WILL CONTINUE OVERNIGHT AHEAD
OF A STORM SYSTEM OVER THE CENTRAL GREAT LAKES...THEN WILL VEER TO
SOUTHWESTERLY AND THEN WESTERLY ON TUESDAY FOLLOWING THE PASSAGE
OF AN OCCLUDED FRONT. SMALL CRAFT ADVISORIES HAVE BEEN EXTENDED
THROUGH TUESDAY NIGHT TO COVER BOTH PERIODS OF GUSTY WINDS. GUSTS
MAY OCCASIONALLY APPROACH GALES BUT NOT REMAIN SUSTAINED FOR ANY
LONGER PERIOD OF TIME.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...LAKE EFFECT SNOW WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY 
     AFTERNOON FOR NYZ006>008.
     WINTER STORM WARNING UNTIL 8 PM EDT TUESDAY FOR NYZ006>008.
     WIND ADVISORY UNTIL 8 AM EDT TUESDAY FOR NYZ006>008.
     WINTER WEATHER ADVISORY UNTIL 11 AM EDT TUESDAY FOR NYZ004-005-
     014.
     WINTER WEATHER ADVISORY UNTIL 6 AM EDT TUESDAY FOR NYZ012-013-
     019>021-085.
MARINE...SMALL CRAFT ADVISORY UNTIL 5 AM EDT WEDNESDAY FOR LEZ020-040-
         041.
         SMALL CRAFT ADVISORY UNTIL 5 AM EDT WEDNESDAY FOR 
         LOZ042>045.

&&

$$

SYNOPSIS...JJR/SMITH
NEAR TERM...JJR/SMITH
SHORT TERM...RSH
LONG TERM...AR
AVIATION...HITCHCOCK
MARINE...JJR/SMITH