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