FXUS61 KBUF 201514 AFDBUF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BUFFALO NY 1014 AM EST TUE JAN 20 2009 .SYNOPSIS... A NORTHWEST FLOW OF VERY COLD AIR WILL PERSIST ACROSS THE REGION TODAY BETWEEN LOW PRESSURE WELL OFF THE EAST COAST AND A RIDGE OF HIGH PRESSURE MOVING EASTWARD INTO THE MISSISSIPPI VALLEY. THIS WILL KEEP SCATTERED SNOW SHOWERS ACROSS THE REGION TODAY AND FOR AWHILE TONIGHT...ESPECIALLY SOUTHEAST OF THE LAKES. A SLOW WARMING TREND IS THEN EXPECTED TO BEGIN WEDNESDAY AND CONTINUE THROUGH THE END OF THE WEEK BEFORE ANOTHER ARCTIC AIRMASS ARRIVES OVER THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... ACTIVITY ON BUF RADAR BRIEFLY INTENSIFIED TO THE NORTH OF BUF-BATAVIA LINE THIS MRNG BUT SINCE ARND 1430Z SHOWING SIGNS OF WEAKENING. WILL CONTINUE TREND OF EARLIER FORECAST TO DROP POPS TO CHC/LKLY RANGE SE OF THE LAKES THIS AFTERNOON. ADDITONAL ACCUMS THIS AFTN GENLY AN INCH OR LESS. EARLIER DISCUSSION BELOW. WEAK TROUGH OF LOW PRESSURE ACROSS THE EASTERN GREAT LAKES AND NEW YORK STATE WILL FILL TODAY. BOUNDARY LAYER WINDS ACROSS THE LAKES WILL BE GENERALLY FROM THE NORTHWEST WHICH WILL BRING SHALLOW LAKE MOISTENED AIR ACROSS THE FORECAST AREA. AS 850MB TEMPS REMAIN IN THE -14C TO -16C RANGE...WE CAN EXPECT LIGHT LAKE EFFECT SNOW TO COVER A LARGE PORTION OF THE REGION...MAINLY OFF LAKE ONTARIO. LESS MOISTURE AND LIFT FROM LAKE ERIE DUE TO MOSTLY ICE COVERED LAKE SURFACE WILL LIMIT LAKE SNOW OVER THE WESTERN SOUTHERN TIER...BUT WILL KEEP LOW LIKELY POPS THERE AS UPSLOPE EFFECTS OF THE TERRAIN SHOULD WRING OUT ANY AVAILABLE MOISTURE AS LIGHT SNOW. ACCUMULATIONS WILL RANGE FROM ONLY A FEW TENTHS OF AN INCH TO AN INCH OR SO EVERY 6 HOURS...GENERALLY 1 TO 2 INCHES OVERALL FOR TODAY THROUGH TONIGHT. TEMPS WILL BE A LITTLE COLDER TODAY THAN ON MONDAY AS THE NORTH/NORTHWEST WINDS AND LAKE INDUCED CLOUDS WILL NOT OFFER MUCH WARMING DURING THE DAY. SOME PARTIALLY SUNNY SPOTS AROUND THE FINGER LAKES AND THE GENESEE VALLEY MAY REACH CLOSE TO 20...AS WILL THE LAKE ONTARIO SHORELINE LOCATIONS WITH MODERATION FROM THE WARMER LAKE WATER. LOWS TONIGHT WILL RANGE MOSTLY WITHIN THE SINGLE NUMBERS...IN THE TEENS RIGHT ALONG THE LAKE ONTARIO SHORE WITH MORE CLOUDINESS AND INFLUENCE OF WARMER LAKE WATER. THE COLDER SPOTS OF THE SOUTHERN TIER WILL BE IN THE LOWER SINGLE DIGITS...AND THE EASTERN LAKE ONTARIO REGION WILL LIKELY FALL BELOW ZERO...BOTH COLDER AREAS LACKING THE LAKE INDUCED CLOUD COVER. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... CONTINUITY FOR WEDNESDAY HAS A CHANCE OF SNOW SHOWERS AS A SURFACE RIDGE MOVES EAST OF OUR REGION AND A TROUGH OF LOW PRESSURE TRACKS EASTWARD ACROSS THE GREAT LAKES AND EASTERN ONTARIO PROVINCE. STEERING WINDS WILL BACK TO WESTERLY AS THE TROUGH APPROACHES AND ISENTROPIC LIFT WILL HELP MOISTEN THE LOWER AND MID LEVELS OF THE ATMOSPHERE DURING THE DAY. WE ARE A LITTLE MORE CONCERNED WITH LAKE EFFECT EAST OF THE LAKES THAN WE WERE YESTERDAY. WE WILL THROW SOME LIKELY POPS IN EAST AND NORTHEAST OF THE LAKES BUT IT STILL LOOKS LIKE ANY ACCUMULATIONS WOULD BE MINOR. PROJECTED SOUNDINGS SHOW JUST ENOUGH LAKE INDUCED CAPE WITH EQUILIBRIUM LEVELS AROUND 4 THOUSAND FEET EAST OF LAKE ERIE AND AROUND 6 THOUSAND FEET EAST OF LAKE ONTARIO. WE ARE ALSO CONCERNED THAT THE LAKE EFFECT ACTIVITY WILL MOVE AS FAR NORTH AS THE BUFFALO AND WATERTOWN AREAS SINCE THE FLOW BENEATH THE EQUILIBRIUM LEVEL IS 240-250 DEGREES. ISENTROPIC LIFT WILL CONTINUE WEDNESDAY NIGHT BUT THIS WILL LOWER THE EQUILIBRIUM LEVEL FURTHER. THIS PATTERN SHOULD MAINTAIN THE POTENTIAL FOR SOME LIMITED SNOWS ACROSS THE ENTIRE AREA BUT LAKE ENHANCEMENT WILL BE DIMINISHED. && .LONG TERM /THURSDAY THROUGH MONDAY/... LATEST MEDIUM RANGE MODELS CONTINUING TO SUGGEST THE RETREAT...AT LEAST TEMPORARILY OF THE DEEP EASTERN CONUS TROUGH WITH A MUCH LESS AMPLIFIED FLOW DEVELOPING DURING THE THURSDAY AND FRIDAY TIME FRAME...BEFORE THE EASTERN TROUGH BECOMES RE-ESTABLISHED OVER THE WEEKEND AND INTO EARLY NEXT WEEK GIVING THE AREA ANOTHER SHOT OF FRESH ARCTIC AIR. LOOKING A LITTLE MORE CLOSELY AT THE FORECAST DETAILS FOR THE END OF THE WEEK AND INTO EARLY NEXT WEEK...WE WILL MAINTAIN THE GENERAL LOW CHANCE PROBABILITIES FOR THE THURSDAY AND FRIDAY TIME FRAME AS A WEAK CLIPPER SYSTEM WORKS ACROSS THE GREAT LAKES. AT THIS POINT... THE PROGRESSIVE SYSTEM WILL HAVE LIMITED MOISTURE AND THE ASSOCIATED WARM AIR ADVECTION PATTERN LOOKS RATHER WEAK...WHICH SHOULD LIMIT POTENTIAL SNOW ACCUMULATIONS WITH THIS SYSTEM. THE CLIPPER WILL MOVE EAST OF THE AREA BY SATURDAY WITH A FRESH SUPPLY OF ARCTIC AIR BUILDING ACROSS THE AREA BEHIND IT. 850 MB TEMPERATURES DROPPING TO NEAR MINUS 20C OR COLDER OVER THE COURSE OF THE WEEKEND SHOULD GENERATE SOME LAKE SNOWS SOUTHEAST OF THE LAKES. LIMITING FACTOR WILL BE ADVECTION OF DRIER AIR INTO THE AREA AT THE SAME TIME. FOR NOW...WILL KEEP LAKE POTENTIAL IN CHANCE RANGE...ALTHOUGH LATER GUIDANCE MAY SUGGEST BETTER CHANCES ESPECIALLY FROM ROCHESTER OVER TO THE TUG HILL. EARLY NEXT WEEK THE GFS AND ECMWF UPPER AIR PATTERNS ARE SIMILAR BUT THERE ARE SOME PRETTY BIG DIFFERENCES FOR THE SURFACE PATTERN. BY MONDAY EVENING THE ECMWF HAS A SURFACE HIGH SPRAWLED FROM THE NORTHERN PLAINS TO THE OHIO VALLEY WHEREAS THE GFS HAS A 1009 MB LOW MOVING NORTHEAST INTO THE OHIO VALLEY WITH A STRONG 1040 MB HIGH CENTERED OVER QUEBEC. NEEDLESS TO SAY THERE ARE SOME CONFIDENSE ISSUES LATE IN THE THIS PERIOD. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... WEAK LOW PRESSURE EXITING ACROSS THE ADIRONDACKS WILL CIRCULATE MORE VERY COLD AIR ACROSS THE EASTERN GREAT LAKES TODAY. THIS COLD CYCLONIC FLOW WILL PRODUCE MVFR CONDITIONS ACROSS THE MAJORITY OF WESTERN NEW YORK THROUGH MUCH OF TODAY WITH CIGS RANGING FROM 2500 TO 3500 FT AND VSBYS OCCASIONALLY FALLING TO BETWEEN 2 AND 5 SM IN LIGHT LAKE EFFECT SNOW. CIGS AND VSBYS MAY BE LOWER AT TIMES AT KJHW AND KROC DUE TO THEIR PROXIMITY TO THEIR RESPECTIVE LAKES (ERIE AND ONTARIO). CONDITIONS WILL TEND TO IMPROVE THIS AFTERNOON SO THAT MOST SITES WILL BECOME VFR. TUESDAY NIGHT...VFR/MVFR IN SCT SNOW SHOWERS. WEDNESDAY...VFR EXCEPT MVFR/IFR IN LAKE EFFECT SNOW SHOWERS EAST OF THE LAKES. THURSDAY AND FRIDAY...MVFR IN SCATTERED SNOW SHOWERS. SATURDAY...VFR EXCEPT MVFR/IFR IN LAKE EFFECT SNOW SHOWERS EAST OF THE LAKES. && .MARINE... A RELATIVELY WEAK PRESSURE GRADIENT WILL CONTINUE ACROSS THE LOWER LAKES REGION THROUGH TONIGHT...AND THIS WILL RESULT IN WINDS AND WAVES REMAINING BELOW SMALL CRAFT CRITERIA. THE GRADIENT ON THE LAKES WILL PICK UP WEDNESDAY WITH THE POTENTIAL FOR SMALL CRAFT CONDITIONS DEVELOPING ON LAKE ONTARIO WEDNESDAY AND THURSDAY. THE NEARSHORE FORECASTS FOR LAKE ERIE AND THE NIAGARA RIVER HAVE ENDED FOR THE SEASON AND WILL RESUME IN MARCH. NEARSHORE FORECASTS FOR LAKE ONTARIO WILL CONTINUE. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...NONE. && $$ SYNOPSIS...SAGE NEAR TERM...JJP/WCH SHORT TERM...SAGE LONG TERM...SAGE/TMA AVIATION...RSH/WCH MARINE...SAGE/TMA