FXUS61 KBUF 232107
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
407 PM EST WED DEC 23 2009

.SYNOPSIS...
HIGH PRESSURE WILL RIDGE SOUTH FROM CANADA...ENDING LINGERING SNOW 
SHOWERS SOUTHEAST OF LAKE ONTARIO...BRINGING FAIR WEATHER THROUGH 
CHRISTMAS MORNING. LOW PRESSURE ACROSS THE MIDWESTERN STATES WILL 
GRADUALLY LIFT TOWARDS THE REGION...WITH PRECIPITATION SLOWLY 
SPREADING FROM WEST TO EAST ON CHRISTMAS DAY. TEMPERATURES WILL BE 
NEAR OR JUST ABOVE FREEZING ON CHRISTMAS DAY...WITH AREAS OF 
FREEZING RAIN POTENTIALLY IMPACTING TRAVEL.

&&

.NEAR TERM /THROUGH THURSDAY/...
SINCE LATE THIS MORNING...THE LAKE EFFECT SNOWS SOUTHEAST OF LAKE 
ONTARIO HAVE WEAKENED MARKEDLY ACROSS THE WAYNE TO OSWEGO COUNTY 
CORRIDOR...COURTESY OF A SHORTWAVE TROUGH PASSAGE THAT HAS DISRUPTED 
THE ACTIVITY...AS WELL AS SLOWLY DROPPING INVERSION HEIGHTS WHICH 
ARE NOW AROUND 4 KFT. ACROSS OUR FORECAST AREA...THE ACTIVITY NOW 
JUST CONSISTS OF SOME LEFTOVER LIGHT SNOW SHOWERS IN THE VICINITY OF 
THE NYS THRUWAY...WITH ANY HEAVIER ACTIVITY NOW LOCATED SOUTH OF THE 
AREA AND LIKELY BEING FORCED MORE BY UPSLOPE PROCESSES THAN ANYTHING 
ELSE. 

WITH CONTINUED WARMING AND SUBSIDENCE ALOFT THROUGH THE REMAINDER OF 
THIS AFTERNOON AND EVENING AND LOW-LEVEL SHEAR EXPECTED TO 
DRAMATICALLY INCREASE BETWEEN NOW AND 00Z...IT NOW APPEARS RATHER 
UNLIKELY THAT THE LAKE SNOWS WILL BE ABLE TO REORGANIZE ENOUGH TO 
PRODUCE ADDITIONAL SIGNIFICANT ACCUMULATIONS. FEEL WE ARE JUST 
LOOKING AT THE LOW LIKELIHOOD OF SOME SNOW SHOWERS THROUGH EARLY 
EVENING WITH UP TO AN ADDITIONAL INCH OF ACCUMULATION AT 
WORST...BEFORE THE ACTIVITY BREAKS DOWN INTO SCATTERED LIGHT SNOW 
SHOWERS AND DISSIPATES COMPLETELY. ACCORDINGLY...WILL PROBABLY DROP 
THE LAKE SNOW ADVISORY WITH THE AFTERNOON PACKAGE...UNLESS SOME 
MARKED REDEVELOPMENT OCCURS BEFORE THAT TIME.

PRECIPITATION IS ALSO RATHER LIMITED ACROSS THE REMAINDER OF THE 
AREA AT THIS TIME...WITH SYNOPTIC SNOW SHOWERS NOW DIMINISHING 
ACROSS THE NORTH COUNTRY BEHIND THE DEPARTING SHORTWAVE...AND JUST 
LEFTOVER FLURRIES/LIGHT SNOW SHOWERS FROM THE ROCHESTER AREA FURTHER 
WEST. EXPECT ALL OF THIS OTHER ACTIVITY TO DIMINISH QUICKLY THROUGH 
EARLY TO MID EVENING WITH CONTINUED SUBSIDENCE AND WARMING ALOFT... 
WITH ONLY SOME MINOR ADDITIONAL ACCUMS ACROSS THE NORTH COUNTRY AND 
LITTLE IF ANYTHING FURTHER WEST. 

OTHERWISE...PLENTY OF LOW LEVEL MOISTURE IS EXPECTED TO REMAIN 
TRAPPED BENEATH THE STRENGTHENING/LOWERING SUBSIDENCE INVERSION 
TONIGHT...WHICH WILL RESULT IN THE BULK OF THE AREA REMAINING MOSTLY 
CLOUDY THROUGH THE NIGHT AND INTO EARLY THURSDAY. WHILE WE CANNOT 
TOTALLY RULE OUT THE DEVELOPMENT OF SOME VERY SPOTTY FREEZING 
DRIZZLE OVERNIGHT GIVEN THE EVENTUAL DISAPPEARANCE OF THE PRIME SNOW 
GROWTH REGION BELOW THE SUBSIDENCE INVERSION...AT THIS POINT FEEL 
THAT THE LOW LEVEL MOISTURE WILL BE TOO SHALLOW TO SUPPORT SUCH 
DEVELOPMENT...THEREFORE WILL NOT MENTION IN THE FORECAST. THE 
EVENING SHIFT WILL NEED TO KEEP AN EYE ON THIS HOWEVER...

THEN AS WE GET INTO THURSDAY...SOME PARTIAL CLEARING MAY BEGIN TO 
WORK INTO FAR SOUTHWESTERN NY STATE IN CONJUNCTION WITH THE ARRIVAL 
OF THE SURFACE RIDGE AXIS FROM THE CENTRAL LAKES...WITH A RATHER 
SLOW SOUTHWEST-NORTHEAST PROGRESSION OF THE CLEARING THEN EXPECTED 
ACROSS THE REST OF THE AREA ON THURSDAY AS RIDGING CONTINUES TO 
BUILD OVERHEAD. OTHERWISE...DRY WEATHER AND SOMEWHAT MILDER 
TEMPERATURES ARE EXPECTED...WHICH IS GOOD NEWS TO ANYONE PLANNING ON 
TRAVELING IN ADVANCE OF THE CHRISTMAS HOLIDAY.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
MAIN FOCUS CONTINUES TO BE ON THE POTENTIAL FOR A WINTRY MIX ON 
CHRISTMAS DAY. AFTER FOLLOWING THIS EVENT FOR A COUPLE DAYS...SOME 
THINGS HAVE COME INTO BETTER FOCUS...WHILE OTHERS STILL A CHALLENGE. 
FIRST...FEEL GOOD ABOUT MODEL CONSENSUS CONCERNING THE START 
TIME...WITH PRECIPITATION SPREADING INTO BUFFALO AND VICINITY AROUND 
MID-DAY FRIDAY...ROCHESTER LATE AFTERNOON...AND WATERTOWN FRIDAY 
EVENING. SEE SEVERAL WAVES OF DYNAMICS...WITH AN INITIAL WAVE OF 
WARM AIR ADVECTION...AND THEN A SECOND WAVE AS A WEAK SURFACE LOW 
TRACKS UP THE EASTERN SEA BOARD. FORTUNATELY...CONSENSUS HAS BACKED 
DOWN ON QPFS A BIT...WITH EACH WAVE BRINGING A QUARTER TO HALF INCH 
OF JUICE.  IN SHORT...PERIODS OF PRECIPITATION WILL ENTER THE CWA 
FRIDAY...LASTING INTO SATURDAY NIGHT WITH CATEGORICAL POPS IN MOST 
LOCATIONS.

NOW FOR THE HARD PART...TEMPERATURES. ACTUALLY FEEL FORECAST 
TEMPERATURES WILL BE WITHIN A FEW DEGREES...THE PROBLEM IS THAT THAT 
ERROR RANGE CROSSES FREEZING. 925 MB WINDS INCREASE TO 40 TO 50 KTS 
FRIDAY AND FRIDAY NIGHT...WITH A STRONG INVERSION BETWEEN THIS AND 
THE SURFACE. THE BEST CHANCE FOR FREEZING RAIN IS IN THE VALLEYS OF 
THE SOUTHERN TIER...WHERE THE VALLEYS ARE SHELTERED...AND 
TEMPERATURES WILL STRUGGLE TO RISE. THE SECOND CONCERN IS FROM 
BUFFALO TO ROCHESTER...WHERE THE SOUTHEAST FLOW WILL BE BLOCKED BY 
THE TERRAIN...ALSO LIMITING TEMPERATURES TO RISE. ON THE OTHER 
HAND...THE LATER START TIME WILL PROVIDE AN OPPORTUNITY FOR SOME 
WARMING. IN THE END...THE OPPORTUNITY FOR RADIATIONAL COOLING (SKY 
AND CALM WINDS) ON THURSDAY NIGHT WILL LIKELY BE THE KEY. 

FOR NOW...EXPECT A PERIOD OF FREEZING RAIN IS LIKELY IN THE SOUTHERN 
TIER CHRISTMAS DAY...AND IN THE NORTH COUNTRY FRIDAY NIGHT. 
ELSEWHERE...FREEZING RAIN IS POSSIBLE...THOUGH ITS A BIT TOO EARLY 
TO PIN DOWN EXACTLY WHERE. EITHER WAY IT WILL BE VERY CLOSE...SO 
THOSE TRAVELING ON CHRISTMAS DAY SHOULD BE ALERT FOR PATCHES OF 
FREEZING RAIN.

FOR FRIDAY NIGHT...PERIODS OF MOSTLY RAIN WILL CONTINUE...THOUGH 
MIXED PRECIP WILL LIKELY HOLD ON IN THE NORTH COUNTRY...WHERE A 
MIXED BAG OF RAIN/SLEET/FREEZING RAIN IS ALL POSSIBLE. ALSO MAY SEE 
PATCHY AREAS OF FREEZING RAIN IN THE VALLEYS OF THE SOUTHERN TIER. 

ON SATURDAY...COLDER AIR WILL MOVE IN FROM THE WEST AS THE UPPER LOW 
MOVES CLOSER. THE GFS IS FASTER THAN THE EUROPEAN...USE A BLEND ON 
TIMING...WITH PRECIPITATION TRANSITIONING TO RAIN OR SNOW SHOWERS IN 
WESTERN PORTIONS SATURDAY AFTERNOON. ELSEWHERE...EXPECT PERIODS OF 
RAIN TO CONTINUE...THOUGH TEMPERATURES WILL STILL BE IN THE 30S...AM 
HOPEFULLY THE PERSISTENT RAIN ALONE WILL BE ENOUGH TO RAISE 
TEMPERATURES ABOVE FREEZING AT LEAST.

FOR SATURDAY NIGHT...TEMPERATURES COOL AT ALL LEVELS...THOUGH RAIN 
HANGS ON IN EASTERN ZONES EARLY. 850 MB TEMPS COOL...WITH LAKE 
EFFECT A POSSIBILITY...THOUGH THE EUROPEAN IS FURTHER SOUTH WITH ITS 
TRACK OF THE UPPER LOW. BY LATE SATURDAY NIGHT...EXPECT IT TO BE 
COOL ENOUGH FOR SNOW ACROSS THE CWA.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
THE UPPER LOW PASSES NEAR THE REGION SUNDAY...BRINGING A CHANCE OF 
SNOW SHOWERS TO ALL. DEPENDING ON THE TRACK OF THE UPPER LOW...MAY 
ALSO SEE A LAKE EFFECT KICK IN ON A SOUTHWEST FLOW AS 850 MB TEMPS 
DROP TO ABOUT -11C RESULTING IN MARGINAL LAKE INDUCED CAPES. THE 
UPPER LOW MOVES EAST ON MONDAY...AND INTO THE MARITIMES 
TUESDAY...BRINGING PROGRESSIVELY COLDER AIR INTO THE REGION. WHILE 
EXACT WINDS HARD TO PIN DOWN...GENERALLY EXPECT SW WINDS TO SHIFT 
MORE NW WITH TIME...WITH SOME LAKE EFFECT ACTIVITY LIKELY...AND 
COOLER TEMPERATURES.

HIGH PRESSURE BUILDS IN ON WEDNESDAY...WITH COOLER TEMPERATURES AND 
A DIMINISHING CHANCE FOR PRECIPITATION.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
BETWEEN NOW AND MIDDAY THURSDAY...AN UPPER LEVEL LOW OVER WESTERN
NEW ENGLAND WILL DRIFT SOUTHEAST INTO THE WESTERN ATLANTIC...WITH
ITS ASSOCIATED SURFACE REFLECTION FOLLOWING ALONG A SIMILAR PATH.
IN THE WAKE OF THIS LOW...RIDGING WILL BUILD EASTWARD ACROSS THE AREA
AT ALL LEVELS...ESPECIALLY ALOFT. INCREASING SUBSIDENCE ASSOCIATED
WITH THIS RIDGE WILL HELP TO TRAP LOW LEVEL MOISTURE LINGERING
BEHIND THE DEPARTING LOW...KEEPING GENERAL MVFR CIGS IN PLACE AT
LEAST THROUGH TONIGHT. AS WE GET INTO THURSDAY...SOME CLEARING MAY
BEGIN TO WORK INTO FAR SOUTHWESTERN NY STATE IN CONJUNCTION WITH
THE ARRIVAL OF THE SURFACE RIDGE AXIS...THOUGH THE PROGRESSION OF
ANY SUCH CLEARING ACROSS THE REST OF THE AREA ON THURSDAY IS
LIKELY TO BE ON THE SLOW SIDE. AS SUCH...HAVE GONE ON THE
PESSIMISTIC SIDE AND KEPT MVFR CIGS ACROSS THE REMAINING TAF SITES
THROUGH THE END OF THE PERIOD.

IN TERMS OF PRECIPITATION...OCCASIONAL SNOW SHOWERS CONTINUE TO
AFFECT PORTIONS OF THE NORTH COUNTRY IN ASSOCIATION WITH A PASSING
SHORTWAVE TROUGH...WHILE SOME LAKE SNOWS CONTINUE SOUTHEAST OF
LAKE ONTARIO. WITHIN BOTH AREAS...CONDITIONS RANGE FROM IFR TO
MVFR...AND THESE ARE EXPECTED TO CONTINUE INTO LATE THIS
AFTERNOON. AFTER THAT TIME...THE SNOWS WILL GRADUALLY WIND DOWN
EARLY THIS EVENING DUE TO A COMBINATION OF SUBSIDENCE/WARMING
ALOFT AND INCREASING SHEAR...RESULTING IN CONDITIONS IMPROVING TO
MVFR. 

OUTLOOK...
FRIDAY...VFR/MVFR CONDITIONS EARLY DETERIORATE TO IFR/MVFR IN RAIN
AND PATCHY FREEZING RAIN. 
SATURDAY...IFR/MVFR WITH RAIN CHANGING TO SNOW FROM WEST TO EAST.
SUNDAY AND TUESDAY...MVFR/VFR WITH A CHANCE OF SNOW SHOWERS.

&&

.MARINE...
CARRY A SMALL CRAFT ADVISORY UNTIL 10 PM FOR MOST OF LAKE ONTARIO. 
WINDS WILL CONTINUE TO DIMINISH THROUGH THURSDAY NIGHT...AS HIGH 
PRESSURE RIDGES IN. CAN SEE EITHER SMALL CRAFT ADVISORY OR POSSIBLY 
GALES FRIDAY AND SATURDAY AS LOW PRESSURE APPROACHES FROM THE 
MIDWEST.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR 
         LOZ042>045.

&&

$$

SYNOPSIS...APFFEL
NEAR TERM...JJR
SHORT TERM...APFFEL
LONG TERM...APFFEL
AVIATION...JJR
MARINE...APFFEL/JJR