FXUS61 KBUF 271813
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
113 PM EST FRI NOV 27 2009

.SYNOPSIS...
LOW PRESSURE CENTERED NEAR CAPE COD THIS MORNING WILL TRACK 
NORTHWARD AND DEEPEN RAPIDLY...REACHING THE CANADIAN MARITIMES BY 
SATURDAY MORNING. THIS WILL DRAW COLDER CANADIAN AIR SOUTHWARD 
ACROSS OUR REGION AND PRODUCE BRISK WINDS. A WEAK RIDGE OF HIGH 
PRESSURE WILL BUILD OVER US SATURDAY NIGHT. TEMPERATURES WILL 
MODERATE A BIT SUNDAY AS A WEAK LOW MOVES EAST FROM THE CENTRAL 
LAKES REGION. A COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL MOVE 
THROUGH THE AREA EARLY MONDAY FOLLOWED BY ANOTHER SHOT OF COLD AIR.

&&

.NEAR TERM /THROUGH TONIGHT/...
PRECIPITATION IS DIVIDED INTO TWO DISTINCT AREAS...WITH ACTUALLY A
NARROW CLEARING LINE SEPARATING THE TWO. FIRST...LOOKING AT THE
NORTH COUNTRY...LOW PRESSURE NEAR CAPE COD IS RAPIDLY
INTENSIFYING...CURRENTLY AT AROUND 990 MB. BANDED PRECIPITATION ON
THE BACK OF THE LOW MATCHES UP FAIRLY CLOSELY WITH
OSWEGO...JEFFERSON...AND LEWIS COUNTIES...WITH LIGHT TO PERHAPS
MODERATE PRECIPITATION FALLING ACROSS THESE REGIONS. 06Z NAM/GFS
BOTH MAKE SENSE IN LIFTING THIS BAND TO THE NORTHEAST THROUGH THIS
AFTERNOON...WITH PRECIPITATION TRANSITIONING TO A MORE MESOSCALE
REGIME IN MINIMAL UPSLOPE/LAKE EFFECT PROCESSES. PROBABLY THE
BIGGEST CONCERN HERE IS THAT TEMPS ALOFT ARE COOLING FROM WEST TO
EAST...WHICH SHOULD LOWER SNOW LEVELS. ALREADY SNOWING AT 1500 FT
AT WORTH...WITH THIS LIKELY LOWERING TO 1000 FT OR LOWER. SNOW
ACCUMULATION SHOULD BE CONFINED TO ABOVE 1000 FT...ROUGHLY KEEPING
THIS IN THE TUG HILL. WILL ADD A MENTION OF 1 TO 2 INCHES THERE.

THE SECOND AREA OF PRECIPITATION IS BEING CAUSED BY THE
COMBINATION OF LAKE EFFECT AND UPSLOPING. 12Z BUF SOUNDING SHOWS
-4 C AT 850 MB...WITH THE BUFFALO NOS AT +9. THIS WILL INCREASE A
BIT WITH TIME...AND TO THE SOUTH WHERE ITS COOLER ALOFT...BUT
STILL EXPECT DELTA T/S TO RUN 13 TO 15 DEGREES C...WHICH IS QUITE
MODEST. HOWEVER...A 20 KNOT NORTHWEST FLOW AT DUNKIRK...SUGGESTS
UPSLOPING WILL ALSO BE A FACTOR...WITH THE BUFFALO RADAR SHOWING
RETURNS ACROSS THE SOUTHERN TIER. PERHAPS THE BEST INDICATION IS
ACTUALLY THE VISIBLE SATELLITE...WHICH SHOWS ENHANCEMENT VERY
CLOSE TO THE SHARP INCREASE IN ELEVATION ON THE CHAUTAUQUA
RIDGE...AND EXPECT A FAIRLY LOCALIZED BAND OF DECENT PRECIPITATION
IS OCCURRING HERE. ALONG THE LAKE SHORE...EXPECT ANY PRECIPITATION
IS FAIRLY LIGHT...AND IS MAINLY RAIN WITH THE LAKE KEEPING SURFACE
TEMPS IN THE UPPER 30S. HOWEVER...ACROSS HIGHER TERRAIN...FEEL 850
MB TEMPS OF -4 TO -6 WILL BE ENOUGH FOR PRIMARILY SNOWFALL. JUST
FOLLOWING SATELLITE ENHANCEMENT...EXPECT ACCUMULATING SNOW BAND TO
FALL IN UPSLOPE REGIONS...ROUGHLY NEAR OR SOUTHEAST OF FINDLEY
LAKE...TO MAYVILLE...TO FORESTVILLE. WILL FORECAST 1 TO 2 INCHES
HERE...THOUGH AMOUNTS ARE TRICKY GIVEN MARGINAL TEMPS AND WET
SNOW...AMOUNTS SHOULD VARY QUITE A BIT FROM LOCATION TO LOCATION.

OTHERWISE...TWEAKED TEMPERATURES TO MATCH OBSERVATIONS...WITH A
BLEND OF NAM12/LAMP WORKING WELL AND THEREFORE USED OUT THROUGH
THE DAY. 

TONIGHT, THE DEEPENING LOW OFF THE MAINE COAST WILL CONTINUE TO MOVE 
NORTHEAST WITH SOME WRAP AROUND PRECIP OVER THE REGION. THE BULK OF
PRECIP WILL BE FROM AREAS EAST OF THE GENESEE VALLEY, EASTWARD 
ACROSS CENTRAL NY AND NORTHERN NY. IN THESE AREAS WILL CARRY 
LKLY/CAT POPS WITH THE PRECIP TAPERING OFF LATER AT NGT ACROSS THE 
FINGER LKS. ACROSS THE HIGHER TERRAIN EAST OF LK ONTARIO EXPECT 
GENLY 1 TO 3 INCHES OF ACCUMULATION AT THIS TIME. THIS MAY HAVE TO 
BE ADJUSTED BY LATER FORECASTS. ELSEWHERE A RAIN/SNOW MIX IS 
EXPECTED OVERNIGHT WITH LITTLE OR NO ACCUM.  

THE NORTHWESTERLY UPSLOPE FLOW ACROSS THE HILLS OF THE SOUTHERN TIER 
WILL CONTINUE. I EXPECT THE UPSLOPE PRECIP TO CONTINUE BUT IT SHLD 
WEAKEN LATER AT NGT AS THE INVERSION HEIGHT LOWERS AND WE LOSE THE 
CRYSTAL GROWTH REGION. ALSO WITH THE NW WINDS INCREASING RESIDENCY 
TIME OVER THE LK WILL BE BRIEF. EXPECT AMNTS GENLY AN INCH OR LESS.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
A CYCLONIC FLOW OF COLD AIR WILL CONTINUE SATURDAY MORNING ON THE 
BACK SIDE OF A VERY DEEP SURFACE LOW OVER THE CANADIAN MARITIMES BUT 
LAKE INDUCED CAPES WILL BE SMALL ALONG WITH DROPPING EQUILIBRIUM 
LEVELS AND VERY LITTLE MOISTURE IN THE SNOW GROWTH AREA. WE WILL 
KEEP CHANCE POPS FOR AWHILE SOUTHEAST OF THE LAKES BUT THEN DIMINISH 
THEM AS HIGH PRESSURE BUILDS EAST FROM THE CENTRAL LAKES REGION. 
SYNOPTIC SCALE FORCING MAY STILL BE AROUND EARLY OVER THE EASTERN 
LAKE ONTARIO REGION BUT IT SHOULD MOVE OFF QUICKLY WITH THE 
DEPARTING LOW. IN GENERAL THE DAY WILL BE CHARACTERIZED BY MOSTLY 
CLOUDY SKIES AND BRISK WINDS. TEMPERATURES WILL BE NEAR NORMAL FOR 
THIS TIME OF YEAR BUT QUITE A BIT COLDER THAN WHAT WE HAVE BECOME 
ACCUSTOMED TO THIS MONTH.  

BOTH THE GFS AND NAM CONTINUE TO SHOW A WEAK SURFACE RIDGE BUILDING 
OVER US SATURDAY NIGHT AS A BROAD FLAT UPPER RIDGE PROGRESSES 
EASTWARD FROM THE CENTRAL LAKES REGION. WINDS WILL BE ON THE 
DECREASE AND SOME PARTIAL CLEARING SHOULD TAKE PLACE AS SUBSIDENCE 
ERODES LOW LEVEL CLOUDINESS.

SUNDAY IS STILL A BIT IN QUESTION. THE GFS DEVELOPS A SHORT WAVE IN 
THE ZONAL UPPER FLOW OVER THE CENTRAL LAKES MORE THAN THE NAM. THIS 
WILL LEAD TO LOWERING SURFACE PRESSURE JUST TO OUR WEST. ONE THING 
FOR SURE IS THAT IT WILL BE A BIT MILDER AS 850 MB TEMPERATURES ARE 
PROGGED TO RISE ABOVE ZERO CELSIUS. CLOUDS WILL BE ON THE INCREASE 
AGAIN BUT NOTHING HIGHER THAN CHANCE POPS AT THIS TIME AS THE 
CENTRAL GREAT LAKES LOW MOVES SLOWLY EAST.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
ANOTHER SHOT OF COLD AIR WILL FOLLOW THE THE GREAT LAKES LOW LATE 
SUNDAY NIGHT AND MONDAY. WE WILL HAVE TO BE CONCERNED WITH SCATTERED 
PRECIPITATION ACCOMPANYING THE COLDER AIR MASS WITH SOME LAKE 
INDUCED CAPE BECOMING INVOLVED AGAIN. AT THIS TIME IT DOESN'T LOOK 
LIKE ANYTHING TOO SERIOUS BUT A WEST NORTHWEST FLOW MONDAY NIGHT 
INTO TUESDAY MORNING MAY LEAD TO ACCUMULATING SNOWS OVER THE HILLS 
OF THE SOUTHERN TIER AND EAST OF LAKE ONTARIO.

THE COLD SHOT WILL BE BRIEF WITH WARM ADVECTION SCHEDULED ONCE AGAIN 
TUESDAY AFTERNOON INTO WEDNESDAY. JUST CHANCE POPS EAST OF THE LAKES 
EARLY TUESDAY OTHERWISE FAIR THROUGH WEDNESDAY NIGHT.

WE WILL KEEP CHANCE POPS FOR THURSDAY WITH PLENTY OF UNCERTAINTY ON 
WHAT HAPPENS TO THE SOUTHERN STREAM ENERGY. THE 00Z RUN OF THE GFS 
KEEPS THE PRECIPITATION SHIELD SOUTH OF US WITH 850 MB TEMPERATURES 
IN THE MINUS 8C RANGE WHILE THE ECMWF HAS A SURFACE LOW PASSING JUST 
TO THE SOUTH OF US WITH 850 TEMPS WARMER THAN 0C. 

FURTHER OUT...BOTH GFS AND ECMWF SHOW WESTERLY FLOW OF INCREASINGLY 
COLDER AIR AROUND STRONG VORTEX OVER UPPER LAKES FROM LATE THURSDAY 
INTO THE FOLLOWING WEEKEND. SUCH A PATTERN WOULD SERVE TO TURN ON 
THE LONG OVERDUE LAKE EFFECT MACHINE FOR US. STAY TUNED.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
BUF/IAG/ROC...GENERALLY MVFR (TO OCCASIONALLY IFR CONDITIONS)
THROUGH THIS EVENING IN CIGS. A BAND OF SHOWERS WILL MOVE ACROSS
FROM NW-SE LATE AFTERNOON AND EARLY EVENING...BUT SHOULD NOT BE
HEAVY ENOUGH TO LOWER VSBY BELOW 5SM. FROM MIDNIGHT TO MID-MORNING
SATURDAY...FEEL MVFR CIGS WILL LIKELY REMAIN IN PLACE...BUT COULD
SEE BREAKS TO VFR. TAFS CURRENTLY ON THE MORE PESSIMISTIC SIDE OF
THE POSSIBILITIES. EXPECT CIGS TO RISE LATE SATURDAY MORNING AS
THE ATMOSPHERE WARMS LIFTING THE CLOUD LAYER A BIT. WIND WILL BE
STRONGEST AT ROC...WHERE GUSTS TO 30 KTS ARE POSSIBLE TONIGHT.

JHW...EXPECT A COMBINATION OF LAKE EFFECT AND UPSLOPING TO
CONTINUE THE -SN THROUGH 00Z...THEN SNOW SHOULD RATHER QUICKLY
TAPER OFF BETWEEN 00Z AND 03Z. EXPECT IFR-LIFR CONDITIONS IN THE
SNOW...WITH A BAND OF MODERATE SNOW CAUSING VSBY TO LOWER BELOW A
MILE FOR AN HOUR OR TWO LATE AFTERNOON. TIMING THE LIFTING OF CIGS
TONIGHT IS DIFFICULT...THOUGH DO FEEL CONFIDENT CIGS WILL
EVENTUALLY RISE TO MVFR WITH TIME AS WINDS ON THE LAKE SHIFT MORE
W-SW. TAFS...IF ANYTHING...ON THE PESSIMISTIC SIDE.

ART...MVFR CONDITIONS LIKELY THROUGH SATURDAY MORNING...IN CIGS. EXPECT
A BAND OF RAIN TO MOVE THROUGH THIS EVENING...WITH LITTLE IMPACT
ON CONDITIONS...THOUGH IT MAY BRIEFLY MIX WITH SNOW. CIGS WILL
LIFT SATURDAY MORNING...WITH A RETURN TO VFR CONDITIONS LIKELY. WIND
WILL ALSO BE AN ISSUE...WITH GUSTS TO 30 KTS POSSIBLE TONIGHT.

OUTLOOK...
SUNDAY...VFR LIKELY. CHC SHOWERS IN WEST IN THE AFTERNOON.
MONDAY...MVFR. CHC RAIN/SNOW SHWRS. 
TUESDAY...VFR/MVFR. CHC RAIN/SNOW SHWRS.

&&

.MARINE...
WINDS WILL BE ON THE INCREASE TODAY AS LOW PRESSURE DEEPENS RAPIDLY 
ALONG THE NEW ENGLAND COAST. SMALL CRAFT ADVISORIES WILL BE NEEDED 
FOR MOST AREAS LATER TODAY INTO SATURDAY. SUSTAINED WINDS OVER THE 
LAKES WILL APPROACH GALE FORCE AND SOME GUSTS WILL BE ABOVE GALE 
FORCE.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EST SATURDAY FOR LEZ040-041.
         SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 10 AM EST 
         SATURDAY FOR LEZ020.
         SMALL CRAFT ADVISORY UNTIL 7 PM EST SATURDAY FOR 
         LOZ042>045.
         SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 1 PM 
         EST SATURDAY FOR SLZ022-024.

&&

$$

SYNOPSIS...SAGE
NEAR TERM...APFFEL/JJP
SHORT TERM...SAGE
LONG TERM...SAGE/SFM
AVIATION...APFFEL/RSH
MARINE...SAGE/APFFEL