FXUS61 KBUF 080249
AFDBUF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
949 PM EST MON DEC 7 2009
.SYNOPSIS...
WEAK LOW PRESSURE WILL DRIFT SLOWLY NORTHEAST FROM THE REGION
OVERNIGHT WITH SNOW SHOWERS BECOMING CONFINED TO AREAS SOUTHEAST OF
THE LAKES. OUR ATTENTION WILL THEN TURN TO A POWERFUL EARLY WINTER
STORM SYSTEM THAT WILL IMPACT OUR REGION FROM LATE TUESDAY NIGHT
INTO FRIDAY. MIXED PRECIPITATION IN ADVANCE OF THE STORM WILL CHANGE
TO RAIN WEDNESDAY WITH VERY STRONG WINDS DEVELOPING. THE STRONG
WINDS WILL THEN BE ACCOMPANIED BY LOWER TEMPERATURES AND WIDESPREAD
LAKE EFFECT SNOW SHOWERS FROM LATER WEDNESDAY NIGHT INTO AT LEAST
FRIDAY.
&&
.NEAR TERM /THROUGH TUESDAY/...
UPDATED THE FORECAST TO INCREASE POPS TO CAT RANGE EAST OF LK ERIE
ACROSS ERIE, GENESEE, WYOMING, CHAU AND CATT COUNTIES. ACTIVITY SHLD
MOVE SOUTH OF NORTHERN ERIE AND GENESEE COUNTIES DURG THE EVENING
AFTER ACCUMS GENLY OF AN INCH OR TWO. INCREASED AMOUNTS TO 1 TO 3
INCHES ACROSS SOUTHERN ERIE, WYOMING, CHAU AND CATT COUNTIES.
EAST OF LAKE ONTARIO, BASED ON LATEST NAM12, HAVE BROUGHT LK EFFECT
A BIT FURTHER SOUTH LATER TONIGHT WITH CAT POPS INTO CENTRAL OSWEGO
COUNTY. AT THIS TIME WILL STAY WITH 1 TO 2 INCHES ACCUMULATION DUE
TO EXPECTED MIGRATION OF THE ACTIVITY SOUTHWARD AS THE NIGHT
PROGRESSES BUT THIS WILL HAVE TO BE WATCHED CLOSELY.
EARLIER DISCO BELOW...
SYNOPTIC SCALE AND MESOSCALE INFLUENCES WILL IMPACT THE AREA TONIGHT
THROUGH PART OF TUESDAY MORNING.
THE WEAK SURFACE LOW THAT IS CENTERED NEAR GEORGIAN BAY THIS
AFTERNOON WILL CONTINUE TO MOVE TO THE EAST AND SLIDE OFF THE SLIDE
OFF THE NEW ENGLAND COAST TONIGHT. LIGHT SNOW CONTINUES TO SPREAD
EAST ACROSS THE CWA AND IS BECOMING A LITTLE BETTER ORGANIZED ACROSS
THE SOUTHERN TIER DUE TO THE ADDED LIFT FROM MID LEVEL SHORT THAT IS
APPROACHING WESTERN NEW YORK. AS THE LOW TRACKS JUST NORTH OF LAKE
ONTARIO LATER THIS AFTERNOON INTO THE EARLY EVENING...THE BOUNDARY
LAYER WINDS WILL LINE UP MORE FROM THE SOUTHWEST. THIS MAY RESULT IN
A BRIEF PERIOD OF LAKE ENHANCED SNOW ACROSS ERIE COUNTY...INCLUDING
THE BUFFALO METRO AREA...BUT ONLY MINOR ACCUMULATIONS ARE EXPECTED.
THE LAKE SNOWS WILL THEN SHIFT TO THE SOUTH...AND IMPACT THE
SOUTHERN TIER TONIGHT...BUT ACCUMULATIONS SHOULD REMAIN BELOW
ADVISORY CRITERIA AS THE LOW LEVEL MOISTURE DECREASES AFTER 06Z AND
THE DIRECTIONAL WIND SHEAR INCREASES.
THE SITUATION EAST OF LAKE ONTARIO WILL BE A LITTLE MORE COMPLICATED
TONIGHT. A SURFACE TROUGH THAT EXTENDS WEST OF THE DEPARTING SURFACE
LOW IS FORECAST TO REMAIN JUST NORTH OF LAKE ONTARIO THROUGH A GOOD
PART OF TONIGHT. THE PRESENCE OF THIS BOUNDARY WILL TEND TO INCREASE
THE LOW LEVEL WIND SHEAR WHICH WILL MAKE IT MORE DIFFICULT FOR
ORGANIZED LAKE SNOW BANDS TO SET UP. HOWEVER...THERE WILL BE
SUFFICIENT CONVERGENCE IN THE VICINITY OF THE TROUGH...COMBINED WITH
SOME RESPONSE FROM THE LAKE AS THE FLOW DOES BECOME BETTER ALIGNED
FROM THE WEST NORTHWEST LATE TONIGHT. BASED ON THESE TRENDS...WILL
MAINTAIN LIKELY POPS ACROSS MOST OF THE NORTH COUNTRY...WITH ANOTHER
1 TO 2 INCHES OF SNOW EXPECTED.
FOR TUESDAY...ANY SNOW THAT LINGERS EAST OF LAKE ONTARIO...SHOULD
BE ENDING BY 15Z. OTHERWISE...HIGH PRESSURE RIDGING OVER THE STATE
WILL BRING DRY CONDITIONS TO THE CWA. THERE WILL BE A GRADUAL
INCREASE IN MID LEVEL CLOUDS DURING THE AFTERNOON AS THE
INTENSIFYING WINTER STORM APPROACHES FROM THE WEST.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
THIS PERIOD OF THE FORECAST WILL BE CHALLENGING AND VERY IMPORTANT
FOR PUBLIC DECISIONS.
A STRONG SHORTWAVE WILL CROSS THE MISSISSIPPI VALLEY AND MIDWEST
TUESDAY NIGHT. THE SFC REFLECTION OF THIS SHORTWAVE...IN THE FORM OF
A POWERFUL EARLY WINTER STORM...WILL MOVE NORTHEAST FROM OKLAHOMA TO
NEAR CHICAGO. BOTH THE GFS AND ECMWF ARE VERY SIMILAR IN THEIR
SOLUTIONS...WITH A CENTRAL PRESSURE DEEPENING TO ARND 980MB BY
DAYBREAK WEDNESDAY.
A MOISTURE RICH SOUTHERLY FLOW (60KT LL JET) WILL DEVELOP ACROSS OUR
WESTERN COUNTIES IN ADVANCE OF THE STORM SYSTEM TUESDAY NIGHT. THE
DEEPENING MOISTURE FIELD WILL COMBINE WITH SEVERAL SOURCES OF LIFT
TO GENERATE WIDESPREAD SNOW AS TUESDAY NIGHT PROGRESSES. THE THREE
MAIN SOURCES OF LIFT WILL INCLUDE ISENTROPIC LIFT FROM THE
WAA...DIFFLUENT FLOW ALOFT AND A COUPLED H25 150KT JET.
WIDESPREAD SNOW WILL BREAK OUT ACROSS THE WESTERN COUNTIES BY
MIDNIGHT WITH THE SNOW GRADUALLY SPREADING NORTH AND EAST ACROSS THE
NORTH COUNTRY. GFS POINT SOUNDINGS ARE STILL SUGGESTING THAT THE
PCPN WILL BE IN THE FORM OF SNOW AT THE ONSET FOR ALL SITES. THE
SNOW MAY MIX WITH SLEET AND FREEZING RAIN OVER MUCH OF THE WRN
SOUTHERN TIER BY DAYBREAK WEDNESDAY. THE TIMING OF THIS CHANGEOVER
WILL BE IMPORTANT AS TO HOW MUCH SNOW ACCUMULATES. EARLY ESTIMATES
FOR SNOWFALL TUESDAY NIGHT WILL GENERALLY BE 2 INCHES OR LESS...BUT
A SLOWER CHANGEOVER COULD EASILY TRANSLATE INTO ADVISORY CRITERIA
SNOWFALL AMOUNTS.
THE NEWLY PHASED STORM WILL THEN TRACK FROM CHICAGO TO GEORGIAN BAY
ON WEDNESDAY WHILE FURTHER DEEPENING TO ABOUT 975MB. AGAIN...THE GFS
AND ECMWF ARE REMARKABLY SIMILAR IN THEIR SOLUTIONS. THE 975MB CENT
PRESSURE WILL BE SOME 3 TO 4 STANDARD DEVIATIONS BELOW NORMAL MID
DECEMBER VALUES...WHICH IS AN EASY CLUE TO A SIGNIFICANT WEATHER
EVENT. IN ANY CASE...THE TRACK OF THIS POWERFUL STORM TO OUR WEST
WILL RESULT IN STRONG WARM ADVECTION ACROSS ALL OF OUR REGION. THIS
WILL CHANGE ALL OF THE WINTRY PCPN TO RAIN WEDNESDAY AS H85 TEMPS
WILL PEAK AT ABOUT +5C.
THE PASSAGE OF A COLD FRONT LATE WEDNESDAY AFTERNOON WILL THEN USHER
THE RETURN OF COLD AIR TO THE REGION...PARTICULARLY THE WRN COUNTIES
WHERE THE RAIN WILL CHANGE BACK TO SNOW BY EVENING. MORE IMPORTANTLY
THE SFC WINDS WILL PICK UP WITHIN THE CYCLONIC COLD ADVECTIVE
PATTERN WITH WINDS INCREASING TO 25 TO 40 MPH WEDNESDAY EVENING WITH
ADDITIONAL STRENGTHENING OF THE WINDS DURING THE COURSE OF WEDNESDAY
NIGHT.
THE DEEP LOW WILL LIFT NORTHEAST TO WESTERN QUEBEC WEDNESDAY NIGHT.
THIS WILL PLACE OUR REGION ON THE BACKSIDE OF A TIGHTLY WOUND WINTER
STORM WITH MUCH COLDER AIR CHARGING INTO OUR AREA ON STRONG WESTERLY
WINDS. THESE WINDS WILL BE AT LEAST ADVISORY CRITERIA LEVELS WITH
THE POTENTIAL FOR WARNING CRITERIA TO BE MET. AS MENTIONED IN
PREVIOUS DISCUSSIONS THOUGH...AN IMPORTANT INGREDIENT MISSING FOR A
CLASSIC HIGH WIND EVENT IS THE STRONG WINDS ALOFT. WINDS WILL ONLY
AVERAGE 50 KNOTS BETWEEN 3-8K FT...BUT THESE WILL STILL BE STRONG
ENOUGH TO CAUSE PROBLEMS.
H85 TEMPS WILL DROP TO -10C WEDNESDAY NIGHT...AND THIS WILL SET UP
STEEP LAPSE RATES IN THE LOWEST 8K FT OR SO OF THE BOUNDARY LAYER
OVER THE LAKES. THIS WILL ALLOW LAKE SNOWS TO DEVELOP EAST OF BOTH
LAKES...BUT DUE TO THE VERY STRONG WINDS...THE SNOW BANDS WILL NOT
BE AS CONCENTRATED OR INTENSE AS THEY WOULD OTHERWISE BE. THEY WILL
ALSO EXTEND FURTHER INLAND. WHILE THE BANDS COULD INITIALLY SET UP
OVER THE BUF AND ART METRO AREAS DURING THE FIRST HALF OF WEDNESDAY
NIGHT...THE BANDS ARE EXPECTED TO SETTLE TO THE SOUTH AS THE FLOW
VEERS TO A MORE WESTERLY FETCH.
THE DEEP LOW WILL CONTINUE TO LIFT AWAY FRO THE REGION ON THURSDAY
AS IT TRACKS ACROSS SOUTHERN QUEBEC. A TIGHT PRESSURE GRADIENT WILL
REMAIN IN PLACE OVER OUR REGION WITH 3-5MB/3HR ISALLOBARIC PRESSURE
RISES FORECAST. THIS WILL MAKE THURSDAY A VERY WINDY DAY...AND WITH
H85 TEMPS FALLING TO -15C...THERE WILL BE WIDESPREAD WIND SWEPT LAKE
EFFECT SNOW SHOWERS. THE STRONG WINDS WILL GREATLY LIMIT THE
RESIDENCY TIME FOR THE AIR OVER THE LAKES...SO ACCUMS BOTH WED NIGHT
AND THURSDAY WILL LIKELY BE LIMITED. EVEN SO...THE VERY STRONG WINDS
AND WIDESPREAD LAKE SNOW SHOWERS WILL COMBINE TO PRODUCE TIMES OF
VERY POOR VISIBILITY. IN FACT...BLIZZARD LIKE CONDITIONS MAY BE
EXPERIENCED AT TIMES.
WHILE SNOWFALL WILL LIKELY BE HELD IN CHECK BY THE STRONG WINDS...
BOTH THE GFS AND ECMWF SUGGEST A STRONG MULTI-LAKE CONNECTION FROM
LAKE SUPERIOR AND HURON...ACROSS LAKE ONTARIO. THIS WELL PRIMED BAND
COULD THUS BE MUCH MORE EFFICIENT AND PERFORM TO A MORE IMPRESSIVE
LEVEL THAN ITS LAKE ERIE COUNTERPART. THIS WILL PUT OSWEGO COUNTY
AND THE TUG HILL REGION WITHIN THE CROSS HAIRS FOR WHAT COULD PROVE
TO BE DANGEROUS CONDITIONS LATER THURSDAY INTO THURSDAY NIGHT AS H85
TEMPS CONTINUE TO PLUMMET TO BETWEEN -16 AND -20C.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
THIS PERIOD WILL START WITH SOME OF THE COLDEST SFC TEMPERATURES FOR
THE SEASON...WITH LAKE EFFECT SNOW CONTINUING DOWNWIND OF THE LAKES.
STILL WINDY ON FRIDAY UNTIL SFC HIGH BUILDS IN SATURDAY WITH
DIMINISHING WINDS...AS WELL AS DIMINISHING LAKE EFFECT. TEMPERATURES
WILL CONTINUE TO RUN BELOW NORMAL INTO THE START OF NEXT WEEK.
FOR FRIDAY 850 HPA TEMPERATURES DROP TO -16 TO -20C BEFORE THE BROAD
BASED ARCTIC LIKE TROUGH OVER THE GREAT LAKES SLOWLY LIFTS OUT.
THIS WILL RESULT IN ACCUMULATING SNOWS DOWNWIND OF BOTH LAKES IN
TRADITIONAL SNOWBELT AREAS. GFS BUFKIT DATA SHOWS SFC WINDS STILL 20
PLUS KNOTS TO START FRIDAY...BUT AS SFC HIGH FROM NOSES IN FROM THE
SOUTH WINDS WILL BEGIN TO SLACKEN THROUGH THE DAY.
THE TROUGH WILL CONTINUE TO LIFT ON SATURDAY WHILE HIGH PRESSURE
WILL WORK NORTHWARDS FROM THE OHIO VALLEY. THIS WILL HELP TO LOWER
THE EQUILIBRIUM LEVEL...AT LEAST ON LAKE ERIE...SO THE LAKE SNOWS
SHOULD START TO DIMINISH IN INTENSITY AND COVERAGE. TEMPS WILL
REMAIN WELL BELOW NORMAL THOUGH....WITH HIGHS IN MOST AREAS STAYING
BELOW FREEZING.
A MID LEVEL RIDGE WILL THEN BUILD ACROSS THE LOWER GREAT LAKES
FRIDAY NIGHT AND SATURDAY. THIS WILL FURTHER DIMINISH THE LAKE SNOW
SHOWERS WITH JUST FLURRIES EXPECTED FOR THE REGION BY SUNDAY
AFTERNOON.
12Z ECMWF AND 12Z GFS BRING ANOTHER TROUGH WITH TRAILING COLDER AIR
ACROSS THE REGION LATER SUNDAY AND INTO SUNDAY NIGHT. THIS WILL
AGAIN INCREASE THE CHANCES FOR SNOW...FIRST NEAR METRO BUFFALO AND
METRO WATERTOWN...BEFORE ANY LAKE EFFECT SNOW SLIDES SOUTHWARD. FOR
NOW WILL GO WITH LOW POPS UNTIL WE GET CLOSER TO NEXT WEEKEND.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
BUF/IAG/ROC...EXPECT VFR CONDITIONS FOR TONIGHT AND TUESDAY.
EXPECT -SHSN TO REMAIN SOUTH OF THESE TAF SITES...WITH ONLY
SPARSE AREAS OF MVFR CIGS FOR THE REMAINDER OF THE NIGHT...LACKING
AREAL COVERAGE TO JUSTIFY A TEMPO GROUP.
JHW...EXPECT LAKE EFFECT -SN TO BE HEAVIEST THROUGH 06Z...THEN
TAPER OFF. BETWEEN 06Z AND 12Z DIFFICULT...WITH CIGS/VSBY IN VERY
LIGHT SNOW HARD TO PIN DOWN...BUT MVFR THE MOST LIKELY RESULT.
CIGS SHOULD LIFT DURING THE DAY TUESDAY GIVING WAY TO VFR
CONDITIONS.
AT ART...EXPECT BAND TO QUICKLY CROSS BEFORE 06Z...ONLY BRINGING AN
HOUR OR TWO OF MVFR CONDITIONS BEFORE SETTLING SOUTH OF THE TAF
SITE. THIS A BIT MORE OPTIMISTIC THAN PREVIOUS TAF...BASED ON
RADAR TRENDS. VFR CONDITIONS EXPECTED TUESDAY.
OUTLOOK...
TUESDAY NIGHT...CONDITIONS LOWERING TO MVFR/IFR IN SNOW AND MIXED
PRECIP. LLWS LIKELY LATE.
WEDNESDAY...MVFR/IFR WITH RAIN/SNOW. LOW LEVEL WIND SHEAR LIKELY
EARLY.
THURSDAY...MVFR/IFR SNOW SHOWERS. STRONG SURFACE WINDS LIKELY.
FRIDAY...VFR/MVFR IN SNOW SHOWERS.
&&
.MARINE...
A WEAK PRESSURE GRADIENT WILL THEN BE FOUND OVER LAKES ERIE AND
ONTARIO TONIGHT THROUGH TUESDAY AS HIGH PRESSURE WILL DRIFT ACROSS
THE REGION. THESE TRANQUIL CONDITIONS WILL QUICKLY GIVE WAY TO VERY
STRONG WINDS LATER TUESDAY NIGHT THROUGH AT LEAST THURSDAY NIGHT AS
A POWERFUL EARLY WINTER STORM WILL LIFT ACROSS THE GREAT LAKES
REGION.
WINDS IN THE WAKE OF THE DEEP STORM SYSTEM WILL REACH AT LEAST HIGH
END GALES WEDNESDAY NIGHT AND THURSDAY...WITH THE LIKELIHOOD OF
STORM FORCE GUSTS. A GALE WATCH WILL BE ISSUED FOR LAKE ERIE
STARTING WEDNESDAY AND FOR LAKE ONTARIO STARTING WEDNESDAY NIGHT.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...GALE WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING FOR
LOZ062>065.
&&
$$
SYNOPSIS...RSH/SAGE
NEAR TERM...JJP/TJP
SHORT TERM...RSH/SAGE
LONG TERM...RSH/THOMAS
AVIATION...APFFEL
MARINE...RSH/SAGE
