FXUS61 KBUF 150856
AFDBUF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
356 AM EST TUE DEC 15 2009
.SYNOPSIS...
LOW PRESSURE WILL TRACK ACROSS NORTHERN NEW ENGLAND
TODAY...STRENGTHENING AS IT MOVES INTO THE CANADIAN MARITIMES
WEDNESDAY. THIS WILL SET UP A NORTHWEST FLOW OF PROGRESSIVELY COLDER
AIR THROUGH THE MIDDLE AND LATTER PART OF THE WEEK. EXPECT A PERIOD
LAKE EFFECT SNOW SOUTHEAST OF LAKE ONTARIO MID-WEEK...WITH MORE
LIMITED ACTIVITY SOUTHEAST OF LAKE ERIE.
&&
.NEAR TERM /THROUGH TONIGHT/...
08Z SURFACE ANALYSIS SHOWS SURFACE LOW PRESSURE LOCATED JUST TO THE
NORTHWEST OF WATERTOWN...WITH ITS TRAILING COLD FRONT EXTENDING BACK
ACROSS THE GENESEE VALLEY. THE TRACK OF THE LOW JUST TO THE NORTH OF
THE FORECAST AREA HAS RESULTED IN TEMPERATURES WARMING INTO THE
LOWER 40S ACROSS THE BULK OF THE AREA DURING THE NIGHT...WITH SOME
MID AND UPPER 30S STILL FOUND ACROSS THE HIGHER ELEVATIONS EAST OF
LAKE ONTARIO. COUPLED WITH THE LACK OF A FAVORABLE DENDRITIC SNOW
GROWTH REGION ALOFT...THESE MILD BOUNDARY LAYER TEMPERATURES HAVE
RESULTED IN THE VAST MAJORITY OF THE PRECIPITATION FALLING IN THE
FORM OF RAIN.
RECENT RADAR IMAGERY SHOWS AREAS OF LIGHT RAIN AND DRIZZLE
PERSISTING ALONG AND BEHIND THE AFOREMENTIONED FRONTAL BOUNDARY...
WITH SOME TERRAIN ENHANCEMENT NOW SHOWING UP ALONG THE CHAUTAUQUA
RIDGE WITH THE LOW LEVEL FLOW TURNING MORE WESTERLY. AS THE FRONT
PUSHES THROUGH THE REMAINDER OF THE AREA AND THE FLOW BECOMES MORE
WESTERLY THIS MORNING...EXPECT THIS GENERAL PATTERN TO GRADUALLY
TRANSITION TO ONE FAVORING THE AREAS OF HIGHER TERRAIN EAST OF BOTH
LAKES...WHICH SHOULD THEN PERSIST THROUGH MIDDAY. ACCORDINGLY...WILL
CONTINUE TO CARRY LIKELY POPS IN THESE AREAS THROUGH THE
MORNING...WHILE DROPPING PROBABILITIES TO THE CHANCE RANGE
ELSEWHERE. WITH WEAK COLD ADVECTION RESULTING IN ONLY A SLOW DROP IN
BOUNDARY LAYER TEMPS..SURFACE TEMPS SHOULD STAY ABOVE FREEZING
THROUGH MIDDAY. THIS FACTOR...COMBINED WITH THE CONTINUED LACK OF A
FAVORABLE SNOW GROWTH REGION ALOFT...SHOULD RESULT IN ANY LINGERING
PRECIP REMAINING IN THE FORM OF RAIN/DRIZZLE THROUGH THE MORNING
HOURS.
AS WE GET INTO THIS AFTERNOON...THE COLD ADVECTION REGIME WILL
INTENSIFY AS UPPER TROUGHING INCREASES BEHIND THE DEPARTING SURFACE
LOW...RESULTING IN 850MB TEMPS DROPPING TO THE -10C TO -12C RANGE BY
EARLY THIS EVENING. AS THE COLD AIR DEEPENS AND A FAVORABLE SNOW
GROWTH REGION IS REINTRODUCED...ANY LINGERING RAIN SHOWERS WILL
CHANGE OVER TO SNOW SHOWERS FROM NORTHWEST TO SOUTHEAST...WITH SOME
LAKE RESPONSE BECOMING LIKELY EAST-SOUTHEAST OF THE LAKES GIVEN THE
PREVAILING WEST-NORTHWESTERLY FLOW THAT WILL BE IN PLACE. LATE IN
THE DAY...A SWATH OF MORE GENERAL SNOW SHOWERS WILL ALSO ARRIVE IN
THE WEST LATER IN THE AFTERNOON IN ASSOCIATION WITH THE APPROACHING
UPPER TROUGH AXIS/ASSOCIATED SHORTWAVE ENERGY. HAVE THEREFORE
CONTINUED TO INDICATE POPS INCREASING TO HIGH LIKELY BY LATE IN THE
DAY IN THE FAVORED LAKE EFFECT AREAS...AND HAVE ALSO BROUGHT SOME
LOW LIKELY POPS INTO THE WEST LATE IN THE AFTERNOON TO ACCOUNT FOR
THE IMPINGING UPPER TROUGH. ALL THIS SAID...ANY ACCUMS THROUGH
SUNSET SHOULD REMAIN ON THE LOW SIDE...GENERALLY AN INCH OR LESS.
DURING TONIGHT...THE AFOREMENTIONED UPPER TROUGH AXIS/ASSOCIATED
SHORTWAVE WILL WORK ACROSS THE AREA DURING THE EVENING...BRINGING
EVERYONE A SEVERAL HOUR PERIOD WHERE SNOW SHOWERS WILL BE
LIKELY...ALONG WITH SOME MINOR ACCUMULATIONS OF AN INCH OR LESS.
EAST SOUTHEAST OF THE LAKES...LAKE EFFECT/UPSLOPE PROCESSES WILL
CONTINUE AS 850 MB TEMPS CONTINUE TO DROP TO THE -14C TO -16C RANGE
BY LATE TONIGHT...AND AS SUCH HAVE INDICATED HIGH LIKELY TO
CATEGORICAL POPS IN THESE AREAS.
SOUTHEAST OF LAKE ERIE...THIS ENHANCEMENT WILL BE KEPT IN CHECK BY
THE SHORT FETCH ACROSS THE LAKE...RELATIVELY LOW INVERSION HEIGHTS
THAT WILL LOWER FROM 5-6 KFT TO AROUND 3 KFT DURING THE COURSE OF
THE NIGHT...AND THE RELATIVELY SHALLOW LAYER OF MOISTURE THAT WILL
BE FOUND BENEATH THIS INVERSION. IN THIS AREA...HAVE INDICATED A
GENERAL 1-2" ON SNOW TONIGHT...WITH THE BULK OF ANY ACCUMS COMING
DURING THE FIRST HALF OF THE NIGHT WHEN CONDITIONS WILL BE MORE
FAVORABLE.
MEANWHILE OFF OF LAKE ONTARIO...THE LAKE-ENHANCED SNOWS SHOULD BE A
BIT STRONGER GIVEN THE PRESENCE OF A SIGNIFICANTLY HIGHER INITIAL
CAP THAT WILL GRADUALLY LOWER FROM 9-10 KFT TO AROUND 6 KFT...A
DEEPER MOISTURE FIELD BELOW THIS CAP...AND THE POTENTIAL FOR AN
UPSTREAM CONNECTION TO LAKE HURON/GEORGIAN BAY. NEGATIVE FACTORS
WILL BE THE SHORT FETCH ACROSS THE LAKE...THE POTENTIAL FOR SOME
SHEAR...AND THE POSSIBILITY OF SOME DISRUPTION WHEN THE
AFOREMENTIONED SHORTWAVE PASSES THROUGH THE AREA. FOR NOW...HAVE
ELECTED TO HOLD OFF ON ANY FLAGS AND JUST RAISE SNOWFALL AMOUNTS TO
THE 2-4 INCH RANGE FOR AREAS FROM ROCHESTER EAST TO OSWEGO/SOUTHEAST
INTO THE NORTHERN FINGER LAKES...THOUGH THE DAY SHIFT WILL NEED TO
MONITOR THIS CLOSELY IN CASE ADVISORY-CRITERIA SNOWS BECOME MORE
LIKELY.
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
RAPIDLY INTENSIFYING LOW PRESSURE IN THE CANADIAN MARITIMES WILL BE
A SEMI-PERMANENT FEATURE IN THE CANADIAN MARITIMES THROUGH THURSDAY
AS THE SURFACE LOW GETS CAPTURED BY THE 500 MB LOW...EFFECTIVELY
CAUSING THE SURFACE LOW TO STALL UNTIL LATER IN THE WEAK.
BY WEDNESDAY...THE FIRST BATCH OF COLD AIR WILL BE IN PLACE...WITH
850 MB TEMPS FORECAST TO BE ABOUT -15 C ACROSS ONTARIO AND -13 C
ACROSS EASTERN LAKE ERIE. WHILE THESE TEMPERATURES ARE FAIRLY
SIMILAR...THE BUFFALO FORECAST SOUNDING SHOWS A LOWER CAP (5K FT VS.
7K FT) LIMITING LAKE INDUCED CAPES...AND RAISING POTENTIAL SNOW
GROWTH ISSUES. SO BASED ON THIS...FEEL ONTARIO IS FAIRLY RIPE FOR A
LAKE EFFECT BAND TO DEVELOP...WITH LAKE ERIE MARGINAL. A WESTERLY
925 MB FLOW OF AROUND 30 KTS DEVELOPS...WITH LIGHT SHEAR TO 850 ON
ONTARIO...WITH MORE SHEAR ON ERIE. FEEL THIS WILL PROVIDE A SOLID 6
HR WINDOW FOR DEVELOPMENT ON LAKE ONTARIO...GENERALLY FALLING
BETWEEN 15Z AND 21Z. BAND WILL MOSTLY LIKELY CENTER NEAR OSWEGO
COUNTY...WITH SNOW ACCUMULATIONS UPPED TO 2 TO 4 INCHES. LOCALLY
HIGHER AMOUNTS ARE POSSIBLE. AFTER 21Z AN APPROACHING ARCTIC FRONT
WILL CAUSE THE BAND TO LIFT TO THE NORTH INTO NORTHERN
OSWEGO/SOUTHERN JEFFERSON COUNTY...HOWEVER THE WIND SHIFT WILL
LIKELY DISRUPT THE BAND AS WELL. ON LAKE ERIE...AM MUCH LESS
IMPRESSED. WHILE THERE IS POTENTIAL FOR SOME HIGHER AMOUNTS...FEEL
THE MOST LIKELY SNOWFALL RANGE WILL BE IN THE 1 TO 3 INCHES ON
WEDNESDAY...AND CAN SEE A SCENARIO WHERE THE SNOW BAND SIMPLY NEVER
REALLY GETS GOING THERE. OUTSIDE OF THE LAKE EFFECT BANDS IT SHOULD
BE A FAIR BUT CHILLY DAY.
WEDNESDAY NIGHT...THE KEY PLAYER IS AN ARCTIC BOUNDARY WHICH IS
PUSHED ALL THE WAY TO NORTHERN PARTS OF THE CWA BY THE INTENSIFYING
LOW. FOR LAKE EFFECT SNOW...LAKE ERIE CONDITIONS REMAIN LARGELY THE
SAME...WITH THE BOUNDARY REMAINING NORTH OF IT UNTIL LATE WHEN THE
NW SHIFT SHOULD NOT PROVIDE ENOUGH TIME ACROSS THE WATERS FOR
DEVELOPMENT. LAKE ONTARIO IS TRICKY...WITH POST FRONTAL SOUNDINGS
SHOW STEEP LOW LEVEL LAPSE RATES...WITH A LOWER CAP AS THE ARCTIC
AIR IS FAIRLY SHALLOW. HOWEVER TEMPERATURES ARE SO COLD THAT THERE
IS SOME POTENTIAL...BUT SEE THIS AS A MUCH MORE QUESTIONABLE IN
TERMS OF LAKE EFFECT...WITH ONLY LIGHT SNOW ACCUMULATIONS
ANTICIPATED. PERHAPS THE BIGGEST WEATHER STORY OF THE NIGHT WILL BE
THE ARCTIC BOUNDARY ITSELF. THE FRONT SHOULD STALL SOMEWHERE ACROSS
SOUTHERN PORTIONS OF THE CWA...AS THE TRUE ARCTIC AIR GROWS SHALLOW
AND GETS TOO FAR FROM ITS PUSH. FEEL THE NAM/GFS OFTEN PUSH THE
ARCTIC AIR TOO FAR IN THESE CASES...THUS ADD A BLEND OF THE SREF FOR
TEMPS. ALSO SHARPEN THIS BOUNDARY...WITH THE NORTH COUNTRY LIKELY
BREAKING IN THE COLD AIR...BELOW ZERO SHOULD BE WITH IN REACH.
EXPECT THE ARCTIC BOUNDARY TO ALSO PICK UP THE LAKE EFFECT MOISTURE
IN FRONT OF IT...BRINGING A PERIOD OF SNOW SHOWERS OR SNOW SQUALLS
TO SOME NON-LAKE EFFECT LOCATIONS. AT THIS TIME...35 KT 850 MB FLOW
ABOVE SHARP INVERSION...SO WILL JUST GO WITH SNOW SHOWERS INSTEAD
OF SQUALLS.
ON THURSDAY COLD AIR IS SHALLOW...WITH THE INVERSION AT ONLY 2-3K
FT. TEMPS ALOFT ARE COLD ENOUGH FOR SNOW GROWTH...BUT QUESTION
WHETHER THERE WILL BE ENOUGH TIME ON THE LAKE IN THE NW FLOW TO PICK
UP ENOUGH MOISTURE FOR LAKE EFFECT BANDS TO DEVELOP. ONLY CARRY
CHANCE POPS...WITH A SIGNIFICANT EVENT NOT ANTICIPATED AT THIS
POINT...THOUGH SOME LIGHT ACCUMULATIONS CANNOT BE RULED OUT. A
QUICKLY AS THE ARCTIC AIR CAME IT...IT WILL STALL AND RETREAT AS THE
LOW WEAKENS. WHILE IT STILL WILL BE A CHILLY DAY...ONLY THE NORTH
COUNTRY IS LIKELY TO REMAIN IN THE ARCTIC AIR...WITH HIGHS ONLY IN
THE TEENS.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
00Z GFS RUN RIGHT IN LINE WITH GOING FORECAST AND 12Z EUROPEAN.
NOTED A BIT OF A SHIFT IN THE 00Z EUROPEAN...HINTING AT A DRY
SUNDAY...BUT WITH THE GFS STILL SHOWING A SYSTEM CROSSING...WILL
HANG ONTO CHC POPS HERE. TWEAKED TEMPERATURES TO BLEND IN 00Z
GUIDANCE WITH A DOWNWARD TREND FOR THE WEEKEND...WITH SOME
INDICATION COLD AIR WILL HANG IN A BIT LONGER...OTHERWISE...MADE FEW
CHANGES DURING THE LONG TERM PERIOD.
COLD BUT RELATIVELY TAME WX IN STORE...MODELS CONTINUE TO DIVERGE
DURING THIS PERIOD BUT DO HAVE SOME SIMILARITIES. THEY AGREE ON
BUILDING A STRONG SFC RIDGE DOWN ACROSS ONTARIO AND THE LAKES INTO
OUR AREA ON FRIDAY. STILL QUITE COLD WITH 850MB TEMPS IN -15C
RANGE...SUPPORTING MAXES IN M20S. FLOW ALMOST NIL...LIGHT NORTHERLY
IF ANYTHING...SO REDUCED POPS TO SGT CHC AS AS ANY LAKE RESPONSE
SHOULD BE MINIMAL. REST OF PERIOD IN DOUBT...GFS SHOWS RETROGRADING
UPPER LOW ACROSS QUEBEC INTO ONTARIO AND THEN SOUTH ACROSS THE LAKES
TO OUR WEST. THIS WOULD PLACE OUR ARE IN A COLD BUT RATHER DRY
REGIME AS FLOW WILL BE BACKING FROM SOUTH TO EAST TO NORTH. ECMWF
AND CAN GEM ON OTHER HAND KEEP UPPER LOW OVER QUEBEC WITH SOUTHERN
STREAM SENDING A LOW UP AND OFF THE COAST. THIS SOLUTION WOULD STILL
KEEP US COLD WITH LIMITED LAKE RESPONSE AS OUR WINDS WOULD BE
GENERALLY NORTHERLY. FOR NOW...WILL GO WITH 20-30 POPS NORTH TO
SOUTH ON SAT AS SYSTEM SLIDES WELL TO OUR SOUTH...THEN BROADBRUSH
TOWARDS CLIMO WITH 30 POPS FOR CHC LGT SNOW BOTH SUN AND MON. TEMPS
STILL BELOW NORMAL AS 850 MB TEMPS REMAIN IN -12 TO -14C
RANGE...U20S MAXES AND M-U TEENS MINS...COLDER NORTH COUNTRY.
&&
.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
CONDITIONS WILL DETERIORATE TO IFR/LIFR TONIGHT WITH APPROACHING LOW
PRESSURE. PRECIP EXPECTED TO REMAIN AS LIGHT RAIN AND DRIZZLE FOR
MOST OF THE AREA WITH THE EXCEPTION OF AREAS EAST OF LAKE ONTARIO
WHERE A MIX OF RAIN AND SNOW WILL OCCUR. A MIX OF RAIN AND SNOW
EXPECTED DURING TUESDAY MORNING AS COLDER AIR FOLLOWS THE LOW
PRESSURE AREA.
CONDITIONS WILL REMAIN IFR THROUGH MUCH OF TUESDAY WITH A SLOW
IMPROVEMENT TO MVFR LATE IN THE DAY...THEN VFR DURING TUESDAY NIGHT.
OUTLOOK...
WEDNESDAY AND THURSDAY...VFR/MVFR IN SNOW SHOWERS...ESP SE OF
LAKES.
FRIDAY...MAINLY VFR.
&&
.MARINE...
WILL ISSUE SCA FOR MUCH OF THE WATERS TODAY...STARTING IMMEDIATELY
ON LAKE ERIE...AND 10 AM ON LAKE ONTARIO. WINDS REMAIN
UP...INCREASING AHEAD OF AN APPROACHING BOUNDARY ON WEDNESDAY. SCA
UP THROUGH WEDNESDAY EVENING...BUT MAY NEED TO EXTEND THE SCA
THROUGH WEDNESDAY NIGHT ON EASTERN ONTARIO...BUT FOR NOW WILL ONLY
GO 3 PERIODS OUT...LETTING FUTURE SHIFTS BETTER PIN DOWN THE DROP
OFF. WINDS TAPER OFF THURSDAY...WITH A QUIET PERIOD ON THE WATERS
EXPECTED TO LAST THURSDAY NIGHT INTO THE WEEKEND.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST WEDNESDAY FOR LEZ040-041.
SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 7 PM
EST WEDNESDAY FOR LOZ042>045.
&&
$$
SYNOPSIS...APFFEL
NEAR TERM...JJR
SHORT TERM...APFFEL
LONG TERM...APFFEL/SFM
AVIATION...JJR
MARINE...APFFEL/JJR
