FXUS61 KBUF 030152
AFDBUF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
852 PM EST WED DEC 2 2009
.SYNOPSIS...
LOW PRESSURE WILL STRENGTHEN OVER THE TENNESSEE VALLEY AND MOVE
NORTH INTO THE OHIO VALLEY TONIGHT. THIS STORM SYSTEM WILL BRING
WIDESPREAD MODERATE TO HEAVY RAIN TO THE AREA TONIGHT INTO
THURSDAY MORNING. THE STORM WILL MOVE INTO QUEBEC LATER THURSDAY
AND DRAW MUCH COLDER AIR INTO OUR REGION. THE COLD AIR WILL
PERSIST INTO THE WEEKEND. THE FLOW WILL BE CONDUCIVE FOR LAKE
EFFECT SNOWS EAST OF THE LAKES...ESPECIALLY THURSDAY NIGHT INTO
SATURDAY.
&&
.NEAR TERM /THROUGH THURSDAY/...
AT 900 PM...LOW PRESSURE WAS CENTERED ACROSS SOUTHWESTERN
OHIO...WITH THE EVENTUAL TRACK THE KEY TO TONIGHT/S FORECAST. THE
18Z RUNS OF THE NAM/GFS AND THE 21Z RUC ALL ESSENTIALLY SHOW TWO
MAIN AREAS OF LOCALLY HEAVY RAINFALL IN THE REGION. THE FIRST IS
ACROSS THE TUG HILL...AND IN PORTIONS OF THE SOUTHERN TIER...WHERE
UPSLOPING FROM THE 40 TO 50 KT 925 MB SE FLOW IS THE LIKELY CAUSE.
THIS IS SUPPORTED BY THE BUFKIT SOUNDING FROM THESE LOCATIONS. THE
SECOND...AND LARGER AREA...ESSENTIALLY EXTENDS FROM LAKE ERIE TO
THE WESTERN HALF OF LAKE ONTARIO. THIS IS LINE OF LOCALLY HEAVIER
RAINFALL IS LIKELY DUE TO THE TRACK OF THE SURFACE LOW...WITH
ENHANCED LIFT JUST NORTHWEST OF THE TRACK. THIS FORECAST
CONSENSUS WOULD KEEP RAINFALL TOTALS IN EXCESS OF AN INCH ROUGHLY
NORTH AND WEST OF BUFFALO IN THE NIAGARA FRONTIER.
OVER THE PAST COUPLE HOURS...PRESSURE FALLS HAVE SHIFTED MORE
WESTWARD...SUPPORTING THE 18Z MODEL RUNS. THIS INCREASES
CONFIDENCE IN QPF FORECASTS.
EXPECT AN INCH OR GREATER OF RAIN NORTHWEST OF BUFFALO...WITH
ISOLATED INCH AMOUNTS IN UPSLOPE REGIONS OF THE TUG HILL AND
SOUTHERN TIER...OTHERWISE...EXPECT RAINFALL AMOUNTS TO LARGELY BE
LESS THAN AN INCH. WHILE THIS DIMINISHES THE FLOOD POTENTIAL FOR
ERIE COUNTY...THE TRACK OF THE LOW IS SIMPLY TOO CLOSE TO DROP THE
WATCH AT THIS TIME. PLAN ON MAINTAINING THE WATCH FOR
NOW...LETTING THE EVENT PLAY OUT.
OTHERWISE...A 40 MPH GUST WAS REPORTED AT WELLSVILLE...WITH GUSTS
OF 30 TO 40 MPH ACROSS THE SOUTHERN TIER LIKELY TO CONTINUE UNTIL
SHORTLY AFTER MIDNIGHT. AN INTERESTING EFFECT IS OCCURRING ALONG
LAKE ERIE...WHERE THE CHAUTAUQUA RIDGE IS SHIELDING THE LAKE SHORE
FROM THE SOUTHEAST FLOW...ALLOWING NORTHEASTERLY WINDS AS SHOWN BY
THE DUNKIRK OB. BASICALLY NO MODEL IS PICKING UP THE NE WINDS
ALONG LAKE ERIE...THOUGH THE WRF DOES SHOW WINDS DROPPING OFF
SIGNIFICANTLY. EXPECT THIS TO CONTINUE UNTIL A BIT AFTER
MIDNIGHT...THEN THE WRF SHOWS WINDS PICKING UP AROUND 09Z...LIKELY
A SIGNAL THAT THE SE TO SW FLOW WILL FINALLY MIX DOWN AS THE LOW
LIFTS ACROSS.
EXPECT THE RAIN TO TAPER OFF FROM WEST TO EAST THURSDAY AS THE LOW
SLIDES EAST ACROSS THE ST LAWRENCE VALLEY. WINDY CONDITIONS WILL
FOLLOW THE LOW...BUT RIGHT NOW IT STILL LOOKS LIKE THE STRONGEST
GUSTS WILL STAY BELOW THE CRITERIA NEEDED FOR A WIND ADVISORY.
THE OTHER CONCERN WILL BE THE TIMING OF ANY POTENTIAL CHANGEOVER TO
SNOW THURSDAY AFTERNOON AS COLDER AIR ADVECTS IN FROM THE WEST. THE
GFS...WHICH TRACKS THE MAIN CENTER OF THE LOW FARTHER TO THE
EAST...BRINGS THE COLDER AIR IN FASTER...WHILE THE NAM HOLDS THE
COLDER AIR (COLD ENOUGH FOR SNOW) OFF UNTIL THURSDAY NIGHT. FOR
NOW...WILL FOLLOW A COMPROMISE SOLUTION AND INDICATE A RAIN/SNOW MIX
ACROSS THE HIGHER ELEVATIONS OF THE SOUTHERN TIER DURING THE
AFTERNOON.
IN TERMS OF TEMPERATURES...THE STRENGTHENING SOUTH TO SOUTHEAST FLOW
AHEAD OF THE LOW WILL KEEP TEMPERATURES IN THE 40S TONIGHT. ON
THURSDAY...EXPECT TEMPERATURES TO JUST HOLD STEADY OR FALL SLOWLY
DURING THE AFTERNOON.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
OUR ATTENTION WILL TURN TO THE MESOSCALE DURING THIS PERIOD AS THE
MAJOR SYNOPTIC STORM PASSES OFF TO OUR NORTHEAST. BIGGEST MODEL
DIFFERENCE APPEARS TO BE WITH THE DEGREE OF COLD AIR ADVECTION
ACROSS THE LOWER LAKES REGION IN WAKE OF THE SYNOPTIC SYSTEM.
LATEST GFS AND NAM SHOWING DIFFERING THERMAL PROFILES WITH THE NAM
HOLDING THE DEEPER COLD AIR FARTHER UPSTREAM...WHILE THE GFS IS
MUCH MORE AGGRESSIVE WITH ITS COLD AIR ADVECTION PATTERN. BOTH THE
GFS AND NAM VERY SIMILAR WITH LOW LEVEL SHEAR PROFILES WITH THE
INDIVIDUAL MODELS REFLECTING NEARLY THE SAME LOW LEVEL STEERING
PROFILES. DEEP MOISTURE ALSO APPEARS SOMEWHAT LACKING WITH THE
BULK OF THE MOISTURE REMAINING BELOW 750 MB.
DO TO THE MODEL DIFFERENCES WE ARE NOT AS CONFIDENT AS THE PAST
COUPLE OF DAYS IN FORECASTING SIGNIFICANT LAKE EFFECT SNOW FOR
THE REGION. HOWEVER...A PLUME OF LAKE EFFECT SNOW DOWNWIND OF BOTH
LAKES DOES LOOK VERY PROMISING. THERE WILL BE PLENTY OF
INSTABILITY DEVELOPING ACROSS THE LAKES REGION WITH LAKE INDUCED
CAPES RISING TO NEAR 500 J/KG AND EQUILIBRIUM LEVELS NEARING OR
EXCEEDING 10K FEET. IF THE GFS THERMAL PROFILES WOULD VERIFY WE
COULD BE LOOKING AT RATHER INTENSE LAKE PLUMES WHILE THE WARMER NAM
IS RATHER UNIMPRESSIVE IN ITS LAKE PLUME DEVELOPMENT. BOUNDARY
LAYER TEMPERATURES OFF THE NAM EVEN SUGGESTING A PERIOD OF PLAIN
RAIN ALTHOUGH ONCE SNOW DOES FALL THROUGH THE LOW LEVELS COOLING
WILL RAPIDLY OCCUR AND PRECIPITATION WILL FALL AS ALL SNOW.
THEREFORE WE ARE NOT CONCERNED WITH ANY MIXED PRECIPITATION AT
THIS TIME.
AT THIS POINT WITH MODEL STEERING WINDS VERY CLOSE WILL SUGGEST A
LAKE PLUME WILL DEVELOP OFF LAKE ERIE THURSDAY NIGHT SOUTH OF THE
BUFFALO AREA ON A 250-260 FLOW THEN AS THE STEERING WINDS BACK TO
SOUTHWEST THE PLUME SHOULD INTENSIFY AS IT WORKS INTO THE BUFFALO
METRO AREA...MOST LIKELY DURING THE AFTERNOON HOURS. BAND INTENSITY
AT THIS POINT STILL IN QUESTION BUT IT SHOULD BE KEPT IN MIND THAT
IF THIS BAND CAN OVERCOME THE LACK OF MOISTURE WE COULD BE LOOKING
AT FAIRLY INTENSE SNOWFALL RATES DURING THE AFTERNOON RUSH HOUR.
THE LAKE PLUME OFF ERIE WILL LIKELY PERSIST ON A 240 FLOW INTO THE
EVENING BEFORE WINDS ALIGN MORE WESTERLY AND SHIFT THE BAND SOUTH OF
THE METRO AREA DURING FRIDAY NIGHT.
THE SAME GENERAL SCENARIO WILL OCCUR OFF LAKE ONTARIO ABOUT 6 HOUR
LATER IN TIME.
WE WILL HOLD OFF ON ISSUING ANY HEADLINES AT THIS POINT DUE TO THE
UNCERTAINTY...BUT THIS TIME PERIOD WILL NEED TO BE MONITORED
CLOSELY AS HEADLINES MAY EVENTUALLY NEED TO BE ISSUED.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
THE LAKE EFFECT WHICH DEVELOPS IN THE SHORT TERM PERIOD MAY HAVE A
HARD TIME CONTINUING THROUGH THE WEEKEND. GFS/ECMWF AND NAM ALL
SUGGESTING LOW LEVEL RIDGING PUSHING INTO THE REGION AS A SURFACE
WAVE WORKS UP THE EAST COAST. MODEL PROFILES SUGGESTING INCREASING
AMOUNT OF SHEAR...TENDING TO WEAKEN AND DISRUPT THE LAKE EFFECT
ACTIVITY.
AIR MASS REMAINS COLD ENOUGH WITH 850 MB TEMPERATURES NEAR MINUS 12C
FOR SUNDAY ON A GENERAL WEST NORTHWEST FLOW. AMOUNT OF MOISTURE
AND PRESENCE OF SHEAR ALOFT MAY LIMIT THE POTENTIAL FOR
SIGNIFICANT AMOUNTS UT WILL HAVE TO WATCH CONTRIBUTION FROM THE
UPPER LAKES DURING THIS TIME FRAME.
RIDGING WORKS ACROSS THE AREA MONDAY WHICH SHOULD BRING AN END TO
THE LAKE EFFECT ACTIVITY. THE RIDGE SHIFTS EAST OF THE AREA BY
TUESDAY SETTING UP A PERIOD OF WEAK WARM AIR ADVECTION AHEAD OF A
LOW MOVING THROUGH THE LAKES REGION INTO CANADA. THERE COULD BE A
GENERAL LIGHT SNOW TUESDAY AND TUESDAY NIGHT BEFORE TEMPERATURES
WARM ENOUGH FOR A CHANGE TO RAIN BY WEDNESDAY.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
EXTENSIVE SHIELD OF RAIN IS LIFTING NORTH ACROSS THE AREA EARLY THIS
EVENING AND WILL QUICKLY OVERSPREAD THE KART VCNTY IN THE NEXT HOUR.
EXPECT STEADY RAIN THROUGH THE FIRST HALF OF TONIGHT...EVENTUALLY
GIVING WAY TO MORE INTERMITTENT SHOWERS LATE TONIGHT. MAIN CONCERN
FOR THE TAFS WILL BE TIMING AND EXTENT OF LOWER CIGS/VSBY LATER
TONIGHT.
AT KBUF/KIAG/KROC...EXPECT CIGS/VSBY TO REMAIN VFR WITH THIS FIRST
BATCH OF RAIN THANKS TO INITIALLY DRY LOW LEVELS WITH LARGE
TEMP/DEWPOINT SPREADS. THIS WILL BE AIDED BY SOUTHEAST DOWNSLOPE
WINDS. LATER THIS EVENING WINDS WILL BACK MORE TO THE EAST THEN
NORTHEAST AS THE SURFACE LOW DEEPENS UPSTREAM OVER OHIO. A NORTHEAST
WIND IS THE MOST FAVORABLE FOR LOW CIGS AT ALL OF THESE TAF SITES...
SO THIS IS THE MOST LIKELY TIME PERIOD FOR IFR CIGS TO DEVELOP. BY
LATE TONIGHT THE SURFACE LOW IS FORECAST TO TRACK OVER EASTERN LAKE
ERIE AND JUST WEST OF THE AREA BY 12Z PER THE LATEST 18Z MODEL
GUIDANCE. WITH THIS TRACK...EXPECT WINDS TO SHIFT MORE TO THE
SOUTHEAST LATE TONIGHT BACK INTO A DOWNSLOPE CONFIGURATION...WHICH
SHOULD ALLOW FOR A RAPID IMPROVEMENT IN CIGS AGAIN TO MVFR OR EVEN
VFR. FINALLY WINDS WILL SHIFT TO THE WSW THURSDAY MORNING AND
RAPIDLY INCREASE...WITH GUSTS IN THE 30-35 KNOT RANGE DURING THE
DAY. EXPECT MVFR CIGS TO IMPROVE TO VFR DURING THE DAY.
AT KJHW...MVFR CIGS HAVE JUST ARRIVED. EXPECT CIGS TO DETERIORATE TO
IFR HERE BY MID TO LATE EVENING AS THE LOW LEVELS SATURATE. IFR CIGS
SHOULD CONTINUE MUCH OF THE NIGHT BEFORE WINDS SWING AROUND TO THE
SSW THEN WSW AROUND DAYBREAK THURSDAY AND ALLOW CIGS TO IMPROVE TO
MVFR. EXPECT MVFR CIGS TO LINGER MOST OF THE DAY THURSDAY WITH LAKE
EFFECT/UPSLOPE RAIN SHOWERS BECOMING LIKELY BY LATE IN THE TAF
PERIOD.
AT KART...RAIN WILL DEVELOP SHORTLY...WITH INITIALLY VFR CIGS WITH
VERY DRY LOW LEVELS. EXPECT CIGS TO DETERIORATE TO IFR AFTER
MIDNIGHT AS THE LOW LEVELS SATURATE AND WINDS BECOME NORTHEAST. IFR
CIGS SHOULD CONTINUE THROUGH EARLY THURSDAY MORNING BEFORE THE WINDS
SWING AROUND TO THE SSW THEN WSW WITH CIGS IMPROVING TO MVFR.
OUTLOOK...
THURSDAY NIGHT...VFR...BUT MVFR/IFR IN STEADIER SNOW SHOWERS EAST OF
THE LAKES.
FRIDAY AND SATURDAY...MVFR IN SCATTERED SNOW SHOWERS. LOCAL IFR/LIFR
IN STEADIER SNOWS EAST OF THE LAKES.
SUNDAY...VFR WITH OCCASIONAL MVFR IN SNOW SHOWERS.
MONDAY...MAINLY VFR.
&&
.MARINE...
OVERNIGHT...NE FLOW HAS DEVELOPED ON LAKE ERIE...AS THE NEARSHORE
IS SHIELDED FROM THE WINDS BY THE CHAUTAUQUA RIDGE. EXPECT THIS
TO LAST UNTIL THE EARLY MORNING HOURS...THEN WINDS WILL SHIFT SE
TO SW ON LAKE ERIE...AND INCREASE. LAKE ONTARIO WILL BE A
DIFFERENT STORY...WITH AN INCREASING E-SE FLOW LATE EVENING UNTIL
SHORTLY AFTER MIDNIGHT. BRIEFLY GUSTY WINDS WILL PUT WESTERN
PORTIONS OF THE LAKE ONTARIO CLOSE TO SCA. WINDS MAY PUSH 30 KNOTS
ACROSS THE CENTER OF THE LAKE...IN RESPONSE TO THE LOW LEVEL
JET...BUT THIS TOO WILL BE RATHER SHORT LIVED...WITH STEADIER
WINDS COMING ON THURSDAY. SCA ARE UP FOR BEHIND THE LOW...STARTING
EARLIEST FROM WEST TO EAST.
ONCE THE LOW LIFTS NORTH OF THE AREA...STARTING THURSDAY NIGHT
STRONG COLD AIR ADVECTION WILL WORK ACROSS THE LAKES REGION
RESULTING IN PERIODS OF STRONG WINDS AND HIGH WAVE CONDITIONS
THROUGH THE WEEKEND. GALES WARNINGS MAY NEED TO BE ISSUED AT SOME
POINT DURING THIS PERIOD.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR NYZ010-085.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM THURSDAY TO MIDNIGHT EST
THURSDAY NIGHT FOR LEZ020-040-041.
SMALL CRAFT ADVISORY FROM 1 PM THURSDAY TO 7 AM EST
FRIDAY FOR LOZ042>045.
&&
$$
SYNOPSIS...TMA
NEAR TERM...APFFEL
SHORT TERM...TMA
LONG TERM...TMA
AVIATION...HITCHCOCK
MARINE...TMA
