Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 222029 AFDBUF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BUFFALO NY 329 PM EST MON DEC 22 2014 .SYNOPSIS... A WEAK LOW PRESSURE SYSTEM WILL MOVE UP THE EAST COAST TONIGHT WHILE ANOTHER LOW MOVES INTO THE CENTRAL GREAT LAKES REGION TUESDAY. BOTH WILL HAVE THE POTENTIAL TO BRING SOME LIGHT SHOWERS TO PORTIONS OF THE STATE. THEN...A MUCH STRONGER SYSTEM WILL MOVE UP THE MISSISSIPPI VALLEY AND INTO THE CENTRAL GREAT LAKES REGION ON WEDNESDAY...WITH ALL OF WESTERN AND CENTRAL NEW YORK SEEING RAIN UNDER AN UNSEASONABLY WARM AIRMASS. A COLD FRONT WILL ARRIVE FOR CHRISTMAS DAY WITH STRONG WINDS...FOLLOWED BY SOME MORE RAIN AND EVENTUAL SNOW SHOWERS OVER THE REGION BUT WITH LITTLE IF ANY ACCUMULATION. && .NEAR TERM /THROUGH TUESDAY/... A PAIR OF GENERALLY WEAK LOW PRESSURE SYSTEMS WILL ATTEMPT TO BRING SHOWERS TO WESTERN AND CENTRAL NEW YORK OVER THE NEXT 24 HOURS. THE FIRST WILL RIDE UP THE EAST COAST OVERNIGHT AND EARLY TUESDAY BEFORE FALLING APART...WHILE A SECOND LOW WILL MOVE INTO THE CENTRAL GREAT LAKES REGION TUESDAY...BEFORE THIS TOO FALLS APART. THESE SURFACE FEATURES WILL NOT BE ABLE TO FULLY DEVELOP AS THE UPPER LEVEL FLOW ACROSS THE US AMPLIFIES...WITH A STRONG RIDGE/TROUGH/RIDGE PATTERN FULLY SETTING UP FROM WEST TO EAST ACROSS THE US BY TUESDAY AFTERNOON. THE RESULT WILL BE NEW SURFACE DEVELOPMENT OVER THE GULF STATES...THE START OF A LONG AWAITED STORM THAT HAS BEEN BUZZING ACROSS THE SOCIAL MEDIA WEATHER WORLD FOR NEARLY A WEEK NOW DUE TO ITS HOLIDAY TIMING. MEANWHILE...TONIGHT...AREAS MAINLY EAST OF THE GENESEE VALLEY WILL SEE A POTENTIAL FOR SOME LIGHT RAIN FROM THE DISTANT COASTAL LOW...POSSIBLY MIXED IN WITH SOME SLEET OR FREEZING RAIN AT THE ONSET DUE TO NEAR FREEZING TEMPERATURES AT THE SURFACE AND WARMER AIR ADVECTING IN ALOFT. THIS AREA OF PRECIPITATION SHOULD MOVE OFF TO THE NORTHEAST AND ACROSS THE EASTERN LAKE ONTARIO REGION DURING THE MORNING. THEN ON TUESDAY...THERE WILL BE AN INCREASING CHANCE OF RAIN...NO WINTRY MIX...OVER FAR WESTERN NY DURING THE DAY FROM THE WEAKENING GREAT LAKES LOW. NEITHER SYSTEM IS EXPECTED TO DROP TOO MUCH PRECIPITATION...AND WILL KEEP THE AMOUNTS UNDER ABOUT .15 INCH FOR THE NEXT 24 HOURS...WITH FAR LESS...IF ANY EXPECTED IN BETWEEN THE TWO SYSTEMS. TEMPERATURES SHOULD STEADILY RISE THROUGHOUT THE DAY...IN TO THE 40S BY THE AFTERNOON. THE WELCOME SUNSHINE ON ONE OF THE SHORTEST DAYS OF THE YEAR WILL BE A DISTANT MEMORY AS SEVERAL DAYS OF NEARLY COMPLETE CLOUD COVER BEGINS. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... PERSISTENT LOW/MID LEVEL WARM ADVECTION AND UPPER LEVEL DIVERGENCE TUESDAY NIGHT WILL CONTINUE TO PRODUCE A WEALTH OF CLOUD COVER AND AT LEAST A FEW SCATTERED SHOWERS. THE INITIAL SERIES OF WEAK LEAD MID LEVEL SHORTWAVES WILL LIFT INTO QUEBEC OVERNIGHT WITH ANY ORGANIZED SHOWERS FOLLOWING. TOWARD WEDNESDAY MORNING A RENEWED PUSH OF STRONGER WARM ADVECTION WILL MOVE INTO THE WESTERN SOUTHERN TIER WITH SHOWERS BECOMING MORE WIDESPREAD. IT WILL REMAIN QUITE MILD WITH LOWS IN THE LOWER TO MID 40S IN MOST AREAS. THESE LOWS ARE LIKELY TO OCCUR EARLY...WITH TEMPERATURES BECOMING EVEN WARMER BY WEDNESDAY MORNING. ON WEDNESDAY A STRONG PUSH OF WARM ADVECTION AND UPPER LEVEL DIVERGENCE WILL PRODUCE A PERIODS OF RAIN ACROSS THE ENTIRE REGION. THE BROAD AREA OF ASCENT WILL BE ENHANCED BY SEVERAL MID LEVEL VORTICITY MAXIMA CROSSING THE REGION DOWNSTREAM OF THE MAIN MID LEVEL TROUGH. A PLUME OF DEEP MOISTURE WILL BE CAPTURED AND SPREAD NORTHWARD BY THIS SYSTEM WITH PWAT RISING TO AROUND 1.25 INCHES...WHICH IS OVER 3 STANDARD DEVIATIONS ABOVE AVERAGE AND NEAR THE MAX OBSERVED FOR LATE DECEMBER. DESPITE THE COPIOUS AMOUNTS OF MOISTURE...IT DOES NOT APPEAR THERE WILL BE ENOUGH OF A FOCUS WITHIN THE BROAD WARM ADVECTION REGIME TO PRODUCE EXCESSIVE RAINFALL IN ANY ONE LOCATION. MAX RAINFALL AMOUNTS SHOULD FOCUS IN AREAS FAVORED BY UPSLOPE SOUTHERLY FLOW...SUCH AS THE SOUTHERN TUG HILL PLATEAU WHERE RAIN AMOUNTS MAY EXCEED 1 INCH. ELSEWHERE EXPECT AROUND A HALF INCH TOTAL ACROSS LOWER ELEVATIONS AND 3/4 INCH ACROSS THE HIGHER TERRAIN OF THE SOUTHERN TIER AND FINGER LAKES. WEDNESDAY NIGHT A STRONG COLD FRONT WILL CROSS THE REGION AND PRODUCE ONE LAST PERIOD OF RAIN FORCED BY STRONG MID LEVEL HEIGHT FALLS AND LOW LEVEL CONVERGENCE ALONG THE FRONTAL ZONE. THE SHOWALTER INDEX DROPS TO JUST BELOW ZERO ALONG THE FRONT...SO THERE MAY EVEN BE A FEW SCATTERED THUNDERSTORMS. GIVEN THE VERY STRONG WIND FIELD ASSOCIATED WITH THE SYSTEM ANY THUNDERSTORM THAT DOES FORM MAY PRODUCE GUSTY WINDS. RAIN WILL QUICKLY END FROM WEST TO EAST OVERNIGHT WITH THE PASSAGE OF THE SURFACE COLD FRONT...WITH A NOTABLE MID LEVEL DRY SLOT CROSSING THE REGION IMMEDIATELY BEHIND THE FRONT. THE MAIN CONCERN WITH THIS SYSTEM CONTINUES TO REVOLVE AROUND WIND WITH SOME POTENTIAL FOR DAMAGING WINDS NORTHEAST OF LAKES ERIE AND ONTARIO. A SURFACE LOW WILL RAPIDLY DEEPEN AS IT MOVES FROM THE LOWER OHIO VALLEY ACROSS MICHIGAN LATE WEDNESDAY BEFORE REACHING WESTERN QUEBEC BY CHRISTMAS MORNING. THIS IS A CLIMATOLOGICALLY FAVORED TRACK TO PRODUCE STRONG WINDS NORTHEAST OF LAKES ERIE AND ONTARIO WHERE WINDS ARE CHANNELLED BY THE LAKES AND TERRAIN. THE LATEST GFS CONTINUES TO SUPPORT A MODERATE INTRUSION OF STRATOSPHERIC AIR WITH THE DYNAMIC TROPOPAUSE FOLDING DOWN TO AROUND 500MB...SUGGESTIVE OF DEEPER MID LEVEL INSTABILITY AND MIXING IN THE DRY SLOT BEHIND THE COLD FRONT. THE BEST ISALLOBARIC FALL/RISE COUPLET IS STILL FORECAST TO PASS THROUGH THE CENTRAL LAKES...BUT MODERATE PRESSURE RISES ON THURSDAY WILL STILL AID IN DOWNWARD MOMENTUM TRANSFER. MODEL GUIDANCE CONTINUES TO SHOW SOME RUN TO RUN VARIANCE WITH RESPECT TO THE EXACT TRACK AND STRENGTH OF THE LOW...AND ALSO A GOOD DEAL OF RUN TO RUN DIFFERENCES WITH WIND SPEEDS ALOFT. THE LATEST 12Z GFS TRENDED A LITTLE FASTER AND SLIGHTLY WEAKER WITH THE SURFACE LOW AND NOTABLY WEAKER WITH WINDS ALOFT...ALTHOUGH PROBABLY STILL JUST STRONG ENOUGH TO PRODUCE 45-50 KNOT GUSTS NORTHEAST OF THE LAKES. GIVEN THAT THIS IS STILL ALMOST 3 DAYS AWAY AND WE ARE STILL SEEING RUN TO RUN MODEL DIFFERENCES...WILL HOLD OFF ON A HIGH WIND WATCH FOR NOW. IT APPEARS THE STRONGEST WINDS WILL OCCUR FROM LATER WEDNESDAY NIGHT THROUGH THE FIRST HALF OF CHRISTMAS DAY ACROSS WESTERN NY NORTHEAST OF LAKE ERIE...AND A FEW HOURS LATER NORTHEAST OF LAKE ONTARIO. OTHERWISE ON CHRISTMAS DAY A BRIEF PERIOD OF WRAP AROUND MOISTURE WILL CROSS THE LOWER LAKES. THERE IS A DISTINCT LACK OF COLD AIR BEHIND THIS SYSTEM WITH 850MB TEMPS ONLY DROPPING TO AROUND -6C BY THE END OF THE DAY. THIS WILL ONLY SUPPORT A FEW WET SNOWFLAKES MIXING IN WITH THE RAIN AT LOWER ELEVATIONS...WITH HIGHER TERRAIN PROBABLY CHANGING OVER TO ALL WET SNOW. COULD SEE SOME MINOR LESS THAN AN INCH ACCUMULATIONS ON THE HILLS...WITH NO ACCUMULATION ACROSS LOWER ELEVATIONS. IT IS NOT EVEN CLOSE TO COLD ENOUGH FOR ANY LAKE RESPONSE. TEMPERATURES WILL START OFF IN THE 40S IN MOST AREAS AT DAYBREAK THEN FALL INTO THE MID TO UPPER 30S THROUGH THE DAY. IT WILL NOT BE A WHITE CHRISTMAS THIS YEAR IN WESTERN NY. ANY LINGERING LIGHT SNOW SHOWERS EAST OF THE LAKES CHRISTMAS EVENING WILL END OVERNIGHT AS A RIDGE OF HIGH PRESSURE BUILDS TOWARDS THE LOWER LAKES AND ANY REMAINING MOISTURE IS STRIPPED AWAY. && .LONG TERM /FRIDAY THROUGH MONDAY/... ON FRIDAY HIGH PRESSURE WILL BUILD THROUGH THE MID ATLANTIC WITH A RIDGE EXTENDING NORTH INTO THE LOWER LAKES AND PROVIDING A DRY DAY WITH EVEN A GOOD CHANCE AT SOME SUNSHINE. WHAT LITTLE COOL AIR BRIEFLY ENTERS THE REGION ON CHRISTMAS DAY WILL BE GONE AS WARM ADVECTION BRINGS 850MB TEMPS TO AROUND +2C. THIS WILL SUPPORT HIGHS BACK INTO THE 40S...A GOOD 10 DEGREES ABOVE AVERAGE. ON SATURDAY A FAST MOVING MID LEVEL TROUGH WILL SWING THROUGH THE GREAT LAKES AND QUEBEC. THIS MAY PRODUCE A FEW RAIN SHOWERS MIXING WITH WET SNOW LATER IN THE DAY AS MODERATE COLD ADVECTION BEGINS. IT MAY BECOME MARGINALLY COLD ENOUGH FOR SOME LIMITED LAKE EFFECT BY SATURDAY NIGHT EAST OF THE LAKES. MODELS DIVERGE SIGNIFICANTLY BY SUNDAY. THE 12Z ECMWF REMAINS CONSISTENT WITH PREVIOUS RUNS IN TAKING A STRONG SOUTHERN STREAM TROUGH THROUGH THE OHIO VALLEY AND INTO THE NORTHEAST...WITH A FRONTAL WAVE SPREADING A BAND OF ACCUMULATING SNOW ACROSS OUR REGION. THE GFS REMAINS CONSISTENT WITH ITS PREVIOUS RUNS IN KEEPING ANY SEMBLANCE OF THIS WAVE SUPPRESSED FAR TO THE SOUTHEAST WITH A WEAK WAVE RUNNING THROUGH THE SOUTHEAST STATES. THE CANADIAN GEM IS CLOSER TO THE ECMWF SOLUTION THROUGH SATURDAY. FOR NOW WILL HEDGE TOWARDS THE ECMWF SCENARIO AND PLACE A CHANCE OF SNOW INTO THE FORECAST FOR SUNDAY AND SUNDAY NIGHT. BOTH THE GFS AND ECMWF THEN SUGGEST A MAINLY DRY MONDAY AS HIGH PRESSURE BUILDS INTO THE NORTHEAST. && .AVIATION /21Z MONDAY THROUGH SATURDAY/... VFR CONDITIONS ARE EXPECTED THROUGH ABOUT 06Z...THEN EXPECT LOWER CLOUDS TO MOVE IN FROM THE SOUTH. SOME -SHRA WILL BE AT POSSIBLE...MAINLY EAST AND SOUTH OF KART AND NORTH AND WEST OF KIAG. THIS WILL LEAVE MOST OF WESTERN NY GENERALLY DRY THROUGH 18Z TUESDAY WITH MVFR CONDITIONS FROM CIGS. OUTLOOK... WEDNESDAY...MOSTLY MVFR AND SOME -SHRA. SOME GUSTY WINDS. THURSDAY...MVFR WITH -SHRA/-SHSN AND GUSTY/STRONG WINDS. FRIDAY...MAINLY VFR. SATURDAY...POSSIBLE MVFR CONDITIONS WITH AREAS OF SHSN. && .MARINE... A WEAK LOW WILL MOVE UP THE EAST COAST TONIGHT AND FALL APART WHILE A SECOND LOW MOVES INTO THE CENTRAL GREAT LAKE REGION AND SIMILARLY WEAKENS ON TUESDAY. ON WEDNESDAY...A MUCH STRONGER AND DEEPENING SYSTEM WILL MOVE UP THE MS VALLEY AND INTO THE CENTRAL GREAT LAKES...WITH SMALL CRAFT AND EVENTUALLY GALE FORE POTENTIAL WINDS LATE WEDNESDAY NIGHT AND THURSDAY OVER LAKE ERIE. GALE FORCE WINDS ARE ALSO POSSIBLE ON LAKE ONTARIO LATER THURSDAY. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...GALE WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY AFTERNOON FOR LEZ040-041. && $$ SYNOPSIS...ZAFF NEAR TERM...ZAFF SHORT TERM...HITCHCOCK LONG TERM...HITCHCOCK AVIATION...ZAFF MARINE...ZAFF

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