Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 270453 AFDBUF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BUFFALO NY 1153 PM EST WED NOV 26 2014 .SYNOPSIS... A NOR`EASTER WILL LIFT ALONG THE ATLANTIC COASTLINE. SNOW WILL TAPER OFF THIS EVENING FROM WEST TO EAST...THOUGH SOME LIMITED LAKE ENHANCED ACTIVITY WILL LINGERING INTO THANKSGIVING MORNING...ESPECIALLY SOUTHEAST OF LAKE ONTARIO. THEN ANOTHER DISTURBANCE WILL CROSS THE REGION THURSDAY NIGHT...BRINGING MORE LIGHT LAKE EFFECT SNOW SHOWERS. && .NEAR TERM /THROUGH THURSDAY/... A COASTAL LOW CENTERED NEAR CAPE COD WILL CONTINUE TO LIFT NORTHEASTWARD ACROSS THE GULF OF MAINE TONIGHT. MOST OF THE PRECIPITATION WRAPPED AROUND THIS LOW HAS ALREADY EXITED TO THE EAST...WITH JUST LIGHT SNOW LINGERING EAST OF LAKE ONTARIO LATE THIS EVENING. AFTER THIS...OUR ATTENTION TURNS TO THE POTENTIAL FOR LAKE ENHANCED SNOW SHOWERS OVERNIGHT. 850MB TEMPERATURES ARE FORECAST TO DROP MODESTLY DOWN TO ABOUT -10C THROUGH DAYBREAK WHICH WILL RESULT IN SMALL VALUES OF LAKE INDUCED INSTABILITY. HOWEVER...WITH A FAIRLY MOIST BOUNDARY LAYER THIS SHOULD BE ENOUGH FOR SOME LIGHT LAKE EFFECT SNOW SOUTH OF THE LAKES. A BLEND OF HIGH RESOLUTION GUIDANCE (NAM/RGEM/HRRR/WRF/ARW) ARE PRETTY CONSISTENT IN FORECASTING LIGHT QPF SOUTH OF LAKE ONTARIO FROM ROCHESTER TO FULTON. THIS WOULD TAKE ADVANTAGE THE LONGER FETCH ACROSS EASTERN LAKE ONTARIO...AND POSSIBLY A SUBTLE CONVERGENCE ZONE. ACCUMULATIONS SHOULD GENERALLY BE LIGHT WITH LAKE EFFECT EXPECTED TO BE MULTI-BANDED AND GENERALLY DISORGANIZED...BUT LOCAL AMOUNTS UP TO 2 INCHES ARE POSSIBLE TONIGHT...AND AGAIN ON THURSDAY. THIS WOULD INCLUDE EASTERN MONROE COUNTY...WAYNE...AND NORTHERN CAYUGA COUNTIES. THE ONLY REAL CHANCE FOR HIGHER (ADVISORY AMOUNTS) WOULD BE IF SNOW HAS A SIGNIFICANT FLUFF FACTOR...OR IF STEADIER SNOWS FOCUS ON ONE LOCATION FOR A LONG TIME. ELSEWHERE...EXPECT LITTLE IF ANY ACCUMULATION...WITH SNOW FLURRIES FURTHER AWAY FROM THE LAKE. HIGH RESOLUTION GUIDANCE (HRRR IN PARTICULAR) HAS PICKED UP ON A CONVERGENCE BOUNDARY DOWN LAKE ERIE...BUT WITH A NORTHEAST FLOW THIS WILL LARGELY FOCUS SOUTH AND WEST OF OUR REGION. SOME LIGHT SNOW MAY MEANDER ONSHORE IN CHAUTAUQUA COUNTY (MAYBE AN INCH OR SO)...BUT OTHERWISE EXPECT ONLY LIGHT SNOW OVERNIGHT AND INTO THURSDAY MORNING. AN UPPER LEVEL SHORTWAVE CROSSING FROM THE CENTRAL GREAT LAKES TO THE EASTERN GREAT LAKES THROUGH THE DAY TOMORROW MAY BRING LIGHT SNOW AGAIN INTO WESTERN NEW YORK BY THE END OF THE AFTERNOON. TEMPERATURES WILL AVERAGE A SEVERAL DEGREES BELOW NORMAL THIS PERIOD. CLOUDS SHOULD RESULT IN A MINIMAL DIURNAL RANGE. LOWS TONIGHT WILL RANGE THROUGH THE 20S AND HIGHS TOMORROW WILL AVERAGE IN THE LOWER 30S. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... THE LATEST SURGE OF ARCTIC AIR WILL BRING A RENEWED THREAT FOR ACCUMULATING LAKE EFFECT SNOWS THURSDAY NIGHT AND INTO FRIDAY TO FAVORED NORTHWEST FLOW AREAS...ESPECIALLY OFF LAKE ERIE WHERE A BETTER ALIGNED LOW LEVEL FLOW WILL EXIST. ALTHOUGH OVER-LAKE INSTABILITY WILL NOT BE OVERLY IMPRESSIVE WITH DELTA T/S AROUND 15C...LAKE INDUCED EQUILIBRIUM LEVELS LOOK TO RISE TO OVER 10K FEET FOR A TIME THURSDAY NIGHT. THIS MAY ALLOW FOR LOCALIZED ACCUMULATIONS OF 2-4" ALONG THE CHAUTAUQUA RIDGE. FRIDAY...COLD AIR ADVECTION WILL CONTINUE ON A NORTHWEST FLOW WHICH SHOULD MAINTAIN SOME MULTIPLE LAKE BANDS SOUTHEAST OF THE LAKES EARLY IN THE DAY. THESE BANDS SHOULD WANE THROUGH THE DAY AS THE LOW LEVEL FLOW BACKS AND INFLUX OF DRY AIR AND LOWER INVERSION HEIGHTS HELP TO DIMINISH THE LAKE ACTIVITY. FRIDAY NIGHT AND SATURDAY...STRONG WARM ADVECTION AND ISENTROPIC ASCENT DEVELOPS AS A CLIPPER SYSTEM WORKS ACROSS THE REGION. MODELS SUGGESTING A SHARP INCREASE IN LOW LEVEL MOISTURE SIGNALING WIDESPREAD SNOW WILL DEVELOP ACROSS THE REGION DURING THIS PERIOD. THE STRENGTHENING OF THE WARM AIR ADVECTION AND MOISTURE SURGE SHOULD BE ABLE TO PRODUCE AT LEAST A COUPLE INCHES OF ACCUMULATING SNOW. HOW MUCH SNOW FALLS WILL BE DEPENDENT ON THE AMOUNT OF MOISTURE AND WARM AIR BEING BROUGHT INTO THE REGION...BUT AT THIS TIME THERE IS NO REASON TO BELIEVE THERE WILL BE ANYTHING MORE THAN MINOR ACCUMULATIONS. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... SOLID WARM UP STILL LOOKS ON TRACK FOR SUNDAY IN WAKE OF A WARM FRONTAL PASSAGE. 925 MB TEMPERATURES LOOK TO RISE TO NEAR +10C...WHICH SHOULD SUPPORT HIGHS FOR MOST AREAS IN THE LOWER TO MID 50S. DOES NOT APPEAR TO BE ANY REAL FORCING MECHANISM FOR PRECIPITATION WITHIN THE WARM SECTOR OTHER THAN WEAK ISENTROPIC LIFT WITH BROAD WARM AIR ADVECTION. THIS WARM UP APPEARS SHORT-LIVED AS A ROUND OF UPPER MIDWEST TO GREAT LAKES HEIGHT FALLS WILL FORCE A COLD FRONT SOUTH ACROSS THE AREA LATE SUNDAY NIGHT INTO MONDAY. BAND OF SHOWERS PRECEDING THE FRONT LIKELY HOLDING OFF UNTIL SUNDAY NIGHT...POSSIBLY ENDING AS A BIT OF LIGHT SNOW AS COLDER AIR SPREADS INTO THE REGION BEHIND THE FRONT. ANY LAKE EFFECT WHICH CAN MATERIALIZE MONDAY SHOULD END BY MONDAY NIGHT AS SUBSIDENCE AND SURFACE RIDGING MOVE INTO WESTERN NEW YORK. HIGH PRESSURE WILL PROVIDE A FAIR WEATHER DAY TUESDAY...BEFORE WARM AIR ADVECTION PRECIPITATION BREAKS OUT AS STRENGTHENING RETURN FLOW SETS UP BEHIND THE DEPARTING HIGH. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... FOR THE 06Z TAF CYCLE...A WEAK NORTHERLY FLOW IS STILL RESULTING IN PERSISTENT CLOUDS NEAR OR JUST BELOW 3K FEET SOUTH OF THE LAKES AND INCLUDING ALL BUT THE ART TAF SITE. LOWER MOISTURE IS TRAPPED ACROSS THE SOUTHERN TIER...WITH IFR CIGS AT JHW. EXPECT JHW TO VARY BETWEEN IFR/MVFR OVERNIGHT AS LOW CIGS PERIODICALLY SCATTER OUT. MID-LEVEL CLOUDS LIFTING FROM SW- NE TO ENHANCE LAKE EFFECT SNOW OFF OF LAKE ONTARIO...WHICH MAY LOWER ROC TO IFR IN SNOW/CIGS. FORECAST CONFIDENCE REMAINS LOW FOR ROC. ELSEWHERE...EXPECT CIGS AROUND 3K FT OVERNIGHT. ON THURSDAY...EXPECT CIGS IMPROVE SOMEWHAT...WITH MOSTLY VFR CONDITIONS BY MID-DAY. PERIODICALLY LOWER CONDITIONS ARE POSSIBLE IN LAKE ENHANCED SNOW SHOWERS AND CLOUDS. A SHORTWAVE WILL BRING A PERIOD OF STEADY SNOW SHOWERS THURSDAY EVENING FROM W-E WITH IFR OR MVFR CONDITIONS LIKELY. OUTLOOK... THURSDAY NIGHT...MAINLY VFR WITH A CHANCE OF MVFR IN SNOW SHOWERS. FRIDAY...MAINLY VFR WITH A CHANCE OF SNOW SHOWERS/MVFR. SATURDAY THROUGH MONDAY...MAINLY VFR WITH A CHANCE OF RAIN AND SNOW SHOWERS. && .MARINE... A DEVELOPING STORM SYSTEM WILL LIFT NORTHEASTWARD ALONG THE ATLANTIC COASTLINE TONIGHT. HAVE ISSUED A BRIEF SCA FOR THE SOUTHEASTERN SHORES OF LAKE ONTARIO BASED ON NE WINDS IN THE 15 TO 20 KT RANGE WHICH ARE LIKELY TO BUILD WAVES UP TO 5 FEET. THIS WILL BE SHORT LIVED AS WINDS DIMINISH LATE TONIGHT. IN THE WAKE OF THIS SYSTEM...A SECONDARY SURFACE TROUGH WILL THEN CROSS THE LOWER LAKES REGION LATER THURSDAY AND THURSDAY NIGHT...AND WILL LIKELY BE ACCOMPANIED BY A PERIOD OF ADVISORY-LEVEL WESTERLIES AND ATTENDANT HIGHER WAVES. && .CLIMATE... AFTER AN EXTENDED PERIOD OF COLD DURING THE MIDDLE OF NOVEMBER IT APPEARS TEMPERATURES WILL AVERAGE ABOVE NORMAL MOST OF THE TIME OVER THE NEXT FEW WEEKS. THERE WILL BE BRIEF PUSHES OF COLDER AIR AT TIMES AS PROGRESSIVE TROUGHS AMPLIFY INTO THE GREAT LAKES...BUT THESE COLD PERIODS WILL BE SHORT LIVED...ONLY LASTING FOR A FEW DAYS AT A TIME...AND WILL BE OUTNUMBERED BY MILD DAYS. LOOKING AT THE HEMISPHERIC PATTERN...A POSITIVE NORTH ATLANTIC OSCILLATION /NAO/ WILL PERSIST INTO THE FIRST FEW DAYS OF DECEMBER BASED ON THE GEFS ENSEMBLE MEAN. THE MEAN LONGWAVE TROUGH OVER THE NORTH ATLANTIC IN SUCH A PATTERN WILL PREVENT ANY COLD FROM LOCKING IN OVER THE NORTHEAST QUARTER OF THE UNITED STATES. THE PACIFIC NORTH AMERICAN PATTERN /PNA/ WILL REMAIN NEGATIVE THROUGH THE FIRST FEW DAYS OF DECEMBER...BEFORE TRENDING POSITIVE BASED ON GEFS ENSEMBLE MEMBERS. THIS TOO WILL PREVENT COLD FROM LOCKING INTO THE NORTHEAST FOR MORE THAN A FEW DAYS AT A TIME. THE MADDEN JULIAN OSCILLATION /MJO/ MAY PLAY AN IMPORTANT ROLE IN DRIVING PATTERN CHANGE THROUGH MID DECEMBER. ANALYSIS OVER THE PAST WEEK HAS SHOWN A MODERATELY STRONG MJO EVENT DEVELOPING OVER THE INDIAN OCEAN. A GEFS ENSEMBLE FORECAST OF THE WHEELER PHASE/SPACE PLOT SHOWS THIS MJO ORBITING THROUGH PHASE 4 AND 5 DURING THE FIRST WEEK IN DECEMBER AS CONVECTION MOVES EAST ACROSS THE MARITIME CONTINENT. A LOOK AT COMPOSITE CHARTS OF PAST EVENTS FAVORS ABOVE NORMAL TEMPERATURES ACROSS MUCH OF THE CENTRAL AND EASTERN UNITED STATES DURING PHASE 4 THROUGH 6 OF THE MJO. EVENTUALLY AS WE GET INTO THE SECOND WEEK IN DECEMBER MJO CONVECTION WILL CONTINUE ITS EASTWARD ORBIT THROUGH THE PACIFIC AND INTO THE WESTERN HEMISPHERE. IF THE MJO CONVECTION PERSISTS ON ITS EASTWARD JOURNEY AND REACHES PHASE 7 OF THE WHEELER PHASE/SPACE PLOT...IT WOULD FAVOR A SIGNIFICANT PATTERN CHANGE TOWARDS COLDER THAN NORMAL TEMPERATURES OVER THE CENTRAL AND EASTERN UNITED STATES. THE MJO ACCOMPLISHES THIS AS SUB-TROPICAL CONVECTION INFLUENCES THE PATTERN OVER THE PACIFIC...FORCING AMPLIFICATION OF THE EASTWARD EXTENSION OF THE EAST ASIAN JET WHICH IN TURN FORCES DOWNSTREAM AMPLIFICATION OF THE PATTERN ACROSS NORTH AMERICA. BASED ON THE FORECAST TIMING OF THE MJO EPISODE THIS WOULD MOST LIKELY OCCUR BY WEEK 2 OR 3 OF DECEMBER AND FEED BACK INTO MORE HIGH LATITUDE BLOCKING AND MORE LONG LASTING COLD. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST THURSDAY FOR LOZ043-044. && $$ SYNOPSIS...THOMAS NEAR TERM...APFFEL/THOMAS SHORT TERM...TMA LONG TERM...TMA AVIATION...APFFEL MARINE...APFFEL/THOMAS CLIMATE...HITCHCOCK

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