Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 240622 AFDBUF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BUFFALO NY 122 AM EST MON NOV 24 2014 .SYNOPSIS... TEMPERATURES WILL WARM FURTHER OVERNIGHT WITH MORE RAIN AS A WARM FRONT LIFTS NORTH OUT OF THE OHIO VALLEY. THE WARMING TEMPERATURES AND RAINFALL COMBINED WITH INCREASINGLY STRONG WINDS TONIGHT AND ESPECIALLY MONDAY THROUGH MONDAY NIGHT WILL ACCELERATE MELTING OF RECENT HEAVY SNOWS...CREATING A SIGNIFICANT FLOODING RISK ACROSS PORTIONS OF WESTERN NEW YORK. A STRONG COLD FRONT WILL CROSS THE REGION MONDAY EVENING...BRINGING A RETURN OF MORE WINTER-LIKE TEMPERATURES AND A CHANCE OF SNOW BY LATER IN THE WEEK. && .NEAR TERM /THROUGH TODAY/... REGIONAL RADAR IMAGERY CONTINUES TO SHOW A BROAD SHIELD OF RAIN MOVING ACROSS WESTERN AND CENTRAL NEW YORK THIS MORNING AS THE WARM FRONT LIFTS NORTH INTO THE REGION. ISENTROPIC ASCENT ALONG THIS WARM FRONTAL ZONE WILL CONTINUE TO BRING WIDESPREAD RAINFALL ACROSS THE REGION AS DEEP LAYERED MOISTURE IS FOCUSED INTO THE REGION ON THE NOSE OF THE STRONG LOW LEVEL JET. DOWNSLOPING SHOULD DIMINISH RAINFALL AMOUNTS ACROSS FAR WESTERN NEW YORK...KEEPING THOSE AMOUNTS TO AROUND A QUARTER OF AN INCH...WITH SLIGHTLY HIGHER AMOUNTS POSSIBLE ELSEWHERE. IN FACT...RADAR RETURNS CURRENTLY SHOW A MARKED DIMINISHMENT OF RETURNS ALONG THE LAKE ERIE SHORELINE ASSOCIATED WITH THIS DOWNSLOPING. DESPITE THE LIMITED RAINFALL THREAT...THE IMMENSE VOLUME OF WATER FROM THE SNOWMELT ACROSS PORTIONS OF WESTERN NEW YORK WILL CREATE A PERSISTENT FLOOD THREAT...PARTICULARLY ALONG THE BUFFALO CREEKS AND AREAS WITH POOR DRAINAGE...ESPECIALLY TONIGHT INTO MONDAY. MORE WARMING EXPECTED MONDAY AHEAD OF APPROACHING COLD FRONTAL BOUNDARY. TEMPERATURES LIKELY PEAKING IN THE MID 50S TO LOWER 60S. BRIEF SUBSIDENCE SUGGESTS A DIMINISHING TREND TO THE SHOWERS... BEFORE AN INBOUND MID LEVEL WAVE WORKS ACROSS THE REGION DURING THE MID TO LATE AFTERNOON. STRONG SIGNAL OF FRONTAL CONVERGENCE TUCKED BENEATH FAVORABLE UPPER JET DYNAMICS SHOULD ALLOW SHOWER COVERAGE TO INCREASE AGAIN LATER IN THE DAY. THE MAIN FORECAST ELEMENT OF CONCERN REMAINS THE WIND POTENTIAL AS STRONG COLD AIR ADVECTION ENSUES BY THE EVENING HOURS. STRONG POST-FRONTAL SOUTHWEST GRADIENT TAKES HOLD DURING THIS TIME. GUST POTENTIAL WILL CAPITALIZE ON A PERIOD OF STRONG 280-285K ISENTROPIC DESCENT AND AN INCREASING MIXING POTENTIAL AS LAPSE RATES STEEPEN WITH THE ADVECTIVE PROCESS. RECENT GUIDANCE MAINTAINS WIND SPEEDS IN THE 50 TO 60 KNOT RANGE AT 925 MB. THIS WOULD INDICATE GUSTS TO 60 MPH DOWNWIND OF LAKE ERIE WITH 50 TO 55 MPH GUSTS ELSEWHERE. GREATEST GUSTS LOOK TO BE CENTERED FROM 21Z AND INTO THE FIRST HALF OF MONDAY NIGHT. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... AS THIS PERIOD OPENS...DEEP LOW PRESSURE NEAR JAMES BAY WILL FINISH PUSHING ITS TRAILING COLD FRONT ACROSS THE AREA EARLY IN THE EVENING. THIS BOUNDARY MAY BE ACCOMPANIED BY A BROKEN/NARROW BAND OF SHOWERS AS IT CLEARS THE FINGER LAKES AND NORTH COUNTRY...WITH STRONG DRY SLOTTING IN ITS WAKE THEN GENERALLY BRINGING DRY WEATHER FOR THE BALANCE OF THE NIGHT IN MOST AREAS. THE POSSIBLE EXCEPTIONS TO THIS WILL BE IN AREAS DOWNWIND OF THE LAKES...WHERE THE COMBINATION OF SOMEWHAT BETTER LOW LEVEL MOISTURE AND THE PREVAILING CYCLONIC LARGE-SCALE FLOW COULD HELP TO GENERATE A FEW ADDITIONAL RAIN AND SNOW SHOWERS. WHILE THE LAKES SHOULD DEFINITELY CONTRIBUTE SOME MOISTURE TO HELP THESE ALONG...THESE WILL NOT BE TRULY LAKE EFFECT IN NATURE GIVEN THAT 850 MB TEMPS WILL ONLY FALL TO -5C/-6C BY LATE IN THE NIGHT...OR LEVELS THAT ARE NOT COLD ENOUGH FOR A PURE LAKE RESPONSE. OF MUCH GREATER CONCERN MONDAY NIGHT WILL BE THE LIKELIHOOD FOR STRONG WINDS. IN THE WAKE OF THE COLD FRONTAL PASSAGE...A STRONG LOW LEVEL JET WILL REMAIN IN PLACE ALOFT WITH 925 MB WINDS AS HIGH AS 55-60 KNOTS AND 850 MB WINDS AS HIGH AS 65-70 KNOTS...AND STRONG COLD AIR ADVECTION SHOULD HELP TO AT LEAST PARTIALLY MIX THESE DOWN TO THE SURFACE. GIVEN THE EXPECTED SOUTHWEST FLOW REGIME AND THE USUAL FUNNELING EFFECTS...THIS WILL LIKELY LEAD TO SOME WARNING- CRITERIA WIND GUSTS FROM CHAUTAUQUA COUNTY NORTHEASTWARD ACROSS THE NIAGARA FRONTIER TO THE ROCHESTER AREA...WITH SIMILAR GUSTS ALSO POSSIBLE /THOUGH NOT AS QUITE A SURE THING/ ACROSS THE NORTH COUNTRY. ELSEWHERE THE WIND GUSTS SHOULD NOT BE QUITE AS STRONG... THOUGH THESE WILL PROBABLY STILL REACH ADVISORY LEVELS. WITH ALL OF THE ABOVE IN MIND...A HIGH WIND WARNING WILL CONTINUE THROUGH MUCH OF THE NIGHT FOR THE FAVORED AREAS DOWNWIND OF LAKE ERIE...WHILE A HIGH WIND WATCH WILL BE IN PLACE EAST OF LAKE ONTARIO...AND A WIND ADVISORY WILL BE IN EFFECT ELSEWHERE. EXPECT THE STRONGEST OVERALL WINDS TO BE IMMEDIATELY DOWNWIND OF LAKE ERIE...WHERE SATURATED GROUND CONDITIONS IN THE WAKE OF THE ONGOING MASSIVE SNOWMELT WILL LEAD TO AN ENHANCED POTENTIAL FOR DOWNED TREES AND POWER OUTAGES...WHICH WILL BE A MAJOR CONCERN FOR THOSE HOPING TO KEEP THEIR BASEMENTS DRY. ON TUESDAY...THE WINDS WILL GRADUALLY RELAX THROUGH THE COURSE OF THE DAY AS THE LOW LEVEL JET WEAKENS/DEPARTS OUR REGION AND THE OVERALL PRESSURE GRADIENT RELAXES...THOUGH IT WILL STILL BE FAIRLY BREEZY TO WINDY RIGHT THROUGH THE DAY WITH SOME LINGERING ADVISORY-TYPE GUSTS STILL POSSIBLE EARLY. IN TERMS OF PRECIP CHANCES...THE COMBINATION OF CONTINUED MODEST COLD AIR ADVECTION AND INCREASING MOISTURE IN ADVANCE OF A SECONDARY SURFACE TROUGH SHOULD HELP TO FUEL THE DEVELOPMENT OF SOME MODEST LAKE EFFECT SNOW AND RAIN SHOWER ACTIVITY NORTHEAST OF THE LAKES...THOUGH THIS IS LIKELY TO REMAIN FAIRLY MODEST IN EXTENT DUE TO EXPECTED MARGINAL TEMPERATURE PROFILES AND LAKE INDUCED EQLS IN THE 5-7 KFT RANGE. AS A RESULT...ANY SNOWFALL ACCUMS SHOULD REMAIN OF THE NUISANCE-TYPE VARIETY. OUTSIDE OF THE MAIN LAKE EFFECT AREAS...CONDITIONS SHOULD REMAIN LARGELY DRY. ADDITIONAL NUISANCE-TYPE LAKE EFFECT SNOW SHOWERS SHOULD THEN CONTINUE INTO TUESDAY NIGHT EAST-NORTHEAST OF THE LAKES...BEFORE GRADUALLY WINDING DOWN OVERNIGHT AND WEDNESDAY MORNING AS HIGH PRESSURE AND ATTENDANT SUBSIDENCE/DRIER AIR BUILDS INTO THE REGION...WHILE ALSO FORCING THE LOW LEVEL WIND FIELD TO BECOME LIGHTER/INCREASINGLY SHEARED. BY MIDDAY WEDNESDAY...EXPECT THIS ACTIVITY TO EITHER END ALTOGETHER OR BE PUSHED OUT OF OUR AREA AS THE LOW LEVEL FLOW BACKS TO AN UNFAVORABLE ORIENTATION FOR LAKE EFFECT ACROSS WESTERN AND NORTH CENTRAL NEW YORK. FOLLOWING THE END OF THE LAKE EFFECT...OUR ATTENTION WILL TURN TO A DEVELOPING COASTAL SYSTEM THAT WILL BE IN THE PROCESS OF LIFTING NORTHEASTWARD ALONG THE ATLANTIC COASTLINE. BOTH THE GFS/ECMWF ARE TRENDING MORE AND MORE DEVELOPED WITH THIS SYSTEM...WHICH COULD ULTIMATELY PRODUCE A PRE-THANKSGIVING SNOWSTORM ACROSS PORTIONS OF EASTERN NEW YORK AND NEW ENGLAND. MEANWHILE FURTHER WEST...IT APPEARS THAT OUR REGION WILL BE MORE ON THE WESTERN FRINGES OF THIS SYSTEM AND THUS SUBJECT TO MUCH LIGHTER PRECIP...THOUGH THE EXACT WESTERN EDGE OF THE PRECIP SHIELD REMAINS VERY MUCH IN QUESTION AT THIS PARTICULAR TIME. TAKING BOTH THE ABOVE MENTIONED MODEL TRENDS AND ALSO THE LINGERING UNCERTAINTY INTO CONSIDERATION...FOR NOW HAVE ELECTED TO INTRODUCE A CHANCE OF SNOW FOR OUR AREA WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT...WITH THE HIGHEST CHANCES OF THIS FOUND ALONG OUR EASTERN PERIPHERY. AS FOR TEMPS...THESE WILL AGAIN FALL BACK TO BELOW NORMAL LEVELS FOLLOWING MONDAY EVENING`S FRONTAL PASSAGE...THEN WILL REMAIN THERE THROUGH THE BALANCE OF THE PERIOD. && .LONG TERM /THURSDAY THROUGH SUNDAY/... IN THE WAKE OF THE DEPARTING COASTAL SYSTEM...A FRESH SHOT OF MUCH COLDER AIR WILL OVERSPREAD THE LOWER LAKES REGION THURSDAY AND THURSDAY NIGHT...WHICH IN CONJUNCTION WITH LINGERING SYNOPTIC-SCALE MOISTURE WILL HELP SET THE STAGE FOR ANOTHER POSSIBLE ROUND OF LAKE EFFECT SNOW. AT THIS POINT...IT APPEARS THAT THE LARGE-SCALE FLOW WILL LARGELY BE WESTERLY OR PERHAPS EVEN A BIT WEST-NORTHWESTERLY IN NATURE...WHICH WOULD FAVOR THE MORE TRADITIONAL SNOW BELTS EAST AND EAST-SOUTHEAST OF THE LAKES. ELSEWHERE...EXPECT JUST A GENERAL CHANCE OF SNOW SHOWERS GIVEN THE LARGE-SCALE COLD CYCLONIC FLOW. ON FRIDAY...BUILDING SURFACE-BASED RIDGING SHOULD FORCE ANY LAKE EFFECT SNOW/SNOW SHOWERS TO DRAMATICALLY WEAKEN AND LIFT NORTHWARD AS THE STEERING WINDS BACK AGAIN...WITH AREAS OUTSIDE OF ANY LAKE INFLUENCES LIKELY TO REMAIN DRY. AFTER THAT...THINGS GET MUCH MORE UNCERTAIN FOR NEXT WEEKEND WITH THE VARIOUS GUIDANCE PACKAGES FLOPPING AROUND BETWEEN TWO GENERAL IDEAS...ONE OF WHICH SUGGESTS A STRONG LOW LIFTING ACROSS THE GREAT LAKES AND PROVIDING OUR AREA A STRONG WARMUP AT SOME POINT...AND THE OTHER INDICATING A MUCH WEAKER TROUGH PASSAGE FOLLOWED BY ANOTHER SHOT OF MUCH COLDER AIR/MORE LAKE EFFECT POTENTIAL. GIVEN THE DISTANT TIME FRAME...OUR PREVIOUS CONTINUITY AND WPC PREFERENCES...HAVE ELECTED TO FOLLOW ALONG WITH THE LATTER SCENARIO FOR NOW. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... REGIONAL RADAR CURRENTLY SHOWS A BROAD SHIELD OF RAIN MOVING ACROSS THE LOWER GREAT LAKES AND WRN/CTRL NY IN ASSOCIATION WITH A WARM FRONT LIFTING NORTH ACROSS THE REGION. CONDITIONS GENERALLY REMAIN VFR WITH MVFR ACROSS THE HIGHER TERRAIN IN THE SOUTHERN TIER AND THE NIAGARA PENINSULA...WHERE HEAVIER RAIN IS CURRENTLY FALLING. THE 50-60KT LLJ DRIVING THIS PRECIPITATION IS ALSO RESULTING IN WIDESPREAD LLWS ACROSS THE FORECAST AREA OVERNIGHT. THIS LLJ IS ALSO GENERATING A NARROW AREA OF STRONG DOWNSLOPING WINDS AND TURBULENCE INVOF THE LAKE ERIE SHORELINE FROM KERI-KDKK. EXPECT THE LLWS TO DIMINISH AS WE MOVE INTO THE LATE MORNING HOURS ON MONDAY...HOWEVER THIS WILL ONLY BE BECAUSE THE STRONG WINDS WILL THEN MIX DOWN TO THE SURFACE...RESULTING IN WIDESPREAD SSW GUSTS OF 35-50KT. STRONGEST GUSTS WILL OCCUR INVOF A COLD FRONT EXPECTED TO CROSS THE FORECAST AREA FROM W-E BETWEEN 23Z MON AND 04Z TUE. EXPECT A SUBTLE WIND SHIFT TO THE SW BEHIND THIS FRONT WITH CONTINUED STRONG GUSTS OF 40-50KT THROUGH THE END OF THE FORECAST PERIOD. OTHERWISE...EXPECT VFR CONDITIONS THROUGHOUT THE DAYLIGHT HOURS WITH SOME DETERIORATION TO MVFR CIGS ACROSS UPSLOPE AREAS BEHIND THE COLD FRONT MON NIGHT. OUTLOOK... MONDAY AND MONDAY NIGHT...VFR/MVFR WITH SHOWERS. VERY WINDY. TUESDAY...MAINLY VFR WITH A CHANCE OF RAIN/SNOW SHOWERS. WEDNESDAY AND THURSDAY...MAINLY VFR/MVFR EXCEPT IFR POSSIBLE IN LAKE EFFECT SNOW SHOWERS EAST OF BOTH LAKES. && .MARINE... SOUTH-SOUTHEASTERLY WINDS WILL CONTINUE TO FRESHEN ON EASTERN LAKE ERIE OVERNIGHT AS A WARM FRONT LIFTS NORTH ACROSS THE REGION AHEAD OF A RAPIDLY DEEPENING LOW PRESSURE SYSTEM THAT IS CURRENTLY CENTERED OVER LAKE MICHIGAN. THESE SOUTHEASTERLY WINDS WILL CONTINUE TO AFFECT THE LAKE ERIE NEARSHORE WATERS AND SMALL CRAFT ADVISORIES ARE CURRENTLY IN EFFECT FOR THE LAKE ERIE NEARSHORE WATERS. THIS LOW WILL CONTINUE TO INTENSIFY AS IT CROSSES THE OTTAWA VALLEY AND MOVES INTO QUEBEC MONDAY EVENING WHILE SWINGING A STRONG COLD FRONT ACROSS THE LOWER GREAT LAKES. GALES WILL DEVELOP ON BOTH EASTERN LAKE ERIE AND LAKE ONTARIO FROM MONDAY THROUGH TUESDAY DUE TO THE VERY STRONG WIND FIELDS ACCOMPANYING THIS DEEP LOW. GALES WILL SUBSIDE LATER ON TUESDAY AS THE LOW PRESSURE SYSTEM RESPONSIBLE TRACKS OFF TO THE NORTHEAST ACROSS LABRADOR. A WEAK AREA OF HIGH PRESSURE IS THEN EXPECTED TO SKIRT THE LAKES WITH LIGHTER WINDS EXPECTED FOR THE MIDDLE PORTION OF THE WEEK BEFORE NORTHERLY WINDS FRESHEN THURSDAY NIGHT AS A DEEPENING COASTAL LOW TRACKS UP THE EASTERN SEABOARD. && .HYDROLOGY... A SNOW SURVEY COMPLETED ON FRIDAY CAME UP WITH A GENERAL 4 TO 6 INCHES OF SNOW WATER EQUIVALENT IN THE HARDEST HIT LAKE EFFECT SNOW AREAS. TEMPERATURES WILL REMAIN VERY MILD TONIGHT AND ONLY FALL INTO THE MID 40S...BEFORE RISING INTO THE 60S ON MONDAY. DEW POINTS ACROSS THE REGION ARE ABOVE 32 AND WILL CONTINUE TO STEADILY RISE INTO THE UPPER 40S TO AROUND 50 BY TONIGHT AND MONDAY. THE HIGHER DEWPOINTS COMBINED WITH STRONG WINDS WILL BE VERY EFFICIENT AT RAPIDLY MELTING THE DEEP SNOW PACK. THIS...ALONG WITH RAINFALL AMOUNTS OF GENERALLY UNDER A QUARTER INCH THROUGH TONIGHT...WILL RESULT IN SIGNIFICANT RISES ON LOCAL TRIBUTARIES WITH AREAL FLOODING EXPECTED FOR THE AREAS IN FAR WESTERN NEW YORK THAT RECEIVED THE TWO LAKE EFFECT SNOW STORMS THIS PAST WEEK. THE FLOOD POTENTIAL WILL BE TWO FOLD. FIRST...THERE IS A GENERAL RISK OF URBAN FLOODING IN THE TOWNS HARDEST HIT BY THE SNOW AS MELT WATER POOLS IN LOW LYING AND POOR DRAINAGE AREAS. EXCESSIVE SNOW PILES AND LEAVES BENEATH THE SNOW MAY BLOCK STORM DRAINS. FLOODING OF SOME STREETS AND RESIDENTIAL BASEMENTS COULD BEGIN ANYTIME NOW WITH MELTING UNDER WAY....SO AN AREAL FLOOD WARNING CONTINUES THROUGH AT LEAST MONDAY AFTERNOON TO ADDRESS THIS THREAT. THERE WILL ALSO BE THE RISK FOR THE FLOODING OF THE VARIOUS CREEKS AND TRIBUTARIES ACROSS FAR WESTERN NEW YORK. THE GREATEST THREAT IS ON THE BUFFALO CREEKS WHICH DRAIN THE HARDEST HIT AREAS FROM THIS WEEKS LAKE EFFECT SNOW. THIS INCLUDES CAZENOVIA...BUFFALO... CAYUGA...AND ELLICOTT. INDIVIDUAL FLOOD WARNINGS FOR THESE CREEKS HAVE BEEN ISSUED...AS ALL ARE NOW FORECAST TO REACH AT LEAST MINOR FLOOD LEVELS. THERE MAY ALSO BE SOME FLOOD RISK FOR CATTARAUGUS CREEK AND SOME OF THE SMALLER CREEKS THAT FLOW THROUGH DUNKIRK AND SILVER CREEK. THERE IS ALSO A FAIRLY HEAVY SNOW PACK IN THE UPPER REACHES OF THE OATKA WATERSHED...BUT NOT AS HIGH AS THE BUFFALO CREEKS. WE WILL CONTINUE TO MONITOR THIS BASIN FOR POSSIBLE FUTURE INCLUSION IN A FLOOD WARNING IF WE SEE STEADY RISES. THE EASTERN LAKE ONTARIO REGION HAD LESS SNOW... WITH TOTALS OF 2 TO 2.5 FEET ON THE TUG HILL. THIS SNOW PACK IS NOT EXCESSIVE FOR THAT AREA...SO HAVE NOT INCLUDED THE NORTH COUNTRY IN A FLOOD WATCH AT THIS TIME. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...HIGH WIND WARNING FROM 1 PM THIS AFTERNOON TO 4 AM EST TUESDAY FOR NYZ001>003-010>012-019-085. WIND ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR NYZ019-085. LAKESHORE FLOOD WATCH FROM THIS AFTERNOON THROUGH LATE TUESDAY NIGHT FOR NYZ010-019-085. HIGH WIND WATCH FROM THIS AFTERNOON THROUGH LATE TONIGHT FOR NYZ006>008. WIND ADVISORY FROM 1 PM THIS AFTERNOON TO 4 AM EST TUESDAY FOR NYZ004-005-013-014-020-021. MARINE...GALE WARNING FROM 1 PM THIS AFTERNOON TO 7 PM EST TUESDAY FOR LEZ020-040-041. SMALL CRAFT ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR LEZ040-041. GALE WARNING FROM 1 PM THIS AFTERNOON TO 7 PM EST TUESDAY FOR LOZ030-042-062. GALE WARNING FROM 4 PM THIS AFTERNOON TO 7 PM EST TUESDAY FOR LOZ043>045-063>065. SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 7 AM EST TUESDAY FOR SLZ022-024. && $$ SYNOPSIS...TMA/WOOD NEAR TERM...WCH/WOOD SHORT TERM...JJR LONG TERM...JJR AVIATION...WOOD MARINE...TMA/WOOD HYDROLOGY...HITCHCOCK/RSH/SMITH

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