Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 300018 AFDBUF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BUFFALO NY 818 PM EDT FRI MAY 29 2015 .SYNOPSIS... A WARM AND HUMID AIR MASS WILL REMAIN OVER THE REGION TONIGHT AND SATURDAY. A SLOW MOVING COLD FRONT WILL CROSS THE REGION STARTING LATE SATURDAY BRINGING WIDESPREAD SHOWERS AND THUNDERSTORMS...WITH THE POTENTIAL FOR HEAVY RAINFALL LASTING INTO SUNDAY. && .NEAR TERM /THROUGH SATURDAY/... AS OF 0015Z...A WEAK SHORTWAVE LIFTING ACROSS THE LOWER LAKES REGION IS INTERACTING WITH A LINGERING INSTABILITY AXIS STRETCHING FROM SOUTHWESTERN NEW YORK INTO WESTERN PA...THE END RESULT OF WHICH IS SOME SCATTERED SHOWER AND THUNDERSTORMS THAT CONTINUE TO LIFT NORTHEASTWARD ACROSS CHAUTAUQUA COUNTY AND NEARBY PORTIONS OF LAKE ERIE. THIS ACTIVITY SHOULD LAST A LITTLE WHILE LONGER THIS EVENING...BEFORE WANING WITH THE LOSS OF HEATING FOLLOWING SUNSET. ONCE THIS DISSIPATES...EXPECT A MAINLY DRY REST OF THE NIGHT IN MOST PLACES...THOUGH SOME ADDITIONAL ISOLATED TO WIDELY SCATTERED POP UP CONVECTION STILL CANNOT BE COMPLETELY RULED OUT OVERNIGHT GIVEN THE WARM AND INCREASINGLY HUMID AIRMASS THAT WILL BE IN PLACE. LATEST MODELS CONTINUING TO SHOW A DEEP UPPER LOW TRACKING FROM NORTHERN ONTARIO INTO NORTHERN QUEBEC SATURDAY. THIS WILL DRIVE A SURFACE COLD FRONT SOUTHWARD...WHICH WILL START TO IMPINGE ON THE AREA BY LATE IN THE DAY. A TIGHTENING HEIGHT GRADIENT ACROSS EASTERN CANADA AHEAD OF THIS WAVE WILL STRENGTHEN AN UPPER JET STREAK TO THE NORTH OF THE REGION. THIS WILL RESULT IN DEEP LAYER FRONTOGENESIS ACROSS WESTERN NEW YORK TIED TO THE ENTRANCE REGION OF THIS UPPER JET. THERE WILL BE AMPLE DEEP LAYER MOISTURE WITH PRECIPITABLE WATER VALUE APPROACHING 1.6 INCHES...2 TO 3 STANDARD DEVIATIONS ABOVE NORMAL ALONG AND AHEAD OF THIS FRONT. THE BULK OF THE 12Z MODEL RUNS HAVE TRENDED SLIGHTLY SLOWER IN BRINGING THE DEEP LAYER FRONTAL CIRCULATION INTO WESTERN NEW YORK SATURDAY. THIS MAY PROVIDE A BIT MORE OPPORTUNITY FOR WEAK TO PERHAPS MODEST DAYTIME DESTABILIZATION TO OCCUR OVER THE REGION. SHORT WAVE IMPULSES LIFTING INTO THE AREA FROM THE SOUTHWEST ARE LIKELY TO INITIATE CONVECTION...TIMING OF WHICH IS UNCERTAIN AT THIS STAGE...BUT THINK THE GREATEST PROBABILITIES OF CONVECTION WILL BE DURING THE MID TO LATE AFTERNOON HOURS. ANY POTENTIAL FOR STORMS TO REACH SEVERE LIMITS SATURDAY AFTERNOON WILL BE HIGHLY DEPENDENT ON THE DEGREE OF INSTABILITY AS THE STRONGER DEEP LAYER SHEAR LOOKS TO ARRIVE AFTER THE BETTER CONVECTIVE POTENTIAL. THE AMOUNT OF DEEP LAYER MOISTURE AND SOME POTENTIAL FOR REGENERATIVE CONVECTION SUGGESTS THAT THERE MAY BE A BETTER RISK FOR SOME LOCALLY HEAVY RAINFALL. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... SATURDAY NIGHT...AN ELONGATED BAROCLINIC ZONE ACROSS RUNNING SW-NE ACROSS NEW YORK STATE WILL BE IN PLACE IN THE RIGHT ENTRANCE REGION OF THE JET STREAM MOVING ACROSS SOUTHERN CANADA. WITH THE BOUNDARY NEAR STATIONARY...BUT SLOWLY SINKING SOUTHWARD THROUGH SUNDAY MORNING...WIDESPREAD PRECIPITATION IS EXPECTED THROUGH SATURDAY NIGHT. ALONG AND JUST AHEAD OF THE COLD FRONT SATURDAY EVENING...ROUGHLY 500 TO 1000J/KG CAPE COMBINED WITH PW VALUES IN THE 90TH PERCENTILE SHOULD RESULT IN THUNDERSTORMS THAT WILL BE HEAVY RAIN PRODUCERS. THE COMBINATION OF DIURNAL STABILIZATION SATURDAY NIGHT AND MORE STABLE AIR MOVING IN BEHIND THE FRONT WILL ALLOW A TRANSITION TO MORE WIDESPREAD STRATIFORM RAINFALL OVERNIGHT. OVERALL 12Z MODEL GUIDANCE HAS SLOWED THE SOUTHWARD PROGRESSION OF THE FRONT...SUCH THAT PRECIPITATION WILL LIKELY CONTINUE ACROSS THE AREA THROUGH SUNDAY MORNING...BEFORE SLOWLY CLEARING FROM NW TO SE BY SUNDAY AFTERNOON. OTHER CONSEQUENCES FROM THE SLOWER MOVING FRONT WILL LIKELY MEAN COOLER DAYTIME HIGH TEMPERATURES ON SUNDAY...ESPECIALLY SOUTH AND EAST OF THE THRUWAY DUE TO DYNAMICAL COOLING FROM ONGOING PRECIPITATION. THE WATERTOWN AND BUFFALO AREAS MAY HAVE THE BEST CHANCE OF SEEING SOME CLEARING BY THE AFTERNOON ON SUNDAY...ALONG WITH THE BEST CHANCE OF SEEING TEMPERATURES REACH THE UPPER 50S TO AROUND 60 DEGREES. BY SUNDAY NIGHT INTO MONDAY...WITH THE BAROCLINIC ZONE STALLED JUST SOUTHEAST OF THE FORECAST AREA...A SHORTWAVE TRACKING OUT OF THE MIDWEST WILL RIDE UP ALONG THE BOUNDARY AND WILL FORCE ANOTHER ROUND OF PRECIPITATION. DETERMINING EXACTLY WHERE THE BOUNDARY WILL STALL WILL BE CRUCIAL IN DETERMINING WHO GETS THE MOST PRECIPITATION SUNDAY NIGHT...BUT CURRENT MODEL PROJECTIONS SUGGEST THE HIGHEST CHANCES RUN FROM THE SOUTHERN TIER...ACROSS THE FINGER LAKES REGION AND INTO THE ADIRONDACKS...WITH SLIGHTLY LOWER CHANCES INTO THE BUFFALO AND ROCHESTER AREAS. WITH THE FORECAST AREA ON THE COOL SIDE OF THE FRONTAL BOUNDARY AND PRECIPITATION AROUND...MONDAY WILL REMAIN IN THE LOW 60S...WITH SLIGHTLY WARMER TEMPERATURES INTO THE MID 60S POSSIBLE FOR BUFFALO AND WATERTOWN WHERE THE FORECAST CALLS FOR THE LOWER PRECIPITATION AMOUNTS. A COMPACT UPPER-LEVEL LOW WILL SLOWLY DRIFT BY NORTH OF THE FORECAST AREA MONDAY NIGHT INTO TUESDAY...PUSHING THE MOIST AIRMASS FARTHER EAST...AND CONFINING THE BETTER PRECIPITATION CHANCES TO NORTH COUNTRY. COOL NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER-LOW WILL SUPPLY WESTERN AND NORTH CENTRAL NEW YORK WITH YET ANOTHER DAY OF BELOW NORMAL TEMPERATURES. HIGHS WILL REMAIN IN THE 60S AGAIN ACROSS THE FORECAST AREA. THIS WEATHER SYSTEM SHOULD HELP PUT AN END TO THE ABNORMALLY DRY CONDITIONS ACROSS PORTIONS WESTERN AND CENTRAL PORTIONS OF NEW YORK STATE. QPF TOTALS FROM SATURDAY THROUGH MONDAY SHOULD RANGE FROM AROUND AN INCH NEAR LAKE ONTARIO UP TO 2 INCHES ACROSS THE FINGER LAKES REGION. LOCALLY HIGHER AMOUNTS ARE CERTAINLY POSSIBLE WITHIN THUNDERSTORMS SATURDAY EVENING/NIGHT. && .LONG TERM /MONDAY THROUGH FRIDAY/... RIDGING ALOFT AND SURFACE HIGH PRESSURE FINALLY BUILD IN ACROSS WESTERN NEW YORK FOR THE SECOND HALF OF THE WORK WEEK. WITH A DRIER AIRMASS MOVING IN ON WEDNESDAY...EXPECT MOST LOCATIONS TO FINALLY CLEAR OUT NICELY AFTER A GLOOMY START TO THE WEEK. TEMPERATURES WILL ALSO RECOVER THROUGH THE SECOND HALF OF THE WEEK AS SOUTHERLY FLOW DEVELOPS ON THE BACK SIDE OF THE HIGH PRESSURE AND WARM AIR ADVECTION PUSHES 850 MB TEMPERATURES BACK INTO THE LOW TEENS CELSIUS ABOVE ZERO. THE WARMING TREND WILL BRING 70S BACK TO THE FORECAST ON WEDNESDAY WITH MID 80S POSSIBLE BY FRIDAY. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... SCATTERED SHOWERS AND THUNDERSTORMS OVER FAR SOUTHWESTERN NEW YORK WILL CONTINUE TO SLOWLY LIFT NORTHEASTWARD AND WEAKEN WITH THE LOSS OF HEATING THIS EVENING...AND SHOULD EVENTUALLY FALL APART ALTOGETHER BY THE LATE EVENING HOURS. THESE COULD PRODUCE SOME BRIEF/HIGHLY LOCALIZED REDUCTIONS TO MVFR BEFORE DISSIPATING...WITH VFR CONDITIONS OTHERWISE EXPECTED TO BE THE GENERAL RULE TONIGHT. ON SATURDAY...MAINLY DRY/VFR CONDITIONS SHOULD PERSIST THROUGH MUCH OF THE MORNING...BEFORE THE COMBINATION OF DAYTIME HEATING AND A SLOWLY APPROACHING COLD FRONTAL BOUNDARY BRINGS AN INCREASING RISK OF SHOWERS AND THUNDERSTORMS DURING THE AFTERNOON AND EARLY EVENING HOURS. EXPECT DIURNALLY-DRIVEN ACTIVITY TO FIRST BLOSSOM INLAND FROM THE LAKES SATURDAY AFTERNOON...BEFORE TURNING MORE WIDESPREAD LATER SATURDAY AFTERNOON AND EVENING AS THE FRONTAL BOUNDARY EASES ITS WAY INTO WESTERN AND NORTH CENTRAL NEW YORK. AS THIS OCCURS...PREVAILING CONDITIONS WILL TREND TOWARD THE LOWER VFR RANGE WITH TIME SATURDAY AFTERNOON AND EVENING...WITH REDUCTIONS TO MVFR POSSIBLE WITHIN ANY CONVECTION. OUTLOOK... SATURDAY NIGHT...SHOWERS ALONG WITH A CHANCE OF THUNDERSTORMS... WITH CONDITIONS DETERIORATING TO IFR/MVFR IN CONJUNCTION WITH A DEVELOPING NORTHEASTERLY UPSLOPE FLOW. SUNDAY...SLOWLY DIMINISHING SHOWERS...WITH IFR/MVFR CIGS CONTINUING. MONDAY THROUGH WEDNESDAY...MAINLY VFR. && .MARINE... A PERIOD OF NON SCA CONDITIONS ARE EXPECTED ON THE EASTERN GREAT LAKES TONIGHT THROUGH EARLY SATURDAY AS HIGH PRESSURE CROSSES OVER THE REGION. LATER SATURDAY SOUTHWEST WINDS WILL INCREASE AHEAD OF A STRONGER COLD FRONT...PERHAPS NECESSITATING THE HOISTING OF SMALL CRAFT FLAGS...ESPECIALLY ON THE RIVERS THROUGH THE DAY WHERE WINDS MAY REACH 20 KNOTS. BEHIND THE COLD FRONT WINDS AND WAVES WILL INCREASE ON THE EASTERN GREAT LAKES SATURDAY NIGHT AND SUNDAY AS NORTH THEN NORTHEAST WINDS DEVELOP IN A COLD AIR ADVECTION REGIME. && .CLIMATE... MAY 2015 WILL GO DOWN AS ONE OF THE WARMEST MAYS ON RECORD...AND POSSIBLY ONE OF THE DRIEST FOR BUFFALO AND WATERTOWN. A MOISTURE LADEN COLD FRONT WILL CROSS THE REGION TO END THE MONTH...AND SHOWERS AND THUNDERSTORMS ALONG THIS FEATURE MAY REMOVE CLIMATE SITES FROM A TOP 10 DRIEST MAY`S ON RECORD. BELOW ARE THE WARMEST MAYS ON RECORD. BUFFALO RANK MEAN TEMPERATURE YEAR 164.3 1991 263.8 2012 363.4 1944 462.8 1998 562.3 2015 (THROUGH 5/29) 662.2 1975 ROCHESTER RANK MEAN TEMPERATURE YEAR 163.7 1911 263.6 2015 (THOUGH 5/29) 363.2 2012 463.2 1944 WATERTOWN RANK MEAN TEMPERATURE YEAR 160.5 2012 260.0 1998 359.3 1975 458.8 2015 (THROUGH 5/29) 558.8 1960 6 58.3 1991 MAY HAS ALSO BEEN A DRY MONTH. OUTSIDE OF A FEW LOCALIZED HEAVY THUNDERSTORMS MANY LOCATIONS ARE WELL BELOW NORMAL FOR THE MONTH. BELOW IS MONTHLY PRECIPITATION FOR THE DRIEST MONTHS ON RECORD FOR OUR THREE CLIMATE SITES. BUFFALO RANK PRECIP YEAR 1 0.53 1877 2 0.54 1934 3 0.60 2005 4 0.83 2015 (THROUGH 5/29) 5 0.90 2012 .. 10 1.11 1926 ROCHESTER RANK PRECIP YEAR 1 0.24 2007 .. 27 1.52 2015 (THROUGH 5/29) 28 1.55 1876 29 1.59 1954 30 1.64 1926 WATERTOWN RANK PRECIP YEAR 1 0.70 1965 2 0.87 2005 3 0.88 1980 4 0.90 1974 5 0.99 1966 6 1.04 2015 (THROUGH 5/29) 7 1.08 1972 8 1.09 1951 9 1.14 1949 10 1.16 1962 AGAIN WITH THUNDERSTORMS IN THE FORECAST TO CLOSE OUT THE MONTH NONE OF OUR THREE CLIMATE SITES MAY HAVE A TOP TEN DRIEST MAY ON RECORD. HOWEVER ALL THREE SITES MAY CONTINUE THE STRETCH OF BELOW NORMAL PRECIPITATION MONTHS. BELOW ARE LISTED THE LATEST MONTH FOR WHEN PRECIPITATION RECORDED WAS ABOVE NORMAL FOR EACH OF OUR THREE CLIMATE LOCATIONS. BUFFALO - OCTOBER 2014 ROCHESTER - FEBRUARY 2015 WATERTOWN - AUGUST 2014 && .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...NONE. && $$ SYNOPSIS...TMA NEAR TERM...JJR/TMA SHORT TERM...THOMAS LONG TERM...THOMAS AVIATION...JJR/TMA MARINE...TMA CLIMATE...THOMAS

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