Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 300244
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
1044 PM EDT FRI MAY 29 2015

.SYNOPSIS...
A WARM AND HUMID AIR MASS WILL REMAIN OVER THE REGION OVERNIGHT AND
SATURDAY. A SLOW MOVING COLD FRONT WILL CROSS THE REGION LATE
SATURDAY AND SATURDAY NIGHT BRINGING WIDESPREAD SHOWERS AND
THUNDERSTORMS...WITH THE POTENTIAL FOR HEAVY RAINFALL LASTING
INTO SUNDAY.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 0230Z...A WEAK SHORTWAVE CONTINUES TO TRIGGER SPOTTY BRIEF
SHOWERS AND ISOLATED THUNDERSTORMS ACROSS PORTIONS OF WESTERN NEW
YORK AS IT LIFTS NORTHEASTWARD ACROSS THE LOWER GREAT LAKES AND
INTERACTS WITH OUR WARM AND INCREASINGLY HUMID AIRMASS...WITH THE
BULK OF THE CURRENT ACTIVITY HAVING BLOSSOMED OVER THE PAST HOUR
AND NOW SITUATED FROM THE NIAGARA FRONTIER NORTHWARD INTO LAKE
ONTARIO. BASED ON THIS...HAVE EXPANDED THE PRE-EXISTING CHANCE
POPS FURTHER NORTHWARD ACROSS THE REMAINDER OF FAR WESTERN NEW
YORK FOR A FEW HOURS...WITH THE EXPECTATION THAT THE ONGOING
SPOTTY CONVECTION SHOULD STILL WANE BY THE EARLY OVERNIGHT
HOURS...ONCE THE RESPONSIBLE SHORTWAVE PASSES BY. FOLLOWING
THIS...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.
GIVEN THE ABOVE IN CONJUNCTION WITH A GRADUALLY INCREASING
SOUTHERLY LOW LEVEL FLOW...OVERNIGHT LOW TEMPS SHOULD MOSTLY RANGE
BETWEEN 65 AND 70.

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 /03Z SATURDAY THROUGH WEDNESDAY/...
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER FAR WESTERN NEW
YORK WILL CONTINUE TO SLOWLY LIFT NORTHEASTWARD IN CONJUNCTION
WITH THEIR PARENT SHORTWAVE...EVENTUALLY EXITING THE REGION DURING
THE EARLY OVERNIGHT HOURS. THESE COULD PRODUCE SOME BRIEF/HIGHLY
LOCALIZED REDUCTIONS TO MVFR...WITH VFR CONDITIONS OTHERWISE
EXPECTED TO BE THE GENERAL RULE OVERNIGHT.

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...
WINDS AND WAVES WILL REMAIN WELL BELOW ADVISORY LEVELS ON THE
LOWER LAKES THROUGH EARLY SATURDAY MORNING.

DURING THE COURSE OF SATURDAY...SOUTHWEST WINDS WILL INCREASE
AHEAD OF A COLD FRONT...WITH THE STRONGEST WINDS /OF APPROXIMATELY
20 KNOTS/ FOUND ACROSS THE SAINT LAWRENCE RIVER...WHERE A SMALL
CRAFT ADVISORY HAS BEEN ISSUED.

BEHIND THE COLD FRONT... WINDS AND WAVES WILL INCREASE ACROSS THE
LOWER 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
            1               64.3         1991
            2               63.8         2012
            3               63.4         1944
            4               62.8         1998
            5               62.3         2015 (THROUGH 5/29)
            6               62.2         1975

ROCHESTER   RANK     MEAN TEMPERATURE    YEAR
            1               63.7         1911
            2               63.6         2015 (THROUGH 5/29)
            3               63.2         2012
            4               63.2         1944

WATERTOWN   RANK     MEAN TEMPERATURE    YEAR
            1               60.5         2012
            2               60.0         1998
            3               59.3         1975
            4               58.8         2015 (THROUGH 5/29)
            5               58.8         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...SMALL CRAFT ADVISORY FROM 10 AM TO 8 PM EDT SATURDAY FOR
         SLZ022-024.

&&

$$

SYNOPSIS...JJR/TMA
NEAR TERM...JJR/TMA
SHORT TERM...THOMAS
LONG TERM...THOMAS
AVIATION...JJR/TMA
MARINE...JJR/TMA
CLIMATE...THOMAS


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