Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 311900
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
300 PM EDT SUN AUG 31 2014

.SYNOPSIS...
SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A SLOW MOVING TROUGH OF
LOW PRESSURE WILL TAPER OFF THIS EVENING. IT WILL REMAIN HUMID
OVERNIGHT...WITH AREAS OF FOG. A FEW SPOTTY SHOWERS AND
THUNDERSTORMS ARE POSSIBLE ON LABOR DAY...BUT THE MAJORITY OF THE
DAY SHOULD BE RAIN FREE WITH TEMPERATURES A LITTLE ABOVE AVERAGE.

&&

.NEAR TERM /THROUGH MONDAY/...
AT 300 PM...A BROAD TROUGH OF LOW PRESSURE EXTENDED FROM SOUTHERN
QUEBEC SOUTHWESTWARD TO EASTERN MICHIGAN. AN ASSOCIATED UPPER LEVEL
TROUGH WILL CONTINUE TO MOVE EASTWARD...WHICH WILL PUSH THIS SURFACE
BOUNDARY GRADUALLY SOUTHWARD THROUGH EARLY EVENING...BEFORE IT
LARGELY WASHES OUT OVERNIGHT.

THE 12Z BUFFALO SOUNDING HAD 1.83 INCHES OF PRECIPITABLE
WATER...SO THERE COULD BE LOCALLY HEAVY RAINFALL. ANY TRAINING
CELLS COULD PRODUCE FLASH FLOODING...HOWEVER THE PROGRESSIVE NATURE
OF THIS TROUGH SHOULD MINIMIZE THIS POTENTIAL. SHOWERS WITH SOME
EMBEDDED THUNDERSTORMS HAVE DEVELOPED SOUTHEAST OF THE SURFACE
TROUGH...WITH MID-AFTERNOON RADAR SHOWING THE STEADIEST ACTIVITY ACROSS
WESTERN PORTIONS OF THE SOUTHERN TIER. THIS WAS CAPTURED
PARTICULARLY WELL BY LOCAL WRF GUIDANCE AND THE HRRR. BOTH GRADUALLY
DROP THESE SHOWERS SOUTHWARD AS THEY WEAKEN BY EARLY EVENING. IT WAS NOTED
THAT LEGACY RADAR UNDERESTIMATED RAINFALL INTENSITY...WHICH IS NOT
SURPRISING GIVEN THE WARM SOUNDING.

SHOWERS SHOULD TAPER OFF LATE THIS AFTERNOON INTO EARLY EVENING...WITH A
CONSENSUS OF GUIDANCE CONTINUING TO PUSH THIS ACTIVITY FURTHER
SOUTH. AFTER THIS...EXPECT THE MAJORITY OF THE NIGHT TO BE
RAIN-FREE...HOWEVER WITH LOTS OF LOW LEVEL MOISTURE THERE IS A
POTENTIAL FOR FAIRLY DENSE AND WIDESPREAD FOG DEVELOPMENT. THERE IS
A MODEST 20KT FLOW FORECAST AT 925MB THROUGH 06Z...WHICH MAY RESULT
IN STRATUS CLOUDS IN SOME AREAS. IF SKIES ALOFT DO CLEAR OUT...FOG
WILL QUICKLY DEVELOP GIVEN THE LIGHT WINDS AT THE SURFACE. LOWS
SHOULD BE IN THE MID TO UPPER 60S...SIMILAR TO THE DEW POINTS.

ON LABOR DAY...EXPECT AT LEAST THE MORNING TO BE DRY...AS STRATUS
AND FOG GRADUALLY DISSIPATE. DAYTIME HEATING WILL RESULT IN MODEST
ML CAPES AVERAGING 500 TO 1000 J/KG DURING THE AFTERNOON.
HOWEVER...THERE WILL NOT BE MUCH TO FOCUS THE CONVECTION...WITH THE
BEST CHANCE PROBABLY ALONG THE LAKE BREEZES (SOUTH OF LAKE ONTARIO
AND EAST OF LAKE ERIE). IN EACH CASE...COVERAGE SHOULD BE RATHER
SPOTTY...WITH THE VAST MAJORITY OF THE DAY LIKELY TO STAY DRY.
TEMPERATURES WILL BE ON THE WARM SIDE...WITH HIGHS IN THE UPPER 70S
TO LOWER 80S.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
A WARM AND STICKY AIRMASS WILL REMAIN ACROSS THE REGION ON
MONDAY...WITH MOST OF THE FORECAST AREA EXPERIENCING MAINLY DRY
CONDITIONS. HOWEVER THERE WILL BE THE CHANCE FOR SCATTERED SHOWERS
AND THUNDERSTORMS IN THE AFTERNOON AND EVENING...MAINLY ACROSS THE
INTERIOR SOUTHERN TIER WHERE THE BEST INSTABILITY WILL RESIDE. CAPE
VALUES BY LATER IN THE AFTERNOON ACROSS THIS REGION WILL RUN IN THE
1000-1500 J/KG RANGE WITH LI`S POSSIBLY AS LOW AS -4. HOWEVER WITH
WEAK 0-6KM BULK SHEAR (~20KTS) AND LACK OF A GOOD SURFACE TRIGGER
(ASIDE FROM A POSSIBLE LAKE BREEZE)...NOT EXPECTING ANY
THUNDERSTORMS TO REACH SEVERE LIMITS. INSTABILITY LOOKS LOWER ACROSS
THE REMAINDER OF THE AREA...AND THUS CONVECTIVE CHANCES LOOK MUCH
LOWER AS WELL. TEMPERATURES WILL AGAIN BE ON THE WARM SIDE WITH
HIGHS IN THE UPPER 70S TO LOWER 80S.

WITH THE LOSS OF DAYTIME HEATING MONDAY NIGHT MOST OF THE DIURNALLY
DRIVEN CONVECTION WILL DIMINISH IN COVERAGE...ALTHOUGH A FEW STORMS
MAY CONTINUE LATE INTO THE EVENING...ESPECIALLY ACROSS PORTIONS OF
THE SOUTHERN TIER. AT THE SAME TIME A COLD FRONT OVER THE UPPER
GREAT LAKES WILL BE ADVANCING TOWARD THE REGION AND BE LOCATED WEST
OF NEW YORK STATE BY TUESDAY MORNING. THAT SAID...MOST OF THE NIGHT
LOOKS TO REMAIN DRY...WITH PRECIP CHANCES STARTING TO INCREASE A BIT
ACROSS WESTERN NEW YORK TOWARD TUESDAY MORNING. ANOTHER MILD
NIGHT CAN BE EXPECTED WITH LOWS IN THE MID TO UPPER 60S FOR MOST
LOCATIONS THANKS TO DEEP SOUTHERLY FLOW OUT AHEAD OF THE APPROACHING
COLD FRONT.

LATEST GUIDANCE PACKAGE HAS THE COLD FRONT NOW MOVING A BIT SLOWER
THAN IN PREVIOUS RUNS. THIS IS MOST LIKELY DUE TO MOST OF THE MODELS
NOW COMING INTO AGREEMENT ON THE DEVELOPMENT OF LOW PRESSURE
SOMEWHERE IN THE OHIO VALLEY ALONG THE FRONT AND THEN TRACKING IT
NORTHEAST ALONG THE BOUNDARY WHICH WOULD SLOW IT DOWN A LITTLE.
THAT SAID...IT NOW APPEARS IT WILL TAKE THE BULK OF THE DAY TUESDAY
FOR THE COLD FRONT TO SWEEP ACROSS THE REGION WITH SHOWERS AN
THUNDERSTORMS LIKELY...WITH LOWER CHANCE POPS BY LATER IN THE DAY
ACROSS WESTERN NEW YORK. HIGH PRECIPITABLE WATER VALUES OF 1.7"-1.9"
TUESDAY AFTERNOON OFFER THE RISK OF HEAVY DOWNPOURS WITH ANY
THUNDERSTORM. SBCAPES OVER 1000 J/KG COMBINED WITH LIFTED INDEX
VALUES AT -4C TO -5C ALSO POINT TO THE POSSIBILITY OF STORMS. THE
MAIN DIFFERENCES FROM MONDAY ARE THAT 0-6KM BULK SHEAR VALUES LOOK
TO BE IN THE 40-45KT RANGE...AND ALSO HAVE THE SURFACE COLD FRONT
CROSSING THE FORECAST AREA WHICH WILL SERVE AS THE FOCAL POINT FOR
STORMS TO FIRE ALONG. ALL THIS SAID...LOOKS AS THOUGH THERE COULD BE
SOME STRONG STORMS...WITH A FEW STORMS POSSIBLY REACHING SEVERE
LIMITS. MAIN THREATS APPEAR TO BE GUSTY WINDS ASSOCIATED WITH BOWING
LINE SEGMENTS AND MARGINALLY SEVERE HAIL. ANOTHER WARM DAY ON TAP
WITH HIGHS IN THE UPPER 70S TO LOWER 80S.

THE COLD FRONT WILL SLIDE SOUTH AND EAST OF THE FORECAST AREA
TUESDAY EVENING...TAKING THE SHOWERS AND STORMS WITH IT. ALTHOUGH A
FEW SHOWERS WILL STILL BE POSSIBLE DURING THE EVENING ACROSS EASTERN
AREAS...BUT EVEN HERE THINGS WILL DRY OUT LATER TUESDAY NIGHT AS
SURFACE HIGH PRESSURE STARTS TO BUILD EAST ACROSS NEW YORK STATE.
LOWS WILL BE GENERALLY IN THE UPPER 50S TO LOWER 60S.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
UPPER LEVEL RIDGING AND SURFACE HIGH PRESSURE WILL BUILD ACROSS THE
REGION WEDNESDAY AND THURSDAY BRINGING IN DRIER AIR AND TEMPERATURES
THAT WILL STILL AVERAGE AT OR JUST A BIT ABOVE NORMAL FOR EARLY
SEPTEMBER. HIGH PRESSURE WILL THEN SLIDE OFF THE NEW ENGLAND COAST
BY FRIDAY. THIS WILL PROVIDE MAINLY DRY CONDITIONS THROUGH
MIDWEEK...BEFORE THE NEXT FRONTAL SYSTEM APPROACHES FOR LATE IN THE
WEEK AND EARLY WEEKEND. TEMPERATURES WILL BE A BIT ABOVE SEASONAL
NORMALS WITH HIGHS IN THE UPPER 70S TO LOW 80S AND LOWS IN THE LOWER
60S.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
AT 18Z...MVFR CIGS WERE IN PLACE ACROSS MOST OF THE REGION. THESE
SHOULD GRADUALLY LIFT AND SCATTER FROM NW-SE AS DRIER AIR IN THE
LOWER-MID LEVELS BUILDS IN FROM THE WEST. FOG MAY HAVE A
SIGNIFICANT IMPACT ON AVIATION LATE TONIGHT AND INTO MONDAY. LOW
LEVEL MOISTURE IS IN PLACE...AND WINDS WILL BE LIGHT AT THE
SURFACE...WITH THE ONLY FORECAST QUESTION WHETHER CIGS DEVELOP
(PROBABLY IFR-MVFR) AND LIMIT GROUND FOG...OR IF SKIES CLEAR OUT
ALOFT AND RESULT IN DENSE GROUND FOG. 20 KT WINDS AT 925MB ARE
FORECAST TO DIMINISH AFTER 06Z...WITH THE GREATEST THREAT FOR
DENSE FOG BETWEEN 08Z AND 12Z MONDAY. ANY FOG SHOULD DISSIPATE AND
LIFT AROUND MID-MORNING MONDAY...PERHAPS LINGERING A BIT LONGER IN
THE SOUTHERN TIER (JHW).

OUTLOOK...
MONDAY AFTERNOON...VFR/MVFR IN SCATTERED SHOWERS AND THUNDERSTORMS.
TUESDAY...SHOWERS AND THUNDERSTORMS LIKELY WITH ASSOCIATED BRIEF
MVFR/IFR. SOME STORMS MAY BE STRONG.
WEDNESDAY AND THURSDAY...VFR.
FRIDAY...MAINLY VFR. A CHANCE OF SHOWERS AND THUNDERSTORMS.

&&

.MARINE...
LOW PRESSURE WILL MOVE ACROSS SOUTHERN QUEBEC TODAY WITH A
SOUTHWEST FLOW ON THE LOWER LAKES. EXPECT A 3 TO 6 HOUR PERIOD OF
15 TO 20 KNOT WINDS AND 3 TO 5 FOOT WAVES ON LAKE ERIE THROUGH
EARLY EVENING. THE PRESSURE GRADIENT RELAXES ACROSS THE LOWER
LAKES TONIGHT AS LOW PRESSURE DISSIPATES OVER SOUTHEAST QUEBEC.
THIS WILL ALLOW WINDS AND WAVES TO SUBSIDE.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR LEZ040-
         041.

&&

$$

SYNOPSIS...APFFEL
NEAR TERM...APFFEL
SHORT TERM...JM
LONG TERM...JM/WCH
AVIATION...APFFEL
MARINE...APFFEL







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