Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 020839
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
439 AM EDT TUE SEP 2 2014

.SYNOPSIS...
SCATTERED SHOWERS AND A FEW ISOLATED THUNDERSTORMS WILL ADVANCE
EASTWARD OVERNIGHT WHILE DIMINISHING IN INTENSITY AND COVERAGE AREA
TOWARDS THE FINGER LAKES AND AREAS EAST OF LAKE ONTARIO. A COLD
FRONT WILL THEN CROSS THE REGION ON TUESDAY WITH MORE WIDESPREAD
SHOWERS AND THUNDERSTORMS...SOME OF WHICH COULD PRODUCE STRONG GUSTY
WINDS ACROSS PORTIONS OF THE SOUTHERN TIER AND FINGER LAKES. IN THE
WAKE OF THE FRONT...HIGH PRESSURE WILL BUILD INTO THE LOWER GREAT
LAKES AND BRING A RETURN TO DRIER AND LESS HUMID WEATHER WEDNESDAY
AND THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
EARLY THIS OVERNIGHT REGIONAL RADARS STILL DISPLAYING LINE OF
WEAKENING SHOWERS STRETCHING FROM MONROE COUNTY SOUTHEAST TO
CATTARAUGUS COUNTY ALL ASSOCIATED WITH A PRE-FRONTAL TROUGH CROSSING
WESTERN NEW YORK. NORTHERN PART OF LINE HAS WEAKENED
CONSIDERABLY...CONTAINING JUST SOME LIGHT SHOWERS...HOWEVER ACROSS
THE SOUTHERN TIER THERE ARE STILL A FEW HEAVIER SHOWERS WITH SOME
EMBEDDED LIGHTNING STRIKES. EXPECT THIS TO BE THE TREND AS THE NIGHT
PROGRESSES WITH SHOWERS/ISOLATED THUNDERSTORMS MOVING THROUGH AND
EXITING CATTARAUGUS AND ALLEGANY COUNTIES BEFORE EXITING TO THE
EAST...WHILE TO THE NORTH OF HERE THE LINE CONTINUES TO ALL BUT
FIZZLE OUT AS IT MOVES THROUGH THE GENESEE VALLEY AND NORTHERN
FINGER LAKES REGION. THAT SAID...THE LLJ OF 30 KNOTS AT 850 HPA
SHOULD MAINTAIN AT LEAST A CHANCE OF SHOWERS ACROSS THIS AREA AND
POINTS EASTWARD THROUGH THE REST OF THE OVERNIGHT.

LOWS TONIGHT WILL REMAIN ON THE MILD SIDE FOR EARLY SEPTEMBER WITH
LOWS IN THE MID 60S TO LOWER 70S...WARMEST ACROSS THE LAKE PLAIN.

ON TUESDAY...THE AXIS OF BROAD MID AND UPPER LEVEL TROUGHING WILL
SLIDE EAST FROM THE UPPER GREAT LAKES TO THE LOWER LAKES REGION...
WITH AN ASSOCIATED WEAK COLD FRONT EASING EASTWARD ACROSS THE
FORECAST AREA DURING THE COURSE OF THE AFTERNOON. IN ADVANCE OF THIS
FRONT...A VERY WARM AND HUMID AIRMASS WILL REMAIN IN PLACE WITH
PRECIPITABLE WATER VALUES APPROACHING TWO INCHES...WHILE LARGE-SCALE
LIFT WILL BE ON THE INCREASE OWING TO A COMBINATION OF INCREASING
CONVERGENCE ALONG THE FRONT/THE NOSE OF A 30-40 KT LOW-MID LEVEL
JET...SUPPORTING SYNOPTIC-SCALE DCVA/HEIGHT FALLS...AND INCREASING
UPPER LEVEL DIFFLUENCE IN THE RIGHT ENTRANCE REGION OF A 120+ KNOT
UPPER LEVEL JET. COUPLED WITH DAYTIME HEATING...ALL OF THIS SHOULD
RESULT IN FAIRLY NUMEROUS SHOWERS AND THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF THE FRONT AS IT CROSSES OUR REGION...FOR WHICH SOME
LIKELY TO LOW-END CATEGORICAL POPS WILL BE IN PLAY.

WHILE THERE WILL BE A FAIR AMOUNT OF WIND IN PLACE ALOFT TO KEEP
THINGS MOVING ALONG...GIVEN THE VERY MOIST AIRMASS THERE STILL WILL
BE AT LEAST SOME THREAT OF LOCALLY HEAVY RAINFALL ON TUESDAY...
ESPECIALLY IF ANY STRONGER/HEAVIER CELLS MANAGE TO TRAIN REPEATEDLY
OVER A PARTICULAR AREA. THE OVERALL SEVERE POTENTIAL IS SOMEWHAT
LESS CLEAR GIVEN LINGERING UNCERTAINTY WITH RESPECT TO HOW MUCH
HEATING/DESTABILIZATION WILL OCCUR PRIOR TO THE ARRIVAL OF THE
FRONT...HOWEVER WITH 35-45 KNOTS WORTH OF 0-6 KM BULK SHEAR IN
PLACE...THE POTENTIAL FOR SOME STRONGER STORMS CAPABLE OF ATTENDANT
STRONG TO SEVERE WIND GUSTS CERTAINLY EXISTS PROVIDED ENOUGH
INSTABILITY CAN ULTIMATELY BE REALIZED. AT THIS POINT...A ROUGH
MODEL CONSENSUS SUGGESTS THAT THE GREATEST POTENTIAL FOR THIS WILL
EXIST FROM INTERIOR PORTIONS OF THE SOUTHERN TIER NORTHEASTWARD
ACROSS THE FINGER LAKES REGION...WHERE THE BEST INSTABILITY AND
LARGE-SCALE DYNAMICS WILL BE SUPERIMPOSED UPON EACH OTHER. NOT
COINCIDENTALLY... THIS AGREES QUITE WELL WITH SPC`S LATEST DAY 2
CONVECTIVE OUTLOOK...WHICH PORTRAYS A SLIGHT RISK OF SEVERE STORMS
ACROSS THIS PARTICULAR REGION.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
BY WEDNESDAY MORNING THE MID LEVEL TROUGH WILL HAVE LIFTED INTO
EASTERN QUEBEC WITH SURFACE HIGH PRESSURE BUILDING INTO THE OHIO
VALLEY. THIS WILL BRING A RETURN TO DRY WEATHER ON WEDNESDAY WITH
DRYING AND SUBSIDENCE ON THE INCREASE. THERE MAY BE SOME LINGERING
LOW LEVEL MOISTURE AND CLOUDS ACROSS THE HIGHER TERRAIN DURING THE
MORNING. DIURNAL CUMULUS FIELDS MAY ALSO DEVELOP ACROSS THE HIGHER
TERRAIN OF THE SOUTHERN TIER AND FINGER LAKES...AND ALSO ALONG A
CONVERGENCE ZONE RUNNING FROM THE NIAGARA PENINSULA TO NEAR
ROCHESTER. THIS MAY YIELD A MIX OF CLOUDS AND SUN IN THESE AREAS FOR
THE AFTERNOON. 850MB TEMPS OF AROUND +12C WILL SUPPORT HIGHS AROUND
80 AT THE LOWER ELEVATIONS OF WESTERN NY WITH MID TO UPPER 70S
ACROSS HIGHER TERRAIN AND THE NORTH COUNTRY.

HIGH PRESSURE WILL BUILD NORTHEAST INTO NEW ENGLAND WEDNESDAY NIGHT
AND THURSDAY WITH RIDGING EXTENDING BACK INTO THE LOWER LAKES. THIS
WILL PROVIDE MORE DRY WEATHER WITH MAINLY CLEAR SKIES MUCH OF THE
TIME. EXPECT DECENT RADIATIONAL COOLING CONDITIONS WEDNESDAY NIGHT
ALTHOUGH THE AIRMASS IS NOT PARTICULARLY COOL OR DRY. LOWS WILL
RANGE FROM AROUND 60 ON THE LAKE PLAINS TO AROUND 50 IN THE COOLEST
SOUTHERN TIER VALLEYS AND TUG HILL REGION.

WARM ADVECTION WILL INCREASE DURING THE DAY THURSDAY. ISENTROPIC
UPGLIDE AND INCREASING MOISTURE MAY PRODUCE SOME PATCHY MID LEVEL
CLOUDS...BUT THE THICKER CLOUD COVER SHOULD REMAIN ON THE CANADIAN
SIDE OF THE INTERNATIONAL BORDER. 850MB TEMPS RISE TO +14C TO +16C
BY THURSDAY AFTERNOON...SUPPORTING HIGHS IN THE MID 80S ACROSS LOWER
ELEVATIONS.

THURSDAY NIGHT WARM ADVECTION WILL INCREASE AS SOUTHWEST FLOW PICKS
UP IN RESPONSE TO A STRONG COLD FRONT MOVING INTO THE WESTERN LAKES.
ONGOING WARM ADVECTION AND ISENTROPIC UPGLIDE WILL BRING SOME
INCREASE IN MID/HIGH CLOUDS. A WARMER AIRMASS AND A MIXING BREEZE
OVERNIGHT WILL KEEP LOWS ON THE WARM SIDE WITH UPPER 60S ON THE LAKE
PLAINS AND LOWER 60S IN THE SHELTERED SOUTHERN TIER VALLEYS AND TUG
HILL REGION.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
THE LONG TERM WILL BE VERY CHANGEABLE WITH ONE OF THE WARMEST DAYS
OF THE YEAR ON FRIDAY FOLLOWED BY A SIGNIFICANT COOL DOWN FOR THE
WEEKEND.

ON FRIDAY A STRONG AND PROGRESSIVE MID LEVEL TROUGH WILL MOVE ACROSS
NORTHWEST ONTARIO TO JAMES BAY. INCREASING SOUTHWEST FLOW AHEAD OF
THIS FEATURE WILL CAPTURE AN ELEVATED MIXED LAYER /EML/ WITH ORIGINS
ACROSS THE DESERT SOUTHWEST. THIS EML PLUME WILL ALLOW 850MB TEMPS
TO SOAR TO AROUND +18C TO +19C. THIS WILL SUPPORT HIGHS IN THE UPPER
80S TO LOWER 90S IN MANY AREAS...WITH THE WARMEST TEMPS LIKELY TO BE
IN THE GENESEE VALLEY. THE EML PLUME WILL PROVIDE A STRONG CAP IN
THE WARM SECTOR AND SHOULD HOLD CONVECTION AT BAY UNTIL AT LEAST
LATE AFTERNOON WHEN THE UPSTREAM COLD FRONT AND TROUGH APPROACH AND
AID IN ERODING THE MID LEVEL CAP.

FRIDAY NIGHT COULD BE ACTIVE WITH A STRONG SURFACE COLD FRONT
DROPPING SOUTHEAST ACROSS THE REGION. THE STRONGEST HEIGHT FALLS AND
UPPER LEVEL SUPPORT WILL SHIFT EAST ACROSS QUEBEC...ALTHOUGH A
TRAILING RIBBON OF STRONGER FLOW IN THE 900-700MB LAYER WILL PROVIDE
ENOUGH CONVERGENCE TO ORGANIZE A BROKEN BAND OF CONVECTION ALONG THE
FRONT. GIVEN THE STRENGTH OF THE FRONT AND BETTER AGREEMENT BETWEEN
THE GFS AND ECMWF ON TIMING...HAVE BUMPED POPS TO LOW LIKELY FOR
FRIDAY NIGHT.

BY SATURDAY MODEL DIFFERENCES BEGIN TO SHOW...WITH THE ECMWF
DEVELOPING A WEAK FRONTAL WAVE IN THE MID ATLANTIC. THIS WOULD HOLD
UP THE FRONT SOMEWHAT AND ALSO FORCE IT TO BECOME MORE ANABATIC IN
NATURE WITH SHOWERS LINGERING ON THE COOL SIDE OF THE BOUNDARY. THE
GFS HAS A FASTER COLD FRONTAL PASSAGE WITH SATURDAY DRY. FOR NOW
WILL HOLD ONTO LOW CHANCE POPS FOR SATURDAY WITH A HEDGE TO THE
SLOWER ECMWF SOLUTION. IN EITHER CASE IT WILL BE NOTABLY COOLER
SATURDAY...WITH HIGHS ONLY IN THE LOWER 70S IN MOST LOCATIONS.

SATURDAY NIGHT THROUGH MONDAY THE FRONT WILL PUSH WELL SOUTHEAST OF
THE REGION WITH HIGH PRESSURE BUILDING INTO THE GREAT LAKES. THIS
WILL BRING A RETURN TO MAINLY DRY WEATHER. TEMPERATURES WILL REACH
THEIR COOLEST ON SUNDAY WHEN HIGHS MAY NOT MAKE IT OUT OF THE UPPER
60S AT LOWER ELEVATIONS AND MID 60S ACROSS HIGHER TERRAIN. AIRMASS
MODERATION WILL BEGIN BY MONDAY WITH HIGHS BACK INTO THE LOWER 70S.

&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
VFR FLIGHT CONDITIONS AT 06Z WILL PERSIST FOR ANOTHER FEW HOURS OR
SO...BEFORE SOME PATCHES OF MVFR CIGS...AND SOUTHERN TIER IFR CIGS
FORM ACROSS THE REGION JUST BEFORE DAWN.

PRE FRONTAL SURFACE IS NOW EAST OF THE KBUF/KIAG/KJHW
TERMINALS...TAKING SHOWERS AND ISOLATED THUNDERSTORM ACTIVITY WITH
IT. KJHW SAW A PERIOD OF MVFR CIGS WITH THE PRECIPITATION...BUT
SKIES HAVE NOW SCATTERED OUT SINCE THE PRECIPITATION MOVED TO THE
EAST. THERE ARE SOME SCATTERED SHOWERS OVER LAKE ERIE. THESE
ARE SHOWING SIGNS OF WEAKENING AS THEY MOVE ONSHORE WHERE AIR IS
JUST A BIT MORE STABLE IN THE WAKE OF THE PASSAGE OF THE TROUGH.
HOWEVER ANY OF THESE SHOWERS THAT DO HOLD TOGETHER ONCE ONSHORE
COULD BRING A BRIEF LIGHT SHOWER TO ANYWHERE ACROSS THE NIAGARA
FRONTIER. MAY SEE A BRIEF SPRINKLE OR LIGHT SHOWER AT KROC THROUGH
07Z WITH THE TROUGH AS IT PASSES THROUGH...THEN JUST SOME PASSING
CLOUDS AFTER THAT. THIS ACTIVITY WILL LIKELY DIMINISH BEFORE
REACHING THE KART AIRFIELD.

ON TUESDAY...A WEAK COLD FRONT WILL SLOWLY EASE EASTWARD ACROSS THE
REGION THROUGH THE COURSE OF THE DAY. COUPLED WITH INCREASING
DAYTIME INSTABILITY...EXPECT MORE WIDESPREAD SHOWERS AND STORMS TO
DEVELOP ALONG AND AHEAD OF THIS FRONT AS IT CROSSES THE AREA...WITH
SOME OF THESE POTENTIALLY BRINGING BRIEF PERIODS OF MVFR/IFR. A FEW
OF THESE STORMS COULD EVEN BECOME STRONG TO SEVERE ACROSS INTERIOR
PORTIONS OF THE SOUTHERN TIER AND FINGER LAKES...WHERE OVERALL
INSTABILITY APPEARS AS IF IT WILL BE THE STRONGEST.

OUTLOOK...
TUESDAY NIGHT...SHOWERS AND THUNDERSTORMS ENDING ACROSS SOUTHERN AND
EASTERN SECTIONS...WITH CONDITIONS MOSTLY RETURNING TO VFR.
WEDNESDAY AND THURSDAY...VFR.
FRIDAY AND SATURDAY...A CHANCE OF SHOWERS AND THUNDERSTORMS WITH
ASSOCIATED BRIEF MVFR/IFR...OTHERWISE VFR.

&&

.MARINE...
A COLD FRONT WILL WORK ACROSS THE UPPER GREAT LAKES
OVERNIGHT...BEFORE CROSSING THE LOWER LAKES REGION ON TUESDAY. IN
ADVANCE OF THE FRONT...SOUTHWESTERLY WINDS WILL INCREASE LATER
TONIGHT AND TUESDAY MORNING...PARTICULARLY ON ON LAKE ERIE WHERE
WINDS AND WAVES WILL CLIMB TO NEAR ADVISORY LEVELS. WILL ISSUE A SCA
FOR LAKE ERIE THROUGH MIDDAY TOMORROW TO ACCOUNT FOR SOME WINDS
NEARING 18-20 KNOTS OVERNIGHT AND THROUGH THE MORNING HOURS. THE
FRONT ITSELF WILL ALSO PRODUCE A ROUND OF SCATTERED TO NUMEROUS
THUNDERSTORMS ON TUESDAY... A FEW OF WHICH COULD PRODUCE STRONG
GUSTY WINDS.

IN THE WAKE OF THE FRONTAL PASSAGE...HIGH PRESSURE WILL BUILD ACROSS
THE REGION TUESDAY NIGHT THROUGH THURSDAY WHILE BRINGING A RETURN TO
FAIR WEATHER AND LIGHTER WINDS.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LEZ040-
         041.

&&

$$

SYNOPSIS...JM/THOMAS
NEAR TERM...JM/THOMAS
SHORT TERM...HITCHCOCK
LONG TERM...HITCHCOCK
AVIATION...JM/THOMAS
MARINE...JM/THOMAS




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