Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 021530
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
1130 AM EDT TUE SEP 2 2014

.SYNOPSIS...
A COLD FRONT WILL SLOWLY CROSS THE REGION THIS AFTERNOON AND EVENING
WITH MORE WIDESPREAD SHOWERS AND THUNDERSTORMS...SOME OF WHICH COULD
PRODUCE STRONG GUSTY WINDS AND HEAVY RAINFALL. 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/...
THE AXIS OF A BROAD MID LEVEL TROUGH WILL SHIFT EAST ACROSS THE
GREAT LAKES TODAY WITH AN ASSOCIATED WEAK SURFACE COLD FRONT EASING
EASTWARD ACROSS WESTERN AND CENTRAL NEW YORK THIS AFTERNOON AND
EVENING. SOME LEADING PRE-FRONTAL SHOWERS ASSOCIATED WITH THE RIGHT
ENTRANCE REGION OF THE UPPER LEVEL JET STREAM ARE CROSSING LAKE ERIE
AND SOUTHWEST ONTARIO AT 15Z. SOME ISOLATED SHOWERS ARE ALSO BEING
FORCED AHEAD OF THIS ACROSS WESTERN NEW YORK. EXPECT THIS FIRST
BATCH OF SHOWERS JUST TO THE WEST TO MOVE INTO WESTERN NEW YORK LATE
THIS MORNING AND EARLY AFTERNOON REACHING NORTH-CENTRAL NEW YORK BY
EARLY TO MID AFTERNOON.

REGIONAL RADARS SHOWING A A SECOND LINE OF SHOWERS ORIENTED ALONG
THE SURFACE COLD FRONT CROSSING DETROIT TOWARD THE WESTERN END OF
LAKE ERIE. THIS WILL BE THE FOCUS FOR STRONGER SHOWERS AND STORMS
THIS AFTERNOON AND EVENING. THUNDERSTORM POTENTIAL REMAINS HIGH WITH
FORECAST SBCAPES GENERALLY RUNNING BETWEEN 1000-1500 J/KG COMBINED
WITH 0-6KM BULK SHEAR WHICH WILL INCREASE TO 40-50KT JUST AHEAD OF
THE FRONT. IN ADDITION...WILL HAVE INCREASING UPPER LEVEL DIFFLUENCE
IN THE RIGHT ENTRANCE REGION OF A 100+ KNOT UPPER LEVEL JET NEARING
THE REGION. THE KEY FACTOR IN SEVERE THREAT STILL APPEARS TO BE THE
AMOUNT OF SURFACE HEATING THAT TAKES PLACE BEFORE FROPA...I.E. CLOUD
COVER LIMITING HEATING...AND THUS LIMITING THE AMOUNT OF INSTABILITY.

A SLIGHT RISK OF SEVERE STORMS IS OUTLINED FROM SPC EXTENDING FROM
THE INTERIOR SOUTHERN TIER ACROSS THE FINGER LAKES INTO CENTRAL NEW
YORK. ELEVATED SHEAR AND LIMITED LAPSE RATES WILL KEEP STRONG GUSTY
WINDS THE MAIN SEVERE THREAT. HIGH PRECIPITABLE WATER VALUES OF
1.7"-1.8" OUT AHEAD OF THE FRONT WILL OFFER THE RISK FOR HEAVY
DOWNPOURS WITH ANY THUNDERSTORM. TEMPERATURES AND HUMIDITY WILL
REMAIN ON THE WARM AND MUGGY SIDE AGAIN TODAY WITH HIGHS MAINLY IN
THE UPPER 70S TO LOWER 80S AND DEWPOINTS IN THE UPPER 60S TO LOW 70S.

THE COLD FRONT WILL SLIDE EAST OF THE FORECAST AREA TONIGHT...TAKING
THE SHOWERS AND STORMS WITH IT. HIGH PRESSURE BEHIND THE FRONT WILL
BUILD EAST ACROSS NEW YORK BEHIND THE FRONT WITH DRYING AND CLEARING
DEVELOPING OVERNIGHT. LOWS WILL BE GENERALLY IN THE UPPER 50S TO
LOWER 60S.

&&

.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 /16Z TUESDAY THROUGH SATURDAY/...
MVFR/LOW VFR CIGS ARE ARRIVING ACROSS WESTERN AND CENTRAL NEW YORK
AHEAD OF A COLD FRONT WHICH WILL CROSS THE REGION THIS EVENING.
EXPECT THE LOWER CIGS TO LINGER INTO THE AFTERNOON WITH WIDESPREAD
SHOWERS AND STORMS THEN DEVELOPING ALONG AND AHEAD OF THE FRONT THIS
AFTERNOON AND EVENING. SOME OF THESE STORMS MAY BRING BRIEF PERIODS
OF MVFR/IFR IN HEAVY DOWNPOURS. A FEW OF THESE STORMS COULD EVEN
BECOME STRONG TO SEVERE ACROSS THE FORECAST AREA WITH STRONG GUSTY
WINDS. OUTSIDE OF ANY SHOWERS AND THUNDERSTORMS...EXPECT VFR FLIGHT
CONDITIONS.

ALL OF THIS ACTIVITY WILL EXIT SOUTH AND EAST OF THE REGION THIS
EVENING...WITH VFR FLIGHT CONDITIONS RETURNING FOR MOST OF THE
NIGHT...WITH MVFR CEILINGS ONCE AGAIN POSSIBLE LATE IN THE TAF
PERIOD ACROSS THE INTERIOR SOUTHERN TIER.

OUTLOOK...
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 CROSS THE LOWER LAKES REGION THIS AFTERNOON AND
EVENING. ON LAKE ERIE WINDS AND WAVES WILL CLIMB TO NEAR ADVISORY
LEVELS AND REMAIN AT OR JUST ABOVE ADVISORY CRITERIA THROUGH LATE
AFTERNOON/EARLY EVENING...A SMALL CRAFT ADVISORY REMAINS IN EFFECT
FOR LAKE ERIE THROUGH 00Z THIS EVENING. THE FRONT ITSELF WILL ALSO
PRODUCE A ROUND OF SCATTERED TO NUMEROUS THUNDERSTORMS TODAY...OF
WHICH A FEW COULD PRODUCE STRONG GUSTY WINDS AND LOCALLY HIGHER
WAVES.

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/SMITH
NEAR TERM...JM/SMITH
SHORT TERM...HITCHCOCK
LONG TERM...HITCHCOCK
AVIATION...JM/SMITH
MARINE...JM/SMITH






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