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000
FXUS61 KBUF 200601
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
201 AM EDT MON MAY 20 2013

.SYNOPSIS...
A SOUTHWEST FLOW OF WARM AND MORE HUMID AIR WILL CONTINUE TO MOVE
INTO THE REGION THROUGH THE FIRST HALF OF THE WEEK. A FRONTAL
BOUNDARY WILL ALSO STALL NEARBY...SETTING THE STAGE FOR INCREASING
CHANCES FOR SEVERAL ROUNDS OF SHOWERS AND THUNDERSTORMS. THE
UNSETTLED WEATHER WILL CONTINUE MUCH OF THE WEEK BEFORE A STRONG
COLD FRONT CROSSES THE AREA THURSDAY NIGHT WITH COOLER AND DRIER AIR
ARRIVING FRIDAY.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 06Z...REGIONAL SATELLITE IMAGERY SHOWS AN EXTENSIVE DECK OF
LOW STRATUS DRAPED FROM INLAND AREAS OF CHAUTAUQUA COUNTY
NORTHEASTWARD ACROSS INTERIOR PORTIONS OF LIVINGSTON/ONTARIO
COUNTIES...THEN ON ACROSS MUCH OF OSWEGO AND LEWIS COUNTIES. THIS
AREA OF LOWER CLOUDS IS CURRENTLY HAVING A HARD TIME MAKING MUCH
FURTHER NORTHWARD PROGRESS...THANKS TO A DOWNSLOPING SOUTHERLY FLOW
ACROSS THE LAKE PLAINS. IN THESE LATTER AREAS...THERE CONTINUES TO
JUST BE VARYING AMOUNTS OF MID AND HIGH CLOUD COVER.

FOR THE BALANCE OF THE NIGHT...EXPECT THE CLOUD COVER ABOVE TO
LARGELY REMAIN AS IS WITH THE SOUTHERLY DOWNSLOPE LOW LEVEL FLOW
HELPING TO KEEP THE STRATUS FROM SPREADING MUCH FURTHER NORTH...SO
HAVE UPDATED THE SKY GRIDS TO BRING THEM MORE IN LINE WITH THIS
SCENARIO/RECENT SATELLITE IMAGERY. HAVE ALSO PULLED THE MENTION OF
PATCHY FOG FROM THE FORECAST...AS THE STRATUS SHOULD HELP TO DETER
FOR FORMATION IN THE AREAS WHERE IT HAS ALREADY ARRIVED...AND THE
AFOREMENTIONED DOWNSLOPE FLOW SHOULD LIKELY DO THE SAME ACROSS THE
REST OF THE AREA BY KEEPING THINGS A BIT MORE MIXED THAN PREVIOUSLY
THOUGHT...WHICH SHOULD RESULT IN GREATER T-TD SPREADS. TEMPERATURES
WILL REMAIN MILD OVERNIGHT...NOT FALLING BELOW THE MID 50S TO LOWER
60S.

ON MONDAY THE WEAK/DIFFUSE FRONTAL BOUNDARY WILL REMAIN STALLED
ACROSS NORTHERN NY. THIS MAY PROVIDE ENOUGH FOCUS FOR A FEW MORE
SCATTERED SHOWERS AT TIMES IN THAT AREA. IN ADDITION...INSTABILITY
WILL BE GREATER ON MONDAY THAN RECENT DAYS AS LOW LEVEL MOISTURE
CONTINUES TO IMPROVE. NAM/GFS BOTH DEVELOP AROUND 1000J/KG OF CAPE
BY AFTERNOON INLAND FROM THE LAKES. THIS IS LIKELY OVERDONE DUE TO
THE PERSISTENTLY OVER-ESTIMATED SURFACE DEWPOINTS SEEN IN MODELS
LATELY...BUT STILL MAY DEVELOP ENOUGH INSTABILITY TO POP A FEW
WIDELY SCATTERED SHOWERS AND STORMS IN THE AFTERNOON. THE MOST
LIKELY AREAS FOR THIS WOULD BE FROM THE INTERIOR SOUTHERN TIER INTO
THE FINGER LAKES AND CENTRAL NY. ONSHORE FLOW ALONG ALL THE
LAKESHORES WILL KEEP STABLE LAKE SHADOWS APPARENT...WITH MORE
SUNSHINE AND MUCH LOWER CONVECTIVE RISK FOR THE AFTERNOON WITHIN
10-20 MILES OF THE LAKESHORES.

SOUTHWEST FLOW ALOFT AND BUILDING HEIGHTS WILL BOOST 850MB TEMPS TO
AROUND +15C IN THE WEST BY AFTERNOON...SUPPORTING HIGHS IN THE LOWER
80S. THE NORTH COUNTRY WILL BE A LITTLE COOLER WITH MORE PERSISTENT
CLOUD COVER...EXPECT MID 70S THERE. AS IS TYPICALLY THE CASE IN
MAY...ONSHORE FLOW WILL KEEP THE LAKESHORES MUCH COOLER.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
MONDAY NIGHT ANY DAYTIME CONVECTION TOWARDS THE EAST WILL QUICKLY
END WITH THE LOSS OF DAYTIME HEATING. THE UPPER LEVEL RIDGE WILL
BEGIN TO WEAKEN AS SLIGHT SHORTWAVES CREST THE TOP OF THE
RIDGE...AND THESE IMPULSES WILL MAINTAIN THE CHANCE FOR AN
OVERNIGHT SHOWER OR THUNDERSTORM.

BOTH TUESDAY AND WEDNESDAY WILL BE WARM AND HUMID AS SOUTHERLY WINDS
SOUTH OF THIS WEAK WARM FRONT CONTINUE TO ADVECT MOISTURE NORTHWARD
ACROSS THE EASTERN GREAT LAKES. DEWPOINTS BOTH DAYS ARE EXPECTED TO
RISE INTO THE LOW TO MID 60S...AND WITH 850 HPA TEMPERATURES BETWEEN
14 AND 17C AFTERNOON HIGHS WILL BE IN THE 70S...LOWER 70S ACROSS THE
NORTH COUNTRY AND MID TO UPPER 70S SOUTH OF LAKE ONTARIO. WEDNESDAY
MAY BE A FEW DEGREES COOLER DUE TO BUILDING MID LEVEL MOISTURE
DECREASING THE AMOUNT OF SUNSHINE.

THIS DAYTIME HEAT COMBINED WITH THE INCREASING MOISTURE WILL BRING
AN UNSTABLE ENVIRONMENT WITH LI`S DROPPING INTO THE -4 TO -7C RANGE.
SBCAPE VALUES BOTH DAYS WILL CLIMB INTO THE 1000 TO 1500 J/KG RANGE
WHICH WILL SUPPORT AN ENVIRONMENT FOR THUNDERSTORMS BOTH TUESDAY AND
WEDNESDAY. THE MID LEVEL LAPSE RATES GENERALLY HOLD IN THE 6 TO 7
C/KM RANGE WHICH ARE NOT TOO IMPRESSIVE AND WITH NO STRONG WIND
FIELDS WILL HOLD THE WORDING TO JUST GENERAL THUNDERSTORMS FOR NOW.
ONE CONCERN WILL BE TUESDAY WHEN THE WIND FIELD IS LIGHT...LESS THAN
25 KNOTS THROUGH 10-12K FEET. THIS LIGHT WIND FIELD MAY ALLOW FOR ANY
THUNDERSTORMS TO BE SLOW MOVING.

BY THURSDAY A SURFACE WAVE RIDING ALONG A FRONTAL BOUNDARY WILL
CROSS THE REGION DRAGGING A COLD FRONT THROUGH THE CWA. THIS AGAIN
WILL TRIGGER SHOWERS AND THUNDERSTORMS...WITH THE FRONT AND FALLING
MID LEVEL HEIGHTS PROVIDING THE LIFT AS INSTABILITY WILL BE MUCH
WEAKER. 850 HPA TEMPERATURES WILL BE A BIT COOLER WHICH WILL ALLOW
FOR COOLER TEMPERATURES IN THE 60S. FALLING DEWPOINTS WILL BRING AN
END TO THE BRIEF HUMID STRETCH.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
THIS TIME PERIOD WILL BE COOLER AND MORE SETTLED THAN PRIOR DAYS
AS AN UPPER LEVEL TROUGH WITH DRIER AIR SETTLES SOUTHWARD. THE 12Z
ECMWF IS DEEPER AND MORE PROGRESSIVE WITH THE TROUGH THAN THE
CORRESPONDING 12Z GFS...AND THE 00Z GEFS ENSEMBLE MEMBERS.

FOR FRIDAY...WILL HAVE A LOW CHANCE FOR A SHOWER EARLY IN THE DAY
TOWARDS THE EAST. OTHERWISE WILL KEEP THE REMAINDER OF FRIDAY AND
INTO SATURDAY DRY AS HIGH PRESSURE FROM THE NORTHERN GREAT LAKES
PUSHES TOWARDS THE EASTERN GREAT LAKES REGION. EXCEPTION WILL BE
ACROSS THE NORTH COUNTRY WHERE IF THE ECMWF SOLUTION WITH THE DEEPER
TROUGH WERE TO VERIFY ADDITIONAL CLOUD COVER AND INSTABILITY SHOWERS
UNDER THE COLD POOL WILL FALL SATURDAY.

DRY WEATHER WILL CONTINUE ON SUNDAY WITH BUILDING HEIGHTS ACROSS
THE GREAT LAKES REGION. A RETURN OF WARMER AIR AT 850 HPA WILL BRING
A RETURN OF MID 60S TO LOWER 70S ACROSS THE REGION.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AS OF 06Z...REGIONAL SATELLITE IMAGERY SHOWS AN EXTENSIVE DECK OF
IFR/MVFR LOW STRATUS DRAPED FROM INLAND AREAS OF CHAUTAUQUA COUNTY
NORTHEASTWARD ACROSS INTERIOR SECTIONS OF THE FINGER LAKES...THEN ON
ACROSS PORTIONS OF THE NORTH COUNTRY. THIS AREA OF LOWER CLOUDS IS
CURRENTLY HAVING A HARD TIME MAKING MUCH FURTHER NORTHWARD
PROGRESS...THANKS TO A DOWNSLOPING SOUTHERLY FLOW ACROSS THE LAKE
PLAINS. IN THESE LATTER AREAS...VFR CONDITIONS CONTINUE TO PREVAIL
UNDER VARYING AMOUNTS OF MID AND HIGH CLOUD COVER.

FOR THE BALANCE OF THE NIGHT...EXPECT THE CONDITIONS ABOVE TO
LARGELY REMAIN AS IS WITH THE SOUTHERLY DOWNSLOPE LOW LEVEL FLOW
HELPING TO KEEP THE STRATUS FROM SPREADING MUCH FURTHER NORTH. AT
THIS POINT DO NOT EXPECT MUCH IN THE WAY OF NOCTURNAL FOG
FORMATION...AS THE STRATUS SHOULD HELP TO DETER FOG DEVELOPMENT IN
THE AREAS WHERE IT HAS ALREADY ARRIVED...AND THE AFOREMENTIONED
DOWNSLOPE FLOW SHOULD LIKELY DO THE SAME ACROSS THE AREA.

ONCE WE GET INTO THE DAYLIGHT HOURS...ANY STRATUS ACROSS THE HIGHER
TERRAIN SHOULD GRADUALLY MIX OUT THROUGH MID TO LATE MORNING...
LEAVING BEHIND GENERAL VFR CONDITIONS FOR THE REST OF THE DAY. IN
TERMS OF PRECIPITATION POTENTIAL...A FEW SCATTERED SHOWERS MAY
CROSS THE NORTH COUNTRY THIS MORNING AS A WEAK BACKDOOR COLD FRONT
BRUSHES ACROSS NORTHERN NY...THEN ADDITIONAL SCATTERED CONVECTION
SHOULD DEVELOP THIS AFTERNOON AWAY FROM THE STABILIZING EFFECTS OF
THE LAKES...SOME OF WHICH COULD PRODUCE VERY BRIEF AND LOCALIZED
IFR/MVFR CONDITIONS. THIS SAID...MOST IF NOT ALL OF THE TAF SITES
SHOULD REMAIN BEHIND DEVELOPING LAKE BREEZE BOUNDARIES AND THUS IN
MORE STABLE AIR...WITH VFR CONDITIONS CONTINUING.

TONIGHT...EXPECT VFR CONDITIONS TO CONTINUE TO PREVAIL FOR MUCH OF
THE NIGHT...WITH THE CHANCE OF SOME ADDITIONAL CONVECTION PUSHING
INTO THE AREA FROM THE WEST LATE.

OUTLOOK...
TUESDAY THROUGH THURSDAY...SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS WITH ASSOCIATED BRIEF MVFR/IFR...OTHERWISE VFR.
FRIDAY...MAINLY VFR WITH A CHANCE OF SHOWERS.

&&

.MARINE...
QUIET CONDITIONS WILL REMAIN IN PLACE ACROSS THE LOWER LAKES THROUGH
MUCH OF THE UPCOMING WEEK. WIND DIRECTIONS WILL BE VARIABLE DUE TO
AFTERNOON LAKE BREEZES...AND ALSO A STALLED OUT FRONTAL BOUNDARY
WHICH WILL BE NEARBY MUCH OF THE WEEK. THUNDERSTORM CHANCES WILL
INCREASE TUESDAY THROUGH THURSDAY...AND SOME STORMS MAY PRODUCE
BRIEF PERIODS OF LOCALLY HIGHER WINDS AND WAVES.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...NONE.

&&

$$

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