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