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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBUF 211131
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
731 AM EDT TUE MAY 21 2013

.SYNOPSIS...
A SOUTHWESTERLY FLOW OF WARM AND MORE HUMID AIR WILL CONTINUE ACROSS
THE REGION FOR MUCH OF THIS WEEK...WHILE A FRONTAL BOUNDARY ALSO
STALLS OUT ACROSS NEW YORK STATE AND SETS THE STAGE FOR PERIODIC
ROUNDS OF SHOWERS AND THUNDERSTORMS. THE MORE UNSETTLED CONDITIONS
WILL LAST THROUGH THURSDAY...BEFORE A COLD FRONT CROSSES THE AREA
AND USHERS IN COOLER AND DRIER WEATHER FOR THE END OF THE WEEK AND
THE MEMORIAL DAY WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 1130Z...REGIONAL RADARS SHOW A SMALL CLUSTER OF SHOWERS AND
EMBEDDED THUNDERSTORMS SLIDING ACROSS EASTERN LAKE ONTARIO AND INTO
PORTIONS OF THE NORTH COUNTRY...WITH ADDITIONAL SCATTERED CONVECTION
AS FAR SOUTH AS WAYNE AND NORTHERN CAYUGA COUNTIES. THIS ACTIVITY IS
SLIDING EAST ALONG A NEARLY STATIONARY FRONTAL BOUNDARY DRAPED
ACROSS THE LENGTH OF LAKE ONTARIO...AND WILL CONTINUE TO DO SO
THROUGH MID MORNING. WILL KEEP SOME CHANCE TO LIKELY POPS IN PLAY
THROUGH MID MORNING TO COVER THE PROGRESS OF THIS AREA ACROSS OUR
EASTERN ZONES...OTHERWISE THE REMAINDER OF THE AREA SHOULD STAY DRY
AND WARM/HUMID.

ONCE THIS INITIAL ACTIVITY EXITS TO OUR EAST...EXPECT MOSTLY DRY/
SUNNY CONDITIONS TO BE THE GENERAL RULE FOR THE REST OF THE
MORNING...WHICH WILL LEAD TO STRONG HEATING OF OUR RATHER WARM AND
INCREASINGLY HUMID AIRMASS...AS MID-60 SFC DEWPOINTS ADVECT INTO THE
REGION FROM THE OHIO VALLEY. AS WE GET INTO THE EARLY AFTERNOON
HOURS...DEVELOPING AREAS OF CONVERGENCE ALONG LAKE BREEZE
BOUNDARIES...TERRAIN FEATURES...AND THE DIFFUSE SURFACE FRONT WILL
BEGIN TO LIFT THIS INCREASINGLY UNSTABLE AIR...AND SHOULD EVENTUALLY
GENERATE SOME SCATTERED CONVECTION AS THE SOMEWHAT WEAKER MID LEVEL
CAP THAT WILL BE IN PLACE COMPARED TO YESTERDAY IS OVERCOME. WITH
THIS IN MIND...HAVE CONTINUED TO RAMP POPS BACK UP THROUGH THE
CHANCE RANGE OVER TIME THIS AFTERNOON AS CONVECTIVE CHANCES
INCREASE.

FROM LATE THIS AFTERNOON INTO THIS EVENING...PRECIP PROBABILITIES
SHOULD BE AT THEIR HIGHEST DUE TO THE COMBINATION OF THE
AFOREMENTIONED DIURNALLY-DRIVEN CONVECTION...AND THE POSSIBILITY OF
SOME ADDITIONAL UPSTREAM SHOWERS/STORMS ADVECTING EAST INTO THE AREA
ALONG THE NEARLY STATIONARY FRONTAL BOUNDARY...AS SUGGESTED BY EACH
OF THE GFS/GEM/ECMWF IN SOME FORM. WITH THE ABOVE IN MIND...WILL
RESERVE THE HIGHEST POPS /LIKELIES/ FOR THIS TIME FRAME...WITH
PRECIP CHANCES THEN DROPPING BACK TO THE CHANCE RANGE OVERNIGHT
FOLLOWING THE PASSAGE OF A MID LEVEL SHORTWAVE...AND AS INSTABILITY
WANES SOMEWHAT.

WITH RESPECT TO TEMPERATURES...EXPECT WARM AND MUGGY CONDITIONS TO
CONTINUE THROUGH THIS PERIOD. 850 MB TEMPS OF +15C TO +16C WILL ONCE
AGAIN SUPPORT WIDESPREAD HIGHS IN THE LOWER TO MID 80S IN AREAS AWAY
FROM ANY LAKE INFLUENCES TODAY...WITH LOWS IN THE LOWER TO MID 60S
THEN FOLLOWING FOR TONIGHT.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
SUMMERY CONDITIONS WILL CONTINUE ACROSS OUR REGION ON WEDNESDAY...
AS A DEEP SOUTHERLY FLOW WILL REMAIN IN PLACE IN ADVANCE OF A
BROAD SFC LOW FOUND OVER LOWER MICHIGAN. WHILE IT WILL BE WARM AND
HUMID WITH TEMPERATURES RESEMBLING THOSE OF JULY...THERE WILL BE
SOME UNSETTLED WEATHER TO DEAL WITH AS WELL. OUR UNSTABLE AIRMASS
WILL CERTAINLY SUPPORT SOME SHOWERS AND THUNDERSTORMS...ALTHOUGH
THE BULK OF THE DAY MAY END UP BEING RAINFREE. LETS LOOK AT THE
PROS AND CONS TO THIS CONVECTION.

WORKING AGAINST WIDESPREAD CONVECTION WILL BE A SHORTWAVE RIDGE THAT
WILL LIFT UP ACROSS OUR REGION. THIS COULD BE A DOUBLE EDGED SWORD
THOUGH...AS THE RIDGE COULD HELP TO THIN SOME OF THE EXPECTED CLOUD
COVER. THAT WOULD LEAD TO GREATER DIURNALLY INDUCED INSTABILITY THAN
IS BEING FORECAST...WHICH IN TURN WOULD LIKELY LEAD TO MORE
AFTERNOON CONVECTION. ON THE OTHER HAND...THE SUBSIDENCE FROM THE
PASSING RIDGE IN TANDEM WITH MOSTLY CLOUDY SKIES COULD MINIMIZE THE
THREAT OF STORMS (AS WAS ALSO EXPRESSED IN A PREVIOUS STORM
PREDICTION CENTER DISCUSSION)...OR AT LEAST HOLD THEM OFF UNTIL MID
TO LATE AFTERNOON.

EITHER WAY YOU SLICE IT...THERE SHOULD BE AT LEAST 500-1000 J/KG OF
SBCAPE BY WEDNESDAY AFTERNOON SO THERE SHOULD BE SHOWERS OR
THUNDERSTORMS TO DEAL WITH AS WE MOVE THROUGH THE DAY. THIS ACTIVITY
WILL LIKELY FOCUS ON TWO AREAS. THE FIRST BEING A NEARLY STALLED
FRONTAL BOUNDARY THAT WILL BE FOUND FROM THE NORTH SHORE OF LAKE
ONTARIO TO THE NORTH COUNTRY...AND THE SECOND BEING A LAKE BREEZE
BOUNDARY THAT SHOULD PUSH EAST OF LK ERIE. THE LATTER WOULD BE OF
MORE CONCERN BECAUSE THIS WOULD BE THE TRIGGER TO RELEASE THE
GREATER INSTABILITY OVER THE WRN COUNTIES. THIS LEADS US TO THE
POTENTIAL FOR SEVERE WEATHER.

LETS STATE RIGHT UP FRONT THAT SPC HAS OUR FORECAST AREA OUTLINED IN
A SLIGHT RISK FOR SEVERE STORMS ON WEDNESDAY. THAT BEING SAID AND
AS WAS THE CASE IN YESTERDAYS MORNING DISCUSSION...AM NOT OVERLY
IMPRESSED WITH THE OVERALL SET UP FOR SEVERE WEATHER. WE COULD HAVE
SUPPRESSED INSTABILITY FROM CLOUD COVER AND ONGOING SHOWER
ACTIVITY...BUT I AM JUST AS UNIMPRESSED WITH 0-3KM BULK SHEAR
(GENERALLY <25 M/S) AND LACKLUSTER MID LEVEL LAPSE RATES OF 6 DEG
C/KM. ONE HAS TO LOOK AT A DEEPER LAYER (0-6 KM) TO FIND IMPRESSIVE
BULK SHEAR VALUES OF 35-40 M/S. A TELLING SIGN WILL LIKELY BE HOW
MUCH SUN WE GET DURING THE MORNING AND MIDDAY. THE MAIN THREAT FROM
ANY STRONG TO SEVERE STORMS WOULD BE STRAIGHT LINE WINDS...AND IF WE
CAN GET OUR CAPES UP OVER 1500 J/KG...SOME LARGE HAIL. PWAT VALUES
>1.5 INCHES WILL ALSO LIKELY LEAD TO SOME TORRENTIAL DOWNPOURS...
BUT THERE SHOULD BE ENOUGH WINDS TO MOVE THE STORMS ALONG AND
MINIMIZE THE POTENTIAL FOR HYDRO ISSUES. BOILING THIS ALL DOWN...
WILL USE LIKELY POPS BUT WILL REFRAIN FROM ADDING ANY ENHANCED TSRA
WORDING. WILL DEFER THIS TO LATER SHIFTS FOR FURTHER REVIEW.

ON WEDNESDAY NIGHT...THE AFOREMENTIONED SFC LOW WILL TRACK BY TO OUR
NORTH WHILE THE CONVECTION FROM THE EVENING HOURS WILL GRADUALLY
SUBSIDE WITH THE LOSS OF DAYTIME HEATING AND SUBSEQUENT
STABILIZATION OF THE LOWEST LEVELS. THIS WILL LEAVE A WARM AND DAMP
NIGHT WITH NOCTURNAL TEMPERATURES ONCE AGAIN NOT FALLING OUT OF THE
60S.

THE VARIOUS GUIDANCE PACKAGES THEN START TO DIVERGE ON THE HANDLING
OF THE WAVY FRONTAL BOUNDARY THAT WILL OOZE ACROSS OUR FORECAST AREA
ON THURSDAY. IN PREVIOUS MODEL RUNS...THE ECMWF HAS BEEN THE FASTER
PACKAGE IN BRINGING THE FRONT THROUGH. IT NOW TRAILS THE GFS...AND
FOR WHAT ITS WORTH...THE NAM. THE SECONDARY WAVE ALONG THE TRAILING
FRONT IS WHAT IS OBVIOUSLY THROWING A MONKEY WRENCH INTO THE
MODELS...BUT IN ANY CASE...THE MODELS ARE IN GENERAL AGREEMENT THAT
THERE WILL BE A WEALTH OF LOW LEVEL MOISTURE THAT WILL BE LIFTED IN
FAIRLY WIDESPREAD SHOWERS. JUST DO NOT SEE ENOUGH INSTABILITY TO
HOLD ONTO THE SLGT CHC THAT WE HAVE FOR THUNDER...AS LAPSE RATES ARE
GENERALLY BELOW 6 DEG C/KM BY MID MORNING. WILL COMPROMISE AND LEAVE
THE MENTION FOR THE MORNING ONLY. OTHERWISE...IT WILL BE A WET AND
NOTICEABLY COOLER DAY WITH TEMPERATURES AVERAGING SOME 10 DEG F
LOWER THAN PREVIOUS DAYS. HIGHS SHOULD GENERALLY BE IN THE UPPER 60S
TO LOWER 70S.

WHILE THE WAVY FRONT WILL BE WELL TO OUR EAST THURSDAY NIGHT...THE
SUPPORTING H5 TROUGH WILL BE JUST CROSSING THE LOWER LAKES. THIS
SHOULD KEEP SOME LEFTOVER SHOWERS OVER THE REGION...ESPECIALLY
DURING THE FIRST HALF OF THE NIGHT. MEANWHILE...TEMPERATURES ARE
EXPECTED TO TUMBLE INTO THE 40S...WHICH WILL BE QUITE REFRESHING
AFTER SEVERAL DAYS OF MID JULY-LIKE WEATHER.

FRIDAY WILL FEATURE SEASONABLY COOL CONDITIONS AS H85 TEMPS IN THE
VCNTY OF 4C WILL ONLY SUPPORT AFTERNOON HIGHS AROUND 60 F. WHAT IS
MUCH LESS CERTAIN IS WHETHER ALL OF THE SHOWER ACTIVITY WILL BE
DONE. THE 00Z GFS IS NOW BEING STUBBORN WITH CLEARING OUT THE
SHOWERS AND LEFTOVER CLOUDS...SO WILL HAVE TO KEEP AT LEAST SLGT CHC
POPS OVER THE REGION DURING THE MORNING AND INCREASE OUR CLOUD COVER
A BIT. WILL STILL LEAN MORE ON THE ECMWF SOLUTION THOUGH...WHICH AT
THIS POINT FAVORS A MORE OPTIMISTIC SCENARIO.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
PLENTY OF SUNSHINE AND SEASONABLY COOL TEMPERATURES WILL BE THE NAME
OF THE GAME THIS WEEKEND AS HIGH PRESSURE WILL SETTLE ACROSS THE
GREAT LAKES. 850MB TEMPS DROPPING TO AROUND 0C SHOULD ONLY YIELD
HIGHS TOPPING OUT IN THE LOWER 60S FOR MOST AREAS ON SATURDAY...
NEARLY 10 DEGREES BELOW NORMAL. LIKEWISE OVERNIGHT LOWS WILL RUN ON
THE CHILLY SIDE WITH READINGS IN THE LOWER 40S ALONG THE LAKE PLAINS
WHILE AREAS FARTHER INLAND ACROSS THE SOUTHERN TIER AND NORTH
COUNTRY COULD DROP INTO MID 30S...POTENTIALLY SETTING THE STAGE FOR
A FROST...PARTICULARLY SATURDAY NIGHT WHEN THE SURFACE HIGH IS
FORECAST TO BE OVERHEAD.

A GRADUAL REBOUND IN TEMPERATURES IS EXPECTED FOR THE LATTER HALF OF
THE WEEKEND AS THE COLDEST AIR ASSOCIATED WITH THE UPPER LEVEL
TROUGH DEPARTS THE REGION AND WARMER AIR BEGINS TO CREEP NORTH FROM
THE OHIO VALLEY ONCE AGAIN. OTHERWISE...EXPECT DRY WEATHER TO
CONTINUE THROUGH THE END OF THE WEEKEND.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
AS OF 1130Z...REGIONAL RADARS SHOW A SMALL CLUSTER OF SHOWERS AND
EMBEDDED THUNDERSTORMS SLIDING ACROSS EASTERN LAKE ONTARIO AND INTO
PORTIONS OF THE NORTH COUNTRY...WITH ADDITIONAL SCATTERED CONVECTION
AS FAR SOUTH AS WAYNE AND NORTHERN CAYUGA COUNTIES. THIS ACTIVITY IS
SLIDING EAST ALONG A NEARLY STATIONARY FRONTAL BOUNDARY DRAPED
ACROSS THE LENGTH OF LAKE ONTARIO...AND WILL CONTINUE TO DO SO
THROUGH MID MORNING. EXPECT THE POSSIBILITY OF SOME LOCALIZED
IFR/MVFR WITHIN THESE SHOWERS/STORMS AS THEY SLIDE EASTWARD...WITH
MAINLY VFR CONDITIONS OTHERWISE EXPECTED ACROSS THE REMAINDER OF THE
AREA.

ONCE THIS AREA OF CONVECTION SLIDES OFF TO OUR EAST...EXPECT MAINLY
DRY VFR CONDITIONS TO PREVAIL THROUGH THE REST OF THE MORNING...WITH
SCATTERED CONVECTION THEN DEVELOPING ACROSS INTERIOR SECTIONS AND
ALONG LAKE BREEZE BOUNDARIES DURING THE AFTERNOON...SOME OF WHICH
COULD PRODUCE ADDITIONAL BRIEF LOCALIZED REDUCTIONS TO IFR/MVFR.

TONIGHT...SOME ADDITIONAL UPSTREAM CONVECTION MAY RIDE EAST ALONG A
STALLED OUT FRONTAL BOUNDARY AND CROSS THE AREA FROM WEST TO EAST
THIS EVENING...BEFORE SOMEWHAT QUIETER WEATHER RETURNS FOR THE
OVERNIGHT HOURS.

OUTLOOK...
WEDNESDAY THROUGH THURSDAY...SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS WITH ASSOCIATED MVFR/IFR...OTHERWISE VFR.
FRIDAY...MAINLY VFR WITH A CHANCE OF SHOWERS.
SATURDAY...VFR.
-- End Changed Discussion --

&&

.MARINE...
THROUGH THURSDAY...WINDS WILL REMAIN RELATIVELY LIGHT AND VARIABLE
IN DIRECTION DUE TO A NEARLY STATIONARY FRONTAL BOUNDARY THAT WILL
REMAIN DRAPED ACROSS THE REGION...AS WELL AS THE DAILY DEVELOPMENT
OF LAKE BREEZES. AS A RESULT...WAVE HEIGHTS SHOULD ALSO REMAIN
RELATIVELY MINIMAL. OTHERWISE...EXPECT A CONTINUED POTENTIAL FOR
SHOWERS AND THUNDERSTORMS THROUGH THURSDAY...SOME OF WHICH MAY
PRODUCE LOCALLY HIGHER WINDS AND WAVES.

LOOKING A BIT FURTHER OUT...A COLD FRONTAL PASSAGE THURSDAY NIGHT
WILL RESULT IN WINDS VEERING TO A NORTHERLY DIRECTION ALONG WITH AN
INCREASE IN WAVE HEIGHTS...ESPECIALLY ALONG THE SOUTH SHORES OF THE
LAKES WHERE SMALL CRAFT ADVISORIES MAY EVENTUALLY BE NEEDED LATER
THURSDAY NIGHT/FRIDAY MORNING.

&&

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

&&

$$

SYNOPSIS...JJR
NEAR TERM...JJR
SHORT TERM...RSH
LONG TERM...RSH/WOOD
AVIATION...JJR
MARINE...JJR