Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 311937
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
337 PM EDT FRI JUL 31 2015

.SYNOPSIS...
A WEAK TROUGH WILL CROSS THE REGION TONIGHT WITH WIDELY SCATTERED
SHOWERS AND THUNDERSTORMS. WIDELY SCATTERED SHOWERS AND
THUNDERSTORMS ARE POSSIBLE AGAIN SATURDAY AFTERNOON AND SUNDAY
AFTERNOON BUT THE VAST MAJORITY OF THE TIME IS EXPECTED TO BE RAIN
FREE. A STRONGER FRONT WILL CROSS THE AREA SUNDAY NIGHT AND MONDAY
WITH A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS. THIS FRONT WILL
USHER IN A MUCH COOLER AIRMASS FOR MUCH OF NEXT WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
VISIBLE SATELLITE IMAGERY SHOWING BANDS OF AGITATED CUMULUS ALONG
THE EDGES OF THE ENHANCED SOUTHWEST FLOW OFF LAKE ERIE. THE BAND OF
TOWERING CUMULUS FROM NEAR NIAGARA FALLS TO HAMLIN HAS PRODUCED A
FEW SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS SO FAR...AND WILL
CONTINUE TO DO SO THROUGH THE LATE AFTERNOON OR EARLY EVENING WHERE
LOW LEVEL CONVERGENCE IS MAXIMIZED. WELL ESTABLISHED STABLE LAKE
SHADOWS WILL KEEP AREAS EAST AND NORTHEAST OF LAKES ERIE AND ONTARIO
SUNNY THROUGH THE EARLY EVENING INCLUDING THE BUFFALO AND WATERTOWN
AREAS.

A WEAK TROUGH WILL CROSS THE REGION TONIGHT. THE STRONGER LARGE
SCALE SUPPORT IN THE FORM OF DPVA AND HEIGHT FALLS WILL REMAIN WELL
NORTH OF THE AREA ACROSS QUEBEC...WITH THE TRAILING LOW LEVEL TROUGH
FEATURING RELATIVELY WEAK CONVERGENCE AND MOISTURE POOLING. THE
LATEST 12Z MODEL GUIDANCE HAS TRENDED WEAKER WITH THIS FEATURE...
AND COMBINED WITH THE LACK OF ANY ORGANIZED UPSTREAM ACTIVITY WAS
COMPELLED TO BACK OFF SOME ON POPS FOR TONIGHT. THE WEAK TROUGH MAY
BRING A FEW WIDELY SCATTERED SHOWERS AND ISOLATED STORMS TO WESTERN
NY AND THE SAINT LAWRENCE VALLEY BY LATER THIS EVENING...THEN
CROSSING THE REST OF THE AREA DURING THE LATE EVENING AND EARLY
OVERNIGHT. GIVEN THE WEAK FORCING AND MARGINAL INSTABILITY EXPECT
ANY STORMS TO REMAIN WEAK...ALTHOUGH A FEW ISOLATED DOWNPOURS ARE
POSSIBLE.

ANY SHOWERS WILL END FROM NORTHWEST TO SOUTHEAST BEFORE DAYBREAK
WITH MOST AREAS SEEING AT LEAST PARTIAL CLEARING BY SATURDAY
MORNING. THE CLEARING WILL BE SHORT LIVED AS ANOTHER WEAK TROUGH
CROSSES THE AREA SATURDAY AFTERNOON. TEMPERATURES WILL BE COOLER
ALOFT ON SATURDAY...AND THE SUBSEQUENT STEEP LOW/MID LEVEL LAPSE
RATES AND SUFFICIENT LOW LEVEL MOISTURE WILL PRODUCE A WIDESPREAD
AREA OF CONGESTED CUMULUS DURING THE LATE MORNING AND AFTERNOON.
MOST AREAS INLAND FROM THE LAKES WILL TREND TOWARDS MOSTLY CLOUDY
SKIES WITH WIDELY SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
DURING THE AFTERNOON IN RESPONSE TO LAKE BREEZE CONVERGENCE AND WEAK
ASCENT FROM THE APPROACHING MID LEVEL TROUGH. STABLE LAKE SHADOWS
WILL KEEP AREAS EAST OF BOTH LAKES SUNNIER AND DRIER THROUGH AT
LEAST MID AFTERNOON...ALTHOUGH THE APPROACH OF THE MID LEVEL TROUGH
MAY FORCE A SHOWER OR TWO THROUGH THE STABLE LAKE SHADOWS BY LATE
AFTERNOON OR EARLY EVENING.

TEMPERATURES WILL BE A LITTLE COOLER ON SATURDAY WITH 850MB TEMPS
AROUND +11C. EXPECT HIGHS IN THE UPPER 70S TO AROUND 80 AT LOWER
ELEVATIONS AND MID 70S ACROSS HIGHER TERRAIN. IT WILL BECOME BREEZY
AGAIN EAST AND NORTHEAST OF LAKES ERIE AND ONTARIO WITH GUSTS AROUND
30 MPH DURING THE MIDDAY AND AFTERNOON.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
SATURDAY NIGHT A
SHORTWAVE WILL BE PASSING THROUGH THE BASE OF AN UPPER LEVEL
LOW...SHIFTING THE AXIS OF LOWER HEIGHTS EASTWARD. A FEW REMAINING
SHOWERS OR PERHAPS A THUNDERSTORMS WILL BE POSSIBLE EARLY SATURDAY
EVENING...BUT WITH WANING DAYTIME INSTABILITY AND THE RISING HEIGHTS
ALOFT EXPECT THE BULK OF THE NIGHT TO BE DRY.

SUNDAY WILL START DRY AS SOUTHWEST FLOW IS FOUND OVER THE EASTERN
GREAT LAKES REGION...THIS FLOW BETWEEN AN AREA OF HIGH PRESSURE OVER
THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS...AND LOW PRESSURE
NEAR HUDSON BAY. THIS SOUTHWEST FLOW WILL BRING WARMER AIR
NORTHWARD...ALONG WITH A DEGREE OR TWO RISE IN DEWPOINTS. DAYTIME
INSTABILITY MAY TRIGGER A SHOWER OR THUNDERSTORM...ESPECIALLY ON LAKE
BREEZE BOUNDARIES...BUT LACKING A GOOD FORCING MECHANISM DONT EXPECT
TOO MANY STORMS. SUNDAY WILL ALSO BE BREEZY AS AREAS DOWNWIND OF THE
EASTERN GREAT LAKES ON A SOUTHWEST WIND MAY GUST 25 TO 30 MPH
THROUGH THE AFTERNOON HOURS.

SUNDAY NIGHT ANOTHER SHORTWAVE TROUGH WILL ROUND THE LARGE HUDSON
BAY UPPER LEVEL LOW. THIS SHORTWAVE IS A LITTLE MORE POTENT AND LIFT
FROM THIS FEATURE/NEARING OF AN UPPER LEVEL THERMAL GRADIENT AND
BUILDING MOISTURE AHEAD OF A COLD FRONT WILL BRING INCREASE CHANCES
FOR SHOWERS AND THUNDERSTORMS LATE OVERNIGHT SUNDAY...ESPECIALLY
OVER FAR NW AREAS OF THE NIAGARA FRONTIER AND THE SAINT LAWRENCE
VALLEY.

TEMPERATURES WILL REMAIN SEASONABLE THROUGH THIS TIME PERIOD.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
FOR THIS TIME PERIOD THE
LONG RANGE MODELS OF THE GFS/ECMWF ARE IN GOOD AGREEMENT WITH
PLACEMENT OF AN UPPER LEVEL LOW OVER EASTERN CANADA...AND A SECOND
UPPER LEVEL LOW NEAR THE BRITISH COLUMBIA COASTLINE. A RIDGE OF HIGH
PRESSURE WILL BE FOUND BETWEEN THESE TWO UPPER LEVEL LOWS...THOUGH
THE RIDGE WILL LIKELY REMAIN WEAK AND FARTHER WEST ENOUGH TO NOT BE
ABLE TO DISLODGE THE UPPER LEVEL TROUGH OVER EASTERN CANADA. THOUGH
THIS UPPER LEVEL TROUGH WILL RETREAT SOME...ITS GENERAL PRESENCE
WILL SPELL AN EXTENDED PERIOD OF COOL TIME FOR THE NORTHEAST.

MONDAY WILL BE THE LAST OF NEAR-TO SLIGHTLY ABOVE NORMAL DAY
TEMPERATURE WISE AS THE AXIS OF THE UPPER LEVEL TROUGH REMAINS JUST
TO OUR WEST. THROUGH THE DAY THIS AXIS WILL SWING ACROSS THE EASTERN
GREAT LAKES REGION DRIVING A SURFACE COLD FRONT THAT WILL TRIGGER
SHOWERS AND THUNDERSTORMS. THIS ACTIVITY WILL END FROM WEST TO EAST
THROUGH THE OVERNIGHT HOURS AS THE SURFACE COLD FRONT EVENTUALLY
CLEARS THE REGION. THE GFS IS DEPICTING A FAIR AMOUNT OF INSTABILITY
WITH SBCAPE VALUES EDGING OVER 1000 J/KG OVER THE GENESEE VALLEY AND
FINGER LAKES REGION. A 40 KNOT LLJ PRODUCING LOW LEVEL CONVERGENCE
MAY BE ABLE TO ORGANIZE A FEW OF THESE THUNDERSTORMS INTO STRONG
STORMS.

TUESDAY THROUGH FRIDAY WILL BE COOL WITH CHANCES FOR A RAIN SHOWER
EACH DAY. MULTIPLE VORTICITY MAXIMA ROTATING THROUGH THIS UPPER
LEVEL TROUGH...COMBINED WITH DAY TIME INSTABILITY MAY BRING A FEW
SHOWERS TO THE BUFFALO CWA. WITH LAKE TEMPERATURES NOW IN THE +21 TO
+23C RANGE...AND 850 HPA DROPPING DOWN TO +6 TO +10C...THERE MAY
EVEN BE SOME LAKE ENHANCEMENT TO THESE SHOWERS DOWNWIND OF BOTH
LAKES ERIE AND ONTARIO.

HIGHS TUESDAY THROUGH FRIDAY WILL GENERALLY BE IN THE UPPER 60S TO
LOW-MID 70S...ABOUT 5-10 DEGREES BELOW NORMAL...WHILE OVERNIGHT LOWS
WILL RUN IN THE 50S. SOME WARMING IS POSSIBLE FRIDAY AS THE UPPER
LEVEL LOW RETREATS NORTHWARD SOME AND A WARM FRONT NEARS THE REGION.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
SCT-BKN DIURNAL CUMULUS WILL CONTINUE THROUGH THE AFTERNOON HOURS
ACROSS MUCH OF WESTERN NY ALONG AND INLAND FROM THE LAKE BREEZE
BOUNDARIES WITH BASES IN THE 4-6K FOOT RANGE. STABLE LAKE SHADOWS
ENE OF LAKES ERIE AND ONTARIO WILL KEEP THE KBUF AND KART AREAS
MAINLY CLEAR.

WIDELY SCATTERED CONVECTION WILL CONTINUE TO FORM ALONG THE
CONVERGENCE ZONE OVER THE NIAGARA PENINSULA NEAR KIAG. TONIGHT A
WEAK TROUGH WILL CROSS THE AREA WITH WIDELY SCATTERED SHOWERS AND
STORMS MOVING IN A BROKEN LINE FROM NORTHWEST TO SOUTHEAST ACROSS
THE AREA. THE COVERAGE OF THIS ACTIVITY LOOKS TO REMAIN ON THE
SPARSE SIDE...SO FOR NOW HAVE JUST GONE WITH VCSH QUALIFIERS AT THE
TAF SITES. ANY HEAVIER SHOWERS THAT DEVELOP MAY CONTAIN BRIEF/LOCAL
MVFR OR IFR CONDITIONS...BUT VFR WILL PREVAIL THE MAJORITY OF THE
TIME.

ANY SCATTERED CONVECTION WILL END LATE TONIGHT WITH AT LEAST PARTIAL
CLEARING FOR SATURDAY MORNING. EXTENSIVE DIURNAL CUMULUS ARE THEN
EXPECTED TO DEVELOP FROM LATE MORNING THROUGH THE AFTERNOON ON
SATURDAY WITH MOST AREAS GOING BKN BY MIDDAY. STABLE LAKE SHADOWS
WILL KEEP SKIES MORE CLEAR EAST OF BOTH LAKES. WIDELY SCATTERED
SHOWERS AND ISOLATED STORMS WILL DEVELOP DURING THE AFTERNOON MAINLY
ALONG AND INLAND FROM THE LAKE BREEZES...BUT AGAIN COVERAGE SHOULD
REMAIN SPARSE.

OUTLOOK...
SUNDAY AND MONDAY...MAINLY VFR WITH WIDELY SCATTERED SHOWERS AND
THUNDERSTORMS.
TUESDAY...MAINLY VFR WITH A CHANCE OF A FEW LIGHT SHOWERS.
WEDNESDAY...MAINLY VFR WITH A SLIGHT CHANCE OF A LIGHT SHOWER.

&&

.MARINE...
MODERATE SOUTHWESTERLIES WILL CONTINUE INTO THIS EVENING ON LAKE
ERIE BEFORE DIMINISHING OVERNIGHT. ANOTHER WEAK TROUGH AND DECENT
PRESSURE GRADIENT WILL BRING ANOTHER ROUND OF SMALL CRAFT ADVISORY
CONDITIONS ON SATURDAY TO THE EASTERN ENDS OF BOTH LAKES ERIE AND
ONTARIO.

THIS SAME BASIC PATTERN WILL CONTINUE THROUGH THE WEEKEND WITH WINDS
DROPPING OFF SOME SATURDAY NIGHT AND EARLY SUNDAY BEFORE INCREASING
TO NEAR SMALL CRAFT ADVISORY CONDITIONS ON BOTH LAKES LATER SUNDAY.
THE SMALL CRAFT ADVISORY CONDITIONS MAY LAST SUNDAY NIGHT INTO
MONDAY AS A STRONGER COLD FRONT CROSSES THE REGION.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LEZ040-
         041.
         SMALL CRAFT ADVISORY FROM 1 PM TO 11 PM EDT SATURDAY FOR
         LEZ040-041.
         SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR
         LEZ020.
         SMALL CRAFT ADVISORY FROM 1 PM TO 8 PM EDT SATURDAY FOR
         LEZ020.
         SMALL CRAFT ADVISORY FROM 10 AM TO 11 PM EDT SATURDAY
         FOR LOZ043>045.

&&

$$

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



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