Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 300609
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
209 AM EDT TUE JUN 30 2015

.SYNOPSIS...
A WARM FRONT WILL LIFT ACROSS WESTERN NEW YORK TONIGHT WITH LOW
PRESSURE CROSSING THE LOWER GREAT LAKES REGION TUESDAY. ANOTHER WEAK
LOW WILL LIFT NORTH ACROSS THE REGION AGAIN WEDNESDAY. EACH OF THESE
PERIODS WILL FEATURE CHANCES OF SHOWERS AND POSSIBLE THUNDERSTORMS.
HIGH PRESSURE WILL BUILD INTO THE GREAT LAKES AND NORTHEAST FOR
THURSDAY AND FRIDAY.

&&

.NEAR TERM /THROUGH TODAY/...
DURING THE REMAINDER OF THE NIGHT...RATHER BROAD/DIFFUSE LOW
PRESSURE OVER THE WESTERN AND CENTRAL GREAT LAKES WILL GRADUALLY
PUSH ITS WARM FRONT NORTHWARD INTO OUR REGION FROM NE OHIO/WESTERN
PA...ALONG WITH ITS ATTENDANT REGION OF SHOWERS AND EMBEDDED
THUNDERSTORMS. WITH THE LEADING EDGE OF THIS ACTIVITY DRYING UP AS
IT MOVES INTO THE DRIER AIRMASS OVER NEW YORK STATE...HAVE SLOWED
DOWN THE ARRIVAL OF THIS PRECIP BY A FEW HOURS FROM OUR EXISTING
CONTINUITY...THOUGH STILL EXPECT A GENERAL LIKELIHOOD OF SHOWERS
TO REACH AS FAR NORTH AS ROCHESTER BY DAYBREAK. AS WEAK TO MODEST
ELEVATED INSTABILITY DEVELOPS INTO OUR REGION...THERE WILL ALSO BE
THE CONTINUED OPPORTUNITY FOR A FEW EMBEDDED THUNDERSTORMS AS
WELL. OTHERWISE...EXPECT A MILDER NIGHT WITH OVERNIGHT LOWS
RANGING FROM THE MID 50S ACROSS THE NORTH COUNTRY TO THE LOWER TO
MID 60S ACROSS THE LAKE PLAINS OF FAR WESTERN NEW YORK.

THE WARM FRONT WILL PUSH NORTH AND EAST ACROSS CENTRAL NEW YORK
DURING THE FIRST HALF OF TUESDAY...WITH SHOWERS AND THUNDERSTORMS.
WHILE THERE WILL BE THE POTENTIAL FOR A SHOWER OR THUNDERSTORM OVER
THE FAR WESTERN COUNTIES IN THE MORNING...IT SHOULD LARGELY BE
RAINFREE.

IN THE WAKE OF THE WARM FRONT...THE AIRMASS OVER THE WESTERN
COUNTIES WILL BECOME INCREASINGLY UNSTABLE DURING THE COURSE OF THE
MORNING AND MIDDAY. NAM MUCAPE IS FORECAST TO RISE TO NEAR 1500
J/KG. THIS WILL SET THE STAGE FOR THE NEXT ROUND OF SHOWERS AND
THUNDERSTORMS WHICH WILL COME THROUGH THE FORECAST AREA DURING THE
MID AND LATE AFTERNOON. THE OHIO VALLEY LOW WILL DRIFT ACROSS
SOUTHERN ONTARIO AT THAT TIME...WITH A PRE FRONTAL TROUGH PASSING
THROUGH OUR REGION. THERE IS UNCERTAINTY AS TO THE AMOUNT OF BREAKS
IN CLOUD COVER THAT WE WILL EXPERIENCE IN THE WARM SECTOR AS WELL AS
TIMING OF A VORT MAX THAT LOOKS TO LIFT ACROSS WESTERN NEW YORK.
THESE TWO UNCERTAINTIES WILL PLAY A SIGNIFICANT ROLE IN THE AMOUNT
OF INSTABILITY AND FORCING AVAILABLE FOR THUNDERSTORM ACTIVITY.
TEMPERATURES ARE FORECAST TO RISE INTO THE 70S ACROSS WESTERN NEW
YORK WITH A FEW 80S POSSIBLE TOWARD THE FINGER LAKES WHICH MAY BRING
A HIGHER RISK FOR THUNDERSTORM ACTIVITY. SPC HAS A MARGINAL RISK FOR
SEVERE STORMS.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
AS WE OPEN THE PERIOD TUESDAY NIGHT THE NEXT IN THE TRAIN OF SYSTEMS
WILL BE AFFECTING THE REGION IN THE FORM OF A SHARPLY AMPLIFIED UPPER
LEVEL TROUGH SWING ACROSS THE LOWER GREAT LAKES WITH AN ATTENDANT
SURFACE LOW TRACKING IN THE VICINITY OF LAKE ONTARIO BEFORE LIFTING
INTO QUEBEC WEDNESDAY. SHOWERS AND THUNDERSTORMS WILL BE FAIRLY
WIDESPREAD IN THE EVENING WITH THE FOCUS SHIFTING TOWARDS THE
EASTERN HALF OF THE FORECAST AREA LATER TUESDAY NIGHT AS THE LEAD
SHORTWAVE LIFTS ACROSS THE AREA. GENERALLY WEAK INSTABILITY SHOULD
NEGATE THE SEVERE THREAT...AND GIVEN THE DYNAMIC NATURE OF THE
FORCING...STORMS SHOULD BE FAST-MOVING ENOUGH THAT FLOODING IS NOT
EXPECTED TO BE AN ISSUE EITHER.

THE FOCUS FOR CONVECTION WILL SHIFT TO EASTERN NEW YORK WEDNESDAY AS
THE SHORTWAVE ENERGY LIFTS OUT ACROSS THE SAINT LAWRENCE VALLEY AND
NEW ENGLAND WITH THE AFOREMENTIONED SURFACE LOW MOVING OFF INTO
QUEBEC. A TRAILING COLD FRONT WILL CROSS THE FORECAST AREA AND WILL
SERVE AS THE FOCUS FOR CONVECTION WITH THE EASTERN LAKE ONTARIO
ZONES SEEING THE BULK OF THE ACTIVITY OWING TO PROXIMITY TO DEEPER
MOISTURE AND UPSLOPE FLOW OFF LAKE ONTARIO. A SOMEWHAT DRIER AND
MORE STABLE AIRMASS WILL ALREADY BE IN PLACE ACROSS WESTERN NEW YORK
ON WEDNESDAY AND THIS SHOULD TAMP DOWN CONVECTION CONSIDERABLY. THAT
SAID...WESTERN NEW YORK WILL STILL BE UNDER THE INFLUENCE OF THE
LONGWAVE TROUGH AND AS SUCH CANNOT RULE OUT SOME SCATTERED
CONVECTION ACROSS THE AREA...PARTICULARLY IF THE FRONTAL PASSAGE IS
SLOWER THAN CURRENTLY EXPECTED.

CONVECTION SHOULD WANE QUICKLY WEDNESDAY NIGHT AS COOLER AND MUCH
DRIER AIR SURGES ACROSS THE LOWER GREAT LAKES IN THE WAKE OF THE
AFOREMENTIONED COLD FRONTAL PASSAGE. THIS REFRESHING AIRMASS WILL
SETTLE ACROSS THE REGION THROUGH THE REST OF PERIOD AS HIGH PRESSURE
MOVES ACROSS THE GREAT LAKES WITH SUNNY AND MILD DAYS WITH HIGHS IN
THE 70S AND EQUALLY MILD NIGHTS WITH LOWS IN THE 50S.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
IT WILL BE A QUIET END TO THE WEEK AS THE REGION WILL BE THE
BENEFICIARY OF A PROGRESSIVE UPPER LEVEL RIDGE THAT WILL BE CROSSING
THE LOWER GREAT LAKES INTO NEW ENGLAND. THE ASSOCIATED RISING
HEIGHTS WILL SIGNAL A RETURN TO MORE SUMMER-LIKE WARMTH IN TIME FOR
THE HOLIDAY WEEKEND. WHILE FRIDAY SHOULD ALMOST CERTAINLY BE
DRY...THIS MAY NOT HOLD TRUE FOR SATURDAY. THE FORECAST AREA WILL BE
CAUGHT IN BETWEEN TWO SYSTEMS...A SOUTHERN STREAM SHORTWAVE OVER THE
OHIO VALLEY AND A NORTHERN STREAM TROUGH OVER NORTHERN
ONTARIO/QUEBEC. OF THE MODELS...THE ECMWF IS MOST AGGRESSIVE IN
PHASING THESE TWO SYSTEMS...RESULTING IN FAIRLY WIDESPREAD
SHOWERS/THUNDERSTORMS FOR THE FOURTH OF JULY WHILE THE GFS KEEPS THE
SYSTEMS MORE SEPARATE...RESULTING IN WEAKER FORCING AND JUST A
CHANCE OF A LAKE BREEZE CONVECTION OR TWO IN THE AFTERNOON. FOR NOW
WILL HAVE TO KEEP A CHANCE OF SHOWERS/THUNDERSTORMS IN THE FORECAST
AS A COMPROMISE PENDING GREATER CLARITY FROM FUTURE RUNS.

WHILE UNCERTAINTY REIGNS THE FIRST HALF OF THE WEEKEND...SATURDAY
NIGHT AND SUNDAY SHOULD REMAIN DRY BY ALL ACCOUNTS AS THE
DISTURBANCES OF CONCERN WILL BE PAST THE FORECAST AREA WITH SOME
MEASURE OF UPPER LEVEL RIDGING MOVING ACROSS THE AREA. THIS SHOULD
HELP MAINTAIN THE SUMMER-LIKE WARMTH WITH HIGHS IN THE UPPER
70S/LOWER 80S.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
BROAD/DIFFUSE LOW PRESSURE SPRAWLED ACROSS THE WESTERN AND
CENTRAL GREAT LAKES AS OF 06Z WILL BECOME SOMEWHAT BETTER
ORGANIZED AS IT SLIDES INTO SOUTHERN ONTARIO TUESDAY...BEFORE
LIFTING INTO QUEBEC PROVINCE TUESDAY NIGHT. IN THE PROCESS...THIS
FEATURE WILL SWING ITS ATTENDANT WARM FRONT ACROSS WESTERN AND
NORTH CENTRAL NEW YORK THROUGH EARLY TUESDAY AFTERNOON...FOLLOWED
QUICKLY BY A TRAILING PRE-COLD-FRONTAL TROUGH TUESDAY AFTERNOON
AND EVENING.

THE ABOVE TWO SURFACE BOUNDARIES WILL BE THE FOCUSING MECHANISMS
FOR A COUPLE ROUNDS OF NUMEROUS SHOWERS AND THUNDERSTORMS...WITH
CONVECTION OTHERWISE TENDING TO REMAIN MUCH MORE SCATTERED DURING
THE BALANCE OF THE PERIOD.

AT THIS JUNCTURE IT APPEARS THAT WHILE VFR CONDITIONS SHOULD TEND
TO DOMINATE THE MAJORITY OF THE TAF PERIOD...REDUCTIONS TO MVFR
WILL BE POSSIBLE WITHIN ANY CONVECTION...PARTICULARLY ANY ACTIVITY
TIED TO THE PASSAGE OF THE TWO BOUNDARIES REFERENCED ABOVE.

OUTLOOK...
WEDNESDAY...VFR/MVFR WITH SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS.
THURSDAY AND FRIDAY...VFR.
SATURDAY...MAINLY VFR WITH A CHANCE OF SHOWERS AND THUNDERSTORMS.

&&

.MARINE...
TWO WEAK AREAS OF LOW PRESSURE WILL TRACK ACROSS THE GREAT LAKES
REGION TONIGHT THROUGH WEDNESDAY EACH WITH SHOWERS AND POSSIBLE
THUNDERSTORMS. WHILE WINDS WILL FRESHEN A BIT IN ADVANCE OF A WARM
FRONT TONIGHT AND TUESDAY...AT THIS POINT IT APPEARS THAT CONDITIONS
SHOULD REMAIN SAFELY BELOW ADVISORY LEVELS RIGHT THROUGH THE
UPCOMING WEEK. HIGH PRESSURE WILL BUILD OVER THE GREAT LAKES
THURSDAY AND FRIDAY.

&&

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

&&

$$

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


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