Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 302158
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
558 PM EDT THU JUL 30 2015

.SYNOPSIS...
A DRIER AIRMASS WILL EXPAND ACROSS THE EASTERN GREAT
LAKES REGION TONIGHT...PROVIDING FOR MAINLY CLEAR SKIES AND MORE
COMFORTABLE LEVELS OF HUMIDITY. AN UPPER LEVEL TROUGH WILL SLIDE
TOWARDS THE REGION BY FRIDAY EVENING AND PRODUCE SCATTERED SHOWERS
AND THUNDERSTORMS THAT WILL REMAIN POSSIBLE THROUGH THE
WEEKEND...THOUGH MUCH OF THE TIME WILL BE RAINFREE.

&&

.NEAR TERM /THROUGH FRIDAY/...
THIS AFTERNOON THE COLD FRONT AND ITS ASSOCIATED DECK OF CLOUDS
ARE NOW WELL TO OUR EAST. A BROAD AREA OF HIGH PRESSURE IS
ADVANCING FROM THE PLAINS EASTWARD TOWARDS THE TENNESSEE AND OHIO
VALLEYS. WATER VAPOR IMAGERY DISPLAYS A TROUGH OF LOW PRESSURE
OVER HUDSON BAY.

BEHIND THE COLD FRONT AND WITHIN COLD AIR ADVECTION SOME DIURNALLY
DRIVEN CUMULUS HAVE FORMED THIS AFTERNOON...CLUSTERED GREATEST ON
LAKE BREEZE BOUNDARIES.

FOR TONIGHT FAIR WEATHER WILL CONTINUE WITH WINDS DIMINISHING WITH
THE SETTING SUN. AS THIS AREA OF HIGH PRESSURE DRAWS CLOSER TO OUR
REGION CLEAR SKIES...AND LIGHT WINDS WILL ALLOW FOR LOWS DROPPING
BACK INTO THE UPPER 50S WELL INLAND...AND LOW TO MID 60S ELSEWHERE.
PATCHY AREAS OF RIVER VALLEY FOG WILL FORM IN THE SOUTHERN TIER.

TOMORROW FAIR WEATHER WILL CONTINUE THROUGH THE BULK OF THE DAY.
WESTERLY FLOW WILL CONTINUE THROUGH THE DAY WITH THE CENTER OF HIGH
PRESSURE WELL TO OUR SOUTH. WITH 850 HPA BETWEEN 13 AND
15C...AFTERNOON HIGHS WILL CLIMB TO NEAR NORMAL...WITH HIGHS AROUND
80F. DEWPOINTS WILL AVERAGE AROUND 60F...COMFORTABLE FOR THIS TIME
OF YEAR.

A SHORTWAVE ROTATING AROUND AN UPPER LEVEL TROUGH OVER EASTERN
CANADA WILL DROP THE BASE OF THE TROUGH SOUTHWARD THROUGH THE DAY
FRIDAY...WITH THE SURFACE HIGH RETREATING SOUTHWARD AS WELL. THIS
WILL ALLOW FOR A FEW SHOWERS ASSOCIATED WITH LIFT AHEAD OF THE
SHORTWAVE TO NEAR NORTHERN NIAGARA FRONTIER...AND THE SAINT LAWRENCE
VALLEY TOWARDS THE LATE AFTERNOON HOURS.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
FRIDAY NIGHT A WEAK MID LEVEL SHORTWAVE AND SURFACE TROUGH WILL
CROSS THE LOWER GREAT LAKES. THE STRONGER LARGE SCALE ASCENT WILL
REMAIN WELL NORTH OF THE INTERNATIONAL BORDER ACROSS QUEBEC...WITH
WEAKER DPVA ALONG THE TRAILING MID LEVEL TROUGH. DESPITE THE WEAK
ASCENT...ENOUGH LOW LEVEL CONVERGENCE WILL BE FOUND ALONG THE
SURFACE TROUGH AND ANY RESIDUAL LAKE BREEZE BOUNDARIES TO SUPPORT
SCATTERED TO NUMEROUS SHOWERS BY MID TO LATE EVENING. MODEST
INSTABILITY WILL LINGER INTO THE EVENING AND SUPPORT A FEW SCATTERED
THUNDERSTORMS AS WELL. WITH THIS IN MIND...HAVE INCREASED POPS TO
LOW LIKELY ACROSS A GOOD PORTION OF THE AREA FOR FRIDAY NIGHT.
OVERNIGHT THE SHOWERS THAT REMAIN WILL WEAKEN AND BECOME SCATTERED
AS THEY EXIT INTO CENTRAL AND EASTERN NY LATE. THE CLOUDS AND
SHOWERS ALONG WITH AN OVERNIGHT BREEZE WILL KEEP LOWS IN THE MID 60S
ON THE LAKE PLAINS AND AROUND 60 IN THE COOLER INTERIOR SOUTHERN
TIER AND TUG HILL REGIONS.

BY SATURDAY MORNING THE MID LEVEL SHORTWAVE AND TROUGH WILL BE EAST
OF THE AREA WITH A TEMPORARY RETURN TO DRY WEATHER AND AT LEAST SOME
PARTIAL SUNSHINE. BY AFTERNOON ANOTHER WEAK MID LEVEL TROUGH WILL
APPROACH WESTERN AND NORTH CENTRAL NY. WEAK ASCENT COMBINED WITH
DIURNAL INSTABILITY AND CONVERGENCE FROM LOCAL LAKE BREEZES WILL
PRODUCE SCATTERED SHOWERS AND STORMS DURING THE AFTERNOON AND
EVENING. TEMPERATURES WILL BE NEAR MID SUMMER NORMALS WITH HIGHS IN
THE LOWER 80S ON THE LAKE PLAINS AND UPPER 70S ON THE HILLS.

SATURDAY NIGHT THE WEAK MID LEVEL SHORTWAVE WILL EXIT TO THE EAST OF
THE AREA. THE LOSS OF SYNOPTIC SCALE ASCENT AND DIURNAL COOLING WILL
BRING AN END TO SCATTERED CONVECTION BY MID TO LATE EVENING. SUNDAY
AND SUNDAY NIGHT YET ANOTHER SUBTLE/WEAK MID LEVEL TROUGH WILL CROSS
THE REGION AND SUPPORT A FEW MORE SCATTERED SHOWERS AND STORMS...
ESPECIALLY DURING THE AFTERNOON AND EVENING.

FOR BOTH SATURDAY AND SUNDAY CONVECTION LOOKS TO BE WIDELY SCATTERED
IN NATURE...WITH BOTH DAYS FEATURING PLENTY OF RAIN FREE TIME AS
WELL. INSTABILITY ON SATURDAY AND SUNDAY WILL BE WEAK TO MODERATE
WITH SBCAPE VALUES GENERALLY 1000-1500J/KG. DEEP LAYER SHEAR WILL BE
DECENT WITH 0-6KM SHEAR VALUES AROUND 40 KNOTS BOTH DAYS. THE
COMBINATION OF SHEAR AND INSTABILITY MAY BE MARGINALLY SUPPORTIVE OF
STRONGER AND MORE ORGANIZED STORMS...ALTHOUGH THE POTENTIAL FOR ANY
SEVERE WEATHER WILL BE TIED TO THE DETAILS OF UPSTREAM CONVECTION
AND SUB-SYNOPTIC SCALE WAVES THAT CAN ENHANCE THE MARGINAL SHEAR AND
INSTABILITY. THESE TYPES OF DETAILS IN SUCH A SUBTLE ENVIRONMENT ARE
GENERALLY NOT APPARENT UNTIL THAT DAY.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
THE LONGWAVE PATTERN WILL BECOME MORE AMPLIFIED THROUGH THE LONG
TERM PERIOD WITH A RIDGE DEVELOPING ACROSS THE ROCKIES AND A
DEEP/BROAD DOWNSTREAM TROUGH DEVELOPING ACROSS EASTERN CANADA. THERE
REMAINS SOME DISAGREEMENT WITH RESPECT TO HOW FAR SOUTH THE TROUGH
BECOMES ESTABLISHED BY THE MIDDLE OF NEXT WEEK...WITH THE GFS MORE
AGGRESSIVE IN DRIVING COOLER AIR INTO THE GREAT LAKES REGION WHILE
THE ECMWF FLATTENS THE TROUGH AND KEEPS TEMPERATURES MORE MILD.

LOOKING AT THE DETAILS...ANOTHER SHORTWAVE TROUGH WILL CROSS THE
AREA MONDAY AND MONDAY NIGHT WITH ADDITIONAL SCATTERED SHOWERS AND
STORMS. THIS WILL BE FOLLOWED BY A MORE SUBSTANTIAL COLD FRONT LATE
MONDAY NIGHT OR TUESDAY. MOST OF THE CONVECTION APPEARS TO FOCUS ON
A PRE-FRONTAL TROUGH...SO EVEN THOUGH THE COLD FRONT MAY BE FAIRLY
STRONG ON TUESDAY IT MAY ALSO BE A MAINLY DRY FRONTAL PASSAGE.

WEDNESDAY AND THURSDAY WILL BE DRY MOST OF THE TIME AS THE DEEP
TROUGH BECOMES ESTABLISHED ACROSS EASTERN CANADA...ALTHOUGH A FEW
LIGHT SHOWERS CANNOT BE RULED OUT EACH DAY IN RESPONSE TO COOL AIR
ALOFT AND WEAK MID LEVEL SHORTWAVES. IF THE COOLER GFS VERIFIES IT
MAY EVEN BE COOL ENOUGH FOR A FEW LAKE ENHANCED SHOWERS.
TEMPERATURES WILL TREND BELOW NORMAL...ALTHOUGH HOW COOL REMAINS IN
QUESTION. FOR NOW HAVE GONE WITH CONSERVATIVE MID 70S ON THE LAKE
PLAINS AND LOWER 70S ON THE HILLS GIVEN THE MILDER ECMWF SOLUTION.
IF THE COOLER GFS VERIFIES...MANY AREAS MAY NOT MAKE IT ABOVE 70
EITHER DAY.

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
AT 21Z VFR FLIGHT CONDITIONS WERE FOUND ACROSS THE REGION. FLIGHT
RESTRICTIONS WILL BE LIMITED THIS TAF PERIOD TO RIVER VALLEY FOG
OVER THE SOUTHERN TIER...WITH FOG POSSIBLY REACHING THE KJHW
TERMINAL BETWEEN 08Z AND 13Z. GUSTY SOUTHWEST WINDS WILL SUBSIDE
THIS EVENING AND OVERNIGHT BEFORE PICKING UP AGAIN THURSDAY
AFTERNOON.

OUTLOOK...FRIDAY THROUGH MONDAY...MAINLY VFR WITH ISOLATED TO
SCATTERED SHOWERS AND THUNDERSTORMS.
TUESDAY...MAINLY VFR.

&&

.MARINE...
FOLLOWING THE PASSAGE OF THE COLD FRONT...A BRISK WESTERLY FLOW
WILL SET UP ACROSS LAKE ERIE AND EASTERN PORTIONS OF LAKE
ONTARIO/ADJOINING PORTIONS OF THE SAINT LAWRENCE RIVER...RESULTING
IN ADVISORY-LEVEL CONDITIONS IN THESE AREAS. FOR THIS
REASON...SMALL CRAFT ADVISORIES WILL REMAIN IN EFFECT AS OUTLINED.

FRIDAY AND INTO THE WEEKEND HIGH PRESSURE WILL SLIDE ACROSS THE OHIO
AND TENNESSEE VALLEYS. THIS WILL MAINTAIN A SOUTHWEST TO WESTERLY
FLOW OVER THE EASTERN GREAT LAKES WATERS...THAT MAY NEAR SMALL CRAFT
ADVISORY LEVEL ON LAKE ERIE FRIDAY.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT FRIDAY FOR LEZ040-041.
         SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR
         LEZ020.
         SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR
         LOZ045.
         SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR
         SLZ022.

&&

$$

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


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