Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 200608
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
208 AM EDT MON APR 20 2015

.SYNOPSIS...
A COMPLEX STORM SYSTEM EVOLVING OVER THE MIDWEST WILL PUSH A WARM
FRONT ACROSS OUR REGION OVERNIGHT AND EARLY MONDAY...AND THIS WILL
RESULT OCCASIONAL SHOWERS ALONG WITH SOME GUSTY WINDS. FOLLOWING THE
PASSAGE OF THE WARM FRONT...A PERIOD OF MAINLY DRY WEATHER WILL
FOLLOW DURING THE DAY ON MONDAY...BEFORE A COLD FRONT USHERS MORE
SHOWERS AND POSSIBLE THUNDERSTORMS THROUGH THE AREA LATER MONDAY
AFTERNOON AND MONDAY EVENING.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 06Z...FAIRLY WIDESPREAD SHOWERS CONTINUE TO SPREAD
NORTHEASTWARD ACROSS THE REGION IN ADVANCE OF AN APPROACHING WARM
FRONT...WITH THE LEADING EDGE OF THESE JUST NOW REACHING OSWEGO
COUNTY...AND THE TRAILING EDGE APPROACHING ERIE PENNSYLVANIA. THESE
WILL CONTINUE LIFTING NORTHEASTWARD ACROSS THE NORTH COUNTRY THROUGH
THE BALANCE OF THE NIGHT...WHILE ACROSS FAR SOUTHWESTERN NEW YORK
THE SHOWERS SHOULD TEND TO GRADUALLY DIMINISH OVER TIME DUE TO THE
COMBINATION OF INCREASING DOWNSLOPING EFFECTS ALREADY APPARENT ON
AREA RADARS...AS WELL AS THE ARRIVAL OF DRIER AIR/SUBSIDENCE BEHIND
THE ADVANCING WARM FRONTAL BOUNDARY. WITH THE INCREASING
SOUTHEASTERLY DOWNSLOPE FLOW AND THE EXPECTED DIMINISHING TREND TO
THE PRECIP...WINDS ACROSS THE CURRENT ADVISORY AREA /AND ESPECIALLY
THOSE ALONG THE LAKE ERIE SHORELINE SOUTHWEST OF BUFFALO/ SHOULD
INCREASE TO ADVISORY LEVELS OVERNIGHT...JUST AS HAS ALREADY BEEN
NOTED UPSTREAM AT KERI.

RAIN WILL DIMINISH IN COVERAGE FROM WEST TO EAST DURING THE DAY
MONDAY AS THE WING OF STRONG ISENTROPIC ASCENT AND A SIZABLE
PERCENTAGE OF MID LEVEL MOISTURE PUSHES OFF TO THE NORTHEAST AND
AREA EMERGES INTO THE WARM SECTOR IN WAKE OF THE WARM FRONTAL
PASSAGE. BY MIDDAY MONDAY...MUCH OF THE AREA SHOULD BE PRIMARILY
RAIN FREE IN THE WARM SECTOR. THE COMBINATION OF THE ABUNDANT
LOW-LEVEL MOISTURE THE THERMAL RIDGE PUSHING EAST AND THE DIURNAL
DESTABILIZATION WILL LEAD TO INCREASE CAPE VALUES ACROSS WESTERN NEW
YORK. WHILE CAPE IS EXPECTED TO BE MODEST / UP TO 500 J/KG / 0-6 KM
WIND SHEAR ON THE ORDER OF 60 KNOTS SHOULD SUPPORT SOME MARGINALLY
ORGANIZED CONVECTION FOCUSED ALONG THE PRE-COLD FRONTAL TROUGH BY
MONDAY AFTERNOON. IN FACT...THE 0-3KM SHEAR OVER 40 KNOTS LINEAR
FORCING SHOULD SUPPORT AN ORGANIZED CONVECTIVE LINE...HINGING OF
COURSE ON THE INSTABILITY DEVELOPING AHEAD OF THE LINE AS EXPECT.
HAVE INCLUDED THE CHANCE OF THUNDERSTORMS WITH THE POTENTIAL FOR
GUSTY WINDS IN THE FORECAST...WHICH MATCHES UP NICELY WITH SPC
MARGINAL RISK FOR MONDAY. IT REMAINS TO BE SEEN HOW THE VERY COLD
LAKE ERIE AND LAKE ONTARIO WILL FACTOR INTO THE CONVECTIVE
DEVELOPMENT AND ORGANIZATION. GIVEN THE ANTICIPATED SURFACE BASED
NATURE OF THE CONVECTION...EXPECT THAT THE CONVECTIVE LINE COULD
STRUGGLE UNTIL GETTING EAST OF BUFFALO.

MONDAY TEMPERATURES...WITH THE STRONG SOUTHEAST TO SOUTHERLY
WINDS...DOWNSLOPING PLUS THE WARM SECTOR 850 MB TEMPS PUSHING +10C
WILL BRING MANY AREAS INTO THE 60S WITH THE MORE DOWNSLOPE PRONE
AREAS FROM BUFFALO TO ROCHESTER PUSHING CLOSE TO 70.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
MONDAY NIGHT A COLD FRONT WILL WORK ITS WAY ACROSS THE REGION WITH
SHOWERS AND SCATTERED THUNDERSTORMS ALONG IT. INSTABILITY WILL
REMAIN MARGINAL...WITH DAYTIME INSOLATION LINGERING SEVERAL HUNDRED
J/KG OF CAPE ACROSS THE REGION. THIS INSTABILITY IN ADDITION TO
UPLIFT ALONG THE COLD FRONT MAY BE ENOUGH TO TRIGGER A FEW
THUNDERSTORMS MONDAY EVENING AND WILL INCLUDE THIS CHANCE IN THE
FORECAST. WINDS WILL REMAIN GUSTY MONDAY EVENING...NEAR 35 MPH EAST
OF LAKE ONTARIO EARLY ON A SOUTHEAST FLOW...AND THEN LATER PICKING
UP TO 35 TO 40 MPH EAST OF LAKE ERIE BEHIND THE COLD FRONT.

TUESDAY AND WEDNESDAY...A BROAD UPPER LEVEL CLOSED LOW WILL SLOWLY
SPIRAL EASTWARD ACROSS SOUTHERN ONTARIO CANADA...WITH ITS CENTER
REMAINING JUST TO THE NORTH OF THE GREAT LAKES. AS POCKETS OF
VORTICITY STREAM AROUND THIS UPPER LEVEL LOW...THEY WILL TRIGGER
SCATTERED SHOWERS...WITH ACTIVITY LIKELY TO PEAK IN COVERAGE DURING
THE AFTERNOON HOURS. WILL CONTINUE WITH CHANCE POPS THROUGH THE
REMAINDER OF THE TIME PERIOD...WITH LIKELY ALL AREAS TO RECEIVE AT
LEAST SOME RAINFALL OVER THIS 2-DAY STRETCH.

THOUGH THE UPPER LEVEL LOW...AND THE CORE OF THE COLD AIR REMAINS
JUST TO OUR NORTH...MID LEVEL LAPSE RATES WILL INCREASE TO 8-9 C/KM.
THESE LAPSE RATES IN ADDITIONAL TO DAYTIME INSOLATION MAY TRIGGER A
FEW RUMBLES OF THUNDER...ACROSS WESTERN NEW YORK ON TUESDAY AND EAST
OF LAKE ONTARIO ON WEDNESDAY. CONFIDENCE REMAINS TOO LOW AT THIS
POINT IN TIME TO INCLUDE THUNDERSTORMS IN THE FORECAST.

FOLLOWING THE PASSAGE OF THE COLD FRONT...THE RECENT NICE STRETCH OF
WARMTH WILL BE ERASED WITH HIGHS TUESDAY AND WEDNESDAY IN THE
40S...AND NIGHTTIME LOWS DROPPING BACK INTO THE 30S. THESE DAYTIME
READINGS WILL AVERAGE 10 DEGREES OR SO BELOW NORMAL.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AN UPPER LEVEL LOW WILL SLOWLY SPIRAL ACROSS THE GREAT LAKES AND
TOWARDS THE NORTHEAST THIS TIME PERIOD. UNDER THIS LOW PRESSURE
EXPECT CLOUDY DAYS WITH SCATTERED RAIN SHOWERS FOR THURSDAY AND
FRIDAY. THOUGH THE UPPER LEVEL LOW WILL ADVANCE EASTWARD FOR NEXT
WEEKEND...THERE WILL BE VORT MAXES ROTATING AROUND THE FEATURE SUCH
THAT A CHANCE FOR RAIN SHOWERS WILL CONTINUE TO BE POSSIBLE...
ESPECIALLY ACROSS EASTERN ZONES WHICH WILL LIE CLOSER TO THE
UPPER LEVEL LOW. SHOWER CHANCES WILL AGAIN BE GREATEST IN THE
AFTERNOON HOURS WITH DAYTIME HEATING...WITH FEWER SHOWERS TO BE
FOUND BY NIGHT. THERE MAY EVEN BE SOME WET SNOW MIXING IN AT NIGHT
ACROSS THE REGION. DAYTIME AIR TEMPERATURES WILL AVERAGE 5 TO 10
DEGREES BELOW NORMAL TO START THIS PERIOD. THEN AS THE UPPER LEVEL
LOW SLOWLY PUSHES EASTWARD SOME MODERATION IN THE AIR TEMPERATURES
ARE EXPECTED FROM WEST TO EAST.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
LOW PRESSURE OVER SOUTHERN LOWER MICHIGAN WILL LIFT DUE NORTH INTO
NORTHERN ONTARIO PROVINCE THROUGH MONDAY NIGHT. IN THE PROCESS...IT
WILL PUSH ITS ASSOCIATED WARM FRONT EASTWARD ACROSS THE AREA THROUGH
MONDAY MORNING...BEFORE SWEEPING ITS TRAILING COLD FRONT ACROSS THE
REGION LATER MONDAY AFTERNOON AND MONDAY NIGHT.

EXPECT PERIODS OF SHOWERS TO PRECEDE AND ACCOMPANY THE PASSAGE OF
BOTH FRONTAL BOUNDARIES...WITH THE COLD FRONTAL PASSAGE ALSO
POTENTIALLY ACCOMPANIED BY A FEW THUNDERSTORMS. IN BETWEEN THE TWO
WILL BE A PERIOD OF MAINLY DRY WEATHER DURING MONDAY...WITH MAINLY
DRY WEATHER THEN ALSO FOLLOWING THE PASSAGE OF THE COLD FRONT MONDAY
NIGHT.

IN TERMS OF FLIGHT CONDITIONS...EXPECT THESE TO REMAIN PREDOMINANTLY
VFR THROUGH MUCH OF MONDAY...SAVE FOR SOME AREAS OF MVFR ACROSS THE
SOUTHERN TIER THROUGH EARLY TO MID MONDAY MORNING. THE COLD FRONT
WILL THEN BRING A PERIOD OF POSSIBLE MVFR AS IT PASSES THROUGH THE
REGION LATER MONDAY AFTERNOON AND MONDAY NIGHT...FOLLOWED BY A
RETURN TO MORE GENERAL VFR CONDITIONS IN ITS WAKE.

A STRONG LOW LEVEL JET PASSING OVERHEAD THROUGH MONDAY MORNING WILL
ALSO PRODUCE GUSTY WINDS ACROSS THE HIGHER TERRAIN OF THE SOUTHERN
TIER AND ALSO ALONG THE LAKESHORE REGION OF CHAUTAUQUA AND SOUTHERN
ERIE COUNTIES...WHERE SURFACE WINDS COULD GUST TO AS HIGH AS 40-45
KNOTS AT TIMES.

OUTLOOK...
TUESDAY THROUGH FRIDAY...VFR/MVFR WITH SCATTERED RAIN SHOWERS...
WHICH MAY BE MIXED WITH SNOW SHOWERS AT NIGHT.

&&

.MARINE...
HIGH PRESSURE OVER EASTERN CANADA WILL DRIFT EAST AND GIVE WAY TO A
DEEPENING...COMPLEX STORM SYSTEM OVER THE MIDWEST. THIS WILL LEAD
TO A TIGHTENING OF THE SURFACE PRESSURE GRADIENT OVER THE LOWER
GREAT LAKES TONIGHT...WITH FRESHENING OFFSHORE WINDS OF 20 TO 30
KNOTS SUPPORTING SMALL CRAFT ADVISORIES FOR ALL OF THE NEW YORK
NEARSHORE WATERS THROUGH MONDAY.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...WIND ADVISORY UNTIL 8 AM EDT THIS MORNING FOR NYZ012-019>021-
     085.
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR LEZ040-041.
         SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR
         LEZ020.
         SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR
         LOZ042-043.
         SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR
         LOZ044-045.

&&

$$

SYNOPSIS...CHURCH/JJR/TMA
NEAR TERM...CHURCH/JJR/TMA
SHORT TERM...THOMAS
LONG TERM...THOMAS
AVIATION...JJR
MARINE...TMA






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