Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 030311
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
1111 PM EDT SUN AUG 2 2015

.SYNOPSIS...
SHOWERS AND THUNDERSTORMS WILL WORK ACROSS THE FORECAST AREA AHEAD
OF A COLD FRONT OVERNIGHT. THE COLD FRONT WILL THEN SHIFT ACROSS NEW
YORK ON MONDAY WITH ANOTHER ROUND OF STRONG TO SEVERE THUNDERSTORMS
POSSIBLE THROUGH MONDAY AFTERNOON. A COMFORTABLY COOL AIRMASS WILL
THEN FOLLOW THE FRONT MONDAY NIGHT AND SHOULD BE SETTLE IN PLACE FOR
THE REMAINDER OF THE WEEK.

&&

.NEAR TERM /THROUGH MONDAY/...
RADAR AT 11PM SHOWS A LINE OF STRONG THUNDERSTORMS APPROACHING THE
NIAGARA FRONTIER. THIS IS OCCURRING FASTER THAN PREVIOUS GUIDANCE
SHOWED SO THE FORECAST HAS BEEN UPDATED LATE THIS EVENING TO REFLECT
THIS. 00Z KBUF SOUNDING SHOWS A MODERATELY UNSTABLE ENVIRONMENT HAS
WORKED OVER THE FORECAST AREA WITH RECENT VAD WIND PROFILES SHOWING
A 40-50 KNOT LOW LEVEL JET ALSO IN PLACE BOTHER SUPPORTING THE LINE
OF STORMS.

A COLD FRONT STRETCHED ACROSS MICHIGAN WITH A STRONG SHORTWAVE
TROUGH ALOFT ARE SUPPORTING THE CONVECTIVE ACTIVITY. MESO GUIDANCE
SLOWS/WEAKENS THIS ACTIVITY OVERNIGHT AS IT DRIFTS OVER WESTERN NEW
YORK SO HAVE TRENDED POPS DOWN TO CHANCE LATE OVERNIGHT.

THE COMBINATION OF A PRESSURE GRADIENT OVER THE EASTERN GREAT LAKES
AND A 50-60KT LOW LEVEL JET WILL BRING GUSTS TO THE 20-30 MPH RANGE
OVERNIGHT OUTSIDE OF ANY CONVECTIVE GUSTS FROM THE STORMS.
TEMPERATURES IN MOST AREAS WILL ONLY FALL INTO THE THE UPPER 60S OR
LOWER 70S.

THE COLD FRONT WILL CROSS WESTERN NEW YORK MONDAY MORNING THEN
SHIFTING TOWARD CENTRAL NEW YORK BY THE AFTERNOON HOURS. DEWPOINT
POOLING AHEAD OF THE FRONT WILL BOOST SURFACE DEWPOINTS INTO THE
MIDDLE TO UPPER 60S. A CAPED ENVIRONMENT PER FORECAST SOUNDING SHOULD
KEEP ANY ACTIVITY TAME IN THE MORNING. LOW LEVEL CONVERGENCE ALONG
THE FRONT WILL PROVIDE LIFT WITH INCREASING INSTABILITY GOING INTO
THE AFTERNOON WITH DIURNAL HEATING. FORECASTED CAPE WILL INCREASE TO
1000-2000 J/KG WITHIN A UNIDIRECTIONALLY SHEARED ENVIRONMENT UP TO
50KTS SUPPORTING THE POTENTIAL FOR SEVERE LINER STORMS WITH POSSIBLE
BOWING SEGMENTS PRODUCING DAMAGING WINDS. THE TIMING OF THE FRONT
WILL PLAY A BIG PART IN EXACTLY WHERE STRONG STORMS WILL SET UP WITH
A BETTER POTENTIAL FROM THE FINGER LAKES EASTWARD. TEMPERATURES
DURING MONDAY WILL CLIMB TO THE UPPER 70S TO LOWER 80S PRIOR TO THE
FRONTAL PASSAGE.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
WATER VAPOR IMAGERY THIS AFTERNOON NICELY DISPLAYS A SHORTWAVE
TROUGH OF LOW PRESSURE REACHING NORTHERN MINNESOTA. THIS SHORTWAVE
WILL BE FORCING A SURFACE COLD FRONT EASTWARD ACROSS OUR REGION
MONDAY NIGHT. EXPECT SHOWERS AND THUNDERSTORMS TO END THROUGH THE
EVENING HOURS WITH THE PASSAGE OF THE COLD FRONT AND LOSS OF
DAYTIME INSTABILITY.

THIS SHORTWAVE TROUGH WILL ALSO DRAW A PERSISTENT UPPER LEVEL LOW
OVER EASTERN CANADA SOUTHWARD. ON TUESDAY A POOL OF COOL AIR ALOFT
WILL BE RESIDING OVER SOUTHERN CANADA AND THE GREAT LAKES REGION.
STEEPENING LAPSE RATES THROUGH THE DAY TUESDAY WILL LIKELY BRING
SCATTERED RAIN SHOWERS THROUGH THE PEAK HEATING OF THE AFTERNOON AND
EARLY EVENING HOURS. THIS COOL AIR ALOFT MAY EVEN BRING SOME LAKE
ENHANCED RAIN SHOWERS TO SE AND E OF LAKE ONTARIO WHERE +6 TO +8C AT
850 HPA WILL BE FLOWING OVER A +22C OR SO LAKE TEMPERATURE.

ON WEDNESDAY THE UPPER LEVEL LOW WILL REMAIN NEARBY THE GREAT LAKES
REGION...HOWEVER LOW LEVEL MOISTURE WILL BE MUCH LESS. EVEN THOUGH
INSTABILITY WILL AGAIN INCREASE THROUGH THE AFTERNOON HOURS THE
LESS PLENTIFUL MOISTURE WITHIN THE ATMOSPHERE SHOULD DECREASE THE
AMOUNT OF AFTERNOON SHOWERS. GREATEST CHANCES FOR A SHOWER WEDNESDAY
WILL BE ACROSS OUR EASTERN ZONES WHICH WILL HAVE SLIGHTLY BETTER
MOISTURE PROFILES.

WEDNESDAY NIGHT SHOWERS SHOULD DIMINISH WITH THE LOSS OF DAYTIME
HEATING AND THE INCREASING STABILITY OF THE ATMOSPHERE.

TEMPERATURES WILL AVERAGE 5 TO 10 DEGREES BELOW NORMAL FOR DAYTIME
HIGHS THIS PERIOD...WHILE OVER NIGHT LOWS WILL AVERAGE A FEW DEGREES
BELOW NORMAL.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
THE FEATURE OF NOTE TO START THIS TIME PERIOD IS PRESENTLY FOUND
OVER THE STATE OF NEVADA AS A SHORTWAVE SLOWLY RIDES NORTHWARD
ALONG THE WESTERN FLANK OF A LONG RANGE RIDGE. TIMING THIS FEATURE
OVER THE ROCKIES...AND NORTHERN PLAIN STATES WILL BRING THE NEXT
WIDESPREAD THREAT OF SHOWERS AND THUNDERSTORMS INTO THE REGION
FRIDAY. THERE MAY BE A FEW STORMS THURSDAY AHEAD OF THIS FEATURE
NEAR THE STATE LINE...BUT BOTH THE 12Z GFS AND 12Z ECMWF SUGGEST
THAT FRIDAY WILL BE THE BEST DAY FOR PRECIPITATION CHANCES. WILL
MAINTAIN LOW CHANCE POPS FRIDAY AS THE MODELS CONTINUE A HIGH
DEGREE OF UNCERTAINTY TO THIS SHORTWAVE TRACK...POSSIBLY TRACKING
FARTHER SOUTHWARD WHICH WOULD LEAVE FRIDAY DRY...ESPECIALLY OUR
NORTHERN ZONES.

THIS SHORTWAVE MAY DRAW THE UPPER LEVEL LOW OVER EASTERN CANADA BACK
SOUTHWARD...LEAVING CHANCES FOR SHOWERS AND THUNDERSTORMS ON
SATURDAY ACROSS WESTERN AND NORTH CENTRAL NEW YORK STATE. THESE
SHOWERS AND THUNDERSTORMS MAY LINGER INTO SUNDAY DEPENDING UPON HOW
QUICKLY THE LOWER HEIGHTS ASSOCIATED WITH THE QUEBEC LOW LINGER OVER
THE EASTERN GREAT LAKES REGION.

WITH THE UPPER LEVEL LOW OVER QUEBEC NEARBY...TEMPERATURES ARE
EXPECTED TO REMAIN JUST BELOW SEASONAL NORMALS THROUGH THIS TIME
PERIOD.

&&

.AVIATION /03Z MONDAY THROUGH FRIDAY/...
LINE OF TSRA APPROACHING THE NIAGARA FRONTIER LATE THIS EVENING. HAVE
AMENDED TAFS TO REFLECT MUCH EARLIER ARRIVAL OF STORMS. VFR EXPECTED
OUTSIDE OF TSRA WITH SOME GUSTY WINDS DEVELOPING. MVFR/IFR POSSIBLE
WITHIN TSRA. A 50KT LOW LEVEL JET PER VAD WIND PROFILES IS ALSO IN
PLACE BRINGING LOW LEVEL WIND SHEAR TO THE TAF SITES.

ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS WILL ACCOMPANY THE COLD
FRONTAL PASSAGE ON MONDAY. THERE MAY BE LOWER MVFR TO IFR CONDITIONS
WITH THE STORMS...AS WELL AS THE RISK OF SEVERE CATEGORY WIND
GUSTS...BUT MOST OF THE TIME WILL BE VFR.

OUTLOOK...

MONDAY NIGHT AND TUESDAY...MAINLY VFR WITH A CHANCE OF A FEW
SHOWERS.
WEDNESDAY AND THURSDAY...MAINLY VFR.
FRIDAY...CHANCE OF
THUNDERSTORMS OVER THE SOUTHERN TIER...OTHERWISE VFR.

&&

.MARINE...
SOUTHWEST WINDS WILL CONTINUE TO GUST TOWARD 20 KNOTS TONIGHT AS A
TIGHT PRESSURE GRADIENT IS IN PLACE AHEAD OF A STRONG COLD FRONT
APPROACHING FROM MICHIGAN. THE GUSTY WINDS ACROSS THE EASTERN GREAT
LAKES AHEAD OF THE APPROACHING COLD FRONT ARE FORECAST TO INCREASE
WAVES ON THE NORTHEASTERN END OF LAKE ERIE TOWARD 6 FEET AT TIMES.
SMALL CRAFT ADVISORIES ARE IN PLACE ACROSS LAKE ERIE AND ONTARIO TO
COVER FOR THESE HIGHER WINDS AND WAVES THROUGH MONDAY. A LINE OF
SHOWERS AND STRONG THUNDERSTORMS WILL ALSO WORK ACROSS THE LAKE ERIE
AND WESTERN LAKE ONTARIO WATERS AHEAD OF THE FRONT OVERNIGHT.

THE COLD FRONT WILL MAKE ITS WAY ACROSS THE LOWER GREAT LAKES MONDAY
MORNING...WITH ANOTHER ROUND OF STRONG TO SEVERE THUNDERSTORMS
POSSIBLE. THE SEVERE THREAT FROM THESE STORMS WILL BE WIND GUSTS
NEARING OR EXCEEDING 50 KNOTS. ALONG WITH THE THREAT OF
CONVECTION...SMALL CRAFT ADVISORIES WILL BE IN EFFECT ACROSS THE
LOWER GREAT LAKES FOR THE BULK OF THE DAY. WINDS WILL TEMPORARILY
SUBSIDE ACROSS THE REGION LATE MONDAY AND MONDAY NIGHT.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT MONDAY FOR LEZ020.
         SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT MONDAY NIGHT FOR
         LEZ040-041.
         SMALL CRAFT ADVISORY UNTIL 8 PM EDT MONDAY FOR LOZ030.
         SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT MONDAY NIGHT FOR
         LOZ042>045.

&&

$$

SYNOPSIS...SMITH/WCH
NEAR TERM...SMITH/WCH
SHORT TERM...THOMAS
LONG TERM...THOMAS
AVIATION...SMITH/WCH
MARINE...SMITH/WCH



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