Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 040237
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
1037 PM EDT MON AUG 3 2015

.SYNOPSIS...
A COLD FRONT WILL DROP SOUTHWARD ACROSS THE REGION OVERNIGHT...FOLLOWED
BY A SECONDARY COLD FRONT ON TUESDAY AND TUESDAY NIGHT. THIS WILL
BRING A CHANCE OF SHOWERS AND POSSIBLY A THUNDERSTORM. OTHERWISE
IT WILL BECOME COOLER WITH BELOW NORMAL TEMPERATURES FOR REMAINDER
OF THE WEEK.

&&

.NEAR TERM /THROUGH TUESDAY/...
A VORT MAX WILL PIVOT AROUND AN UPPER LEVEL TROUGH LOCATED IN
CENTRAL CANADA. THIS WILL PUSH A SERIES OF COLD FRONTS ACROSS OUR
REGION THROUGH TUESDAY.

THE INITIAL COLD FRONT IS IN THE PROCESS OF CROSSING OUR REGION
EARLY THIS EVENING...WITH THE BOUNDARY EXPECTED TO CONTINUE TO
DROP SOUTHWARD ACROSS THE CWA OVERNIGHT. THIS MAY SPARK SOME
SPARSE SHOWERS OVERNIGHT...BUT RADAR/MODEL TRENDS SUPPORT A MAINLY
DRY OVERNIGHT PERIOD. A PARTIAL CLEARING MAY ALLOW PATCHY FOG TO
DEVELOP...ESPECIALLY IN THE VALLEYS OF THE SOUTHERN TIER.
TEMPERATURES WILL BE COOLER TONIGHT WITH LOWS RANGING FROM THE
MID-50S TO LOWER 60S.

A MORE SUBTLE SECONDARY BOUNDARY WILL GRADUALLY PUSH INTO THE
REGION ON TUESDAY. THIS COMBINED WITH THE UPPER LEVEL TROUGH
SHOULD BE ENOUGH FOR SOME SHOWERS AND POSSIBLY THUNDERSTORMS TO
DEVELOP. 00Z NAM AND THE LATEST HRRR GUIDANCE SUGGEST THE MOST
WIDESPREAD SHOWERS WILL BE EAST OF LAKE ONTARIO AS A SUBTLE WAVE
CROSSES WITH THE FRONT. THIS WAVE WILL EXIT...BUT AS THE FRONT
SAGS SOUTH AND WITH DAYTIME HEATING EXPECT ANOTHER BATCH OF
STEADIER SHOWERS TO DEVELOP SOUTH OF LAKE ONTARIO ALONG THE
SURFACE CONVERGENCE BOUNDARY. THIS SAID...WITH A CYCLONIC FLOW
ALOFT DUE TO THE UPPER LEVEL TROUGH...IT IS DIFFICULT TO RULE OUT
AT LEAST A CHANCE FOR SHOWERS AT ANY LOCATION. HIGHS WILL BE
NOTABLY COOLER...ONLY IN THE LOWER TO MID 70S IN MOST AREAS.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
EVENING UPDATE...A LOBE OF UNSEASONABLY COOL -1SD TO -2SD 850MB AIR
WILL SWING ACROSS THE EASTERN GREAT LAKES TUESDAY NIGHT AND
WEDNESDAY. THIS WILL INCREASE LAKE INDUCED INSTABILITY LEVELS OVER LAKES
ERIE AND ONTARIO WITH THE POTENTIAL FOR LAKE ENHANCED RAIN SHOWERS
EMBEDDED WITHIN MORE WIDESPREAD CHANCES OF SHOWERS AHEAD OF A
500MB VORT MAX.

PREVIOUS DISCUSSION...THE LONGWAVE TROUGH AXIS WILL BE CENTERED
ACROSS THE LOWER GREAT LAKES AS WE MOVE INTO THE MIDWEEK...RESULTING
IN A COOL AND UNSETTLED START TO THE PERIOD. THE COMBINATION OF DPVA
AND COLDER AIR ALOFT ASSOCIATED WITH THE TROUGH WILL MAKE TUESDAY
NIGHT AND WEDNESDAY MORNING THE MOST UNSETTLED PART OF THE PERIOD.
IN FACT...WITH 850MB TEMPS FALLING TO +8C TO +10C AND CYCLONIC
WESTERLY FLOW IN PLACE ACROSS THE AREA...IT IS QUITE POSSIBLE THAT
WE COULD SEE THE DEVELOPMENT OF LAKE EFFECT RAIN SHOWERS DOWNSTREAM
OF LAKE ERIE...AND TO A GREATER EXTENT EAST OF OF LAKE ONTARIO WHERE
LONGER FETCH SHOULD COMPENSATE FOR THE LACK OF DEEP MOISTURE.

AS ELUDED TO ABOVE...AREAS DOWNWIND OF LAKE ERIE WILL BE ON THE
SOUTHERN FRINGE OF THE DEEPER SYNOPTIC MOISTURE...HENCE THE LOWER
POPS ACROSS WESTERN NY. HOWEVER IT IS WORTH NOTING THAT A STRONG
VORT MAX IS PROGGED TO BE CROSSING THE FORECAST AREA OVERNIGHT...AND
THIS WILL YIELD AT LEAST A CHANCE OF SHOWERS ELSEWHERE.
NONETHELESS...EVEN WHERE WE DON`T SEE LAKE EFFECT SHOWERS...WE WILL
LIKELY SEE AN ABUNDANCE OF CLOUD COVER. THE COOL AIR ASSOCIATED WITH
THE TROUGH WILL YIELD LOWS IN THE 50S EXCEPT FOR IMMEDIATELY ALONG
THE LAKE WHERE TEMPS WILL BOTTOM OUT AROUND 60.

ANY LINGERING SHOWERS SHOULD TAPER OFF WEDNESDAY MORNING AS THE MAIN
VORT MAX MOVES INTO EASTERN NEW YORK AND DIURNAL HEATING DISRUPTS ANY
LINGERING LAKE EFFECT SHOWERS. HOWEVER WE MAY SEE A RESURGENCE OF
SHOWER ACTIVITY EAST OF LAKE ONTARIO BY WEDNESDAY AFTERNOON AS THE
CORE OF THE UPPER LEVEL TROUGH WILL STILL BE OVERHEAD THE NORTH
COUNTRY AND EASTERN NEW YORK WITH A DECENT AMOUNT OF DIURNAL
CLOUDINESS ELSEWHERE ACROSS THE FORECAST AREA ALONG WITH SEASONABLY
COOL TEMPERATURES FEATURING HIGHS IN THE LOWER 70S.

THE CORE OF THE COLD AIR ALOFT WILL MOVE ACROSS THE REGION WEDNESDAY
NIGHT...CAUSING TEMPERATURES TO RUN A COUPLE OF DEGREES COOLER WITH
LOWS IN THE LOW TO MID 50S EXCEPT IMMEDIATELY ALONG THE LAKESHORES
WHERE LOWS RUN CLOSE TO THE 60 DEGREE MARK. UNLIKE TUESDAY
NIGHT...LAKE EFFECT SHOWERS ARE NOT EXPECTED TO BE AN ISSUE OWING TO
INCREASINGLY DRY AIR ALOFT AND NOMINALLY STRONGER SHEAR.
HOWEVER...WE MAY SEE A FEW AREAS OF LAKE-INDUCED CLOUDINESS LINGER
EAST OF LAKE ONTARIO AS THE BACK EDGE OF THE TROUGH MOVES THROUGH
THE AREA.

CONDITIONS WILL REMAIN DRY THURSDAY AND THURSDAY NIGHT AS THE UPPER
LEVEL TROUGH GIVES WAY TO ZONAL FLOW ALOFT. THE QUESTION MARK IS A
STORM SYSTEM PROGGED TO CROSS THE OHIO VALLEY AND CENTRAL
APPALACHIANS THURSDAY AND THURSDAY NIGHT. THIS SYSTEM MAY BRING A
FEW SHOWERS TO THE SOUTHERN TIER DEPENDING ON HOW FAR NORTH IT
DRIFTS...HOWEVER FOR NOW WILL MAINTAIN LOW CHANCE POPS FOR THE TIME
BEING. WITH NO SIGNIFICANT TEMPERATURE ADVECTION GOING
ON...TEMPERATURES WILL RUN CLOSE TO WEDNESDAY/WEDNESDAY NIGHT`S
READINGS WITH HIGHS IN THE LOWER 70S AND LOWS IN THE 50S.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
THE LONGWAVE TROUGH WILL MAINTAIN ITS POSITION OVER EASTERN CANADA
THROUGH THE WEEKEND AS A SERIES OF SHORTWAVES MOVING ALONG THE U.S.
CANADIAN BORDER WILL LIKELY RE-AMPLIFY THE TROUGH ACROSS THE GREAT
LAKES. WHILE THERE ARE CONSIDERABLE DIFFERENCES ON THE DETAILS IN
THE EVOLUTION OF THIS SCENARIO...THIS GENERAL TREND SUGGESTS THAT WE
WILL SEE AT LEAST A CHANCE OF SHOWERS THIS WEEKEND WITH TEMPERATURES
THAT WILL CONTINUE TO RUN ON THE COOLER SIDE OF AVERAGE.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
EXPECT MAINLY VFR CONDITIONS LATE THIS EVENING AS THE FIRST OF
TWO COLD FRONTS DROPS SOUTH OF THE REGION. AREAL COVERAGE OF
SHOWERS SHOULD BE QUITE SPARSE WITH ONLY A SMALL CHANCE FOR BRIEF
VSBY RESTRICTIONS. PERHAPS THE BIGGER CONCERN FOR AVIATION IS THE
POTENTIAL FOR FOG TO DEVELOP TONIGHT. IT APPEARS THAT FOG WILL BE
MOST WIDESPREAD ACROSS THE VALLEYS OF THE SOUTHERN TIER...WHICH
MAY IMPACT JHW. FOG CANNOT COMPLETELY BE RULED OUT ELSEWHERE...BUT
THE CHANCE IS SMALL.

THE SECOND COLD FRONT WILL APPROACH THE AREA TUESDAY MORNING AND
GRADUALLY ACROSS THE REGION THROUGH TUESDAY NIGHT. THIS WILL BRING
AN INCREASE IN CLOUDS...AND SOME SHOWERS WHICH WILL BECOME MORE
NUMEROUS DURING THE AFTERNOON HOURS. SHOWERS...AND POSSIBLY A
THUNDERSTORM...MAY RESULT IN PERIODS OF MVFR OR LOWER CONDITIONS.

OUTLOOK...

TUESDAY NIGHT AND WEDNESDAY...MAINLY VFR. A CHANCE OF SHOWERS.
WEDNESDAY NIGHT THROUGH MONDAY...VFR.

&&

.MARINE...
WINDS HAVE DIMINISHED WHICH HAS ALLOWED THE SMALL CRAFT ADVISORY
TO BE DROPPED. A FALL LIKE AIRMASS IN THE WAKE OF THIS SECOND
COLD FRONT COULD SET THE STAGE FOR WATERSPOUTS ON LAKE ONTARIO
TUESDAY NIGHT AND WEDNESDAY. BUFKIT SOUNDINGS SHOW STEEP
CONVECTIVE CLOUD DEPTHS AND LAKE-850 DELTA-TS OF AROUND 15C WHICH
FIT THE SZILAGYI WATERSPOUT NOMOGRAM POTENTIAL FOR UPPER LOW
WATERSPOUTS. A SLIGHT CHANCE HAS BEEN ADDED INTO THE FORECAST OVER
THE LAKES.

&&

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

&&

$$

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


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