Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 062131
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
531 PM EDT MON JUL 6 2015

.SYNOPSIS...
SCATTERED SHOWERS AND THUNDERSTORMS ACROSS FAR WESTERN NEW YORK
EARLY THIS EVENING WILL DIMINISH AFTER SUNSET. A WARM AND MUGGY
AIRMASS WILL THEN REMAIN IN PLACE TONIGHT AND TUESDAY WITH SHOWERS
AND THUNDERSTORMS BECOMING MORE WIDESPREAD TUESDAY AFTERNOON AND
EVENING. SOME OF THE THUNDERSTORMS TUESDAY AND TUESDAY EVENING
WILL HAVE THE POTENTIAL TO BECOME SEVERE WITH DAMAGING WINDS BEING
THE MAIN THREAT. A COLD FRONTAL PASSAGE TUESDAY NIGHT WILL THEN
USHER IN COOLER AND DRIER WEATHER FOR WEDNESDAY INTO THURSDAY.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 520 PM...WITH RECENT SPC MESOANALYSIS SHOWING 1000-1500
J/KG OF SBCAPE IN PLACE ACROSS MUCH OF WESTERN NEW YORK AND RECENT
SATELLITE AND RADAR IMAGERY BOTH SHOWING AN UPTICK IN CONVECTIVE
DEVELOPMENT /INCLUDING THUNDERSTORMS/ WEST OF THE GENESEE
VALLEY...HAVE THROWN OUT A QUICK UPDATE TO THE FORECAST TO UP
THUNDERSTORM CHANCES THROUGH THE EARLY EVENING HOURS...AND
HIGHLIGHT THAT THIS ACTIVITY SHOULD BE LARGELY SCATTERED IN
NATURE. THIS ACTIVITY IS BEING FORCED BY LIFT FROM LOCAL LAKE
BREEZE BOUNDARIES AND A WEAKENING UPPER LEVEL LOW CENTERED OVER
EASTERN OHIO...AND WILL CONTINUE INTO THIS EVENING BEFORE
DIMINISHING AFTER SUNSET WITH THE LOSS OF HEATING.

OTHERWISE...IT WILL BE A WARM AND SULTRY NIGHT ACROSS THE REGION
AS THE MOIST SOUTHERLY FLOW WILL BE MAINTAINED WITH DEWPOINTS
REMAINING WELL INTO THE 60S. AS SUCH...LOOK FOR OVERNIGHT LOWS TO
RANGE FROM THE MID TO UPPER 60S WITH WARMEST AREAS BEING FOUND
ALONG THE LAKE PLAINS. THE AIRMASS WILL BECOME EVEN WARMER ON
TUESDAY AS 850MB TEMPS WILL BE RUNNING ABOUT A DEGREE WARMER THAN
TODAY...AROUND +17C...WHICH WILL TRANSLATE TO AFTERNOON HIGHS IN
THE MID TO UPPER 80S...WITH THE GENESEE VALLEY CREEPING INTO THE
LOWER 90S THANKS TO A FRESHENING DOWNSLOPE SW WIND.

CONVECTION WILL BECOME MUCH MORE LIKELY ON TUESDAY AS THE WEAK UPPER
LEVEL RIDGING ENCOMPASSING MUCH OF THE AREA WILL BE REMOVED IN
FAVOR OF THE SECOND SYSTEM OF NOTE IN THIS AFTERNOON`S WV
IMAGERY...A MUCH STRONGER UPPER LEVEL TROUGH CURRENTLY OVER THE
UPPER GREAT LAKES. WITH SBCAPES CLIMBING TOWARDS 1500 J/KG ACROSS
WESTERN NEW YORK IN THE AFTERNOON...IT IS QUITE LIKELY THAT WE WILL
SEE CONVECTION INITIATE ALONG THE LAKE BREEZE BOUNDARIES BY MID-
AFTERNOON. WHILE SHEAR IN THE AFTERNOON WILL NOT BE PARTICULARLY
IMPRESSIVE...AROUND 25 KTS...A SIGNIFICANT AMOUNT OF MID-LEVEL DRY
AIR MAY ALLOW FOR THE DEVELOPMENT OF DOWNBURSTS THAT MAY PRODUCE
ISOLATED DAMAGING WINDS. AS WE MOVE INTO THE EVENING HOURS...THE
MAIN UPPER LEVEL TROUGH AND ACCOMPANYING COLD FRONT WILL APPROACH
THE REGION...LIKELY RESULTING IN ANOTHER ROUND OF CONVECTION TUESDAY
EVENING.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
TUESDAY NIGHT A MID LEVEL TROUGH WILL SWING EAST ACROSS QUEBEC WITH
A TRAILING COLD FRONT CROSSING THE LOWER LAKES. MOST OF THE LARGE
SCALE FORCING FOR ASCENT WILL REMAIN WELL NORTH ACROSS CANADA...WITH
WEAK DPVA ON THE SOUTHERN EDGE OF THE TROUGH CROSSING OUR REGION.
MOST OF THE FORCING WILL COME FROM MESOSCALE FEATURES...INITIALLY
THE LAKE BREEZE CONVERGENCE BOUNDARIES LATE TUESDAY AFTERNOON AND
EVENING FOLLOWED BY CONVERGENCE ALONG THE COLD FRONT OR PRE-FRONTAL
TROUGH. MODERATE INSTABILITY WILL BE PRESENT UPSTREAM ACROSS OHIO
WHERE RICHER BOUNDARY LAYER MOISTURE EXISTS...WITH WEAKER
INSTABILITY EXTENDING INTO WESTERN NY.

SUFFICIENT INSTABILITY AND FORCING LOOK TO BE PRESENT ALONG THE
ADVANCING FRONT TO JUSTIFY HIGH LIKELY POPS FOR TUESDAY EVENING.
DEEP LAYER SHEAR IS MARGINAL AT AROUND 30 KNOTS...BUT IF STORMS CAN
ORGANIZE INTO LINES SOME MAY PRODUCE GUSTY WINDS. SPC HAS CONTINUED
A MARGINAL RISK FOR A PORTION OF THE AREA...AND THIS LOOKS
REASONABLE GIVEN UNCERTAINTY ON CONVECTIVE EVOLUTION UPSTREAM. IF A
STRONGER LINE CAN DEVELOP UPSTREAM...THERE IS SOME RISK FOR DAMAGING
WINDS ACROSS WESTERN NY DURING THE EVENING. PWAT WILL REACH 2 INCHES
JUST AHEAD OF THE FRONT...AND THIS WILL BRING A RISK OF VERY HEAVY
DOWNPOURS WITH ANY STRONGER CONVECTION. IF TRAINING OR BACKBUILDING
OCCURS THIS MAY RESULT IN SOME ISOLATED FLOOD RISK.

LATER TUESDAY NIGHT THE FRONT WILL ADVANCE SOUTHEAST AND AWAY FROM
THE AREA. SHOWERS AND THUNDERSTORMS WILL TAPER OFF FROM NORTHWEST TO
SOUTHEAST WITH THE PASSAGE OF THE COLD FRONT OVERNIGHT.

ON WEDNESDAY THE FRONT WILL PUSH SOUTH INTO CENTRAL PA AND STALL...
WITH ONE OR TWO WEAK WAVES RIPPLING ALONG THE FRONT. LATEST 12Z
GUIDANCE CONTINUES TO KEEP THE FRONTAL ZONE FAR ENOUGH SOUTH TO KEEP
OUR ENTIRE REGION DRY WEDNESDAY. A COOLER AND LESS HUMID AIRMASS
WILL ARRIVE WITH HIGHS IN THE MID 70S ACROSS LOWER ELEVATIONS AND
AROUND 70 ON THE HILLS.

LATER WEDNESDAY NIGHT AND THURSDAY A CONVECTIVELY GENERATED MID
LEVEL WAVE WILL MOVE NORTHEAST ALONG THE FRONTAL ZONE ACROSS THE
OHIO VALLEY AND SPAWN ANOTHER WEAK WAVE OF LOW PRESSURE. THIS WAVE
IS FORECAST BY THE 12Z GFS/NAM/ECMWF SUITES TO BRING THE FRONTAL
ZONE BACK NORTHWARD INTO WESTERN AND CENTRAL NY. EVEN WITH THE MODEL
CONSISTENCY IN THE 12Z RUN...PREVIOUS MODEL RUNS HAVE SHOWN A GOOD
DEAL OF VARIABILITY WITH RESPECT TO THE TIMING AND PLACEMENT OF THIS
WAVE. COMBINE THAT WITH THE FACT THAT THE SYSTEM OF INTEREST IS
BEING GENERATED FROM SUBTLE MONSOONAL CONVECTION ACROSS THE FOUR
CORNERS REGION...AND CONFIDENCE IS STILL ONLY AVERAGE AT BEST FOR
THURSDAY. WITH THIS IN MIND WILL KEEP POPS IN THE CHANCE RANGE FOR
SHOWERS AND THUNDERSTORMS THURSDAY...WITH THE GREATER CHANCES FOR
SOUTHERN AREAS.

THURSDAY NIGHT THIS FRONTAL WAVE WILL EXIT INTO NEW ENGLAND WITH
RAIN CHANCES DIMINISHING FROM WEST TO EAST.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
FRIDAY AND SATURDAY A BUBBLE OF HIGH PRESSURE WILL STALL IN PLACE
OVER THE LOWER LAKES AND NEW ENGLAND WHILE A STALLED FRONTAL ZONE
REMAINS TO THE WEST ACROSS THE LOWER OHIO VALLEY AND WESTERN LAKES.
THIS SHOULD BRING DRY WEATHER BOTH DAYS WITH TEMPERATURES SLOWLY
WARMING BACK TO JUST ABOUT AVERAGE AFTER A FEW COOLER DAYS MIDWEEK.
THIS WILL TRANSLATE INTO HIGHS IN THE LOWER 80S ACROSS LOWER
ELEVATIONS.

SUNDAY INTO EARLY NEXT WEEK A MID LEVEL TROUGH WILL MOVE FROM THE
UPPER MIDWEST INTO THE WESTERN LAKES. THIS WILL FORCE INCREASING
MOISTURE AND INSTABILITY BACK INTO OUR REGION...WITH LARGE SCALE
FORCING INCREASING BY MONDAY AS THE MID LEVEL WAVE AND WEAK SURFACE
REFLECTION MOVE TOWARDS THE LOWER LAKES. THIS WILL BRING A CHANCE OF
SHOWERS AND STORMS AGAIN FROM LATER SUNDAY THROUGH MONDAY.
TEMPERATURES WILL REMAIN WARM SUNDAY AND MONDAY AS LONG AS SHOWERS
DONT BECOME TOO WIDESPREAD...WITH HIGHS IN THE LOWER 80S BOTH DAYS.
HUMIDITY WILL BE ON THE INCREASE AS WELL.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
A WEAKENING UPPER LEVEL LOW OVER THE UPPER OHIO VALLEY WILL
TRIGGER SCATTERED SHOWERS AND THUNDERSTORMS THROUGH THE EARLY
EVENING HOURS ACROSS FAR WESTERN NEW YORK...WITH THIS ACTIVITY
THEN DIMINISHING AFTER SUNSET WITH THE LOSS OF HEATING. EXPECT
VFR CONDITIONS TO PREVAIL THROUGH TONIGHT OUTSIDE OF ANY EVENING
CONVECTION...WHICH WILL HAVE THE POTENTIAL TO PRODUCE BRIEF/
LOCALIZED REDUCTIONS IN CIG/VSBY.

CONVECTION WILL BE MORE WIDESPREAD AND STRONGER TUESDAY AFTERNOON
AHEAD OF AN APPROACHING COLD FRONT. AFTER A QUIET START TOT HE
DAY...EXPECT SHOWERS AND THUNDERSTORMS TO BREAK OUT ALONG LAKE
BREEZE BOUNDARIES AFTER 15Z. A FEW OF THESE THUNDERSTORMS MAY
BECOME SEVERE LATER IN THE AFTERNOON WITH LOCALIZED DAMAGING
WINDS. ANOTHER ROUND OF THUNDERSTORMS IS LIKELY TUESDAY
EVENING...AROUND 00Z AS THE COLD FRONT MOVES ACROSS THE FORECAST
AREA. THERE IS A POTENTIAL FOR A SQUALL LINE TO ACCOMPANY THIS
FRONTAL PASSAGE...ONCE AGAIN BRINGING A POTENTIAL FOR STRONG AND
POSSIBLY DAMAGING WINDS.

OUTLOOK...

TUESDAY NIGHT...AREAS OF MVFR AND BRIEF IFR/GUSTY WINDS WITH SHOWERS
AND THUNDERSTORMS LIKELY.
WEDNESDAY...VFR.
THURSDAY...MAINLY VFR WITH A CHANCE OF SHOWERS AND THUNDERSTORMS.
FRIDAY AND SATURDAY...VFR.

&&

.MARINE...
LIGHT WINDS WILL PERSIST THROUGH TONIGHT WITH TRANQUIL CONDITIONS ON
THE LAKES. SOUTHWESTERLY WINDS WILL FRESHEN TO AROUND 15KTS ON
TUESDAY AHEAD OF AN APPROACHING COLD FRONT...HOWEVER CONDITIONS
SHOULD REMAIN BELOW SMALL CRAFT LEVELS ON TUESDAY.

THE COLD FRONT WILL CROSS THE LAKES TUESDAY EVENING...POTENTIALLY
GENERATING A SQUALL LINE THAT MAY SWEEP ACROSS THE LAKES. WINDS WILL
QUICKLY SLACKEN BEHIND THE FRONT AS WEAK HIGH PRESSURE MOVES ACROSS
THE REGION AND LINGERS THROUGH THE REST OF THE WEEK.

&&

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

&&

$$

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



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