Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 261942
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
342 PM EDT WED AUG 26 2015

.SYNOPSIS...
PERSISTENT LOW PRESSURE JUST NORTH OF THE GREAT LAKES WILL CONTINUE
TO BRING PLENTY OF CLOUD COVER AND A FEW LAKE EFFECT RAIN SHOWERS
SOUTHEAST OF THE LAKES THROUGH THURSDAY MORNING. HIGH PRESSURE WILL
THEN BRING A RETURN TO DRY WEATHER FOR THE END OF THE WEEK WITH
TEMPERATURES WARMING BACK TO ABOVE NORMAL OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH THURSDAY/...
RADAR IMAGERY SHOWING LAKE EFFECT SHOWERS HAVE EVOLVED INTO
SCATTERED DIURNAL SHOWERS THIS AFTERNOON IN RESPONSE TO THE PEAK OF
DAYTIME MIXING AND SURFACE HEATING. EXPECT MOST OF THE SCATTERED
SHOWERS TO FOCUS ACROSS THE HIGHER TERRAIN OF THE SOUTHERN TIER AND
WESTERN FINGER LAKES AS WELL AS THE TUG HILL REGION THROUGH EARLY
EVENING IN RESPONSE TO UPSLOPE FLOW. A CONVERGENCE ZONE ACROSS THE
NIAGARA FRONTIER MAY ALSO PRODUCE A FEW SCATTERED SHOWERS. OTHERWISE
EXTENSIVE STRATOCUMULUS WILL BRING CLOUDY SKIES TO MOST AREAS WITH
JUST A FEW ODD SUNNY BREAKS.

TONIGHT THE SCATTERED SHOWERS WILL TRANSITION BACK TO LAKE EFFECT AS
THE BOUNDARY LAYER COOLS AND DEEP DIURNAL MIXING DIMINISHES...
ALLOWING THE SUBTLE LAKE GENERATED CONVERGENCE BANDS THAT AID LAKE
EFFECT FORMATION TO DOMINATE THE LOW LEVEL CIRCULATION ONCE AGAIN.
850MB TEMPS AROUND +7C WILL YIELD LAKE INDUCED EQUILIBRIUM LEVELS
AROUND 25K FEET WITH LAKE INDUCED CAPE AROUND 500J/KG. THE PASSAGE
OF A MID LEVEL TROUGH THIS EVENING WILL PROVIDE SOME LARGE SCALE
ASCENT AS WELL THIS EVENING...AND WILL ALSO FORCE THE BOUNDARY LAYER
FLOW TO VEER MORE TO THE NORTHWEST LATE TONIGHT AS THE SHORTWAVE
MOVES OFF INTO NEW ENGLAND.

OFF LAKE ONTARIO...EXPECT LAKE EFFECT RAIN SHOWERS TO BECOME
ORGANIZED AGAIN BY LATE EVENING ACROSS OSWEGO COUNTY AND THE TUG
HILL REGION. OVERNIGHT THE LAKE EFFECT RAIN SHOWERS WILL PUSH SOUTH
ACROSS OSWEGO COUNTY AND MOVE ONSHORE FROM THE MONROE COUNTY
SHORELINE INTO WAYNE/NORTHERN CAYUGA COUNTIES. A FEW SCATTERED
SHOWERS MAY MOVE ONSHORE AS FAR WEST AS ORLEANS AND NIAGARA COUNTIES
AND EXTEND INTO THE NORTHERN FINGER LAKES AS WELL. EXPECT RAINFALL
AMOUNTS OF A QUARTER TO THIRD OF AN INCH IN MORE PERSISTENT BANDS...
WITH THE SHIFTING BAND POSITION PREVENTING ANYTHING EXCESSIVE.
THURSDAY MORNING A FEW SCATTERED SHOWERS WILL CONTINUE SOUTHEAST OF
THE LAKE MAINLY FROM THE EAST SIDE OF ROCHESTER EASTWARD TO OSWEGO
COUNTY.

OFF LAKE ERIE...LESS MOISTURE AND UPPER LEVEL SUPPORT WILL KEEP THE
SHOWERS LESS ORGANIZED THAN OFF LAKE ONTARIO. EXPECT A RELATIVE PEAK
IN ACTIVITY BY LATE EVENING ACROSS CHAUTAUQUA AND WESTERN
CATTARAUGUS COUNTY AND POSSIBLY SOUTHERN ERIE COUNTY. THIS WILL THEN
SLOWLY WEAKEN TO SCATTERED LIGHT SHOWERS OVERNIGHT AS FLOW BECOMES
MORE NORTHWEST AND SHORTENS FETCH. EXPECT RAINFALL AMOUNTS OF AROUND
A TENTH OF AN INCH IN THE MORE PERSISTENT SHOWERS.

OTHERWISE OUTSIDE OF LAKE EFFECT RAIN AREAS EXPECT THE SCATTERED
SHOWERS TO END BY LATE EVENING WITH THE LOSS OF DIURNAL INSTABILITY.
EXTENSIVE STRATOCUMULUS WILL LINGER TONIGHT THROUGH THURSDAY MORNING
WITH MOSTLY CLOUDY SKIES.

BY EARLY THURSDAY AFTERNOON LAKE EFFECT SHOWERS WILL TRANSITION TO
SCATTERED DIURNAL SHOWERS AGAIN ACROSS THE HIGHER TERRAIN WELL
INLAND FROM THE LAKES...WITH THESE SHOWERS ENDING BY MID AFTERNOON.
A PUSH OF DRIER AIR WILL MOVE INTO THE AREA FROM SOUTHERN ONTARIO
WITH INCREASING AMOUNTS OF SUNSHINE ON THE LAKE PLAINS DURING THE
AFTERNOON. UPSLOPE FLOW WILL KEEP CLOUDS LONGER ACROSS HIGHER
TERRAIN...WITH PARTIAL CLEARING THERE BY EVENING.

CLOUD COVER WILL HELP KEEP TEMPERATURES UP SOMEWHAT TONIGHT...WITH
LOWS IN THE MID TO UPPER 50S ON THE LAKE PLAINS AND LOWER 50S ACROSS
THE INTERIOR SOUTHERN TIER AND TUG HILL REGION. THURSDAY WILL REMAIN
COOL WITH HIGHS AROUND 70 AT LOWER ELEVATIONS AND MID 60S ON THE
HILLS.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
HIGH PRESSURE WILL BUILD ACROSS THE REGION THURSDAY NIGHT AND THEN
SLOWLY DRIFT EAST INTO NEW ENGLAND THROUGH FRIDAY NIGHT. THIS WILL
BRING DRY WEATHER AND PROGRESSIVELY WARMER TEMPERATURES TO THE
REGION.

ANY LINGERING LAKE EFFECT CLOUDS SHOULD DISSIPATE THURSDAY NIGHT
WITH DIMINISHING WINDS UNDER THE SURFACE HIGH. THIS WILL RESULT IN
PRETTY GOOD RADIATIONAL COOLING...AND PROBABLY SOME FOG IN THE
TYPICAL SOUTHERN TIER VALLEYS.

FRIDAY SHOULD FEATURE SUNNY SKIES AND PLEASANT TEMPERATURES WITH
HIGHS IN THE MID TO UPPER 70S.

A WEAK SHORTWAVE WILL APPROACH THE REGION LATE FRIDAY NIGHT...WITH
MODEL CONSENSUS KEEPING THIS TO OUR NORTH OR WEST THROUGH SATURDAY.
THIS SHOULD RESULT IN CONTINUED DRY WEATHER...BUT PERHAPS SOME CLOUD
COVER. MEANWHILE A WEAK SOUTHERLY RETURN FLOW WILL RESULT IN WARMER
TEMPERATURES ON SATURDAY WITH HIGHS IN THE UPPER 70S TO LOWER 80S.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
THERE CONTINUES TO BE POOR MODEL AGREEMENT HANDLING A SHORTWAVE
WHICH SHOULD...EVENTUALLY...CROSS OUR REGION. THE 12Z GFS/GGEM
SUGGEST THIS SHORTWAVE WILL BE WEAK AND PROGRESSIVE...AND MOVE
ACROSS THE REGION SATURDAY NIGHT INTO SUNDAY. THE ECMWF HAS BEEN
CONSISTENTLY SLOWER BECAUSE IT CUTS OF THE LOW AND THEREFORE DOES
NOT HAVE IT REACHING OUR AREA UNTIL SUNDAY NIGHT OR MONDAY. EITHER
WAY...THE FEATURE IS WEAK AND WILL SPARK MINIMAL AND DIURNALLY
INFLUENCED SHOWERS. BASED ON THIS...WILL INTRODUCE SLIGHT CHANCE
POPS INTO MOST AREAS...WITH SOME LOW-END CHANCE POPS ACROSS SOUTHERN
INTERIOR SECTIONS.

SUMMER RETURNS NEXT WEEK WITH THE GFS/ECMWF BOTH FORECASTING A BROAD
500 MB RIDGE TO BUILD ACROSS THE EASTERN CONUS. ANY WEAK REMNANTS OF
THE DEPARTING SHORTWAVE ARE NOT ENOUGH TO JUSTIFY CHANCE POPS...WITH
PERHAPS AN ISOLATED DIURNALLY DRIVE THUNDERSTORM POSSIBLE TUESDAY OR
WEDNESDAY AFTERNOONS. MEANWHILE TEMPERATURES WILL BE ABOVE
NORMAL...WITH HIGHS EXPECTED TO CLIMB WELL INTO THE 80S.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
LAKE EFFECT SHOWERS HAVE TRANSITIONED INTO SCATTERED DIURNAL SHOWERS
THIS AFTERNOON WITH THE PEAK OF DAYTIME MIXING. EXPECT SCATTERED
SHOWERS ACROSS MUCH OF THE AREA THROUGH EARLY EVENING. VFR WILL
PREVAIL...ALTHOUGH THE HEAVIER SHOWERS WILL PRODUCE BRIEF MVFR
CONDITIONS. SOME MVFR CIGS WILL ALSO LINGER ACROSS THE HIGHER
TERRAIN EAST OF LAKES ERIE AND ONTARIO WITH SOME ADDED LAKE EFFECT
MOISTURE.

AFTER SUNSET SHOWERS WILL TRANSITION BACK TO MORE LAKE EFFECT IN
NATURE...WITH THE MAJORITY OF THE SHOWERS FOCUSING EAST AND
SOUTHEAST OF LAKE ONTARIO AFTER 03Z AND TO A LESSER EXTENT ACROSS
THE WESTERN SOUTHERN TIER. CIGS WILL TEND TO LOWER TO MVFR OVERNIGHT
WITHIN THE LAKE EFFECT BANDS EAST OF BOTH LAKES AND ALSO ACROSS
HIGHER TERRAIN. SOME MVFR OR EVEN IFR VSBY MAY BRIEFLY DEVELOP IN
ANY HEAVIER LAKE EFFECT RAIN BANDS...ESPECIALLY SOUTHEAST OF LAKE
ONTARIO.

THURSDAY MORNING MVFR CIGS WILL BE AT THEIR MOST WIDESPREAD...
POSSIBLY EVEN ACROSS THE LAKE PLAINS AS WINDS BECOME NORTHWEST AND
INTRODUCE SOME UPSLOPE COMPONENT. SCATTERED SHOWERS SOUTHEAST OF THE
LAKES WILL END DURING THE AFTERNOON AS MUCH DRIER AIR BUILDS INTO
THE LOWER LAKES REGION. MVFR CIGS WILL IMPROVE TO VFR FIRST ACROSS
LOWER ELEVATIONS AROUND MIDDAY...THEN IMPROVE ACROSS HIGHER TERRAIN
BY MID AFTERNOON.

OUTLOOK...
FRIDAY AND SATURDAY...MAINLY VFR.
SUNDAY...MAINLY VFR WITH A CHANCE OF SHOWERS AND THUNDERSTORMS
AND ASSOCIATED BRIEF MVFR.
MONDAY...MAINLY VFR.

&&

.MARINE...
WEST WINDS IN THE 15-17 KNOT RANGE WILL CONTINUE ON LAKE ONTARIO
TONIGHT WITH WIND AND WAVE ACTION JUST BELOW SMALL CRAFT ADVISORY
CONDITIONS ON THE EAST HALF OF THE LAKE. WINDS WILL BE A LITTLE
LIGHTER ON LAKE ERIE...BUT STILL ENOUGH TO PRODUCE CHOPPY CONDITIONS
AT TIMES. WINDS WILL START TO DIMINISH SOME ON THURSDAY AS LOW
PRESSURE BEGINS TO PULL AWAY FROM THE REGION. HIGH PRESSURE WILL
THEN BUILD INTO THE REGION FRIDAY AND SATURDAY WITH LIGHT WINDS AND
FLAT WAVE ACTION.

&&

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

&&

$$

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



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