Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 060013
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
813 PM EDT TUE MAY 5 2015

.SYNOPSIS...
A WEAK WAVE OF LOW PRESSURE SLIDING ALONG A STALLED OUT FRONT OVER
NORTHERN PENNSYLVANIA WILL BRING SHOWERS TO A SIGNIFICANT PORTION OF
WESTERN NEW YORK TONIGHT WHILE AREAS FROM ROCHESTER NORTH AND EAST
REMAIN DRY. SHOWER ACTIVITY SHOULD RETREAT FROM THE BUFFALO METRO
LATER TONIGHT WHILE LINGERING ACROSS THE SOUTHERN TIER AND FINGER
LAKES THROUGH WEDNESDAY. FOLLOWING THE PASSAGE OF THIS WAVE...THE
REMAINDER OF THE WORK WEEK WILL FEATURE A RETURN TO DRY WEATHER
AND ABOVE NORMAL TEMPERATURES...BEFORE THE NEXT CHANCE FOR
PRECIPITATION ARRIVES THIS WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
DURING THIS PERIOD...THE REMNANT SHORTWAVE FROM AN EARLIER MCS WILL
SLIDE EASTWARD ALONG A STALLED OUT FRONTAL BOUNDARY DRAPED ACROSS THE
NORTHERN OHIO VALLEY AND NORTHERN PA. THIS WILL BRING SOME SHOWERS TO
AREAS PRIMARILY SOUTH OF KBUF-KROC...THE BULK OF WHICH WILL COME
BETWEEN LATE THIS AFTERNOON AND MID WEDNESDAY MORNING...THOUGH SOME
SCATTERED LEFTOVER ACTIVITY COULD POTENTIALLY LINGER INTO WEDNESDAY
AFTERNOON.

AFTER THE 00Z AND 06Z RUNS OF THE SHORT TERM GUIDANCE TRENDED FURTHER
NORTHWARD WITH THE TRACK OF THE RESPONSIBLE SHORTWAVE AND CONSEQUENTLY
HEAVIER/FURTHER NORTH WITH ITS PRECIP OVER OUR AREA...THE 12Z
GUIDANCE SUITE HAS UNIVERSALLY TRENDED AT LEAST SOMEWHAT BACK IN THE
OPPOSITE DIRECTION. WITH THIS CHANGE...A CONSENSUS OF THE SHORT TERM
GUIDANCE NOW KEEPS THE BULK OF THE PRECIP LARGELY SOUTH OF THE
BUFFALO AND ROCHESTER AIRPORTS... WITH THE STEADIEST AND MOST
PERSISTENT SHOWER ACTIVITY PRIMARILY CONFINED TO THE SOUTHERN TIER..
WHERE THIS SAME CONSENSUS NOW SUGGESTS EVENT NOTABLY LIGHTER TOTAL
RAINFALL AMOUNTS OF A QUARTER TO A HALF AN INCH. AS ALL OF THIS
SEEMS TO MAKE PERFECT SENSE JUDGING FROM CURRENT UPSTREAM RADAR
TRENDS AND THE POSITION OF THE MAIN SURFACE FRONT...WE HAVE ELECTED
TO TREND THE FORECAST IN THIS DIRECTION THIS AFTERNOON...WHILE ALSO
SIGNIFICANTLY TIGHTENING UP THE POP GRADIENT SOUTH OF LAKE ONTARIO
IN THE PROCESS.

WITH THE ABOVE CHANGES...WE NOW EXPECT THE BEST CHANCES FOR SHOWERS
TO COME ACROSS THE SOUTHERN TIER AND ADJOINING PORTIONS OF SOUTHERN
ERIE AND WYOMING COUNTIES TONIGHT...WITH PRECIP CHANCES THEN SHARPLY
DROPPING OFF WITH INCREASING NORTHWARD EXTENT...AND EVENTUALLY
REACHING SUB-MENTIONABLE LEVELS ACROSS THE COUNTIES BORDERING THE
SOUTH SHORE OF LAKE ONTARIO. FROM THERE ON NORTHWARD...CONDITIONS
SHOULD REMAIN DRY RIGHT THROUGH THE PERIOD...ALONG WITH NOTICEABLY
THINNER/HIGHER CLOUD COVER.

WITH RESPECT TO TEMPERATURES...EXPECT TONIGHT/S LOWS TO RANGE FROM
THE UPPER 40S AND LOWER 50S ACROSS MOST AREAS SOUTH OF LAKE ONTARIO
WHERE MUCH GREATER/THICKER CLOUD COVER WILL BE IN PLACE...TO AROUND
40 DEGREES ACROSS THE NORTH COUNTRY. AWAY FROM LAKE INFLUENCES...
WEDNESDAY/S HIGHS WILL THEN GENERALLY RANGE FROM THE MID 60S ACROSS
THE SOUTHERN TIER TO THE MID 70S ACROSS THE NORTH COUNTRY...WITH
THIS GRADIENT IN TEMPS AGAIN DUE TO CONSIDERABLY LOWER/THINNER CLOUD
COVER WITH INCREASING NORTHWARD EXTENT.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
THE FRONTAL ZONE WILL SINK FARTHER SOUTH WEDNESDAY NIGHT AND WASH
OUT...WITH HIGH PRESSURE BUILDING OVER THE LOWER LAKES AND NEW
ENGLAND. SKIES WILL CLEAR AS SUBSIDENCE AND DRYING TAKE HOLD BEHIND
THE WEAKENING FRONTAL ZONE. THE HIGH PRESSURE WILL DRIFT OFF THE
EASTERN SEABOARD THURSDAY AND GRADUALLY ADVECT WARMER AIR INTO THE
REGION. TEMPERATURES WILL RISE INTO THE UPPER 70S TO AROUND 80 IN
MOST INLAND LOCATIONS. WITH THE LIGHT FLOW A SHALLOW LAKE BREEZE
SHOULD DEVELOP DURING THE AFTERNOON HOURS. UPPER LEVEL RIDGING
SHOULD SUPPRESS ISOLATED SHOWERS TO OUR SOUTH AND WEST ON THURSDAY
AFTERNOON...SO WILL STAY WITH A DRY FORECAST.

EXPECT MORE DRY WEATHER THURSDAY NIGHT WITH THE CREST OF THE UPPER
LEVEL RIDGE ACROSS THE REGION. AFTER THIS...MODEL CONSENSUS SLIDES
THE 500 MB RIDGE AXIS INTO NEW ENGLAND WHICH WILL BRING A SLIGHTLY
MORE WARM AND MOIST AIRMASS INTO OUR REGION. NAM/GFS/GGEM/ECMWF ALL
FORECAST SOME QPF ACROSS PORTIONS OF THE CWA FRIDAY AFTERNOON. THIS
IS MISLEADING SINCE ANY PRECIPITATION WILL BE CONVECTIVE AND
SCATTERED IN NATURE. THERE DOES APPEAR TO BE AMPLE INSTABILITY FOR A
FEW SHOWERS...BUT THESE SHOULD BE CONFINED TO THE SOUTHERN TIER
INLAND OF THE LAKE BREEZE. ELSEWHERE...THE UPPER RIDGE DEPARTING
FROM THE NORTH COUNTRY AND THE STABILIZING LAKE BREEZE SHOULD
PREVENT ANY INSTABILITY SHOWERS FROM FORMING. OTHERWISE THE BIG
STORY IS THE ABOVE NORMAL TEMPERATURES WITH DAYTIME HIGHS LIKELY TO
RISE INTO THE 80S IN MOST LOCATIONS OFF THE IMMEDIATE LAKESHORE.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
OVERALL IT WILL BE A VERY SUMMER-LIKE PATTERN THROUGHOUT THE
PERIOD. ON FRIDAY NIGHT THE UPPER LEVEL RIDGE AXIS WILL STILL BE
NEAR THE REGION...BUT THIS RIDGE IS FORECAST TO VERY GRADUALLY BREAK
DOWN WITH A SLOW MOVING FRONTAL BOUNDARY EVENTUALLY FORECAST TO
CROSS THE REGION. TIMING THIS SLOW MOVING FRONT DIFFERS
SIGNIFICANTLY...AND BY SIGNIFICANTLY THERE IS ALMOST A TWO DAY
DIFFERENCE BETWEEN THE 12Z GFS/ECMWF. THE DIFFERENCE IN POSITION IS
NOT THAT LARGE...BUT WEAK FORCING AND SLOW MOVING BOUNDARY LEADS TO
THE HUGE DIFFERENCE IN TIMING. THIS IS SIMILAR TO 00Z RUNS OF EACH
MODEL...WITH THE GGEM GENERALLY SUPPORTING THE ECMWF SOLUTION.
FORECAST WILL USE A WEIGHTED BLEND OF GUIDANCE...WHICH HEDGES CLOSER
TO THE SLOW ECMWF TIMING.

THIS MEANS A GRADUALLY INCREASING CHANCE FOR SHOWERS AND
THUNDERSTORMS. INITIALLY THIS WILL BE A SMALL AND DIURNALLY DRIVEN
CHANCE ON SATURDAY...BUT AS THE BOUNDARY GETS CLOSER SHOWERS MAY
OCCUR AT NIGHT AS WELL. UNTIL THIS FRONT PASSES...TEMPERATURES WILL
BE ABOVE NORMAL WITH FORECAST HIGHS IN THE UPPER 70S TO LOWER 80S
FOR THE WEEKEND. IF THE DRIER ECMWF/GGEM VERIFY...HIGHS WILL BE
SEVERAL DEGREES WARMER THAN THAT WITH MORE SUN AND LESS CHANCE FOR
SHOWERS. HOWEVER...IF THE GFS IS CORRECT THESE TEMPERATURES ARE
PROBABLY TOO WARM. WHATEVER THE CASE...THE BOUNDARY SHOULD PUSH
THROUGH BY TUESDAY WITH BOTH THE GFS/ECMWF FORECASTING A MORE
SIGNIFICANT SHORTWAVE TO PUSH THROUGH. THERE IS A GOOD CHANCE FOR
SHOWERS AND THUNDERSTORMS MONDAY NIGHT INTO TUESDAY WHEN THIS WAVE
AND FRONT ARE MOST LIKELY TO CROSS THE REGION. THIS ALSO WILL USHER
IN COOLER...BUT STILL FAIRLY SEASONABLE...AIR INTO THE REGION FOR
MID-WEEK.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
A WEAK UPPER LEVEL
DISTURBANCE SLIDING ALONG A STALLED OUT FRONTAL BOUNDARY IS
BRINGING WIDESPREAD -SHRA TO A SIGNIFICANT PORTION OF WRN/CTRL NY
THIS EVENING. WHILE ACTIVITY HAS TRACKED SLIGHTLY FARTHER NORTH
THAN EARLIER PROGGED...LATEST RADAR TRENDS SUGGEST THAT -SHRA
SHOULD LARGELY REMAIN SOUTH OF A KIAG-KPEO LINE. WHILE CONDITIONS
SHOULD REMAIN VFR ACROSS THE KBUF/KIAG TO KROC CORRIDOR...MVFR
CONDITIONS WILL BE FOUND IN THE -SHRA TO THE SOUTH...PARTICULARLY
ACROSS HIGHER TERRAIN AREAS OF THE SRN TIER AND FINGER LAKES. CIGS
ARE EXPECTED TO LOWER TO IFR AFTER 09Z ACROSS HIGHER
ELEVATIONS...INCLUDING KJHW...GIVEN THE HEAVIER RAINFALL/INCREASED
MOISTURE AND HIGHER TERRAIN.

ELSEWHERE...LOOK FOR VFR CONDITIONS AND GENERALLY LIGHT WINDS TO
PERSIST THROUGH THE FORECAST PERIOD. ACROSS THE SOUTHERN TIER AND
FINGER LAKES...IFR CONDITIONS ARE EXPECTED TO LINGER WELL INTO THE
MORNING BEFORE MIXING OUT AT LEAST TO MVFR BY WED AFTERNOON.

OUTLOOK...
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...VFR.
FRIDAY...MAINLY VFR WITH A CHANCE OF SHOWERS SOUTHEAST OF LAKE ERIE.
SATURDAY THROUGH MONDAY...MAINLY VFR...WITH A CHANCE OF SHOWERS/
THUNDERSTORMS AND ATTENDANT MVFR.

&&

.MARINE...
WITH A WEAK PRESSURE GRADIENT REMAINING IN PLACE ACROSS THE LOWER LAKES
REGION THROUGH THE END OF THE WORK WEEK...EXPECT RELATIVELY LIGHT WINDS
AND MINIMAL WAVES TO CONTINUE THROUGH FRIDAY.

&&

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

&&

$$

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


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