Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 261430
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
1030 AM EDT SUN APR 26 2015

.SYNOPSIS...
A PERSISTENT UPPER LEVEL LOW WILL CONTINUE TO SPIRAL OVER NEW ENGLAND
TODAY...SENDING ONE LAST WAVE OF MOISTURE...CLOUDS AND LIGHT SHOWERS
ACROSS THE REGION TONIGHT AND MONDAY MORNING BEFORE EXITING THE
REGION TUESDAY. MAINLY DRY WEATHER WITH NEAR NORMAL TEMPERATURES ARE
EXPECTED FOR TUESDAY AND WEDNESDAY BEFORE ANOTHER WEAK SYSTEM BRINGS
ANOTHER CHANCE OF SHOWERS BY THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
ON THE WATER VAPOR IMAGERY THIS MORNING AN UPPER LEVEL LOW SPINS
JUST OFF THE NEW ENGLAND COASTLINE. THIS IS THE SAME LOW THAT HAS
SLOWLY CROSSED EASTERN NORTH AMERICA THIS PAST WEEK. A SHORTWAVE IS
SEEN ON WATER VAPOR OVER FAR SW QUEBEC.

VISIBLE SATELLITE IMAGERY SHOWING A VARIETY OF CLOUD COVER ACROSS
THE REGION THIS MORNING. AN EXPANSIVE AREA OF STRATUS COVERS MOST OF
WESTERN NY...THE GENESEE VALLEY AND FINGER LAKES. SKIES HAVE BEEN
CLEAR THIS MORNING EAST OF LAKE ONTARIO...BUT THIS IS QUICKLY
CHANGING AS LAPSE RATES STEEPEN WITH DIURNAL WARMING AND THE
CONVECTIVE TEMP IS REACHED. CUMULUS ARE STARTING TO DEVELOP...AND
SHOULD QUICKLY FORCE SKIES TO MOSTLY CLOUDY BY EARLY AFTERNOON.
FARTHER WEST...EXPECT THE HIGHER TERRAIN OF THE SOUTHERN TIER AND
FINGER LAKES TO REMAIN CLOUDY AS THE STRATUS DECK EVOLVES INTO
EXTENSIVE CUMULUS AND STRATOCUMULUS WITH DAYTIME HEATING...SUPPORTED
BY NORTHERLY UPSLOPE FLOW. THE LAKE PLAINS SOUTH OF LAKE ONTARIO
INCLUDING THE NIAGARA FRONTIER AND ROCHESTER MAY SEE SOME SUNSHINE
AGAIN LATER THIS AFTERNOON AS A LAKE SHADOW TRIES TO DEVELOP.

A FEW SPRINKLES OR LIGHT SHOWERS MAY DEVELOP ACROSS THE NORTH
COUNTRY BY LATE AFTERNOON AS DEEPER MOISTURE MOVES INTO THE AREA AND
A MID LEVEL SHORTWAVE APPROACHES WITH DPVA PRODUCING INCREASING
LARGE SCALE ASCENT. ANYTHING THAT DOES DEVELOP WILL BE LIGHT AND
WIDELY SCATTERED.

AFTER A COOL START HIGHS SHOULD REBOUND INTO THE UPPER 40S AND LOWER
50S. COOLEST AREAS WILL BE SOUTH OF THE LAKES WHERE A LIGHT
NORTHWESTERLY FLOW OVER THE YET STILL COOL LAKE WATERS KEEPS AREAS
NEAR THE SOUTHERN LAKE SHORES IN THE LOWER 40S.

TONIGHT A SHORTWAVE TROUGH WILL PASS ACROSS THE REGION FROM THE
NORTH. THIS FEATURE COMBINED WITH INCREASING LOW LEVEL MOISTURE WILL
BRING A FEW LIGHT RAIN SHOWERS/DRIZZLE TO THE REGION. WITH LITTLE
FORCING ALOFT AS WIND FIELDS REMAIN WEAK WILL CONTINUE JUST CHANCE
POPS OVERNIGHT.

THE LIGHT MOIST NORTHERLY FLOW THROUGH THE NIGHT WILL UPSLOPE SUCH
THAT LOW CLOUDS AND PATCHY AREAS OF FOG AND DRIZZLE (POSSIBLE
FREEZING DRIZZLE) WILL BE POSSIBLE OVER HIGHER TERRAIN OF SOUTHERN
NY. THE TRADITIONALLY COLDER VALLEYS OF SOUTHERN NEW YORK MAY DROP
PAST THE FREEZING MARK OVERNIGHT AND WITH LITTLE MOISTURE IN THE
SNOW GROWTH ZONE...FREEZING DRIZZLE WILL BE POSSIBLE. EAST OF LAKE
ONTARIO THE MOISTURE FIELD SHOULD BE DEEP ENOUGH TO SUPPORT EITHER
RAIN OR SNOW SHOWERS OVERNIGHT.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
MODEL CONSENSUS CONSISTENTLY KEEPS AN UPPER-LEVEL LOW STALLED NEAR NOVA
SCOTIA THROUGHOUT THE PERIOD. A TROUGH EXTENDING TO THE WEST FROM THIS
LOW WILL DROP SOUTHWARD ACROSS OUR REGION ON MONDAY WITH A MORE
SUBTLE DISTURBANCE FORECAST TO FOLLOW THIS MONDAY EVENING. LIFT WITH
THIS FEATURE WILL BE VERY WEAK...WITH NAM/GFS BUFKIT SHOWING NEARLY
ALL THE OMEGA BELOW 850MB. MOST OF THIS IS PROBABLY DUE TO UPSLOPING
FROM THE NORTHERLY FLOW. UPSLOPING CAN BE OVERDONE BY MODEL GUIDANCE
SINCE PRECIPITATION DEPENDS HEAVILY ON HOW SATURATED THE BOUNDARY
LAYER IS. THERE IS A FAIR AMOUNT OF BOUNDARY LAYER MOISTURE UPSTREAM
WITH THIS FEATURE...SO WILL MAINTAIN CHANCE POPS MONDAY INTO MONDAY
EVENING. ANY PRECIPITATION THAT DOES OCCUR WILL BE LIGHT WITH
AMOUNTS BARELY ENOUGH TO WET THE GROUND.

THERE SHOULD BE FAIRLY EXTENSIVE CLOUD COVER MONDAY AND MONDAY
NIGHT. CONSIDERING THE WARM BIAS OF MOST GUIDANCE THE PAST COUPLE
DAYS...AND 850MB TEMPS OF -2C WILL NUDGE HIGHS ON MONDAY DOWN A BIT.
UNLESS THERE ARE SIGNIFICANT BREAKS OF SUNSHINE...EXPECT HIGHS TO
MAINLY BE IN THE MID TO UPPER 40S. HOWEVER THE CLOUD COVER WILL KEEP
TEMPERATURES FROM DROPPING MUCH MONDAY NIGHT WITH LOWS IN THE UPPER
30S TO LOWER 40S. SOME PATCHY UPSLOPE FOG IS POSSIBLE MONDAY NIGHT
DEPENDING ON HOW MUCH MOISTURE IS TRAPPED IN THE BOUNDARY LAYER.

ALTHOUGH THE UPPER LOW WILL REMAIN NEARLY STATIONARY THE PASSAGE OF
THE TROUGH AXIS WILL ALLOW A SUBTLE UPPER LEVEL RIDGE TO BUILD
TOWARD THE REGION TUESDAY AND TUESDAY NIGHT. THIS WILL RESULT IN
GRADUALLY CLEARING SKIES AND WARMING TEMPERATURES. HIGHS ON TUESDAY
WILL DEPEND ON HOW MUCH SKIES CLEAR...WITH MODEL GUIDANCE DIFFERING
ON THIS SOMEWHAT. USING A PARTIAL CLEARING MODEL CONSENSUS HIGHS ON
TUESDAY SHOULD RISE INTO THE UPPER 50S TO LOWER 60S AWAY FROM THE
LAKES...WITH TEMPERATURES 5 TO 10 DEGREES COOLER ALONG THE IMMEDIATE
LAKESHORE. THE NW FLOW SHOULD ALLOW KEEP MOST OF THE BUFFALO METRO
AREA ON THE WARM SIDE OF THE LAKE BREEZE. BY TUESDAY NIGHT EXPECT
MOSTLY CLEAR SKIES WITH DECENT RADIATIONAL COOLING ALLOWING
TEMPERATURES TO DROP TO THE MID 30S TO LOWER 40S.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
FAIRLY TYPICAL SPRING WEATHER TO CONTINUE THROUGH THE EXTENDED
FORECAST PERIOD. BY WEDNESDAY...THE UPPER-LEVEL LOW THAT HAS BEEN
HANGING AROUND WILL FINALLY DEPART OFF THE NEW ENGLAND COAST. MODELS
ARE IN AGREEMENT THAT THIS WILL BE FOLLOWED BY A NORTHERN STREAM
SHORTWAVE INTERACTING WITH A CUTOFF LOW EXITING FROM THE FOUR
CORNERS REGION. HOWEVER...THAT IS WHERE THE AGREEMENT ENDS...AS THE
GLOBAL MODELS ALL HANDLE THIS INTERACTION DIFFERENTLY. LOOKING AT
RECENT RUNS OF THE GGEM/ECMWF/GFS...ABOUT TWO-THIRDS OF THE GUIDANCE IS
SIMILAR TO THE 00Z GGEM/ECMWF WHICH FORECAST A WEAK AND DISORGANIZED
TROUGH WITH WARMER TEMPERATURES AND ONLY A LOW CHANCE FOR
PRECIPITATION LATE IN THE WEEK. THE LESS LIKELY 00Z GFS SOLUTION HAS
A STRONGER CUT-OFF LOW DEVELOPING WHICH WOULD BRING COOLER
TEMPERATURES AND A BETTER CHANCE FOR PRECIPITATION. FORECAST WILL
USE A CONSENSUS OF ALL GUIDANCE...WHICH SHOULD EVENTUALLY TREND TO
ONE OF THESE TWO CAMPS. IN GENERAL...THIS APPROACH LEADS TO SLIGHTLY
WARMER TEMPERATURES TO THE PREVIOUS FORECAST WITH LITTLE CHANGE TO
POPS.

BY NEXT WEEKEND...THE MODEL CONSENSUS IS TO BUILD A RIDGE ACROSS THE
UPPER GREAT LAKES...WITH SOME NORTHWEST FLOW IN PLACE ACROSS THE
LOWER GREAT LAKES. THIS SHOULD RESULT IN A WARMER WEEKEND AS COLDER
AIR WILL BE SUPPRESSED WELL TO THE NORTH.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
AT 14Z VFR FLIGHT CONDITIONS WERE FOUND ACROSS THE REGION...AND
THESE CONDITIONS ARE EXPECTED TO PERSIST FOR ANOTHER 18 TO 24 HOURS
ACROSS THE REGION. SOME PASSING MID LEVEL CLOUDS THIS MORNING FROM
THE NORTH WILL THICKEN THROUGH THE DAY AS DEEPER MOISTURE DROPS
SOUTHWARD FROM SOUTHERN CANADA. THIS MOISTURE MAY TRIGGER A FEW
SPRINKLES/SHOWERS ACROSS AREAS EAST OF LAKE ONTARIO THIS LATE
AFTERNOON...AND AFTER 00Z FOR THE REMAINDER OF THE REGION. AS SUCH
WILL NOT INCLUDE ANY WX CODE INTO THE TAFS UNTIL THE DEEPER MOISTURE
ARRIVES OVERNIGHT. DUE THE THE SCATTERED NATURE WILL ONLY INCLUDE A
VCSH IN THE TAFS.

WITHIN THE DEEPER MOISTURE IN THE LOWER LEVELS SOME MVFR CIGS ARE
POSSIBLE WITH THE LIGHT NORTHERLY FLOW. ALSO ACROSS THE HIGHER
TERRAIN LIGHT DRIZZLE AND IFR FLIGHT CONDITIONS ARE PROBABLE.

THESE LOWER CONDITIONS ARE LIKELY NOT TO START UNTIL AFTER 03Z. THE
BEST CHANCES FOR ANY SHOWERS THIS TIME PERIOD WILL BE FROM 03Z
MONDAY TO 21Z MONDAY.

OUTLOOK...
MONDAY AFTERNOON...ANY SHOWERS DIMINISHING...MAINLY VFR.
TUESDAY THROUGH THURSDAY...MAINLY VFR.

&&

.MARINE...
LOW PRESSURE REMAINING OVER NEW ENGLAND TODAY WILL MAINTAIN
RELATIVELY LIGHT NORTHWEST WINDS ON THE LOWER LAKES THROUGH THE
MIDDLE OF NEXT WEEK. WINDS WILL OCCASIONALLY BECOME STRONG ENOUGH TO
PRODUCE CHOPPY WAVE ACTION...BUT SHOULD STAY JUST BELOW SMALL CRAFT
ADVISORY CRITERIA.

&&

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

&&

$$

SYNOPSIS...THOMAS
NEAR TERM...HITCHCOCK/THOMAS
SHORT TERM...APFFEL
LONG TERM...APFFEL/CHURCH
AVIATION...THOMAS
MARINE...THOMAS






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