Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 212351
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
651 PM EST WED JAN 21 2015

.SYNOPSIS...
A WEAK LOW PRESSURE SYSTEM WILL SLIDE ACROSS PENNSYLVANIA TONIGHT.
THIS WILL DROP A COUPLE INCHES OF SNOW NEAR THE PENNSYLVANIA
BORDER WITH LITTLE IF ANY TO AREAS FURTHER NORTH. HIGH PRESSURE AND
MAINLY DRY WEATHER WILL THEN RETURN FOR THURSDAY AND FRIDAY...BEFORE
ANOTHER WEATHER SYSTEM POTENTIALLY BRINGS SOME LIGHT SNOW SATURDAY
AND SUNDAY.

&&

.NEAR TERM /THROUGH THURSDAY/...
A WEAK TROUGH ALOFT IS MOVING EAST ACROSS THE OH VALLEY WITH A
SIMILARLY WEAK SURFACE LOW.  THERE IS ENOUGH LIFT AND MOISTURE IN A
WEAK DEFORMATION ZONE STRETCHING FROM LOWER MI ESE TO THE ATLANTIC
COAST FOR FOR A BAND OF LIGHT SNOW.  EXPECT THIS BAND TO PIVOT
MAINLY OVER PA/SW NY...WITH SOME LIGHT SNOW BRUSHING THE WESTERN
SOUTHERN TIER OF NY.  WILL CONTINUE WITH LIGHT SNOW AMOUNTS /STORM
TOTAL UNDER 2 INCHES/ NEAR THE BORDER THROUGH PART OF TONIGHT...WITH
LITTLE IF ANY SNOW ACCUMULATION FURTHER NORTH.

ON THURSDAY...EXPECT ANY SNOW TO BE EAST OF THE REGION AS THE LOW
QUICKLY INTENSIFIES WELL OFFSHORE AND HIGH PRESSURE BUILDS OVER THE
NORTHERN AND CENTRAL GREAT LAKES REGION.  RESIDUAL LOW CLOUDS WILL
LIKELY PLAGUE THE SOUTHERN TIER PER MODEL SOUNDINGS...AND AT LEAST
EARLY ON CLOSER TO THE LAKES.  IN GENERAL...EXPECT DECREASING CLOUDS
NEAR THE LAKES BY OR IN THE AFTERNOON...ALTHOUGH MODELS TEND TO HAVE
A DIFFICULT TIME HANDLING RESIDUAL LOW LEVEL MOISTURE...SO
CONFIDENCE IS LOW FOR CLOUD COVER FORECAST.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
FOR MOST OF THE AREA HIGH PRESSURE RIDGING FROM THE OHIO VALLEY WILL
BRING FAIR WEATHER FOR THURSDAY NIGHT. A VERY WEAK SHORTWAVE WILL
PASS TO THE NORTH AND BRING A GLANCING SHOT OF COLDER AIR WHICH
MAY PROMOTE A MODEST LAKE RESPONSE OFF LAKE ONTARIO. THE COLD AIR
WILL BE SHALLOW...WITH EQUILIBRIUM LEVELS ONLY ABOUT 6K FEET AND A
FAIR AMOUNT OF DIRECTIONAL WIND SHEAR. THE COMBINATION OF MODEST
LAKE INDUCED INSTABILITY AND UPSLOPING MAY BE JUST ENOUGH TO BRING
AN INCH OR TWO EAST OF LAKE ONTARIO. WHATEVER LAKE RESPONSE DOES
OCCUR SHOULD FOCUS ON OSWEGO COUNTY THURSDAY EVENING AND THEN LIFT
SLOWLY NORTHWARD THROUGH FRIDAY MORNING.

850MB TEMPS WILL WARM ON FRIDAY AS THE HIGH NUDGES NORTH AND THE
MID-LEVEL FLOW BECOMES MORE ZONAL BEHIND THE EXITING SHORTWAVE. ANY
LAKE EFFECT SNOW SHOULD TAPER OFF BY FRIDAY AFTERNOON WITH FAIR
WEATHER. NAM/GFS BUFKIT BOTH SHOW A SHALLOW LAYER OF MOISTURE
BENEATH 2K FT WHICH MAY RESULT IN A STRATUS CLOUD DECK OR IT MAY
REMAIN MIXED. SO EVEN WITH THE HIGH PRESSURE RIDGE THERE PROBABLY
WILL BE SOME PATCHY LOW CLOUDS FOR MOST OF THE DAY. OTHERWISE...
TEMPERATURES WILL BE WARMER WITH HIGHS 30 TO 35 IN MOST AREAS.

NAM/GFS/GGEM/SREF GUIDANCE CONTINUES TO KEEP OUR REGION BETWEEN A
SHORTWAVE APPROACHING FROM THE UPPER LAKES AND A DEVELOPING COASTAL LOW
NEAR THE CAROLINAS. GUIDANCE CONTINUES TO KEEP THE COASTAL LOW WELL
TO OUR EAST WHILE A WEAK SHORTWAVE AHEAD MOVES OUT AHEAD OF AS
STRONG COLD FRONT. THIS SHORTWAVE MAY BRING SOME VERY LIGHT SNOW
SHOWERS OR FLURRIES SATURDAY AFTERNOON. TEMPERATURES WILL AVERAGE
NEAR TO SLIGHTLY ABOVE NORMAL...WITH HIGHS ON SATURDAY IN THE LOWER
TO MID 30S.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
LONG TERM GUIDANCE IS IN FAIRLY GOOD AGREEMENT ON THE GENERAL
PATTERN THROUGH EARLY NEXT WEEK...BUT THIS STILL DOES NOT MAKE IT A
HIGH CONFIDENCE FORECAST. THE COMPLEXITY OF THE PATTERN AND RECENT
MODEL VARIATIONS WOULD SUGGEST THAT MODEL GUIDANCE WILL CONTINUE TO
SHOW A GOOD DEAL OF CHANGE FROM RUN TO RUN.

THE MAIN FORECAST CHALLENGE IS HOW FAR SOUTH AN ARCTIC FRONTAL
BOUNDARY WILL DROP...WITH THE 12Z GGEM KEEPING THE COLD AIR TO THE
NORTH WHILE THE 12Z GFS/00Z ECMWF DROP AT LEAST SOME OF THE ARCTIC
AIR INTO OUR REGION. THE FRONT WILL PROBABLY MOVE INTO OUR REGION
LATE SATURDAY NIGHT OR SUNDAY MORNING WHICH WILL PROBABLY RESULT IN
SOME SNOW SHOWERS.

AFTER THIS...A WAVE OF LOW PRESSURE IS FORECAST TO TRACK ALONG THE
BOUNDARY. THIS WILL BRING A PERIOD OF STEADIER SNOW AND SOME LIGHT
ACCUMULATIONS ON THE ORDER OF SEVERAL INCHES TO SOMEWHERE. IF THE
GFS/ECMWF ARE CORRECT MOST OF THIS WILL BE TO THE SOUTH OF OUR
CWA....WHILE THE FURTHER NORTH FRONTAL POSITION OF THE GGEM WOULD
BRING STEADIER SNOW TO OUR REGION. A CONSENSUS BRINGS THE BEST
CHANCE FOR SNOW ACROSS SOUTHERN PORTIONS OF THE CWA LATE SUNDAY AND
SUNDAY NIGHT. EITHER WAY...AFTER THE WAVE PASSES THERE WILL BE A
PERIOD OF LAKE EFFECT SNOW SOUTH OF LAKE ONTARIO DUE TO THE
NORTHERLY FLOW AND COLD AIR ALOFT.

THE POSITION OF THIS FRONT WILL ALSO HAVE A BIG IMPACT ON
TEMPERATURES. IT WILL BE COLD EITHER WAY...BUT MUCH COLDER IF THE
FRONT PASSES THROUGH WITH DAYTIME HIGHS IN THE TEENS POSSIBLE. LAKE
ENHANCED CLOUD COVER WILL LIMIT RADIATIONAL COOLING SOUTH OF LAKE
ONTARIO...BUT IF THE FRONT PUSHES FAR ENOUGH SOUTH...THERE WILL BE
EXCELLENT RADIATIONAL COOLING EAST OF LAKE ONTARIO SUNDAY AND MONDAY
NIGHTS. LOWS MAY FALL WELL BELOW ZERO IN THE 10 TO 20 BELOW
RANGE...OR IF CLOUDS LINGER LOWS WOULD ONLY BE IN THE SINGLE DIGITS.

AFTER THIS...THE GFS/ECMWF DIFFER ON THE LARGE SCALE PATTEN WITH THE
GFS BRINGING ANOTHER CLIPPER LOW WHILE THE ECMWF ESTABLISHES HIGH
PRESSURE ACROSS THE REGION. WILL GO WITH A MIDDLE OF THE ROAD
APPROACH WITH LOW CHANCE POPS. TEMPERATURES WILL REMAIN BELOW NORMAL
NO MATTER WHICH MODEL VERIFIES AS A LONGWAVE TROUGH REMAINS
ENTRENCHED ACROSS THE NORTHEASTERN STATES.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
A WEAK DISTURBANCE WILL PASS SOUTH OF NEW YORK STATE TONIGHT. THIS
FEATURE WILL PUSH LOWER CIGS NORTHWARDS ACROSS THE WESTERN COUNTIES
DURING THE FIRST HALF OF TONIGHT...WITH CONDITIONS DETERIORATING TO
AT LEAST MVFR. LIGHT SNOW THAT WILL ACCOMPANY THE CLOUD COVER WILL
FURTHER LOWER CONDITIONS TO IFR LEVELS.

THE IFR TO MVFR CONDITIONS WILL PERSIST ACROSS MUCH OF WESTERN NEW
YORK LATE TONIGHT...WITH IMPROVEMENT SLATED DURING THE COURSE OF
THURSDAY. AREAS OF EAST OF LAKE ONTARIO WILL REMAIN VFR THROUGH THE
TAF PERIOD.

OUTLOOK...
FRIDAY...NO SIGNIFICANT WEATHER EXPECTED.
SATURDAY THROUGH MONDAY...CHANCE OF SNOW SHOWERS.

&&

.MARINE...
A WEAK SYSTEM WILL MOVE THROUGH THE OH VALLEY AND EVENTUALLY OUT TO
SEA BY THURSDAY.  WINDS WILL BE RELATIVELY LIGHT AS THE LOW PASSES
TO THE SOUTH AND EVENTUALLY SE...WITH NE WINDS BACKING TO THE N
OVERNIGHT AND NW BY THURSDAY.

THE NEXT PERIOD OF STRONGER WINDS AND WAVES COMES FRIDAY INTO
SATURDAY AS SOUTHWESTERLY WINDS INCREASE AHEAD OF AN APPROACHING
WEATHER SYSTEM.

PLEASE NOTE THAT DUE TO INCREASING ICE COVERAGE...THE SMALL CRAFT
ADVISORY PROGRAM FOR THE LAKE ERIE NEARSHORE WATERS AND NIAGARA
RIVER HAS BEEN SUSPENDED FOR THE REMAINDER OF THE WINTER SEASON...
AND WILL RESUME IN THE SPRING ONCE THE ICE MELTS.

&&

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

&&

$$

SYNOPSIS...ZAFF
NEAR TERM...RSH/ZAFF
SHORT TERM...APFFEL
LONG TERM...APFFEL
AVIATION...RSH
MARINE...ZAFF







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