Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 171806
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
106 PM EST WED DEC 17 2014

.SYNOPSIS...
A RAIN SNOW MIX WILL CHANGE OVER TO ALL SNOW ACROSS MUCH OF THE
REGION TODAY AS COLD AIR CONTINUES TO SPREAD ACROSS THE LOWER GREAT
LAKES. SNOW OVERNIGHT WILL HAVE GREATEST ACCUMULATIONS OVER THE TUG
HILL PLATEAU AND THE HILLS OF THE SOUTHERN TIER. HIGH PRESSURE WILL
RETURN BY FRIDAY AND SATURDAY WITH DRYING CONDITIONS AND NEAR-NORMAL
TEMPERATURES.

&&

.NEAR TERM /THROUGH TONIGHT/...
LOW PRESSURE CENTERED OVER THE UPPER SAINT LAWRENCE RIVER WILL GIVE
WAY TO A DEEPENING COASTAL LOW OVER THE GULF OF MAINE BY THIS EVENING.
THIS COASTAL LOW WILL CONTINUE TO DRAW COLD AIR OVER THE FORECAST
AREA INTO TONIGHT.

RADAR AND SURFACE OBS SHOW WET SNOW HAS DEVELOPED ACROSS MUCH OF
WESTERN NEW YORK THIS AFTERNOON WITH RAIN STILL FOUND FROM ROCHESTER
EASTWARD. EXPECT THAT WITH THE COOLING TEMPS THROUGH THE AFTERNOON A
MIX OF WET SNOW AND RAIN WILL DEVELOP HERE CHANGING TO WET SNOW BY
LATE AFTERNOON/EARLY EVENING. ONLY EXPECT UP TO A SLUSHY INCH OF
SNOW TODAY ACCUMULATING MAINLY ON GRASSY SURFACES.

WESTERLY WINDS WILL DIRECT THE REGIONS MOST CONDUCIVE TO SNOW
ACCUMULATION ACROSS THE HIGHER TERRAIN OF THE WESTERN SOUTHERN TIER
AND OVER THE TUG HILL REGION TONIGHT. A CAPPED BOUNDARY LAYER WILL
LIMIT VERTICAL DEVELOPMENT AND THUS THE AMOUNT OF SNOW THIS EVENING
AND TONIGHT. EXPECT A COUPLE 1-3 INCHES IN THESE FAVORED AREAS WITH
A SLUSHY INCH OR SO ELSEWHERE. THE BULK OF THE MOISTURE IS FOUND
BENEATH THE PRIME DENDRITIC SNOW GROW ZONE SO THE WET NATURE OF THE
FLAKES WILL KEEP ACCUMULATIONS LIGHT.

PERSISTENT COLD AIR ADVECTION WILL KEEP TEMPERATURES ON A SLOW
DOWNWARD TREND THROUGH THE DAY FROM WEST TO EAST AND FROM HIGH
ELEVATIONS TO LOW ELEVATIONS. TEMPS WILL FALL TO UPPER 20S AND
LOW 30S BY THE LATE AFTERNOON. LOW TEMPS TONIGHT WILL SETTLE TO THE
MID TO UPPER 20S INLAND AND THE LOW 30S ACROSS LOWER ELEVATIONS AND
CLOSER TO THE LAKES.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
ON THURSDAY A MID LEVEL CLOSED LOW AND ASSOCIATED SURFACE LOW WILL
ACCELERATE EASTWARD INTO THE CANADIAN MARITIMES LEAVING BEHIND A
MODESTLY COLD NORTHWEST FLOW REGIME ACROSS THE LOWER LAKES. ONE LAST
MID LEVEL VORTICITY MAXIMA WILL CROSS THE AREA IN THE MORNING ON THE
WESTERN PERIPHERY OF THE CLOSED LOW...PROVIDING A TEMPORARY INCREASE
IN LARGE SCALE ASCENT. LAKE INDUCED INSTABILITY WILL BE VERY
MARGINAL ON THURSDAY WITH EQUILIBRIUM LEVELS OF 4-5K FEET...JUST
ENOUGH TO SUPPORT VERY MODEST LAKE ENHANCEMENT SOUTHEAST OF THE
LAKES. ANY ACCUMULATIONS WILL BE LIMITED TO A COATING TO AN INCH IN
MOST AREAS. THE CHAUTAUQUA RIDGE WILL BENEFIT FROM UPSLOPE FLOW AND
POSSIBLY A WEAK CONNECTION TO LAKE HURON...WHICH MAY PRODUCE
ADDITIONAL AMOUNTS OF AROUND 2 INCHES IN SPOTS. TEMPERATURES WILL BE
VERY CLOSE TO SEASONAL NORMS WITH HIGHS IN THE MID 30S AT LOWER
ELEVATIONS AND AROUND 30 ON THE HILLS.

THURSDAY NIGHT AND FRIDAY MORNING LOW PRESSURE WILL CONTINUE TO MOVE
EAST INTO THE NORTH ATLANTIC WITH ANY SYNOPTIC SCALE SUPPORT COMING
TO AN END. THIS WILL JUST LEAVE NORTHWEST FLOW WITH SHALLOW
INVERSION HEIGHTS AND ANEMIC LAKE INDUCED INSTABILITY. THIS WILL
JUST SUPPORT SCATTERED FLURRIES AND LIGHT SNOW SHOWERS FOR THE MOST
PART WITH ANOTHER SPOTTY DUSTING TO AN INCH SOUTHEAST OF THE LAKES.
IT APPEARS TEMPERATURES BENEATH THE INVERSION REMAIN JUST COLD
ENOUGH AT -10C TO KEEP ICE NUCLEI IN THE CLOUD LAYER AND PREVENT
FREEZING DRIZZLE. OTHERWISE IT WILL REMAIN OVERCAST WITH NAM AND GFS
MODEL POINT SOUNDINGS SHOWING YET ANOTHER PERIOD OF ABUNDANT LOW
LEVEL MOISTURE TRAPPED BENEATH A STEEPENING SUBSIDENCE INVERSION.

BY FRIDAY AFTERNOON HIGH PRESSURE WILL BEGIN TO BUILD INTO THE LOWER
LAKES AND BRING AN END TO THE LIMITED LAKE EFFECT. THIS HIGH WILL
BUILD ACROSS SOUTHERN QUEBEC AND NEW ENGLAND FRIDAY NIGHT WITH A
CONTINUATION OF DRY WEATHER. IT APPEARS STRATUS WILL REMAIN LOCKED
IN PLACE WITH WEAK FLOW AND A STEEPENING INVERSION WITH GRAY
OVERCAST SKIES. THE ONE EXCEPTION MAY BE ACROSS THE NORTH COUNTRY
FRIDAY NIGHT WHERE MODEL GUIDANCE CONTINUES TO SHOW A STRONGER PUSH
OF DRYING MOVING SOUTH OUT OF CANADA.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
HIGH PRESSURE WILL REMAIN IN PLACE SATURDAY ACROSS NORTHERN NEW
ENGLAND AND PROVIDE ANOTHER DRY DAY ALTHOUGH THERE MAY STILL BE A
GOOD DEAL OF CLOUD COVER. SATURDAY NIGHT AND SUNDAY THE LATEST GFS
AND ECMWF RUNS CONTINUE TO SHOW A VERY WEAK SYSTEM WITH A MID LEVEL
TROUGH LIFTING OUT OF THE OHIO VALLEY AND ACROSS THE LOWER LAKES AND
NEW ENGLAND. THIS MAY PRODUCE A FEW FLURRIES OR VERY LIGHT SNOW OF
LITTLE CONSEQUENCE.

FOLLOWING THIS SYSTEM DRY WEATHER WILL RETURN FOR SUNDAY NIGHT AND
MONDAY WITH WEAK HIGH PRESSURE IN PLACE. BY TUESDAY A STRONG TROUGH
WILL BEGIN TO DIG AND AMPLIFY INTO THE MID SECTION OF THE NATION.
THIS WILL FORCE DOWNSTREAM HEIGHT RISES AND WARM ADVECTION ACROSS
OUR REGION. THIS WILL BRING WARMER TEMPERATURES AND A CHANCE OF A
FEW RAIN SHOWERS.

LOOKING A LITTLE FARTHER AHEAD...THE GEFS ENSEMBLE MEAN TRENDS THE
NAO AND AO INDICES STEADILY DOWNWARD THROUGH THE END OF THE MONTH
INDICATING A GREATER POTENTIAL FOR HIGH LATITUDE BLOCKING. THE
STRONG ZONAL EASTWARD EXTENSION OF THE EAST ASIAN JET WILL GIVE WAY
TO MORE AMPLIFICATION ACROSS THE NORTH PACIFIC BY NEXT WEEK AND
ALLOW THE PATTERN ACROSS NORTH AMERICA TO AMPLIFY. EXPECT MID WINTER
COLD TO ARRIVE NEAR CHRISTMAS AND HAVE SOME STAYING POWER. THERE
CONTINUES TO BE STRONG SUPPORT IN OPERATIONAL AND ENSEMBLE GUIDANCE
OF A SIGNIFICANT SYSTEM USHERING IN THIS PATTERN CHANGE AROUND
CHRISTMAS. GIVEN THE STRENGTH AND COMPLEXITY OF THE EVOLVING PATTERN
FOCUSING ON THE OUTPUT OF ANY ONE MODEL RUN IS POINTLESS AT THIS
TIME RANGE...IT WILL STILL BE A FEW MORE DAYS BEFORE MODELS BEGIN TO
CONVERGE ON A COMMON SOLUTION. NONETHELESS A HIGH IMPACT SYSTEM
AROUND THE HOLIDAY APPEARS LIKELY SOMEWHERE IN THE NORTHEAST QUARTER
OF THE NATION. STAY TUNED.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
LOW PRESSURE OVER THE UPPER SAINT LAWRENCE VALLEY WILL GIVE WAY TO A
COASTAL LOW OVER THE GULF OF MAINE BY TONIGHT. THIS WILL CONTINUE
WET SNOW SHOWERS ACROSS MUCH OF WNY TODAY INTO TONIGHT WITH RAIN
CHANGING TO SNOW ACROSS CENTRAL NEW YORK THROUGH THE AFTERNOON AS
THE COLDER AIR WORKS EASTWARD. THE SNOW ALONG WITH LINGERING LOW
LEVEL MOISTURE WILL MAINTAIN IFR/MVFR CIGS/VIS THROUGH MUCH OF TODAY
AND TONIGHT.

ON THURSDAY THE COASTAL LOW WILL LIFT ACROSS THE CANADIAN MARITIMES
WITH WINDS VEERING TO NORTHWEST. THE SYNOPTIC MOISTURE WILL BE THIN
BUT THE NORTHWEST FLOW WILL PROVIDE SOME LAKE AND UPSLOPE
ENHANCEMENT FOR LIGHT SNOW SHOWERS MAINLY EAST OF THE LAKES. EXPECT
MOST SITES TO IMPROVE TO MVFR WITH IFR ONLY CONTINUING ACROSS THE
SOUTHERN TIER. THERE IS A LOW CHANCE FOR FREEZING DRIZZLE INSTEAD OF
SNOW AS MOISTURE WILL BE THIN BUT TEMPS SHOULD MAINLY SUPPORT WET
SNOW.

OUTLOOK...
THURSDAY NIGHT...CHANCE OF LIGHT SNOW SHOWERS MAINLY EAST OF THE
LAKES AND MVFR.
FRIDAY...MAINLY VFR WITH A CHANCE OF SNOW SHOWERS.
SATURDAY...VFR.
SUNDAY...VFR/MVFR WITH A CHANCE OF SNOW SHOWERS.
MONDAY...VFR.

&&

.MARINE...
SURFACE LOW PRESSURE OVER THE UPPER SAINT LAWRENCE RIVER WILL GIVE
WAY TO A COASTAL LOW OVER THE GULF OF MAINE BY TONIGHT. THE SURFACE
PRESSURE GRADIENT AND COLD ADVECTION WILL CONTINUE STRONGER
SOUTHWEST TO WESTERLY WINDS...WHICH WILL MAINTAIN SMALL CRAFT
ADVISORIES FOR BOTH LAKES AND THE NIAGARA RIVER. HIGH PRESSURE
BUILDS IN FRIDAY AND SATURDAY WITH A RETURN TO MORE RELAXED
CONDITIONS.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST THURSDAY FOR LEZ020.
         SMALL CRAFT ADVISORY UNTIL 10 PM EST THURSDAY FOR LEZ040-
         041.
         SMALL CRAFT ADVISORY UNTIL 4 AM EST THURSDAY FOR
         LOZ030.
         SMALL CRAFT ADVISORY UNTIL 4 AM EST FRIDAY FOR LOZ043>045.
         SMALL CRAFT ADVISORY UNTIL 10 PM EST THURSDAY FOR LOZ042.

&&

$$

SYNOPSIS...SMITH/WCH
NEAR TERM...SMITH/WCH
SHORT TERM...HITCHCOCK
LONG TERM...HITCHCOCK
AVIATION...SMITH/WCH
MARINE...SMITH/WCH






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