Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 220434
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
1134 PM EST FRI NOV 21 2014

.SYNOPSIS...
NORTHWEST WINDS WILL SHIFT TO SOUTHWESTERLY THROUGH THE EVENING
HOURS...DRIVING LAKE EFFECT SNOW EAST OF THE LAKES NORTHWARD...WHILE
ALSO SIGNALING THE BEGINNING OF A WARM-UP. A FEW LIGHT RAIN
SHOWERS...WITH A POSSIBLE WINTRY MIX IN THE HILLS...WILL ARRIVE
TOMORROW AND MODERATE RAINFALL EXPECTED SUNDAY NIGHT WITH THE
PASSAGE OF A WARM FRONT. THIS WARM-UP WILL BRING THE RISK OF
FLOODING TO AREAS WHICH WERE BURIED IN LAKE EFFECT SNOW THIS WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
OFF LAKE ERIE...RADAR IMAGERY SHOWS THE BAND COMPLETELY GONE NOW
WITH ANY FLURRIES COMING TO AN END. LAKE EFFECT CLOUDS STRETCHING
FROM THE NIAGARA FRONTIER TO ROCHESTER AND THE WESTERN FINGER LAKES
WILL LIFT NORTHWARD OVERNIGHT AND INTO CANADA...LEAVING MAINLY CLEAR
SKIES. OFF LAKE ONTARIO THE BAND HAS BROADENED INTO A WEAK AREA OF
FLURRIES AND LIGHT SNOW AS DENDRITIC CRYSTAL GROWTH IS LOST. THIS
SHOULD ONLY LAST FOR A FEW MORE HOURS BEFORE DISSIPATING...WITH
NOTHING MORE THAN A FRESH DUSTING.

OUTSIDE OF THE LAKE EFFECT CLOUDS EXPECT CLEARING OVERNIGHT ACROSS
THE SOUTHERN TIER AND FINGER LAKES.

FOR TOMORROW WE WILL CONTINUE TO WARM ALOFT WITH ISENTROPIC UPGLIDE
MOTION PROVIDING FOR CLOUDY SKIES AND LIGHT PRECIPITATION.
SYNOPTICALLY THE LEFT EXIT REGION OF A 110 KNOT 250 HPA JET WILL
PROVIDE SOME VERTICAL LIFT OVER THE EASTERN GREAT LAKES THAT IN
ADDITION TO THE LOW LEVEL ISENTROPIC LIFT SHOULD ALLOW FOR HIGH
CONFIDENCE IN LOW QPF RAINFALL. THE CONFIDENCE WILL BE LACKING IN
THE P-TYPE AS A SHALLOW LAYER OF SUBFREEZING AIR MAY LINGER
SATURDAY. FOR NOW WILL CONTINUE WITH CHANCES FOR FREEZING RAIN IN
THE VALLEYS ACROSS THE INTERIOR SOUTHERN TIER AT THE ONSET OF THE
PRECIPITATION...AND ALSO LATER ACROSS AREAS LEWIS COUNTY. THERE IS
STILL TOO MUCH UNCERTAINTY OF ANY FREEZING RAIN GIVEN THE SHORT
WINDOW OF NEAR FREEZING TEMPS WHEN THE PRECIP ARRIVES...SO FOR NOW
WILL HOLD OFF ON ANY HEADLINES FOR THIS POTENTIAL.

LOWS TONIGHT WILL RANGE THROUGH THE TEENS TO NEAR 20 NEAR THE LAKE
SHORELINES...COLDER INLAND. HIGHS ON SATURDAY WILL BE IN THE UPPER
30S TO LOWER 40S.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
THREE SEPARATE WARM FRONTAL SEGMENTS WILL LIFT ACROSS THE LOWER
LAKES THROUGH THE SHORT TERM PERIOD...EACH BRINGING WITH IT A PERIOD
OF ENHANCED ISENTROPIC UPGLIDE AND MOISTURE. THE FIRST WARM FRONTAL
SEGMENT WILL LIFT ACROSS THE AREA LATER SATURDAY AND SATURDAY
EVENING. MOST OF THE SHOWERS WILL BE DURING THE EVENING WITH A
DRYING TREND OVERNIGHT. OVERALL AMOUNTS WITH THIS FIRST BATCH APPEAR
LIGHT...WITH A TENTH OF AN INCH OR SO...MAYBE A LITTLE MORE ACROSS
THE NORTH COUNTRY IN UPSLOPE AREAS.

THE SECOND WARM FRONTAL SEGMENT WILL LIFT ACROSS THE REGION ON
SUNDAY AND BRING A FEW MORE SHOWERS. THIS WILL BE VERY LIGHT...WITH
JUST A SPOTTY COUPLE HUNDREDTHS OF AN INCH IN SCATTERED SHOWERS.

THE THIRD WARM FRONTAL SEGMENT WILL BE THE STRONGEST AS A STRONG
AREA OF LOW PRESSURE MOVES INTO THE CENTRAL LAKES SUNDAY NIGHT AND
MONDAY. THIS WILL FORCE A STRONG PERIOD OF ISENTROPIC UPGLIDE ACROSS
THE LOWER LAKES LATER SUNDAY NIGHT. THE PERIOD OF STRONGEST ASCENT
DOES NOT LAST LONG...BUT MAY PRODUCE A 3 TO 5 HOUR PERIOD OF
STEADIER RAIN. THIS IS THE PERIOD TO WATCH AS FAR AS QPF POTENTIAL
GOES...WITH A QUARTER TO HALF INCH POSSIBLE. THIS RAIN WILL QUICKLY
TAPER OFF TO WIDELY SCATTERED SHOWERS FROM SOUTHWEST TO NORTHEAST ON
MONDAY MORNING AS A DRY SLOT MOVES OUT OF THE OHIO VALLEY.

IN ADDITION TO THE RAINFALL...A STRONG SOUTHERLY LOW LEVEL JET WILL
MOVE ACROSS THE LOWER LAKES LATE SUNDAY NIGHT AND EARLY MONDAY. SOME
MODEL GUIDANCE SHOWS A 70+ KNOT JET...WHICH MAY PRODUCE STRONG
DOWNSLOPE WINDS ALONG THE LAKE ERIE SHORE AND ALONG OTHER NORTHWARD
FACING SLOPES IN WESTERN NY AND THE FINGER LAKES...AND POSSIBLY THE
BLACK RIVER VALLEY. THIS WILL NEED TO BE MONITORED...IF THE STRONGER
LOW LEVEL JET VERIFIES SOME OF THESE AREAS MAY SEE AT LEAST WIND
ADVISORY GUSTS...WITH SOME LOW POTENTIAL FOR NEAR WARNING CRITERIA
GUSTS ALONG THE LAKE ERIE SHORE. STILL NOT ENOUGH CONFIDENCE FOR A
HIGH WIND WATCH AT THIS TIME GIVEN MODEL DIFFERENCES ON THE STRENGTH
AND DIRECTION OF THE LOW LEVEL JET. A LOW LEVEL JET FROM A MORE
SOUTHEASTERLY DIRECTION AND MORE PERPENDICULAR TO THE TERRAIN WOULD
BE MORE FAVORABLE.

A COLD FRONT WILL CROSS THE AREA LATER MONDAY OR MONDAY EVENING WITH
A FEW MORE SHOWERS. THIS FRONT WILL USHER IN A STEADILY COLDER
AIRMASS FOR TUESDAY WITH A FEW RAIN/SNOW SHOWERS POSSIBLE BUT
NOTHING SIGNIFICANT.

AS FAR AS TEMPERATURES GO...EXPECT HIGHS TO REACH AROUND 50 ON THE
LAKE PLAINS ON SUNDAY...THEN SURGE INTO THE LOWER OR EVEN MID 60S ON
MONDAY. OVERNIGHT LOWS SUNDAY NIGHT WILL BE VERY MILD...POSSIBLY
ONLY DOWN AROUND 50 ON THE LAKE PLAINS. DEWPOINTS WILL RISE TO NEAR
50 BY MONDAY MORNING. THE COMBINATION OF HIGH TEMPERATURES...HIGH
DEWPOINTS...AND STRONG WINDS WILL GREATLY SPEED UP SNOWMELT.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
TEMPERATURES WILL RETURN TO BELOW AVERAGE FOR THE THANKSGIVING
HOLIDAY AS A POSITIVE PNA PATTERN BECOMES RE-ESTABLISHED ACROSS
NORTH AMERICA. A DEVELOPING RIDGE OVER THE ROCKIES WILL FORCE A
DOWNSTREAM TROUGH TO CARVE INTO THE GREAT LAKES AND NORTHEAST BY
WEDNESDAY AND THURSDAY. THE MID LEVEL TROUGH AND A WEAK SURFACE LOW
MAY BRING A FEW SNOW SHOWERS FOR THANKSGIVING THURSDAY. THE AIRMASS
MAY GROW COLD ENOUGH TO SUPPORT LAKE EFFECT SNOW AGAIN BY WEDNESDAY
AND THURSDAY AS WELL...BUT AT THIS POINT IT DOES NOT LOOK UNSTABLE
ENOUGH FOR A SIGNIFICANT EVENT. AT THIS EARLY JUNCTURE THE NEW DAY 7
FRIDAY LOOKS TO BE DRY AS A RIDGE OF HIGH PRESSURE BUILDS INTO THE
LOWER LAKES.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
WEAK LAKE EFFECT FLURRIES EAST OF LAKE ONTARIO WILL PRODUCE AREAS OF
MVFR VSBY FOR A FEW MORE HOURS BEFORE ENDING. OTHERWISE A PLUME OF
LAKE EFFECT CLOUDS OFF BOTH LAKES WILL CONTINUE TO PRODUCE MVFR CIGS
FOR A FEW MORE HOURS BEFORE LIFTING NORTH INTO CANADA AND LEAVING
VFR BEHIND.

OUTSIDE OF LAKE EFFECT AREAS VFR WILL PREVAIL OVERNIGHT WITH SOME
HIGH CLOUDS INCREASING LATE. ON SATURDAY HIGH CLOUDS WILL THICKEN
AND LOWER INTO A MID LEVEL DECK IN THE MORNING AS A WARM FRONT
APPROACHES. THIS WARM FRONT WILL PRODUCE A FEW LIGHT SHOWERS FROM
WEST TO EAST IN THE AFTERNOON. A BRIEF PERIOD OF FREEZING RAIN IS
POSSIBLE AT THE ONSET ACROSS THE SOUTHERN TIER VALLEYS AND LEWIS
COUNTY. CIGS/VSBY WILL REMAIN VFR INITIALLY...BUT CIGS WILL DROP TO
MVFR LATER IN THE AFTERNOON AS THE LOW LEVELS BEGIN TO SATURATE.

FINALLY...SOME LOW LEVEL WIND SHEAR WILL DEVELOP SATURDAY AFTERNOON
ACROSS MUCH OF THE AREA. THERE WILL BE SOME WIND AT THE SURFACE...
HOWEVER WINDS JUST OFF THE DECK WILL INCREASE TO AROUND 50 KNOTS AND
THERE WILL BE A GOOD CHANGE IN WIND DIRECTION WITH HEIGHT...FROM SSW
AT THE SURFACE TO WESTERLY AT 2K FEET.

OUTLOOK...
SATURDAY NIGHT THROUGH MONDAY...PERIODS OF IFR/MVFR IN RAIN.
SIGNIFICANT LLWS POSSIBLE SUNDAY NIGHT AND INTO MONDAY MORNING.
TUESDAY...MAINLY VFR WITH A CHANCE OF RAIN/SNOW SHOWERS.
WEDNESDAY...MAINLY VFR/MVFR EXCEPT IFR POSSIBLE IN LAKE EFFECT SNOW
SHOWERS EAST OF BOTH LAKES.

&&

.MARINE...
HIGH PRESSURE WILL CROSS FROM THE OHIO VALLEY THIS AFTERNOON TO THE
EASTERN SEABOARD BY SATURDAY.

SOUTHWEST WINDS WILL INCREASE AGAIN TONIGHT AND TOMORROW AND SCA
WILL AGAIN CONTINUE ON THE LAKES.

ANOTHER STORM SYSTEM WILL LIFT NORTH OUT OF THE LOWER MISSISSIPPI
RIVER VALLEY SUNDAY TO MICHIGAN BY SUNDAY NIGHT. THIS DEEPENING
STORM SYSTEM WILL BRING SOME ELEVATED WINDS WITH POSSIBLE GALES ON
LAKE ERIE AND ADVISORIES POSSIBLE ON LAKE ONTARIO BY MONDAY.

&&

.HYDROLOGY...
WE COMPLETED A SNOW SURVEY TODAY TO GET SNOW DEPTH AND SNOW WATER
EQUIVALENTS FROM THE HARDEST HIT AREAS. THE SURVEY CAME UP WITH A
GENERAL 4 TO 6 INCHES OF SWE IN THE HARDEST HIT AREAS. SEE
BUFPNSBUF FOR THE SPECIFICS.

TEMPERATURES WILL RISE TO NEAR 50 ON SUNDAY...THEN INTO THE LOWER
60S ON MONDAY WITH VERY MILD LOWS SUNDAY NIGHT. DEWPOINTS WILL
RISE INTO THE UPPER 40S TO AROUND 50 SUNDAY NIGHT AND MONDAY. THE
HIGHER DEWPOINTS COMBINED WITH STRONG WINDS WILL RESULT IN VERY
RAPID SNOWMELT. THIS WILL COMBINE WITH RAIN AMOUNTS AVERAGING
ABOUT A HALF INCH FROM SUNDAY THROUGH MONDAY.

THE FLOOD POTENTIAL WILL BE TWO FOLD. FIRST...THERE IS A GENERAL
RISK OF URBAN FLOODING IN THE TOWNS HARDEST HIT BY THE SNOW AS
MELT WATER POOLS IN LOW LYING AND POOR DRAINAGE AREAS. EXCESSIVE
SNOW PILES AND LEAVES BENEATH THE SNOW MAY BLOCK STORM DRAINS.

THERE MAY ALSO BE A RISK FOR RIVER AND CREEK FLOODING. THE
GREATEST RISK IS ON THE BUFFALO CREEKS WHICH DRAIN THE HARDEST HIT
AREAS. THIS INCLUDES CAZENOVIA...BUFFALO...CAYUGA...AND ELLICOTT.
THERE MAY ALSO BE SOME FLOOD RISK FOR CATTARAUGUS CREEK AND SOME
OF THE SMALLER CREEKS THAT FLOW THROUGH DUNKIRK AND SILVER CREEK.
WITH THIS IN MIND WE HAVE EXPANDED THE FLOOD WATCH INTO THE
WESTERN SOUTHERN TIER IN ADDITION TO ERIE...GENESEE...AND WYOMING
COUNTIES.

THERE IS ALSO A FAIRLY HEAVY SNOWPACK IN THE UPPER REACHES OF THE
OATKA WATERSHED...BUT NOT AS HIGH AS THE BUFFALO CREEKS. WE WILL
CONTINUE TO MONITOR THIS BASIN FOR POSSIBLE FUTURE INCLUSION IN
THE FLOOD WATCH. THE EASTERN LAKE ONTARIO REGION HAD LESS SNOW...
WITH TOTALS OF 2 TO 2.5 FEET ON THE TUG HILL. THIS SNOWPACK IS NOT
EXCESSIVE FOR THAT AREA...SO HAVE NOT INCLUDED THE NORTH COUNTRY
IN A FLOOD WATCH AT THIS TIME.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...FLOOD WATCH FROM SUNDAY AFTERNOON THROUGH WEDNESDAY MORNING
     FOR NYZ010>012-019-020-085.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EST SUNDAY FOR LEZ040-041.
         SMALL CRAFT ADVISORY FROM NOON SATURDAY TO 1 AM EST SUNDAY
         FOR LEZ020.
         SMALL CRAFT ADVISORY UNTIL 1 PM EST SUNDAY FOR
         LOZ043>045.
         SMALL CRAFT ADVISORY UNTIL 7 AM EST SUNDAY FOR LOZ042.

&&

$$

SYNOPSIS...THOMAS
NEAR TERM...HITCHCOCK/THOMAS
SHORT TERM...HITCHCOCK
LONG TERM...HITCHCOCK
AVIATION...HITCHCOCK/THOMAS
MARINE...THOMAS
HYDROLOGY...HITCHCOCK




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