February 28, 2012 Forecast Discussion

000
FXUS61 KALY 282141
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
441 PM EST TUE FEB 28 2012

.SYNOPSIS…
HIGH PRESSURE WILL MOVE EAST OF THE REGION TONIGHT…WHILE A COMPLEX
STORM SYSTEM APPROACHES FROM THE UPPER MIDWEST AND GREAT LAKES
REGION. A WARM FRONT ASSOCIATED WITH THE STORM SYSTEM WILL INITIALLY
BRING SNOW TO THE REGION WEDNESDAY AFTERNOON INTO THE EVENING BEFORE
TRANSITIONING TO A WINTRY MIX WEDNESDAY NIGHT INTO THURSDAY.
ADDITIONAL SNOWFALL IS POSSIBLE MAINLY NORTH OF ALBANY ON
THURSDAY…AS A DOUBLE BARREL LOW PRESSURE SYSTEM GRADUALLY TRACKS
EASTWARD ACROSS NEW YORK AND NEW ENGLAND.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/…
AS OF 400 PM…HIGH PRESSURE WILL DRIFT OVER THE AREA THIS EVENING
INTO THE OVERNIGHT HOURS…WITH TRANQUIL CONDITIONS EXPECTED TO
PREVAIL THROUGH SUNRISE WEDNESDAY. MAINLY CLEAR TO PARTLY CLOUDY
SKIES TO START EARLY THIS EVENING…FOLLOWED BY INCREASING CLOUDS
OVERNIGHT ASSOCIATED WITH THE STORM SYSTEM OVER THE UPPER MIDWEST
AND GREAT LAKES THAT WILL IMPACT THE REGION STARTING TOMORROW. MIN
TEMPS ARE EXPECTED TO BE CLOSE TO NORMAL.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/…

— Changed Discussion —
A SIGNIFICANT WINTER STORM IS STILL EXPECTED TO IMPACT MUCH OF
THE REGION WEDNESDAY THROUGH THURSDAY…

WINTER STORM WATCH REMAINS IN EFFECT FOR MUCH OF THE REGION FOR
WEDNESDAY AFTERNOON THROUGH THURSDAY AFTERNOON. ONLY CHANGE IN
HEADLINES AT THIS TIME IS ISSUANCE OF A WINTER WEATHER ADVISORY FOR
EASTERN ULSTER…DUTCHESS…AND LITCHFIELD COUNTIES WHERE THERE IS
GREATER CONFIDENCE FOR ADVISORY LEVEL ACCUMULATIONS OF SNOW…SLEET
AND FREEZING RAIN. ELSEWHERE WE DID NOT HAVE ENOUGH CONFIDENCE TO
EITHER UPGRADE TO WARNINGS OR ISSUE ADVISORIES.

BY LATE WEDNESDAY MORNING INTO EARLY AFTERNOON THE WARM FRONT
ASSOCIATED WITH THE CYCLONE OVER UPPER MIDWEST WILL BE POSITIONED TO
OUR SOUTH AND WEST. THE WARM FRONT WILL APPROACH AND CAUSE
ISENTROPIC LIFT ON THE 295K SURFACE TO INCREASE SUBSTANTIALLY FROM
SOUTHWEST TO NORTHEAST ACROSS OUR AREA. THIS WILL ALLOW FOR SNOW TO
DEVELOP AND INCREASE IN INTENSITY FOR THE LATE AFTERNOON INTO EARLY
EVENING. THIS WILL LIKELY RESULT IN A MESSY EVENING COMMUTE WITH
HIGH IMPACT. SNOWFALL RATES COULD APPROACH ONE INCH PER HOUR AND
THIS WILL BE A WET SNOWFALL.

IT IS STILL DIFFICULT TO DETERMINE IF ENOUGH SNOW WILL FALL TO
WARRANT WARNINGS FROM THIS SHOT OF ISENTROPIC LIFT. INITIALLY TEMPS
WILL BE IN THE LOWER TO PERHAPS MID 30S FOR MOST VALLEY AREAS SO
SNOW MAY NOT ACCUMULATE AT A FAST RATE AT THE ONSET. HOWEVER…AS
SNOWFALL RATES INCREASE TOWARDS LATE AFTERNOON AND EVENING…A
PLOWABLE SNOWFALL SHOULD OCCUR. THERE IS SOME UNCERTAINTY AS TO HOW
FAR NORTH THIS MODERATE TO OCCASIONALLY HEAVY BURST OF SNOW WILL
OCCUR…BUT GENERAL MODEL CONSENSUS IS FOR THE BEST FORCING TO OCCUR
FROM THE CAPITAL REGION AND MOHAWK VALLEY SOUTHWARD. SHORTLY AFTER
SUNSET…ENOUGH WARMING ALOFT COULD START TO CHANGE THE SNOW TO A
SLEET/FREEZING RAIN MIX ACROSS FAR SOUTHERN AREAS WHICH WOULD TEND
TO LIMIT SNOW ACCUMULATIONS…THUS THE ISSUANCE OF THE WINTER
WEATHER ADVISORY.

THE WEDNESDAY EVENING TO THE OVERNIGHT TIME FRAME IS WHEN THE
FORECAST GETS A BIT MURKY IN TERMS OF UNCERTAINTY. AFTER THE INITIAL
PERIOD OF ISENTROPIC LIFT MOVES THROUGH…GUIDANCE STILL SUGGESTING
PRECIP CONTINUING AS LOW LEVEL SOUTHERLY WINDS INCREASE AND HIGH
PRESSURE TO OUR NORTH AND EAST CONTINUES A LOW LEVEL COLD AIR
DRAINAGE INTO THE REGION. SO…INTENSITY OF PRECIP IS IN QUESTION AS
THE MAIN FORCING MECHANISM OF WARM ADVECTION SHIFTS EAST.
ALSO…WARM NOSE ALOFT WILL INTRUDE BUT THE MAGNITUDE AND NORTHERLY
ADVANCEMENT OF THE WARM NOSE IS ALSO VERY MUCH IN QUESTION. OUR BEST
INDICATION FOR NOW IS FOR SLEET TO MIX IN WITH THE SNOW FROM AROUND
THE CAPITAL REGION AND MOHAWK VALLEY SOUTHWARD…WITH SLEET AND
FREEZING RAIN POSSIBLE IN A CORRIDOR FROM SOUTHERN HERKIMER COUNTY
SOUTHEASTWARD THROUGH THE EASTERN CATSKILLS AND MID HUDSON VALLEY.
SO…WILL MENTION ADDITIONAL SNOW ACCUMULATIONS EXCEPT FOR EXTREME
SOUTHERN ZONES…WITH GENERALLY A FEW ADDITIONAL INCHES BUT POSSIBLY
MORE NORTH OF THE CAPITAL REGION.

ON THURSDAY…WE WILL BE DEALING WITH PART TWO OF THE STORM…AS THE
UPPER LOW CENTER IS EXPECTED TO PASS BY JUST NORTH OF THE AREA BUT
THERE IS STILL VARIATION AMONG MODEL GUIDANCE. THE CYCLONIC
VORTICITY ADVECTION AND TO A LESSER DEGREE UPSLOPE FLOW WILL BE THE
PRIMARY FORCING MECHANISMS. FROM THE SOUTHERN ADIRONDACKS…EASTWARD
THROUGH THE SARATOGA/LAKE GEORGE REGION AND THROUGH SOUTHERN
VERMONT/NORTHERN BERKSHIRES…THE STRONGEST LIFT IS EXPECTED WITH
TEMP PROFILES COLD ENOUGH FOR SNOW. SO THERE IS HIGHER CONFIDENCE
FOR ADDITIONAL SNOW ACCUMULATIONS IN THESE AREAS. HOWEVER…FROM THE
MOHAWK VALLEY AND CAPITAL REGION SOUTHWARD…THERE ARE SEVERAL
COMPLICATING FACTORS THAT LOW CONFIDENCE. WHILE TEMPS WILL BE
COOLING ALOFT…SURFACE TEMPS COULD WARM INTO THE UPPER 30S TO LOWER
40S WHICH WOULD RESULT IN MAINLY RAIN. ALSO…IT APPEARS THESE AREAS
WILL BE SOUTH OF WHERE THE BEST LIFT/QPF WILL BE. RAIN COULD CHANGE
BACK TO SNOW TOWARDS EVENING BEFORE TAPERING OFF THURSDAY NIGHT.

BOTTOM LINE IS THAT THERE IS STILL A LOT OF UNCERTAINTY FOR HOW THIS
COMPLEX WINTER STORM WILL EVOLVE IN TERMS OF THE DIFFERENT PHASES OF
THE STORM.
— End Changed Discussion —

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/…
— Changed Discussion —
MOS GUIDANCE. THE DRY PATTERN APPEARS TO FINALLY HAVE BROKEN DOWN
AS WE HEAD INTO THE EXTENDED PERIOD. STRENGTHENING LOW PRESSURE
CENTERED NEAR OKLAHOMA ON FRIDAY TRACKS RAPIDLY UP THROUGH THE
CENTRAL GREAT LAKES THROUGH FRIDAY NIGHT…SPREADING A WINTRY MIX
QUICKLY ACROSS OUR FORECAST AREA. GFS HAS 850-925 TEMPS CLIMBING TO
BETWEEN 0 AND 2 DEGREES C OVERNIGHT FRIDAY…PARTICULARLY FROM ALB
SOUTH AND WEST…WHILE A STRONG WARM FRONT STAYING SOUTH SHOULD
ALLOW TEMPERATURES TO COOL…AT LEAST EVAPORATIVELY…TOWARD
DAYBREAK.

THE LOW CONTINUES ON UP THROUGH LABRADOR THROUGH SATURDAY NIGHT AND
THE ACTIVITY TRANSLATES TO MORE OF A LAKE EFFECT SNOW SHOWER REGIME
ON SUNDAY. WITH HIGH PRESSURE BUILDING IN BY MONDAY NIGHT… THIS
SHOULD ALSO CURTAIL. A SYSTEM IN SOUTHERN CANADA ON TUESDAY WILL
BRING A SLIGHT CHC OF RAIN OR SNOW SHOWERS TO SOUTHERN ZONES ON
TUESDAY.
— End Changed Discussion —

&&

.AVIATION /22Z TUESDAY THROUGH SUNDAY/…
VFR CONDITIONS ARE EXPECTED INTO WEDNESDAY MORNING WITH CONDITIONS
LOWERING TO MVFR WITH THE ONSET OF SNOW. IFR CONDITIONS ARE EXPECTED
AFTER 18Z/WEDNESDAY.

HIGH PRESSURE OVER THE REGION WILL CONTINUE TO SHIFT OFF TO OUR EAST
AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT LAKES. CLOUDS WILL BE
ON THE INCREASE TONIGHT…THICKENING AND LOWERING AFTER SUNRISE WITH
WARM AIR ADVECTION SNOW DEVELOPING LATE IN THE MORNING INTO THE EARLY
AFTERNOON. THE SNOW WILL BECOME STEADIER AND HEAVIER DURING THE
AFTERNOON WITH CEILINGS AND VISIBILITIES LOWERING TO IFR.

GUSTY NORTHWESTERLY WINDS WILL DIMINISH THIS EVENING…BECOMING
LIGHT AND VARIABLE TO CALM OVERNIGHT. A LIGHT SOUTHEASTERLY FLOW
WILL DEVELOP WEDNESDAY MORNING INTO THE AFTERNOON.

OUTLOOK…
WED NIGHT…IFR IN SNOW CHANGING TO A WINTRY MIX.
THU…MVFR/IFR. SNOW AT KGFL. RAIN/SNOW AT KALB. RAIN AT KPOU.
THU NIGHT…IMPROVING TO VFR. CHC -SHSN IN THE EVNG.
FRI…VFR. NO SIG WX.
FRI NIGHT…VFR/MVFR. CHC -RA/-SN.
SAT…MVFR WITH CHC IFR. RAIN SHOWERS LIKELY.
SAT NIGHT…VFR/MVFR. CHC -SHRA/-SHSN.
SUN…VFR. WINDY.

&&

.HYDROLOGY…
NO HYDRO PROBLEMS ARE EXPECTED FOR THE NEXT 5 DAYS ON THE MAIN STEM
RIVERS. SOME HYDRO GAGES ARE STILL BEING IMPACTED BY ICE FROM THE
MOHAWK RIVER VALLEY NORTHWARD INTO THE ADIRONDACKS.

A MODERATE TO HEAVY PRECIPITATION EVENT IS EXPECTED WEDNESDAY INTO
THURSDAY WITH TOTAL QPF AROUND THREE QUARTERS OF AN INCH TO JUST
OVER ONE INCH. THERE COULD BE SOME LOCALLY HIGHER AMOUNTS. A LARGE
PORTION OF THE PRECIPITATION WILL FALL AS SNOW AND SLEET…MIXING
WITH SOME RAIN OR FREEZING RAIN ESPECIALLY ACROSS SOUTHERN AREAS.
SEVERAL INCHES OF SNOW AND SLEET ARE EXPECTED FOR MUCH OF THE
REGION…SO NOT MUCH RIVER RESPONSE IS ANTICIPATED EXCEPT FOR SOME
MINOR RISES ACROSS SOUTHERN AREAS WHERE SOME OF THE PRECIP WILL FALL
AS RAIN AND THERE WILL SLIGHT RUNOFF.

DRY WEATHER WILL BRIEFLY RETURN ON FRIDAY…BEFORE ANOTHER SYSTEM
BRINGS A ROUND OF RAIN AND POSSIBLY SNOW TO THE REGION ON SATURDAY.

FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES…INCLUDING OBSERVED
AND FORECAST RIVER STAGES AND LAKE ELEVATIONS…PLEASE VISIT THE
ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE.

&&

.ALY WATCHES/WARNINGS/ADVISORIES…
CT…WINTER WEATHER ADVISORY FROM NOON WEDNESDAY TO NOON EST
THURSDAY FOR CTZ001-013.
NY…WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
MORNING FOR NYZ063.
WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
AFTERNOON FOR NYZ032-033-038>043-047>054-058>061-082>084.
WINTER WEATHER ADVISORY FROM NOON WEDNESDAY TO NOON EST
THURSDAY FOR NYZ064>066.
MA…WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
AFTERNOON FOR MAZ001-025.
VT…WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
AFTERNOON FOR VTZ013>015.

&&

$$
SYNOPSIS…JPV
NEAR TERM…JPV
SHORT TERM…JPV
LONG TERM…ELH
AVIATION…IAA
HYDROLOGY…JPV

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