February 28, 2012 Forecast Discussion

000
FXUS61 KALY 281159
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
659 AM EST TUE FEB 28 2012

.SYNOPSIS…
HIGH PRESSURE WILL BUILD IN FROM THE GREAT LAKES REGION
WITH SEASONABLY COLD AND DRY WEATHER TODAY INTO TONIGHT. A COMPLEX
STORM SYSTEM WILL APPROACH FROM THE UPPER MISSISSIPPI RIVER VALLEY
AND THE GREAT LAKES REGION WEDNESDAY MORNING. THE WARM FRONT TO THE
SYSTEM WILL INITIALLY BRING SNOW TO THE REGION WEDNESDAY AFTERNOON
BEFORE TRANSITIONING TO A WINTRY MIX OF SNOW…SLEET…FREEZING
RAIN…AND RAIN WEDNESDAY NIGHT INTO THURSDAY…AS THE DOUBLE BARREL
LOW PRESSURE SYSTEM IMPACTS NEW YORK AND NEW ENGLAND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
— Changed Discussion -
AS OF 650 AM EST…THE CLIPPER LOW HAS MOVED EAST OF THE GULF OF
MAINE. A SECONDARY COLD FRONT IS BEGINNING TO MOVE ACROSS CNTRL-
ERN NY INTO NEW ENGLAND. THE MOST PERSISTENT SNOW SHOWERS AND
FLURRIES CONTINUE TO BE IN THE WRN DACKS. WE KEPT THEM GOING UNTIL
THE LATE MORNING. THE SATELLITE TRENDS INDICATE MOSTLY
CLOUDY/CLOUDY CONDITIONS THIS MORNING…BEFORE THINNING IN THE
LATE MORNING/EARLY PM. THE WINDS HAVE BEEN BLUSTERY THIS MORNING.
WE INCREASED THE GUSTS TO 25-30 KTS. THIS IS DUE TO THE STRONG
LOW-LEVEL PRESSURE GRADIENT BETWEEN THE DEPARTING LOW INTO NOVA
SCOTIA…AND HIGH PRESSURE OVER THE LOWER GREAT LAKES REGION…AND
SRN ONTARIO. MIN TEMPS WILL BE MUCH HIGHER THIS MORNING. WE
RETOOLED THE HOURLY T/TD/RH APPARENT TEMPS TRENDS BASED ON
OBSERVATIONS. TEMPS COULD BE STEADY OR DROP A LITTLE AFTER
NOONTIME WITH THE SECOND PUSH OF COLD ADVECTION.

HIGH PRESSURE WILL CONTINUE TO BUILD IN FROM THE GREAT LAKES
REGION…AND E/SE ONTARIO. THE SUBSIDENCE INVERSION WILL LOWER
ASSOCIATED WITH THE ANTICYCLONE ENDING THE ISOLD-SCT FLURRIES AND
SNOW SHOWERS…AND DECREASING THE CLOUD COVER ACROSS THE REGION IN
THE AFTERNOON. THE LOW AND MID LEVEL COLD AIR ADVECTION WILL
CONTINUE INTO THE AFTERNOON…WITH H850 TEMPS FALLING TO -8C TO
-11C FROM THE CAPITAL REGION NORTH AND WEST…AND -3C TO -8C SOUTH
AND EAST.

TEMPS TODAY WILL AVERAGE CLOSE TO SEASONAL READINGS WITH MID 30S TO
L40S IN THE VALLEYS LOCATIONS…AND U20S TO M30S OVER THE HILLS
AND MTNS.
- End Changed Discussion -

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/…
— Changed Discussion —
…A WINTER STORM WATCH HAS BEEN ISSUED FOR THE ENTIRE FORECAST
AREA STARTING AT NOONTIME WEDNESDAY…

TONIGHT…THIS WILL BE THE CALM BEFORE THE STORM…AS HIGH
PRESSURE WILL CREST OVER SRN QUEBEC…NY AND NEW ENGLAND. MID AND
HIGH CLOUDS WILL BE INCREASING QUICKLY FROM THE SOUTH AND WEST.
THE ANTICYCLONE WILL FUNNEL SOME SHALLOW…COLD…AND DRY AIR INTO
REGION. THE WINDS SHOULD DECOUPLE AND BECOME LIGHT TO CALM WITH
SOME RADIATIONAL COOLING THROUGH THE THIN CIRRUS OR MID LEVEL
CLOUDS. LOWS WILL GENERALLY BE IN THE UPPER TEENS TO LOWER
20S…WITH SOME UPPER SINGLE DIGITS TO MID TEENS OVER THE SRN
DACKS. MEANWHILE…UPSTREAM A CLOSED H500 LOW WILL BE MOVING INTO
THE UPPER MIDWEST. THIS PRIMARY LOW AT THE SFC WILL SLOWLY CHURN
INTO THE GREAT LAKES REGION ON WED…AS THE WARM FRONT IN ADVANCE
OF IT WILL RACE TOWARDS THE OHIO VALLEY AND PA BY DAYBREAK.

WEDNESDAY…THE CONSENSUS WAS TO GO WITH THE ECMWF/NAM/CAN GGEM AND
LATEST SREF WAS THE WAY TO GO WITH THE STORM SYSTEM WED PM THRU THU.
THE GFS THERMAL FIELDS WERE TO WARM TOO FAST. THE QUESTION WILL BE
HOW FAST THE LOW LEVEL DRY AIR WILL HOLD IN PLACE BEFORE THE
STRONG ISENTROPIC LIFT ON THE 295K COMMENCES THE SNOWFALL. THE NAM
SHOWS VERY STRONG LIFT GENERATED FROM THE THERMAL ADVECTION. IT
SHOULD MOVE IN QUICKLY FROM SOUTHWEST TO NORTHEAST DURING THE LATE
MORNING INTO THE AFTERNOON.

OUR CONFIDENCE IS MODERATE FOR THE WATCH /AT THE 50 PERCENT
LEVEL/. THIS WILL BE A MILLER TYPE B SYSTEM WITH A PRIMARY AND
SECONDARY LOW IMPACTING THE FORECAST AREA. THE INITIAL THRUST OF
SNOWFALL WILL GENERALLY PRODUCE 2 TO 5 INCHES FROM THE CAPITAL
REGION SOUTH BEFORE NIGHTFALL…AND 1 TO 3 INCHES NORTH OF THE
CAPITAL REGION. THE AFTERNOON COMMUTE WILL BE IMPACTED BY THE
SNOWFALL. DESPITE THE VERY LATE FEB SUN ANGLE…WE BELIEVE THE WET
BULB/EVAPORATIVE COOLING WILL START THE PCPN AS SNOW. THERE COULD
BE SOME MIXING TOWARDS 00Z/THU OVER THE EXTREME SOUTH WITH SOME
SLEET…AS WARMER AIR MOVES IN ABOVE H850. THE CRITICAL PARTIAL
THICKNESSES START TO INCREASE WELL ABOVE 1540 METERS /MORE LIKE
1560 METERS/ ON THE NAM AROUND 00Z.

WEDNESDAY NIGHT INTO THURSDAY…PRECARIOUS FORECAST TIME FRAME ON
WHAT PTYPES OCCUR WHERE IN THE FORECAST AREA. THE LATEST SREFS AND
GEFS INDICATE ICING ZONE MAY GET UP INTO THE CAPITAL REGION WITH
MEAN ICE VALUES IN THE TENTH TO QUARTER OF AN INCH RANGE. THE
QUESTION WILL BE HOW FAST A SECONDARY LOW PRESSURE /RAPID
CYCLOGENESIS/ FORMS NEAR COASTAL NJ…OR SOUTH OF LONG ISLAND. IF
IT FORMS QUICKER…THEN THE LOW LEVEL AGEOSTROPHIC WIND MAY TURN
NORTHERLY KEEPONG SNOW…AND SLEET MAINLY FROM ALBANY NORTH.
NONETHELESS…THE WINTER STORM WATCH IS POSTED FOR THE ENTIRE
FORECAST AREA FROM NOON ON WED TO 6 PM ON THU. WE ENDED IT EARLIER
FOR ULSTER…DUTCHESS…AND LITCHFIELD AT NOONTIME ON THU. THE ICY
MIX MAY CHANGE TO RAIN QUICKLY THERE BY THE LATE MORNING…AS
TEMPS RISE WELL ABOVE FREEZING. WE ARE VERY CONCERNED ABOUT AN
ICING ZONE SOMEWHERE IN THE FORECAST AREA WITH A TENTH TO A
QUARTER OF AN ICE. BASED ON THE GUIDANCE…ESPECIALLY THE ECMWF
AND NAM AS WELL AS MODEL SOUNDINGS IN THESE LOCATIONS…THIS COULD BE
SOMEWHERE FROM THE ERN CATSKILLS E/NE IN TO THE MID HUDSON
VALLEY/CAPITAL REGION/BERKSHIRES. OVERALL…WE ARE LOOKING AT ONE
TO TWO TENTHS OF ICE ACCRETIONS IN MOST OF THE FORECAST
AREA…EXCEPT THE SRN DACKS…AND LAKE GEORGE REGION…WHERE
POTENTIALLY A HALF A FOOT TO A FOOT OF SNOW AND SLEET MAY OCCUR BY
THURSDAY LATE AFTERNOON. MOST OTHER LOCATIONS MAY HAVE 3 TO 8 OR
SO INCHES OF SNOW WITH A TENTH OR TWO OF ICE. THIS IS WHY WE PUT
OUT THE LATE 3RD TO 5TH PERIOD WATCH.

THE PRECIPITATION IS EXPECTED TO CHANGE TO RAIN IN THE VALLEYS AND
LOCATIONS SOUTH AND EAST OF THE CAPITAL REGION BRIEFLY THU
AFTERNOON…BUT THE PRIMARY LOW AND ITS ASSOCIATED UPPER LEVEL LOW
MOVE OVER UPSTATE NY. THE MID LEVEL LAPSE RATES STEEPEN…AND THE
CYCLONIC VORTICITY ADVECTION KICKS OFF CONTINUED SNOWFALL
ESPECIALLY FROM THE CAPITAL REGION NORTH AND WEST. AS THE SFC
REFLECTION SHIFTS EASTWARD…THE LOW AND MID LEVEL DEFORMATION
ZONE KEEPS THE SNOWFALL GOING INTO THE EARLY EVENING. WE WENT
CLOSER TO COLDER METMOS GUIDANCE FOR TEMPS…WED NIGHT AND THU.
THE GFS HAD MUCH WARMER TEMPS WITH A DRY SLOT MOVING IN…WE
DIDN/T BUY INTO THIS SCENARIO.

THU NIGHT…THE SNOW TAPERS TO SCATTERED SNOW SHOWERS AND
FLURRIES…LINGERING ESPECIALLY IN THE FAVORED WESTERLY UPSLOPE
AREAS OF THE WRN DACKS…SRN GREENS…AND TACONICS. ADDITIONAL
LIGHT ACCUMULATIONS WILL BE POSSIBLE.

STAY TUNED FOR UPDATES WITH THIS STORM…AND SLIGHT CHANGES WITH
THE PRECIPITATION TYPE…AND TRACK AND EVOLUTION OF THIS COMPLEX
STORM COULD MAKE A TREMENDOUS DIFFERENCE.

THANK YOU FOR THE COLLABORATION WITH WFO/S
BUF…BGM…OKX…BOX…AND BTV. ALSO THANKS FOR COLLAB WITH HPC/S
WINTER WEATHER DESK.
— End Changed Discussion —

&&

.LONG TERM /FRIDAY THROUGH MONDAY/…
ACTIVE WEATHER EXPECTED FOR THE EARLY PORTION OF THE LONG TERM
PERIOD WITH MUCH QUIETER WEATHER FOR THE LATER HALF OF THE WEEKEND
INTO EARLY NEXT WEEK. A RIDGE OF HIGH PRESSURE IS EXPECTED TO BE
OVER THE REGION ON FRIDAY. THIS WILL BE FOLLOWED BY A MID LEVEL
TROUGH WHICH IS EXPECTED TO MOVE EAST FROM THE UPPER GREAT LAKES
INTO SOUTHEAST CANADA AND THE NORTHEAST US…AS THE SURFACE LOW
TRACKS THROUGH THE UPPER GREAT LAKES AND EASTERN QUEBEC LIFTING A
WARM FRONT TOWARD OUR REGION SATURDAY MORNING AND DRAGGING AN
OCCLUDED FRONT THROUGH OUR REGION SATURDAY EVENING.

ON FRIDAY EXPECT A LULL IN THE PCPN WITH SFC HIGH PRESSURE BRIEFLY
BUILDING INTO FA. EXPECT HIGHS ON FRIDAY IN THE LOWER 30S TO LOWER
40S.

FRIDAY NIGHT INTO SATURDAY NIGHT…BOTH GFS AND ECMWF SHOW A DEEP
UPPER LOW AND SURFACE LOW LIFTING NORTHEAST FROM THE UPPER GREAT
LAKES PASSING SOUTH OF JAMES BAY. HOWEVER DIFFERENCES EXIST IN THE
EXACT TRACK…SPEED OF SYSTEM AND AMOUNT OF DEEPENING. THIS SYSTEM
WILL BRING MORE PCPN TO THE FA WITH THE GEFS PLUMES INDICATING A
MAINLY RAIN TO SNOW SCENARIO…ALTHOUGH IT MAY BE INITIALLY COLD
ENOUGH FOR SOME LIGHT SNOW AT THE ONSET WHEN PCPN ARRIVES LATER
FRIDAY NIGHT. HOWEVER…AS STRONG WARM AIR ADVECTION IS EXPECTED
WITH A WARM FRONT LIFTING NORTH INTO THE REGION ON SATURDAY…A
QUICK CHANGEOVER TO RAIN IS LIKELY…BEFORE CHANGING BACK TO
SCATTERED SNOW SHOWERS SATURDAY NIGHT IN THE WAKE OF THE OCCLUDED
FRONT WHICH IS EXPECTED TO BE WELL EAST OF THE FA BY LATE SATURDAY
NIGHT. SOME STRONG GUSTY SOUTHERLY WINDS ARE POSSIBLE LATE FRIDAY
NIGHT INTO SATURDAY AFTERNOON…HOWEVER STRENGTH OF WINDS WILL BE A
FUNCTION OF SURFACE LOW TRACK AS WELL AS SPEED AT WHICH LOW DEEPENS
AND TOO MUCH UNCERTAINTY EXISTS TO INCLUDE IN HWO AT THIS TIME.
EXPECT LOWS FRIDAY NIGHT IN THE MID 20S TO MID 30S WITH HIGHS ON
SATURDAY IN THE 40S TO LOWER 50S AND LOWS SATURDAY NIGHT IN THE 20S
TO LOWER 30S.

SUNDAY THROUGH MONDAY LOOKS MAINLY DRY AT THIS POINT IN TIME WITH
SOME SCATTERED LAKE EFFECT SNOW SHOWERS IMPACTING MAINLY THE WESTERN
HALF OF THE FA ON SUNDAY. HIGHS ON SUNDAY ARE EXPECTED TO BE IN THE
IN THE 30S EXCEPT LOW TO MID 40S IN THE HUDSON VALLEY AND FAR
SOUTHEAST PORTION OF FA WITH LOWS SUNDAY NIGHT MAINLY IN THE TEENS
AND 20S AND HIGHS ON MONDAY RANGING FROM THE MID TO UPPER 20S
NORTHWEST TO MID 40S SOUTHEAST.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/…
— Changed Discussion —
VFR CONDITIONS ARE EXPECTED TO PERSIST AT THE TAF SITES THROUGH THE
TAF PERIOD ENDING AT 12Z WEDNESDAY. GUSTY WEST TO NORTHWEST WINDS
REMAIN AT KGFL AND KALB IN THE WAKE OF THE COLD FRONT ASSOCIATED
WITH THE CLIPPER TYPE SYSTEM. EXPECT MAINLY STRATOCU BKN-OVC040-060
THROUGH EARLY TO MID MORNING AND THEN CLEARING AS A RIDGE OF HIGH
PRESSURE BUILDS IN FROM THE EASTERN GREAT LAKES. MID AND HIGH CLOUDS
WILL START TO INCREASE LATE THIS AFTERNOON AND BECOME THICKER THIS
EVENING WITH STRATOCU DEVELOPING LATE TONIGHT AHEAD OF THE NEXT
STORM SYSTEM MOVING INTO THE WESTERN GREAT LAKES WEDNESDAY MORNING.

WEST TO NORTHWEST WINDS 6-14 KTS WITH GUSTS 15-28 KTS WILL GRADUALLY
DIMINISH LATER THIS MORNING EXCEPT AT KALB WHERE NORTHWEST WINDS OF
12 KTS WITH GUSTS TO 22 KTS WILL PERSIST THRU MUCH OF THE DAY DUE TO
CHANNELING DOWN THE MOHAWK VALLEY. NORTHWEST WINDS WILL DIMINISH TO
5-10 KTS LATE THIS AFTERNOON AND BECOME LIGHT AND VARIABLE THIS
EVENING AND REMAIN LIGHT AND VARIABLE OR CALM OVERNIGHT.

OUTLOOK…
WED-THU…MVFR BCMG IFR/LIFR WITH A WINTRY MIX OF PCPN.
THU NGT-FRI…BCMG VFR PCPN ENDING.
FRI NGT-SAT…CHC MVFR/IFR -SHRA/-SHSN. WINDY.
— End Changed Discussion —

&&

.HYDROLOGY…
NO HYDRO WIDESPREAD HYDRO RELATED 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 IN THE ALBANY
HYDRO SERVICE AREA NORTHWARD.

A MODERATE TO HEAVY PRECIPITATION EVENT IS LIKELY WEDNESDAY INTO
THURSDAY WITH TOTAL QPF IN THE THREE QUARTERS OF AN INCH TO ONE INCH
RANGE. THERE COULD BE SOME LOCALLY HIGHER AMOUNTS OF QPF. A LARGE
PORTION OF THE PRECIPITATION MAY FALL AS SNOW AND SLEET…MIXING
WITH SOME RAIN OR FREEZING RAIN ESPECIALLY FROM THE CAPITAL REGION
MOHAWK VALLEY…SOUTH AND EAST. SEVERAL INCHES OF SNOW AND SLEET
ARE EXPECTED NORTH AND WEST OF THE CAPITAL REGION.

DRY WEATHER WILL BRIEFLY RETURN ON FRIDAY…BEFORE ANOTHER SYSTEM
BRINGS SOME RAIN AND SNOW SHOWERS ON THE WEEKEND.

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 STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
MORNING FOR CTZ001-013.
NY…WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
MORNING FOR NYZ063>066.
WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
AFTERNOON FOR NYZ032-033-038>043-047>054-058>061-082>084.
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…WASULA
NEAR TERM…WASULA
SHORT TERM…WASULA
LONG TERM…11
AVIATION…11
HYDROLOGY…WASULA

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