February 28, 2012 Forecast Discussion

000
FXUS61 KALY 281802
AFDALY

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

.SYNOPSIS…
HIGH PRESSURE WILL MOVE ACROSS THE REGION THIS AFTERNOON
AND TONIGHT. A COMPLEX STORM SYSTEM WILL APPROACH FROM THE
UPPER MISSISSIPPI RIVER VALLEY AND THE GREAT LAKES REGION WEDNESDAY
MORNING. THE STORM/S WARM FRONT WILL INITIALLY BRING SNOW TO THE
REGION WEDNESDAY AFTERNOON BEFORE TRANSITIONING TO A WINTRY MIX OF
SNOW…SLEET…FREEZING RAIN…AND RAIN FOR WEDNESDAY NIGHT INTO
THURSDAY…AS THE DOUBLE BARREL LOW PRESSURE SYSTEM IMPACTS NEW YORK
AND NEW ENGLAND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
HIGH PRESSURE WILL MOVE ACROSS UPSTATE NEW YORK DURING THE
AFTERNOON HOURS. SKIES HAVE CLEAR OUT ACROSS THE MAJORITY OF THE
REGION…WITH JUST SCT CU AROUND. THE EXCEPTION IS ACROSS THE FAR
WESTERN MOHAWK VALLEY/NORTHERN CATSKILLS/WESTERN SCHOHARIE
COUNTY…WHERE SOME LAKE INDUCED STRATOCU CLOUDS ARE IN PLACE.
EVEN THESE CLOUDS SHOULD FINALLY ERODE OVER THE NEXT FEW HOURS
WITH THE LOWERING INVERSION HEIGHT…ALLOWING FOR PARTLY TO MOSTLY
SUNNY SKIES FOR THE EARLY TO MID AFTN. WITH THE SUNSHINE…TEMPS
HAVE WARMED A LITTLE BIT MORE THAN ANTICIPATED IN SOME PLACES…SO
HAVE ADJUSTED MAX TEMPS UP IN A FEW AREAS. MAX TEMPS AROUND THE
CAPITAL REGION WILL BE AROUND 40 DEGREES AND LOWER TO MID 40S FOR
THE MID HUDSON VALLEY…WITH UPPER 20S TO MID 30S FOR THE HIGHER
TERRAIN…BEFORE TEMPS START TO TUMBLE LATE THIS AFTN AND INTO THE
EVENING HOURS.

WITHIN DAYTIME MIXING…WESTERLY WINDS WILL BE GUSTY AT
TIMES…WITH A FEW GUSTS TO AROUND 20-25 MPH. WIND GUSTS SHOULD DROP
OFF RAPIDLY WITH THE LOSS OF HEATING BY THE EVENING HOURS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/…
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 KEEPING 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.

&&

.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 /18Z TUESDAY THROUGH SUNDAY/…
— Changed Discussion —
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 AFTER MIDNIGHT.
THU…MVFR/IFR. SNOW AT KGFL. RAIN/SNOW AT KALB. MAINLY RAIN AT KPOU.
THU NIGHT…IMPROVING TO VFR. CHC -SHSN IN THE EVNG.
FRI…VFR/ NO SIG WX.
FRI NIGHT…VFR/MVFR. CHC -SHRA/-SHSN.
SAT…MVFR WITH CHC IFR. RAIN SHOWERS LIKELY.
SAT NIGHT…VFR/MVFR. CHC -SHRA/-SHSN.
SUN…VFR. 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…FRUGIS/WASULA
NEAR TERM…FRUGIS
SHORT TERM…WASULA
LONG TERM…11
AVIATION…IAA
HYDROLOGY…WASULA

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