March 7, 2013 Forecast Discussion

000
FXUS61 KALY 072128
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
428 PM EST THU MAR 7 2013

.SYNOPSIS…
A STRONG STORM SYSTEM WELL SOUTH AND EAST OF CAPE COD
WILL BRING AN ACCUMULATING SNOWFALL TO EASTERN NEW YORK AND WESTERN
NEW ENGLAND TONIGHT. THE HEAVIEST SNOWFALL IS ANTICIPATED OVER THE
HIGHER TERRAIN OF WESTERN NEW ENGLAND…AND THE EASTERN CATSKILLS.
THE SNOW WILL END FROM NORTHWEST TO SOUTHEAST ACROSS THE REGION
TOMORROW AFTERNOON…WITH HIGH PRESSURE BUILDING IN WITH MODERATING
TEMPERATURES TO ABOVE NORMAL READINGS…AND DRY WEATHER FOR THE
UPCOMING WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/…
AS OF 415 PM EST…A POTENT OCEAN CYCLONE A FEW HUNDRED MILES
SOUTHEAST OF THE 40N/70W BENCHMARK WILL CONTINUE TO INTERACT WITH
A STRONG UPSTREAM UPPER LEVEL DISTURBANCE OVER SRN ONTARIO…THE
CNTRL AND ERN GREAT LAKES REGION. THE UPSTREAM UPPER LEVEL
DISTURBANCE WILL TRY TO MERGE WITH THE OCEANIC CYCLONE. IN DOING
SO…MOISTURE WILL BE CAPTURED FROM THE OCEAN CYCLONE AND THE
BROAD DEFORMATION ZONE WILL KEEP THE SNOWFALL GOING THROUGH THE
OVERNIGHT.

THE TRENDS FROM THE GFS…ECMWF…THE CANADIAN GGEM…AND FINALLY
THE 18Z NAM WILL BE FOR THE UPPER LOW WEST OF THE REGION TO SLIDE
S/SE ACROSS PA TONIGHT…AND BE OVER THE DELMARVA REGION BY
TOMORROW MORNING. THIS UPPER LOW ON THE 1.5 PVU SFC IS THE MORE
IMPRESSIVE OF THE TWO DISTURBANCES ACCORDING TO THE GFS ON THE
DYNAMIC TROP…WITH POTENTIAL TEMPS FALLING TO BELOW 290K ON THE 1.5
PVU SFC.

THE LATEST GFS SHOWS A DECENT 850-700 HPA FGEN REGION BLOSSOMING
OVER ERN NY AND WRN NEW ENGLAND BTWN 00Z-06Z. THE LATEST VWP FROM
KENX SHOWS THE LOW-LEVEL BOUNDARY LAYER FLOW OUT OF THE NORTH. JUST
ABOVE THE BOUNDARY LAYER THE WINDS ARE E/NE. MODEL TRENDS FOR THE
AGEOSTROPHIC COMPONENT OF THE WIND KEEP THE LOW LEVEL FLOW N/NE
TONIGHT. THE PREDOMINANT PTYPE WILL BE SNOW WITH EVAPORATIVE
COOLING ONGOING INITIALLY. THE LARGE SFC T/TD TRENDS ARE LOWERING THIS
AFTERNOON…AS THE COLUMN COOLS CONSIDERABLY. ALSO THE LOWERING SUN
ANGLE SHOULD LET ACCUMS BEGIN QUICKLY ON THE SURFACES IN THE VALLEYS
TONIGHT.

THE UPPER DYNAMICS STRENGTHEN TONIGHT WITH THE QG FORCING INCREASING
WITH THE STRONG LOW TO MID LEVEL FGEN WITHIN THE BROAD
DEFORMATION ZONE OF THE STORM SYSTEM. BETTER PCPN EFFICIENCY
OCCURS IN THE FAVORABLE DENDRITIC SNOW GROWTH REGION FROM THE
HUDSON RIVER VALLEY EAST TONIGHT. THE SNOW GROWTH REGION STARTS
OUT HIGH FOR THE ALY BUFKIT PROFILE AT 9-15 KFT AGL…AND THEN
GRADUALLY LOWERS. THIS SHOULD FAVORS LOCATIONS EAST OF THE CAPITAL
REGION TONIGHT…WHERE WE HAVE THE HIGHER SNOW TALLIES. THIS IS A
VERY ATYPICAL SITUATION FOR MODERATE TO HEAVY SNOW AMOUNTS OVER
THE FCST AREA. SNOW BANDLETS…AND BANDS OF SNOW SHOULD PIVOT IN
OVER THE REGION AT TIMES TONIGHT. ELEVATION WILL ALSO PLAY A KEY
ROLE WHERE THE HIGHER TOTALS OCCUR.

THE ADVISORIES REMAIN UP FOR THE ERN
CATSKILLS…HELDERBERGS…SCHOHARIE VALLEY…TACONICS…AND WRN
NEW ENGLAND. TONIGHT EXPECT ACCUMULATIONS OF 3 TO 7 INCHES IN
THESE AREAS. EXPECT 1 TO 3 INCHES IN THE CAPITAL DISTRICT…AND
THE MID HUDSON VALLEY. A HALF AN INCH TO A FEW INCHES NORTH AND
WEST OF THE HUDSON RIVER VALLEY. THERE WILL BE A SHARP GRADIENT
WITH THE SNOWFALL. SNOW TO LIQUID RATIOS OF 8-10:1 WERE USED FOR
THE DURATION OF THE EVENT.

MIN TEMPS TONIGHT WILL GENERALLY BE IN THE MID 20S TO NEAR 30F
OVER THE VALLEY LOCATIONS…AND LOWER TO M20S OVER THE MTNS.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/…
TOMORROW…THE SNOW GRADUALLY DIMINISHES FROM NW TO SE ACROSS THE
FCST AREA AFTER SUNRISE…AS THE UPSTREAM/SECONDARY UPPER LOW
SLIPS SOUTH OF THE REGION…AND MERGES WITH THE SPRAWLING OCEANIC
LOW. ADDITIONAL SNOW AMOUNTS WILL BE ON THE LIGHT SIDE FROM A
COATING TO A FEW INCHES. WE ARE EXPECTING STORM TOTALS OF 4-8
INCHES OVER THE SRN VT…THE BERKSHIRES…AND THE LITCHFIELD HILLS.
THERE ALSO COULD BE SOME 4-8 INCH AMOUNTS OVER PARTS OF THE
CATSKILLS…AND HELDERBERGS. 3-6" AMOUNTS WILL BE COMMON IN THE
TACONICS…SCHOHARIE AND MONTGOMERY COUNTIES. THE CAPITAL DISTRICT
AND MID HUDSON VALLEY WILL RECEIVE 2-4". THE LAKE GEORGE REGION AND
THE W-CNTRL MOHAWK VALLEY WILL LIKELY GET 1-3". THE SRN DACKS MAY
ONLY GET A HALF AN INCH TO TWO INCHES OR SO…AS THEY WILL BE ON
THE WRN PERIPHERY OF THE STORM SYSTEM.

THERE COULD BE SOME 7 OR 8" AMOUNTS OVER THE HIGHER WRN NEW
ENGLAND TERRAIN…BUT IT WILL OCCUR IN A 18-24-HR OR SO TIME
FRAME. OUR CURRENT CRITERIA FOR 24 HRS IS 9". IT WILL BE HARD
PRESSED TO GET WIDESPREAD 9" AMOUNTS WITH THIS SYSTEM.

SLIGHT CHC OR LOW CHC POPS TAPER FROM THE CAPITAL REGION SOUTH AND
EAST IN THE AFTERNOON. THE PCPN COULD CHANGE TO LIGHT RAIN WITH THE
INCREASING SUN ANGLE…AND THE BOUNDARY LAYER WARMING. SOME
SUNSHINE COULD OCCUR FROM THE CAPITAL REGION NORTH AND WEST. THE
LOW LEVEL WINDS WILL STRENGTHEN FROM THE N/NW AT 15 TO 25 MPH WITH
GUSTS TO 35 MPH ESPECIALLY FROM THE CAPITAL REGION SOUTHWARD.
TEMPS WILL RISE INTO THE U30S TO L40S IN THE VALLEYS…WITH GENERALLY
LOWER TO MID 30S OVER THE MTNS. HIGH PRESSURE WILL BE BUILDING IN
FROM THE GREAT LAKES REGION…AND OHIO VALLEY LATE IN THE DAY.

TOMORROW NIGHT…THE WINDS WILL GRADUALLY DIMINISH WITH THE SFC
HIGH BUILDING IN. THE SUBSIDENCE FROM THE ANTICYCLONE WILL YIELD
CLEAR/MOSTLY CLEAR AND COLD CONDITIONS WITH LOWS IN THE TEENS
NORTH OF THE CAPITAL DISTRICT…AND LOWER TO MID 20S TO THE SOUTH.

SATURDAY…LOW AND MID LEVEL HEIGHTS INCREASE OVER THE NORTHEAST
WITH A RIDGE BUILDING IN FROM THE SOUTHEAST AND MID ATLANTIC REGION.
THE SFC HIGH WILL SETTLE OVER QUEBEC AND THE NORTHEAST. WARM
ADVECTION WILL BE OCCUR AT H850 WITH TEMPS OF +1C TO +2C MOVING
OVER THE FCST AREA. MAX TEMPS WILL NUDGE ABOUT 5 DEGREES ABOVE
NORMAL WITH MOSTLY SUNNY/SUNNY SKIES AND LIGHT WINDS.

SATURDAY NIGHT…IDEAL RADIATIONAL COOLING NIGHT WITH CLEAR SKIES
AND LIGHT TO CALM WINDS TO START…SHOULD ALLOW TEMPS TO PLUMMET
BELOW FREEZING TO SLOW DOWN ANY DIURNAL SNOW MELT DURING THE DAYTIME.
EXPECT LOWS IN THE 20S…EXCEPT SOME TEENS OVER THE LAKE GEORGE
REGION…AND THE SRN DACKS.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/…
HIGH PRESSURE SHOULD CONTROL THE WEATHER SUNDAY THROUGH SUNDAY
NIGHT…BUT AS THE HIGH PRESSURE EXITS OFFSHORE AND THE NEXT SYSTEM
BEGINS TO APPROACH…WARM ADVECTION SHOULD INCREASE THROUGH THE
PERIOD…AND CLOUDS SHOULD INCREASE…ESPECIALLY THROUGH SUNDAY
NIGHT. HIGHS SUNDAY IN THE 40S TO NEAR 50.

STRONG WARM ADVECTION AND INCREASING ISENTROPIC LIFT SHOULD RESULT
IN INCREASING CHANCES FOR SHOWERS MONDAY INTO MONDAY NIGHT…WITH
LIKELY FOR MONDAY NIGHT. DEPENDING ON HOW EARLY THE SHOWERS ARRIVE
MONDAY MORNING…SOME WESTERN AREAS COULD SEE A MIX AT THE BEGINNING
OF THE PRECIPITATION. TEMPERATURES SHOULD WARM TO HIGHS IN THE 40S
TO AROUND 50 MONDAY. THEN…MONDAY NIGHT…DEPENDING ON WHEN THE
FRONT TRACKS THROUGH…MANY AREAS SHOULD REMAIN ABOVE FREEZING
MONDAY NIGHT. THE AREA THAT COULD GET TO AROUND FREEZING WOULD BE IN
THE WESTERN MOHAWK VALLEY AND SOUTHERN ADIRONDACKS WHERE SNOW
SHOWERS COULD MIX IN.

MORE SCATTERED SHOWERS ASSOCIATED WITH THE DECENT BOUNDARY LAYER
THERMAL GRADIENT ASSOCIATED WITH THE FRONT INTO TUESDAY MORNING.
STILL…BEFORE THE DEEP COLD ADVECTION BEGINS LATER TUESDAY…HIGHS
COULD GET INTO THE 40S TO AROUND 50 AGAIN. DEEPER COOLING OCCURS
LATER TUESDAY AND THROUGH WEDNESDAY…BUT ONLY TO NEAR NORMAL
TEMPERATURES. THERE COULD BE SOME LAKE EFFECT SNOW SHOWER ACTIVITY
THAT SETS UP IN THE WESTERN MOHAWK VALLEY…SOUTHERN ADIRONDACKS…
SCHOHARIE VALLEY AND EASTERN CATSKILLS THROUGH THURSDAY.

HOWEVER…BECAUSE THE COOLING IS NOT TOO EXTREME…SNOW SHOWER
ACTIVITY AT NIGHT WILL TREND TO A MIX OF RAIN AND SNOW SHOWERS
DURING THE DAY…ESPECIALLY IN THE CENTRAL AND EASTERN MOHAWK
VALLEY…HUDSON VALLEY AND NW CT…WITH HIGHER ELEVATIONS SEEING THE
BETTER CHANCES AT JUST CONSISTENT SCATTERED SNOW SHOWERS. HIGHS
WEDNESDAY IN THE LOWER TO MID 40S…MID TO UPPER 30S IN HIGHER
ELEVATIONS. HIGHS THURSDAY IN THE UPPER 30S TO LOWER 40S…LOWER TO
MID 30S HIGHER ELEVATIONS.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/…
LIGHT SNOW OR FLURRIES HAS OVERSPREAD MOST OF THE REGION. EXPECT
MAINLY VFR/MVFR LIGHT SNOW AT KALB/KGFL DUE TO NORTHERLY WINDS
BRINGING DRIER AIR INTO THE REGION. AT KPOU/KPSF EXPECT MVFR LIGHT
SNOW TO OCCASIONALLY IFR SNOW FOR THE REST OF THE AFTERNOON. AS THE
UPPER LOW OVER THE GREAT LAKES REGION TRACKS TO THE SOUTHWEST OF THE
REGION TONIGHT…THE SNOW WILL BECOME MORE WIDESPREAD TONIGHT. AFTER
00Z THIS EVENING HAVE GENERALLY FORECAST IFR CONDITIONS AT ALL THE
TAF SITES THROUGH EARLY FRIDAY MORNING…WITH A SLOW IMPROVEMENT
FROM NORTH TO SOUTH TO MVFR AND THEN VFR CONDITIONS.

NORTH TO NORTHEAST WINDS WILL PERSIST AT 8-12 KT THROUGH
TODAY…WITH OCCASIONAL GUSTS OF 15-25 KT POSSIBLE…ESP AT KPOU AND
KALB. WINDS WILL GRADUALLY BACK MORE INTO THE NORTH AT AROUND 10 KT
AFTER SUNSET…THEN PICK UP FROM THE NORTH TO NORTHWEST ON FRIDAY AT
10 TO 15 KTS WITH GUSTS OF 20 TO 25 KTS.

OUTLOOK…
FRI AFTN…MAINLY VFR…POSSIBLE MVFR/IFR IN -SN LIKELY AT KPOU AND
KPSF.
FRI NT-SUN NT…VFR. NO SIG WX.
MON…VFR/MVFR. CHC RAIN SHOWERS.

&&

.HYDROLOGY…
NO WIDESPREAD HYDRO PROBLEMS ARE EXPECTED THE NEXT 5 DAYS.
HOWEVER…SNOW MELT WILL BE ON THE INCREASE DURING THE WEEKEND
INTO NEXT WEEK…AS TEMPERATURES RISE ABOVE NORMAL.

THE CURRENT STORM SYSTEM IS EXPECTED TO BRING A QUARTER TO THREE
QUARTERS OF LIQUID EQUIVALENT TO THE FCST AREA TONIGHT INTO FRIDAY
AFTERNOON. DRY WEATHER IS EXPECTED FOR MOST OF THE WEEKEND. THE
HIGHER QPF WILL BE ACROSS PORTIONS OF WESTERN NEW ENGLAND. LESS
AMOUNTS OVER THE SRN DACKS REGION. THE NERFC QPF WAS USED CLOSELY
THIS CYCLE.

NO TIDAL FLOODING IS EXPECTED NEAR POUGHKEEPSIE AT THIS TIME BASED
ON THE LATEST FORECASTS FROM THE NERFC…AND THE LOW LEVEL WINDS BE
FROM THE NORTH TO NORTHEAST TONIGHT INTO TOMORROW.

TEMPERATURES ARE EXPECTED TO MODERATE TO ABOVE NORMAL ON THE
WEEKEND…HOWEVER WITH TEMPERATURES FALLING BELOW FREEZING AT
NIGHT…SO THERE WILL BE DIURNAL SNOWMELT. A COLD FRONT MAY BRING
SOME SHOWERS TO THE REGION MONDAY NIGHT THROUGH TUESDAY.

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 UNTIL NOON EST FRIDAY FOR CTZ001-013.
NY…WINTER WEATHER ADVISORY UNTIL NOON EST FRIDAY FOR NYZ040-047-
048-051-054-058-061-063-066.
MA…WINTER WEATHER ADVISORY UNTIL NOON EST FRIDAY FOR MAZ001-025.
VT…WINTER WEATHER ADVISORY UNTIL NOON EST FRIDAY FOR VTZ013>015.

&&

$$
SYNOPSIS…WASULA
NEAR TERM…WASULA
SHORT TERM…WASULA
LONG TERM…NAS
AVIATION…GJM
HYDROLOGY…BGM/WASULA

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