December 2, 2014 Forecast Discussion

000
FXUS61 KALY 021747
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
1247 PM EST TUE DEC 2 2014

.SYNOPSIS…
HIGH PRESSURE WILL MOVE ACROSS SOUTHEAST CANADA THIS
AFTERNOON…AND INTO THE CANADIAN MARITIMES TONIGHT…BRINGING
COLDER AIR TO THE REGION. A FAST MOVING STORM SYSTEM WILL BRING A
LIGHT WINTRY MIX TO THE REGION TONIGHT AND EARLY WEDNESDAY INCLUDING
SNOW…SLEET AND FREEZING RAIN…BEFORE CHANGING TO PLAIN RAIN
WEDNESDAY MORNING. HIGH PRESSURE WILL ONCE AGAIN BUILD ACROSS THE
REGION FOR THURSDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
AS OF 1236 PM EST…A 1042 HPA SFC ANTICYCLONE CONTINUES TO SLOWLY
SHIFT EASTWARD OVER SRN QUEBEC AND NEW BRUNSWICK. LOW PRESSURE
CONTINUES TO LIFT NORTHEAST FROM KY AND TN. THE LATEST SATELLITE
PICTURE CONTINUES TO SHOW MID AND HIGH CLOUDS INCREASING FROM THE
SOUTH AND WEST. IT HAS ALREADY BECOME MOSTLY CLOUDY OVER THE MID
HUDSON VALLEY AND ERN CATSKILLS. SOME LIGHT OVER RUNNING PCPN HAS
ALREADY BEGUN OVER ERN PA AND N-CNTRL NJ. THE COLUMN IS MUCH DRIER
IN THE LOW TO MID LEVELS BASED ON THE 12Z KALB SOUNDING. THE
STRENGTHENING ISENTROPIC LIFT DURING THE AFTERNOON WILL ALLOW
LIGHT SNOW TO BREAK OUT…ESPECIALLY FROM THE CAPITAL REGION SOUTH
BETWEEN 3 AND 6 PM. IT WILL TAKE MORE TIME TO SATURATE THE COLUMN
FURTHER TO THE NORTH. ANY ACCUMS SHOULD REMAIN LIGHT DURING THIS
TIME FRAME…GENERALLY A COATING TO PERHAPS A FEW TENTHS OF AN
INCH CLOSE TO INTERSTATE 84…AND PERHAPS A DUSTING IN PORTIONS OF
THE CAPITAL REGION. A HALF INCH OR LESS IS POSSIBLE OVER THE ERN
CATSKILLS. THE WINTER WX ADVISORY LOOKS GOOD AT THIS POINT. MAX
TEMPS WERE LOWERED A FEW DEGREES BASED ON THE INCREASING CLOUDS
AND THE CHILLY AIR FUNNELING DOWN THE CHAMPLAIN VALLEY INTO ERN
NY.

EXPECT MAX TEMPS TO REACH THE 30-35F RANGE IN VALLEY AREAS…AND
MAINLY 25-30F ACROSS THE HIGHER TERRAIN THIS AFTERNOON.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/…
WINTER WEATHER ADVISORIES IN EFFECT FOR MOST OF THE FORECAST
AREA FOR TONIGHT/EARLY WEDNESDAY…

TONIGHT…A MID LEVEL SHORTWAVE WILL APPROACH FROM THE OHIO VALLEY
REGION EARLY TONIGHT. AHEAD OF THIS FEATURE…A STRONG LOW LEVEL
JET WILL DEVELOP AND TRANSLATE ACROSS THE REGION THROUGH THIS
EVENING…PROPELLED BY H850 WINDS OF 50-60 KT. VERY STRONG LOW
LEVEL ISENTROPIC LIFT…ENHANCED BY MOISTURE TRANSPORT FROM THE
NEARBY ATLANTIC OCEAN…WILL ALLOW PRECIPITATION TO BLOSSOM ACROSS
THE REGION BETWEEN 7 AND 10 PM. IN FACT…THERE ARE SOME
SUGGESTIONS OF WEAK ELEVATED INSTABILITY…AS NOTED BY STEEPENING
LAPSE RATES WITHIN THE H700-H500 LAYER. SO…EMBEDDED CONVECTIVE
ELEMENTS WITHIN A BAND OR AREA OF STRATIFORM PRECIP WILL LIKELY
PRODUCE MODERATE TO HEAVY PRECIP…SHORTLY AFTER ITS ONSET. THE
THERMAL PROFILE SHOULD INITIALLY BE COLD ENOUGH FOR SNOW…SO A
BURST OF MODERATE TO HEAVY SNOW COULD OCCUR EARLY TONIGHT. FOR
AREAS MAINLY SOUTH OF INTERSTATE 90…MILDER AIR WILL EDGE
NORTHWARD…LIMITING THE DURATION THAT THE SNOW WILL OCCUR…AND
LIMITING SNOWFALL AMTS TO GENERALLY 1-3 INCHES…LEAST ACROSS THE
MID HUDSON VALLEY AND SOUTHERN LITCHFIELD CO. HOWEVER…FURTHER N
AND W…WHERE THE COLD AIR WILL REMAIN DEEPER A BIT
LONGER…GREATER SNOWFALL ACCUMS ARE EXPECTED…WITH 3-6 INCHES
POSSIBLE ACROSS PORTIONS OF THE LAKE GEORGE REGION…THE NORTH SIDE
OF THE MOHAWK VALLEY…AND PORTIONS OF THE WESTERN
ADIRONDACKS…ESP HAMILTON CO WHERE UPSLOPE FLOW WILL FURTHER
ENHANCE PRECIPITATION EFFICIENCY.

WE EXPECT A TRANSITION TO A SLEET/FREEZING RAIN MIX FROM SOUTH TO
NORTH TO OCCUR BETWEEN ROUGHLY 9 PM AND MIDNIGHT FOR AREAS SOUTH
OF INTERSTATE 90…AND BETWEEN 11 PM AND 1 AM TO THE NORTH…WITH
MAINLY RAIN EXPECTED IN SOUTHERN LITCHFIELD CO AFTER THE INITIAL
PERIOD OF SNOW/SLEET. ICE ACCRETION SHOULD MAINLY BE ONE TENTH OF
AN INCH OR LESS…BUT MAY BE LOCALLY HIGHER…PERHAPS ONE QUARTER
TO ONE THIRD OF AN INCH…ACROSS PORTIONS OF THE MOHAWK RIVER
VALLEY…AND HIGHER ELEVATIONS OF SOUTHERN VT. PRECIP SHOULD
CHANGE TO PLAIN RAIN FROM S TO N BETWEEN MIDNIGHT AND 6 AM FOR
AREAS S OF I-90…AND 6 TO 9 AM TO THE NORTH. HOWEVER…WE WILL
HAVE TO WATCH TEMPS CLOSELY…AS A LOW LEVEL AGEOSTROPHIC NE WIND
MAY ALLOW SUBFREEZING TEMPS TO LINGER EVEN LONGER ACROSS PORTIONS
OF THE SOUTHERN ADIRONDACKS AND VT. THIS MAY REQUIRE ADDITIONAL
MODIFICATIONS OF THE END TIMES OF THE CURRENT SUITE OF WINTER
WEATHER ADVISORIES.

WITH THE STRONG LOW LEVEL JET PASSING BY TONIGHT…SOME PORTIONS OF THE
TACONICS…SOUTHERN GREEN MTNS AND NORTHERN BERKSHIRES MAY HAVE
SOME GUSTY WINDS AT TIMES…POSSIBLY REACHING 35 MPH AT TIMES.

WED…RAIN AND/OR LINGERING POCKETS OF FREEZING RAIN/DRIZZLE
SHOULD TAPER OFF BY MID MORNING AS THE BEST ISENTROPIC LIFT MOVES
N AND E OF THE REGION. SOME ISOLATED TO SCATTERED SHOWERS AND/OR
PATCHY DRIZZLE WILL THEN LINGER THROUGH MUCH OF THE DAY…WITH AN
INCREASES THREAT OF SHOWERS FOR AREAS NEAR AND N OF INTERSTATE 90
LATE IN THE DAY WITH THE APPROACH OF THE UPPER LEVEL TROUGH FROM
THE WEST. SOME SNOW MAY MIX IN LATE IN THE DAY ACROSS HIGHER
ELEVATIONS OF THE WESTERN ADIRONDACKS. OTHERWISE…WE EXPECT TEMPS
TO WARM UP A BIT…BUT NOT QUITE AS WARM AS MONDAY…DUE TO A MORE
SOUTHERLY LOW LEVEL WIND FLOW AS OPPOSED TO SOUTHWEST/WEST.
SO…HAVE SIDED WITH OR BELOW A MAV/MET MOS BLEND…WITH GENERALLY
LOWER/MID 40S IN VALLEYS…AND UPPER 30S ACROSS HIGHER ELEVATIONS.
SLIGHTLY WARMER MAX TEMPS COULD DEVELOP ACROSS PORTIONS OF THE MID
HUDSON VALLEY…PERHAPS 45-50.

WED NT-THU…IN THE WAKE OF THE UPPER LEVEL TROUGH…EXPECT PARTLY
CLOUDY SKIES WED NT AND THU…WITH MORE CLEARING POSSIBLE ACROSS
SOUTHERN AREAS. SOME LAKE/OROGRAPHIC EFFECT SNOW SHOWERS WILL BE
POSSIBLE ACROSS THE SOUTHERN ADIRONDACKS AND SOUTHERN VT LATE WED
NT INTO THU. HOWEVER…INVERSION LEVELS ARE FORECAST TO BECOME
RATHER LOW…AND UNSUPPORTIVE OF MORE SIGNIFICANT LAKE EFFECT
SNOWBANDS. WED NT MINS ARE FORECAST TO FALL INTO THE 20S TO LOWER
30S…WITH THU MAX TEMPS MAINLY REMAINING IN THE 35-40 RANGE IN
VALLEYS…AND MID 20S TO LOWER 30S ACROSS HIGHER ELEVATIONS. IT
WILL ALSO BECOME QUITE BREEZY AT TIMES WED NT INTO THU.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/…
HIGH PRESSURE BUILDING INTO THE REGION FROM CANADA CONTROLS OUR
WEATHER THURSDAY NIGHT INTO FRIDAY NIGHT. AS HIGH PRESSURE BUILDS
EAST AND RETURN FLOW SETS UP ACROSS THE REGION…WARM ADVECTION WILL
INCREASE AND CLOUD COVER WILL ALSO INCREASE…ESPECIALLY THROUGH
FRIDAY AFTERNOON AND NIGHT. HIGHS FRIDAY IN THE MID TO UPPER 30S
WITH AROUND 30 IN HIGHER TERRAIN.

COMPLEX…CHAOTIC SPLIT FLOW UPPER PATTERN SETS UP THIS WEEKEND INTO
THE BEGINNING OF NEXT WEEK. ONE PIECE OF UPPER ENERGY TRACKS A
LITTLE SOUTH OF THE REGION…BUT THE NORTHERN EDGE OF THE UPPER
ENERGY…ALONG WITH WARM ADVECTION AND ISENTROPIC LIFT COULD SUPPORT
ISOLATED TO SCATTERED SNOW OR RAIN SHOWERS FRIDAY NIGHT THROUGH
SUNDAY. A WEAK WAVE OF LOW PRESSURE COULD FORM JUST OFFSHORE THE MID
ATLANTIC. HIGHS SATURDAY IN THE UPPER 30S TO LOWER 40S…MID 30S IN
THE HIGHER TERRAIN. HIGHS SUNDAY AROUND 40 TO THE MID 40S…WITH MID
TO UPPER 30S HIGHER TERRAIN.

STRONGER UPPER ENERGY APPROACHING FROM THE WEST MAY INTERACT WITH
THE LOW LEVEL TROUGHING OR WAVE OF LOW PRESSURE JUST OFFSHORE. THERE
ARE MIXED SIGNALS FROM LONG RANGE GUIDANCE/ENSEMBLES AS TO THE
TIMING AND DETAILS OF THE DEVELOPMENT AND TRACK OF A POTENTIALLY
STRENGTHENING COASTAL SYSTEM TOWARD THE BEGINNING OF NEXT WEEK.
ALSO…THERE MAY NOT BE MUCH COLD AIR OVER THE REGION. SO…JUST
KEEPING CHANCES FOR RAIN AND SNOW SUNDAY NIGHT INTO MONDAY. HIGHS
MONDAY IN THE LOWER TO MID 40S…UPPER 30S TO AROUND 40 HIGHER
TERRAIN.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/…
FLYING CONDITIONS WILL RAPIDLY DETERIORATE THIS EVENING AND INTO
TONIGHT AS A STORM SYSTEM PRODUCES A WINTRY MIX ACROSS THE REGION.

THIS AFTERNOON…HIGH PRESSURE WILL MOVE OFF NORTHEAST OF THE REGION
WITH CLOUD COVER INCREASING FROM SOUTH TO NORTH AHEAD OF A STORM
SYSTEM DEVELOPING ACROSS THE MID-ATLANTIC REGION. CLOUDS WILL
INITIALLY START AS HIGH CLOUDS AND GRADUALLY DECREASE TO AN OVERCAST
STRATUS DECK BETWEEN 3-5 KFT THIS EVENING. HAVE PLACED VCSH IN THE
TAFS AT KPOU STARTING AT 21Z AND AT KALB AND KPSF STARTING AT 23Z
FOR SCATTERED SNOW SHOWERS THAT MAY MOVE INTO THE REGION LATE THIS
AFTERNOON. WINDS WILL BE OUT OF THE NORTHEAST EARLY THIS AFTERNOON
BEFORE SHIFTING TO THE SOUTHEAST BY THIS EVENING GENERALLY 5-10
KNOTS.

TONIGHT INTO WEDNESDAY…FLYING CONDITIONS WILL RAPIDLY DETERIORATE
AFTER 00Z AS INITIALLY SNOW OVERSPREADS THE REGION…EXCEPT FOR A
MIXTURE OF SNOW AND SLEET AND KPOU. FLYING CONDITIONS WILL INITIALLY
BE MVFR BETWEEN 00Z-03Z…BEFORE CEILINGS DIMINISH TO IFR AFTER 03Z
AS MORE STEADY PRECIPITATION MOVES INTO THE REGION.

AS WARM AIR MOVES IN ALOFT…A TRANSITION TO A WINTRY MIX WILL OCCUR
AT THE TAF SITES BETWEEN 03Z-09Z WITH A MIX OF FREEZING RAIN…SNOW
AND SLEET AT KGFL…KALB AND KPSF WITH A MIX OF RAIN…SNOW AND
SLEET AT KPOU. A TRANSITION TO RAIN SHOULD OCCUR AROUND 09Z AT KPOU
AND KALB WITH A WINTRY MIX CONTINUING AT KGFL AND KPSF UNTIL 12Z.
DEPENDING ON HOW FAST WARM AIR MOVES INTO THE REGION…THESE TIMES
MAY NEED TO BE ADJUSTED BY A FEW HOURS WITH THE NEXT TAF ISSUANCE.

ALL TAF SITES SHOULD SEE RAIN SHOWERS BY 15Z AS WARMER AIR BUILDS
INTO THE REGION. PRECIPITATION COVERAGE WILL DECREASE TO A SHOWERY
NATURE AFTER 12Z AS THE STORM SYSTEM QUICKLY EXITS EAST OF THE
REGION. WINDS TONIGHT WILL BE OUT OF THE SOUTHEAST AROUND 5 KNOTS
BEFORE BECOMING SOUTHERLY AROUND 4-8 KNOTS WEDNESDAY.

OUTLOOK…

WEDNESDAY NIGHT: NO OPERATIONAL IMPACT. NO SIG WX.
THURSDAY: LOW OPERATIONAL IMPACT.BREEZY NO SIG WX.
THURSDAY NIGHT: NO OPERATIONAL IMPACT. NO SIG WX.
FRIDAY: NO OPERATIONAL IMPACT. NO SIG WX.
FRIDAY NIGHT: MODERATE OPERATIONAL IMPACT. SCATTERED SHSN.
SATURDAY: MODERATE OPERATIONAL IMPACT. SCATTERED SHRA…SHSN.
SATURDAY NIGHT: MODERATE OPERATIONAL IMPACT. SCATTERED SHSN.
SUNDAY: ISOLATED SHRA…SHSN.

&&

.HYDROLOGY…
NO SIGNIFICANT HYDROLOGIC PROBLEMS ARE EXPECTED THE NEXT 5 DAYS
ENDING SATURDAY.

THE NEXT CHANCE FOR PRECIPITATION WILL BE TONIGHT AND WEDNESDAY AS
A FAST MOVING STORM SYSTEM MOVES ACROSS THE REGION. LIQUID
EQUIVALENT AMOUNTS OF ONE QUARTER TO ONE HALF OF AN INCH ARE
POSSIBLE…BUT THE PRECIPITATION WILL COME IN THE FORM OF LIGHT
SNOW CHANGING TO A WINTRY MIX AND THEN RAIN.

MILD TEMPS ON WEDNESDAY WILL RESULT IN SOME SNOW MELT…BUT
TEMPERATURES ARE EXPECTED TO COOL OFF QUICKLY WEDNESDAY NIGHT WELL
BELOW FREEZING.

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 4 PM THIS AFTERNOON TO 6 AM EST
WEDNESDAY FOR CTZ001.
NY…WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM EST
WEDNESDAY FOR NYZ047>054-058>061-063>066.
WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 9 AM EST
WEDNESDAY FOR NYZ032-033-038>043-082>084.
MA…WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM EST
WEDNESDAY FOR MAZ001-025.
VT…WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 9 AM EST
WEDNESDAY FOR VTZ013>015.

&&

$$
SYNOPSIS…KL/WASULA
NEAR TERM…KL/11/WASULA
SHORT TERM…KL
LONG TERM…NAS
AVIATION…IRL
HYDROLOGY…IRL/KL

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