December 8, 2013 Forecast Discussion

000
FXUS61 KALY 081824
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
124 PM EST SUN DEC 8 2013

.SYNOPSIS…
SNOW WILL OVERSPREAD THE AREA TONIGHT. WARMER AIR WILL WORK IN
MONDAY MORNING…SO THE SNOW WILL MIX WITH AND CHANGE TO SLEET AND
OR FREEZING RAIN. EVENTUALLY…A CHANGEOVER TO PLAIN RAIN IS
EXPECTED ACROSS SOUTHERN PORTIONS OF THE AREA BY EARLY MONDAY
AFTERNOON. TRAVEL CONDITIONS MAY BE HAZARDOUS DURING THE MONDAY
MORNING COMMUTE.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
THE LAKE RESPONSE HAS ENDED. THE HIGH WILL CONTINUE TO GRADUALLY
MOVE EASTWARD. CLOUDS WILL THICKEN AND LOWER. HIGHS WILL ONLY BE
IN THE MID 20S TO LOWER 30S ACROSS MOST OF THE REGION. SOME VERY
LIGHT SNOW WITH THE LEADING EDGE OF THE WARM ADVECTION PCPN TO THE
COMPLEX LOW PRESSURE SYSTEM WILL GET CLOSE TO THE LOWER HUDSON
VALLEY EARLY THIS EVENING.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/…
A WINTER WEATHER ADVISORY HAS BEEN ISSUED FOR ALL OF OUR REGION
FROM THIS EVENING THROUGH MONDAY MORNING SOUTH AND THROUGH MONDAY
NORTH.

ADJUSTED TIMING OF PRECIPITATION OVERSPREADING THE AREA THIS
EVENING FROM SOUTH TO NORTH. LOOKING AT SNOW WITH MIXED
PRECIPITATION BRINGING TO OCCUR EARLY MONDAY MORNING. OVERALL
FORECAST ON TRACK. UPDATED THE WINTER WEATHER STATEMENT/MESSAGE.

TONIGHT THROUGH MONDAY NIGHT LOOKS TO BE FAIRLY ACTIVE AS THE
SURFACE HIGH DEPARTS ACROSS NORTHERN NEW ENGLAND AND EASTERN
CANADA WHILE A DOUBLE BARREL WAVE OF LOW PRESSURE MOVES NORTHEAST
FROM THE SOUTHEAST STATES LATE TODAY INTO THE UPPER GREAT LAKES
AND JUST OFF CAPE MAY MONDAY MORNING. THE ORIENTATION OF THE
DEPARTING SURFACE HIGH WILL BE SUCH THAT COLD AIR DAMMING WILL BE IN
PLACE WHILE WARMER AIR ALOFT ATTEMPTS TO RIDE OVER THE TOP OF THE
DEPARTING RIDGE. PTYPE FROM PARTIAL THICKNESS VALUES WAS USED FOR
DETERMINING PTYPE TONIGHT THROUGH MONDAY NIGHT. INITIALLY ALL OF
THE PTYPE WILL BE SNOW TONIGHT…HOWEVER LATER AT NIGHT THE PCPN
IS LIKELY TO CHANGE TO SLEET AND FREEZING RAIN ESPECIALLY SOUTH
AND EAST OF THE CAPITAL DISTRICT. GEFS PLUME DIAGRAM FOR KALB
SHOWS A NUMBER OF MEMBERS FAVORING THE CHANGE TO FREEZING RAIN
LATE AT NIGHT AS DO THE SREF PTYPE PROBABILITY FIELDS. QPF
AMOUNTS ARE NOT EXPECTED TO BE GREAT GENERALLY BETWEEN A QUARTER
OF AN INCH AND HALF AN INCH…HOWEVER A FEW INCHES OF SNOW
FOLLOWED BY LIGHT ICING MAY RESULT IN A DIFFICULT MORNING COMMUTE
ON MONDAY. DURING THE DAY ON MONDAY TEMPS ARE EXPECTED TO WARM
INTO THE MID 30S TO LOWER 40S WITH A CHANGEOVER TO RAIN EVERYWHERE
EXCEPT PERHAPS THE FAR NRN PTN OF THE FA WHICH WILL HAVE MIXED
PRECIP DURING THE AFTERNOON. THE WINTRY PCPN IS EXPECTED TO
CONTINUE INTO AT LEAST MONDAY EVENING WITH A CHANGE BACK FROM RAIN
TO SNOW AS COLDER AIR IS DRAWN BACK INTO THE REGION. ALTHOUGH BY
THIS TIME THE PCPN WILL BE TAPERING OFF SO JUST HAVE CHANCE POPS
MONDAY NIGHT. A FEW AREAS SUCH AS THE ERN CATSKILLS AND LITCHFIELD
HILLS MAY PICK UP A TENTH OF AN INCH OF ICING TOTAL WITH SNOWFALL
AMOUNTS ACRS THE AREA GENERALLY 1 TO 4 INCHES WITH THE HIGHEST
AMOUNTS ACROSS THE WESTERN ADIRONDACKS. EXPECT LOWS TONIGHT IN THE
MID TEENS TO MID 20S WITH TEMPS RISING LATE AT NIGHT. HIGHS ON
MONDAY ARE EXPECTED TO RANGE FROM THE MID 30S TO LOWER 40S WITH
LOWS MONDAY NIGHT IN THE UPPER TEENS TO MID 20S.

TUESDAY AND TUESDAY NIGHT…IT WILL BE COLD AND DRY ACROSS MUCH OF
THE FA WITH LAKE EFFECT SNOW ACROSS THE SOUTHERN ADIRONDACKS AND
MOHAWK VALLEY. WHILE IT IS TOO EARLY TO GET SPECIFIC ON ANY SNOW
AMOUNTS A COUPLE OF INCHES OF SNOW WOULD BE POSSIBLE ACROSS THE
WESTERN ADIRONDACKS TUESDAY NIGHT. EXPECT HIGHS ON TUESDAY IN THE
MID 20S TO MID 30S WITH LOWS TUESDAY NIGHT IN THE TEENS TO AROUND
20.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/…
HAVE POPULATED MUCH OF THIS PORTION OF THE DATABASE WITH 00Z/08
HPC…WITH SOME EXCEPTIONS AS NOTED BELOW.

IT APPEARS THAT THIS PERIOD WILL BE DOMINATED BY BROAD CYCLONIC MID
AND UPPER TROPOSPHERIC FLOW…WITH FAST MOVING…EMBEDDED
DISTURBANCES PASSING THROUGH WITHIN THIS FLOW. EACH DISTURBANCE THAT
PASSES WILL REINFORCE THE ARCTIC AIR ACROSS THE REGION…AND WILL
ALSO ACT TO SHIFT LAKE EFFECT SNOWBANDS ACROSS FAVORABLE PORTIONS OF
THE SOUTHWEST ADIRONDACKS…WESTERN MOHAWK VALLEY…AND SCHOHARIE
VALLEY…WITH SOME EXTENSIONS OF THESE BANDS POSSIBLY REACHING INTO
PORTIONS OF THE HUDSON RIVER VALLEY FROM ALBANY NORTH…AND ALSO
BECOMING LOCALLY ENHANCED WITHIN FAVORABLE UPSLOPE AREAS ACROSS
WESTERN NEW ENGLAND. HOWEVER…GIVEN SOMEWHAT LOW PREDICTABILITY OF
THE FAST MOVING DISTURBANCES…THE TIMING AND AREAL LOCATION OF
THESE SNOWBANDS AT THIS TIME RANGE REMAIN UNCERTAIN. MUCH BELOW
NORMAL TEMPS WILL CONTINUE THROUGH THIS PERIOD.

HERE ARE SOME MORE SPECIFICS…

WED-THU NT…AGAIN…SEVERAL FAST MOVING DISTURBANCES WILL PASS
THROUGH…WITH THE HIGHEST PROBABILITY APPEARING TO BE WED OR WED
NT…AND THEN POSSIBLY AGAIN LATE FRI OR EARLY SAT. HAVE INDICATED
MAINLY LAKE EFFECT SNOW ACROSS THE WESTERN ADIRONDACKS/MOHAWK VALLEY
AND SCHOHARIE VALLEY…BUT AGAIN…BANDS WILL LIKELY BE SHIFTING
NORTH AND SOUTH WITH EACH PASSING DISTURBANCE…AND NOT REMAINING IN
ONE PARTICULAR AREA THROUGH THE WHOLE PERIOD. AT TIMES…THESE BANDS
COULD EXTEND INTO VALLEY AREAS…AND ALSO HIGHER ELEVATIONS ACROSS
WESTERN NEW ENGLAND…ESP WHEN LOW LEVEL INSTABILITY IS MAXIMIZED
WITH THE PASSING DISTURBANCES. TEMPS WILL REMAIN WELL BELOW
NORMAL…WITH MAX TEMPS ONLY REACHING THE 20S IN VALLEYS…AND TEENS
ACROSS HIGHER ELEVATIONS…AND OVERNIGHT LOWS FALLING INTO THE
SINGLE DIGITS TO AROUND 10 ABOVE IN MOST AREAS…EXCEPT FOR AROUND
OR UNDER ZERO ACROSS THE SOUTHERN ADIRONDACKS.

FRI NT-SAT…SOME MODELS…PARTICULARLY THE 00Z/08 GEM AND THE
00Z/08 ECMWF…HINT AT A PARTICULARLY BITTER COLD AIR MASS SEEPING
SOUTHWARD INTO THE REGION LATE FRI INTO SAT…WHILE THE MAJORITY OF
00Z/08 GEFS MEMBERS AND THE 00Z/08 GFS KEEP THE CORE OF THE COLDEST
AIR ACROSS SOUTHEAST CANADA…WITH MILDER TEMPS ACROSS OUR REGION
WITHIN A MORE PROGRESSIVE/ZONAL FLOW PATTERN. SHOULD SOME OF THIS
BITTER COLD AIR REACH OUR REGION…MAX TEMPS MAY ONLY REACH THE
SINGLE DIGITS AND TEENS DURING THE DAY…WITH WIDESPREAD SUBZERO
READINGS POSSIBLE AT NIGHT…ALONG WITH POTENTIALLY DANGEROUS WIND
CHILLS. TRENDS WILL NEED TO BE WATCHED ON HOW FAR SOUTH THIS
EXTREMELY COLD AIR WILL REACH.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/…
HIGH PRESSURE WILL MOVE EAST OF NY AND NEW ENGLAND THIS AFTERNOON
WITH A COMPLEX STORM SYSTEM MOVING NORTHEAST FROM THE GREAT LAKES
REGION AND MID ATLANTIC CORRIDOR TONIGHT. THIS STORM SYSTEM WILL
BRING MIXED PRECIPITATION TO THE TERMINALS OVERNIGHT INTO TOMORROW.

VFR CONDITIONS ARE EXPECTED PRIOR TO 00Z/MON FOR KGFL/KPSF/KALB/KPOU
ASIDE FOR AS PATCH OF HIGH MVFR STRATUS THAT DRIFTED DOWN THE MOHAWK
RIVER VALLEY INTO KALB/KPSF. A TEMPO GROUP WAS USED FOR THE TWO
HOURS PRIOR TO 20Z/SUN TO ADDRESS THIS. CLOUDS WILL BE THICKENING
AND LOWERING FROM THE SOUTH AND WEST INTO THE PM.

OVER RUNNING PCPN AHEAD OF AN APPROACHING WARM FRONT AND A SECONDARY
WAVE OF LOW PRESSURE WILL SPREAD NORTHEAST…ACROSS THE TAF SITES
BETWEEN 01Z-06Z FROM SOUTH TO NORTH. THE PRECIPITATION TYPE WILL
INITIALLY BE LIGHT SNOW BASED ON THE NAM/GFS MODEL SOUNDINGS AND
CRITICAL THICKNESS PROFILES. OUR FORECAST SLIGHTLY FAVORS THE COLDER
NAM SOUNDINGS….ALTHOUGH SOME SLEET MAY ALSO BE MIXED IN AT KPOU
STARTING AT 07Z. THE PRECIPITATION SHOULD TRANSITION TO
SLEET/FREEZING RAIN AROUND 11Z/MON AT KPOU…WITH A MIX OF
SNOW/SLEET AT KALB AND KPSF. KGFL SHOULD HOLD AS SNOW THE LONGEST
UNTIL 14Z/MON BEFORE MIXING WITH SLEET.

THE PCPN WILL FURTHER TRANSITION TO SLEET AND FREEZING RAIN AT
KALB/KPSF BTWN 12Z-13Z…AND THEN TO -FZRA/-RA IN THE LATE
MORNING…AS THE SFC TEMPS WARM ABOVE FREEZING. KGFL MIGHT NOT
TRANSITION TO FREEZING RAIN OR RAIN UNTIL THE AFTERNOON. KPOU IS
EXPECTED TO GO TO RAIN BY 14Z/MON. CIGS AND VSBYS WILL GRADUALLY
LOWER TO MVFR LEVELS WITH THE ONSET…AND TOWARDS 12Z…SOME IFR
CONDITIONS IN TERMS OF CIGS WILL BE POSSIBLE AT ALL THE TAF SITES.

LIGHT/VARIABLE WINDS THIS AFTERNOON WILL BECOME EAST TO NORTHEAST AT
5 TO 10 KTS TONIGHT INTO TOMORROW…BEFORE VEERING TO THE SOUTHEAST
TO EAST BY THE LATE MORNING INTO THE AFTERNOON.

OUTLOOK…
MON NT: MODERATE OPERATIONAL IMPACT. BREEZY SLIGHT CHANCE OF SHSN.
TUES: NO OPERATIONAL IMPACT. NO SIG WX.
TUE NT: LOW OPERATIONAL IMPACT. SLIGHT CHANCE OF SN.
WED-WED NT: MODERATE OPERATIONAL IMPACT. CHANCE OF SHSN.
THU: LOW OPERATIONAL IMPACT. SLIGHT CHANCE OF SHSN.

&&

.HYDROLOGY…
NO HYDRO RELATED CONCERNS ARE EXPECTED OVER THE NEXT 5 DAYS.

ANOTHER ROUND OF PRECIPITATION IS EXPECTED SUNDAY NIGHT AND
MONDAY….HOWEVER THE QPF IS EXPECTED TO BE LIGHT GENERALLY
BETWEEN A QUARTER AND HALF AN INCH LIQUID EQUIVALENT AND
MOSTLY IN THE FORM OF MIXED PRECIPITATION. OTHERWISE…MAINLY
LAKE EFFECT SNOWS ARE EXPECTED DURING THE WEEK.

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 10 PM THIS EVENING TO NOON EST
MONDAY FOR CTZ001-013.
NY…WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO NOON EST
MONDAY FOR NYZ038>040-047>054-058>061-063>066.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 6 PM EST
MONDAY FOR NYZ032-033-041>043-082>084.
MA…WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO NOON EST
MONDAY FOR MAZ001-025.
VT…WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 6 PM EST
MONDAY FOR VTZ013>015.

&&

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

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