December 9, 2013 Forecast Discussion

000
FXUS61 KALY 091457
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
1000 AM EST MON DEC 9 2013

.SYNOPSIS…
A WEAK STORM SYSTEM ALONG THE NORTHEAST COAST WILL CONTINUE TO
IMPACT OUR REGION THROUGH TODAY. WARMER AIR ALOFT WILL CHANGE
PRECIPITATION TO LIGHT FREEZING RAIN OR FREEZING DRIZZLE…MAKING
FOR SLICK SPOTS. EVENTUALLY…A CHANGEOVER TO PLAIN RAIN IS EXPECTED
ACROSS MOST OF THE LOCAL AREA BY
AFTERNOON…ESPECIALLY FOR VALLEY LOCATIONS. ANOTHER STORM SYSTEM
MAY IMPACT EXTREME SOUTHEAST PORTIONS OF THE AREA ON
TUESDAY…OTHERWISE MUCH OF THE REMAINDER OF THE WEEK WILL BE COLD
AND DRY…WITH SOME LAKE EFFECT SNOW SHOWERS ACROSS THE ADIRONDACKS
AND MOHAWK VALLEY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
A WINTER WEATHER ADVISORY REMAINS IN EFFECT.

AS OF 930 AM EST…RADAR TRACKING PATCHES OF PRECIPITATION ACROSS
OUR REGION…NOT A STEADY SHIELD. THE IFR SATELLITE PICTURES
INDICATE LITTLE IF ANY ICE LEFT IN THE CLOUDS…AT LEAST FROM THE
CAPITAL REGION SOUTHWARD. ANY SNOW TO THE NORTH OF THE CAPITAL
REGION SHOULD CHANGE TO FREEZING RAIN OR FREEZING DRIZZLE BY MIDDAY.

TEMPERATURES STILL BELOW FREEZING EVERYWHERE…MID 20S NORTH TO
AROUND 32 SOUTH. THEY SHOULD SLOWLY RISE BUT DECIDED TO DELAY THEM
RISING ABOVE FREEZING AND LOWERED HIGH TEMPERATURES A CATEGORY.

FOR THIS AFTERNOON…TEMPS WILL BE WARM ENOUGH TO ALLOW ANY PRECIP TO
CHANGEOVER TO RAIN UP THE HUDSON VALLEY INTO THE CAPITAL DISTRICT
AND ACROSS LITCHFIELD COUNTY BY EARLY AFTERNOON. IT WILL TAKE LONGER
ACROSS THE HIGHER TERRAIN OF THE EASTERN
CATSKILLS…TACONICS…BERKSHIRES INTO SOUTHERN VERMONT. AREAS
FURTHER NORTH MAY NEVER CHANGE TO PLAIN RAIN.

HIGHS TODAY WILL RANGE FROM THE MID TO UPPER 30S…WITH SOME LOWER
30S TO THE NORTH.

PRECIPITATION WILL BE RATHER SPOTTY. THE CHANCE FOR PRECIP DECREASES
AS THE AFTN GOES ON. THERE WILL BE A LOSS OF ICE IN THE CLOUDS BY
THE AFTN HOURS AS WELL…SO PRECIPITATION MAY JUST BE DRIZZLE OR
FREEZING DRIZZLE BY THAT POINT.

SNOWFALL AMOUNTS WILL BE LIGHT DUE TO THE LIMITED AMOUNT OF QPF
/GENERALLY 0.25 TO 0.33 OF LIQUID EQUIVALENT/. TOTAL SNOW TOTALS
WILL RANGE FROM JUST A COATING TO 3 INCHES…HIGHEST IN THE
ADIRONDACKS…CATSKILLS…AND BERKSHIRES. VALLEY LOCATIONS…SUCH
AS THE MID HUDSON VALLEY AND CAPITAL REGION…WILL LIKELY BE ON
THE LOWER END OF THIS RANGE WITH ONLY A DUSTING TO AN INCH. ICE
ACCRETION UP TO A TENTH OF AN INCH IS POSSIBLE AS WELL…ESP FOR
THE SOUTHERN HALF OF THE REGION…AND THE SLIPPERY COATING OF ICE
IS THE REASON WHY THE ADVISORY REMAINS IN EFFECT AND LOOKS TO BE
THE MAIN THREAT THROUGH THE NEAR TERM PERIOD.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/…
FOR TONIGHT…ANY LINGERING MIXED PRECIPITATION WILL CHANGE BACK
TO SNOW THIS EVENING AS COLDER AIR WORKS BACK INTO THE REGION AND
THE LOW PRESSURE CENTER MOVES AWAY FROM THE NORTHEAST COAST. THE
SNOW WILL BE MAINLY LIGHT AND CONFINED TO THE NORTHWEST PORTION OF
THE FA AHEAD OF A COLD FRONT MOVING TOWARD THE FA FROM THE GREAT
LAKES REGION. EXPECT LOWS TONIGHT TO RANGE FROM THE UPPER TEENS
NORTHWEST TO THE UPPER 20S SOUTHEAST.

FOR TUESDAY…A WAVE OF LOW PRESSURE IS EXPECTED TO FORM ALONG A
FRONTAL BOUNDARY STALLED WELL TO OUR SOUTH ACROSS THE CAROLINA AND
VIRGINA COAST AND MOVE EAST ALONG THIS BOUNDARY ON TUESDAY. THE
NORTHERN EDGE OF THE PCPN SHIELD ASSOCIATED WITH THIS SYSTEM MAY
IMPACT SOUTHEAST PORTIONS OF THE FA WHERE WE HAVE PLACED HIGH
CHANCE TO LOW LIKELY POPS ON TUESDAY AND WHERE AN INCH OR TWO OF
SNOW IS POSSIBLE.

TUESDAY NIGHT…EVEN COLDER AIR WILL BE POURING INTO THE REGION
SETTING THE STAGE FOR THE BEGINNING OF A PROLONGED LAKE EFFECT
EVENT. INITIALLY THE FETCH OFF LAKE ONTARIO WILL BE SUCH THAT THE
WESTERN ADIRONDACKS WILL BE IMPACTED THE MOST. FOR TUESDAY NIGHT
HAVE PLACED LIKELY POPS ACROSS MUCH OF NORTHERN HERKIMER AND PARTS
OF HAMILTON COUNTY WITH UP TO 4 INCHES OF ACCUMULATION POSSIBLE.
IF THIS LIKELIHOOD OF THE LAKE EFFECT BECOMES MORE CERTAIN THEN
LAKE EFFECT HEADLINES MAY BE ISSUED. FOR NOW WILL MENTION THIS IN
THE HWO. EXPECT LOWS TUESDAY NIGHT TO BE IN THE UPPER SINGLE
DIGITS AND MID TEENS.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/…
HAVE POPULATED MUCH OF THIS PORTION OF THE DATABASE WITH A 50/50
BLEND OF 00Z/09 HPC AND GMOS.

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.

A STORM SYSTEM MAY BRING SNOW OR SNOW SHOWERS TO THE REGION SAT-SUN.

MUCH BELOW NORMAL TEMPS WILL CONTINUE THROUGH THIS PERIOD.

HERE ARE SOME MORE SPECIFICS…

WED-WED NT…AN ARCTIC COLD FRONT LOOKS TO CROSS THE REGION LATE WED
OR WED NT. BOTH AHEAD OF…AND IMMEDIATELY AHEAD OF THE FRONT…LOW
LEVEL INSTABILITY MIGHT BE QUITE STRONG…WITH SFC-700 MB LAPSE
RATES APPROACHING 7.5-8 C/KM AS INDICATED BY THE 00Z/09 NAM12.
SEVERAL FORECAST PARAMETERS SEEM TO HINT AT POSSIBLE WINDEX RELATED
SNOW SQUALL ACTIVITY ACROSS AT LEAST THE NORTHERN HALF OF THE REGION
WED AFTERNOON INTO THE FIRST HALF OF WED NT…INCLUDING 0-3 KM CAPES
OF 30-40 J/KG…RH VALUES OF 70 PERCENT OR HIGHER WITHIN THE MAX
DENDRITIC SNOW CRYSTAL GROWTH ZONE…AND THE AFOREMENTIONED STEEP
LOW LEVEL LAPSE RATES. SO…AT THE VERY LEAST…THINK SCATTERED TO
NUMEROUS SNOW SHOWERS AND SQUALLS WILL DEVELOP ACROSS NORTHERN AREAS
WED AFTN…THEN SHOULD SPREAD SOUTH AND EAST INTO THE CAPITAL
REGION…SOUTHERN VT AND WESTERN MA WED EVE THROUGH AT LEAST
MIDNIGHT WED NT. THESE SNOW SHOWERS/SQUALLS WILL LIKELY LEAD TO VERY
QUICK…MINOR ACCUMS…GENERALLY OF AN INCH OR LESS…BUT COULD
PRODUCE BRIEF PERIODS OF VERY POOR VISIBILITY AND DRIVING
CONDITIONS. IT WILL BE BRISK BOTH AHEAD OF…AND BEHIND THE FRONTAL
BOUNDARY…WITH WIND GUSTS OF 30-40 MPH POSSIBLE. TEMPS WILL LIKELY
REACH THE UPPER 20S TO LOWER 30S IN VALLEY AREAS WED…WITH MAINLY
UPPER TEENS TO MID 20S FOR HIGHER ELEVATIONS…WITH TEMPS FALLING
INTO THE SINGLE DIGITS TO MID TEENS FOR WED NT/THU AM.

THU-THU NT…IN THE WAKE OF THE AFOREMENTIONED ARCTIC COLD
FRONT…VERY COLD TEMPS WILL BE THE RULE…WITH MAX TEMPS ONLY
REACHING 20-25 IN VALLEY AREAS…WITH TEENS ACROSS THE HIGHER
TERRAIN…ALTHOUGH EVEN COLDER TEMPS COULD OCCUR IN AREAS WHERE A
DEEPER SNOW PACK EXISTS. FOR THU NT/FRI AM…EXPECT THE COLDEST MINS
IN MOST AREAS FOR THE COLD SEASON THUS FAR…WITH WIDESPREAD SINGLE
DIGITS EXPECTED…AND SOME SUBZERO READINGS ACROSS PORTIONS OF THE
SOUTHERN ADIRONDACKS…AND HIGHER ELEVATIONS ACROSS WESTERN NEW
ENGLAND. WIND CHILL VALUES COULD APPROACH ADVISORY CRITERIA ACROSS
HIGHER ELEVATIONS THU NT. AS FOR LAKE EFFECT SNOW
POTENTIAL…VEERING WINDS SHOULD FAVOR SNOWBANDS SHIFTING INTO THE
SCHOHARIE VALLEY AND EASTERN CATSKILLS AND AREAS TO THE SOUTH AND
WEST…WITH AN OVERALL DECREASING TREND AS INVERSION HEIGHTS LOWER.

FRI-FRI NT…MODELS HAVE TRENDED TOWARD A PERIOD OF WARM
ADVECTION…WELL AHEAD OF LOW PRESSURE APPROACHING FROM THE WEST. AS
LOW LEVEL WINDS BACK MORE INTO THE SOUTHWEST…SOME LAKE EFFECT SNOW
SHOWERS COULD RETURN TO PORTIONS OF THE WESTERN MOHAWK VALLEY AND
ADIRONDACKS…ALTHOUGH INVERSION HEIGHTS SHOULD REMAIN LOW…SO AT
THIS POINT…IT APPEARS THAT ACCUMS SHOULD BE RELATIVELY MINOR. AS
FOR TEMPS…EXPECT LOWER/MID 20S IN VALLEY AREAS…AND TEENS ACROSS
HIGHER ELEVATIONS FOR MAXES…AND SINGLE DIGITS ABOVE AND SLIGHTLY
BELOW ZERO FOR FRI NT/SAT AM.

SAT-SUN…MODELS ARE HINTING AT THE POSSIBILITY OF SNOW OR SNOW
SHOWERS…AS LOW PRESSURE APPROACHES FROM THE GREAT LAKES/OHIO
VALLEY REGION. THE 00Z/09 GEFS GENERALLY CLUSTER THE LOWEST PRESSURE
ACROSS THE GREAT LAKES INTO NORTHERN NEW ENGLAND…WHICH WOULD FAVOR
MORE IN THE WAY OF SNOW SHOWERS FOR THE REGION…ALTHOUGH THERE ARE
A FEW MEMBERS INDICATING A MUCH STRONGER SYSTEM POTENTIALLY MOVES
ACROSS THE REGION. THE 00Z/ECMWF ALSO HINTS AT A STRONGER STORM
SYSTEM…WHICH TRACKS FURTHER SOUTH…AND INTENSIFIES SOUTH OF LONG
ISLAND…WHICH WOULD BRING POTENTIALLY A STEADY SNOWFALL TO A GOOD
PORTION OF THE REGION LATE SAT INTO SUN. TAKING A LOOK AT PV ANOMALY
TRACES…IT APPEARS THAT THIS POTENTIAL SYSTEM WILL BE…IN
PART…FROM ONE PIECE OF ENERGY EJECTING FROM AN UPPER LEVEL PV
ANOMALY CURRENTLY SOUTHWEST OF THE ALEUTIANS…ALONG WITH ANOTHER
PIECE OF ENERGY DRIVING SOUTHWARD FROM NORTHERN CANADA. AT THIS
TIME…DUE TO UNCERTAINTY…HAVE INDICATED CHC POPS FOR SNOW SHOWERS
THROUGH THE WEEKEND…HOWEVER TRENDS WILL NEED TO BE WATCHED FOR THE
POSSIBILITY OF A STEADIER SNOWFALL IMPACTING A PORTION OF THE REGION
DURING THIS TIME PERIOD…AND FOLLOWED BY ANOTHER SURGE OF BITTER
COLD ARCTIC AIR.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/…
MOST SNOW HAS CHANGED TO FREEZING RAIN OR FREEZING
DRIZZLE…ESPECIALLY KALB SOUTHWARD. LOOK FOR GENERALLY MVFR
CONDITIONS THIS AFTERNOON…OCCASIONALLY IFR DUE TO LOW CIGS. WILL
CONTINUE THE WIND SHEAR IDEA EVEN THOUGH THERE HAVE BEEN NO OFFICIAL
REPORTS OF LOW LEVEL WIND SHEAR.

AFTER 16Z/MON…THE STEADIER PRECIPITATION SHOULD TAPER OFF FROM
SOUTH TO NORTH…BUT AREAS OF DRIZZLE WILL LINGER WELL INTO THIS
AFTERNOON. CONDITIONS SHOULD FALL INTO THE IFR RANGE LATER THIS
MORNING INTO THE LATE AFTERNOON FOR LOW CLOUDS AND AREAS OF DRIZZLE.
SOME FREEZING DRIZZLE COULD LINGER AT KGFL INTO THE EARLY AFTERNOON.

AS A FRONTAL SYSTEM MOVES EASTWARD ACROSS THE TAF SITES THIS
EVENING…IFR CIGS/VSBYS SHOULD IMPROVE INTO THE MVFR TO VFR
RANGE…AS WINDS SHIFT INTO THE SOUTHWEST TO WEST.

WINDS WILL GENERALLY BE FROM THE EAST TO NORTHEAST THROUGH MID
MORNING AT 5-10 KT…ALTHOUGH MAY TREND INTO THE SOUTHEAST AT
KALB. LATER THIS MORNING…WINDS WILL BECOME MAINLY E TO SE AT
5-10 KT…THEN SHIFT INTO THE SOUTHWEST TO WEST THIS EVENING AT
SIMILAR SPEEDS.

OUTLOOK…
TUESDAY NIGHT: LOW OPERATIONAL IMPACT.BREEZY NO SIG WX.
WEDNESDAY: MODERATE OPERATIONAL IMPACT.BREEZY CHANCE OF SHSN.
WEDNESDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF SHSN.
THURSDAY: LOW OPERATIONAL IMPACT. SLIGHT CHANCE OF SHSN.
THURSDAY NIGHT: NO OPERATIONAL IMPACT. NO SIG WX.
FRIDAY: NO OPERATIONAL IMPACT. NO SIG WX.

&&

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

ANOTHER ROUND OF PRECIPITATION TODAY. THE QPF WILL BE LIGHT WITH
A QUARTER TO A THIRD OF AN INCH EXPECTED. IN ADDITION MOST WILL
BE IN THE FORM SNOW. 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 UNTIL NOON EST TODAY FOR CTZ001-013.
NY…WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NYZ038>040-
047>054-058>061-063>066.
WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR NYZ032-
033-041>043-082>084.
MA…WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR MAZ001-025.
VT…WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR
VTZ013>015.

&&

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

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