December 16, 2013 Forecast Discussion

000
FXUS61 KALY 162129
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
429 PM EST MON DEC 16 2013

.SYNOPSIS…
A RIDGE OF HIGH PRESSURE WILL BUILD IN FROM THE GREAT LAKES
TONIGHT…AND BRING MAINLY CLEAR AND COLD WEATHER. A CLIPPER TYPE
SYSTEM WILL MOVE TO OUR SOUTH ON TUESDAY…AND STRENGTHEN SOUTH OF
THE NEW ENGLAND COAST. THIS SYSTEM WILL BRING A WIDESPREAD LIGHT
SNOW TO THE AREA TUESDAY. SCATTERED SNOW SHOWERS ARE FORECAST FOR
WEDNESDAY.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/…
AS OF 425 PM EST…MOST OF THE AREA IS CLEAR TO PARTLY CLOUDY.
WITH SNOW COVER…DIMINISHING WINDS AND CLEARING SKIES…TEMPS
SHOULD DROP QUICKLY THIS EVENING. TEMPS LIKELY TO BOTTOM OUT
SHORTLY AFTER MIDNIGHT AS CLOUDS BEGIN TO INCREASE IN ADVANCE OF
APPROACHING CLIPPER TYPE LOW PRESSURE SYSTEM. LOWS OVERNIGHT BELOW
ZERO UP NORTH TO SINGLE DIGITS SOUTH.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/…
FOR LATE TONIGHT/EARLY TOMORROW MORNING…LIGHT SNOW SHOULD BREAK
OUT BETWEEN 5 AND 8 AM OVER OUR NEW YORK ZONES…WITH PERHAPS A
COATING TO AN INCH POSSIBLE BY DAYBREAK OVER THE NORTHEASTERN
CATSKILLS…WESTERN MOHAWK VALLEY…SCHOHARIE VALLEY AND MID
HUDSON VALLEY. FOR OUR NEW ENGLAND ZONES…SNOW IS FORECAST TO
BEGIN BETWEEN 6 AND 8 AM…ALTHOUGH SNOW MAY HOLD OFF UNTIL AROUND
9 AM IN THE CONNECTICUT RIVER VALLEY.

FIRST BURST OF SNOW LOOKS TO BE DRIVEN BY WARM ADVECTION AT 850MB.
WINDS AT 850MB ARE FORECAST TO INITIALLY BE FROM THE SOUTHWEST.
BUMPED UP TUESDAY MORNING SNOWFALL SLIGHTLY FROM GUIDANCE OVER
THE WESTERN MOHAWK VALLEY AND SOUTHWESTERN ADIRONDACKS AS THESE
AREAS USUALLY SEE ENHANCED PRECIPITATION IN THESE SOUTHWEST WARM
ADVECTION SITUATIONS.

LATER TUESDAY…CLIPPER TYPE SYSTEM WILL RAPIDLY MOVE FROM THE
GREAT LAKES REGION TUE MORNING…AS A SECONDARY LOW WILL DEVELOP
JUST SOUTH OF LONG ISLAND…AND THEN TRACK RAPIDLY EAST NORTHEAST
TUESDAY AFTERNOON AND EVENING. ISENTROPIC LIFT AND FGEN SHOULD
INCREASE OVER THE SOUTHEAST PART OF THE AREA AS THE DAY GOES ON IN
RESPONSE TO THE DEEPENING LOW PRESSURE SYSTEM SOUTH OF NEW
ENGLAND. A FEW BANDS OF MODERATE SNOW MAY DEVELOP WITH THIS
FORCING. SNOW SHOULD GRADUALLY END FROM WEST TO EAST DURING THE
AFTERNOON HOURS. MODELS SUGGEST SOME DEFORMATION SNOW COULD LINGER
ON THE BACKSIDE OF THE SYSTEM. 12Z/NAM IN BETWEEN FASTER 12Z/GFS
AND SLOWER 12Z/EURO IN CLOSING OFF 850MB LOW. NAM SUGGESTS A
DEFORMATION BAND OF SNOW MAY LINGER OVER BERKSHIRE COUNTY MA AND
BENNINGTON AND WINDHAM COUNTIES IN VT THROUGH THE EVENING HOURS.

FOR FORECAST SNOWFALL IN CLOSE AGREEMENT WITH WPC…GENERALLY 2-4
INCHES WITH SOME HIGHER AMOUNTS OF 4-6 INCHES POSSIBLE IN THE
CATSKILLS…BERKSHIRES…TACONICS…LITCHFIELD HILLS AND GREENE
MOUNTAINS OF SOUTHERN VERMONT…HENCE THE ADVISORY ISSUED. SINCE THE
GROUND WILL BE SO COLD…SNOW WILL ACCUMULATE ON ROAD SURFACES…MAKING
FOR SLOW TRAVEL CONDITIONS TUESDAY. TEMPS WILL LIKELY ONLY REACH THE
TEENS TO LOWER 20S IN MOST AREAS…WARMEST ACROSS THE MID HUDSON
VALLEY…MID 20S.

TUE NIGHT…THE UPPER TROUGH WILL MOVE ACROSS OUR AREA…WITH
SCATTERED SNOW SHOWERS.

ON WEDNESDAY…LAKE EFFECT SNOW SHOWERS EAST OF LAKE ONTARIO
SHOULD REACH INTO NORTHWESTERN ZONES. THE 850 MB TEMPS ARE NOT
OVERLY COLD…AROUND -12C…BUT WINDS DO ALIGN WITH THE LONG AXIS
OF THE LAKE FOR PART OF THE DAY…AND THE INVERSION HEIGHT REMAINS
AT OR ABOVE 7000FT.

FOR WEDNESDAY NIGHT…SOME WARM ADVECTION CLOUDS AND LIGHT SNOW OR
SNOW SHOWERS COULD AFFECT NW AREAS. EXPECT COLD TEMPS THROUGH THE
PERIOD…WITH TEMPS BELOW NORMAL.

TEMPS A BLEND OF MAV/MET MOS.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/…
THE EXTENDED FORECAST BEGINS FAIRLY TRANQUIL…THEN BECOMES
INCREASINGLY UNSETTLED HEADING INTO NEXT WEEKEND.

HAVE FOLLOWED CLOSELY THE LATEST WPC DATA WITH SOME SLIGHTLY WARMER
TRENDS FOR THE LATTER HALF OF THE WEEKEND. SOME SIGNIFICANT
SENSIBLE WX CHANGES ARE POSSIBLE FOR THE WEEKEND WITH THE PLACEMENT
OF A FRONTAL BOUNDARY…AND A WAVE OF LOW PRESSURE MOVING ALONG IT.

THURSDAY…HIGH PRESSURE MOVES OFF THE MID ATLANTIC COAST WITH A
WARM FRONT APPROACHING FROM THE SOUTH AND WEST. THE H500 FLOW
BECOMES INCREASINGLY ZONAL WITH MILDER AIR APPROACHING THE REGION.
H850 TEMPS RISE TO 0C TO -4C FROM THE CAPITAL REGION SOUTH…AND -4C
TO -7C TO THE NORTH AND WEST. THERE WILL BE AN ISOLD THREAT FOR
SOME SPOTTY SNOW SHOWERS OVER THE SRN DACKS REGION DURING THE DAY.
OTHERWISE TEMPS RISE CLOSE TO NORMAL WITH MID AND U30S FOR THE
MOHAWK VALLEY…CAPITAL REGION…MID HUDSON VALLEY…TACONICS…SRN
BERKS…AND NW CT. U20S TO L30S WILL BE COMMON OVER THE HIGH PEAKS
OF THE ERN CATSKILLS…SRN DACKS…SRN GREENS…AND PARTS OF THE
LAKE GEORGE REGION.

THURSDAY NIGHT INTO FRIDAY…LOW PRESSURE APPROACHES FROM THE UPPER
MS RIVER VALLEY…AND GREAT LAKES REGION. THE LOW AND MID LEVEL
WARM ADVECTION INCREASES OVER THE NRN HALF OF THE FCST AREA FOR SOME
RAIN AND SNOW SHOWERS…THERE MAYBE A LIGHT SPOTTY MIX ACCORDING TO
SOME OF THE GEFS…THOUGH THE DETERMINISTIC GUIDANCE LEANS TOWARDS
RAIN/SNOW. THE PCPN LOOK LIGHT INTO FRIDAY. ACTUALLY…TEMPS MAY
SURGE ABOVE NORMAL BY 4 TO 8 DEGREES IN THE CONFLUENT MID AND UPPER
FLOW. THE BEST CHC OF SHOWERS WITH THE FRONTAL BOUNDARY…AND THE
LOW-LEVEL CONVERGENCE WITH THE SFC WAVE PASSING OVER NRN NY AND NRN
NEW ENGLAND APPEARS TO BE DURING THE DAY ON THE WPC/ECMWF/GFS/CAN
GGEM GUIDANCE. POPS WERE INCREASED TO HIGH CHC AND LOW LIKELY
VALUES NORTH OF THE I-90 CORRIDOR…AND LOW CHC VALUES TO THE SOUTH
AND EAST. AFTER LOWS IN THE 20S…EXPECT MAX TEMPS TO RISE INTO THE
U30S TO M40S OVER THE FCST AREA.

FRIDAY NIGHT INTO SATURDAY…THE FRONTAL BOUNDARY SAGS SOUTH OF MOST
OF THE REGION WITH HIGH PRESSURE ATTEMPTING TO BUILD IN FROM SE
ONTARIO/SRN QUEBEC BRIEFLY. THE PCPN TYPE MAY BE TRICKY
HERE…DEPENDING ON THE DEPTH OF THE SUBFREEZING AIR. THE PCPN IS
EXPECTED TO BE LIGHT WITH CHANCES OF RAIN AND SNOW SHOWERS
MAINTAINED. AS STATED EARLIER…HAVE SIDED WITH THE WPC GUIDANCE
WHICH FAVORS A COLDER SCENARIO WITH THE SFC HIGH BUILDING IN PUSHING
THE FRONT SOUTH OF COASTAL SRN NEW ENGLAND AND NYC. LOWS FRI NIGHT
RANGE FROM THE TEENS TO L20S OVER THE NW PORTION OF THE FCST
AREA…TO U20S TO L30S OVER THE SE PORTION. HIGHS SATURDAY WILL
GENERALLY RANGE FROM THE M20S TO L30S OVER THE NRN TIER…AND MID
30S TO L40S FROM THE CAPITAL REGION/MOHAWK VALLEY SOUTH AND EAST.

SATURDAY NIGHT THROUGH SUNDAY NIGHT…LOW CONFIDENCE FORECAST HERE
WITH THE FRONTAL BOUNDARY PLACEMENT AND THERMAL PROFILES VARIABLE IN
THE ENSEMBLES AND MEDIUM RANGE GUIDANCE. A BROAD UPPER LEVEL TROUGH
IS CARVED OUT OVER THE WRN THIRD OF THE LOWER 48 WITH SOUTHWESTERLY
FLOW ALOFT DOMINATING OVER THE NORTHEAST. A STRONG WAVE OF LOW
PRESSURE IS EXPECTED TO IMPACT THE REGION FOR THE 2ND HALF OF THE
WEEKEND WITH THE TRACK NORTH OF THE ST LAWRENCE RIVER VALLEY /WARM
SCENARIO/…OR SOUTH OF IT /COLDER SCENARIO/ WITH RAIN…SNOW…OR A
VARIETY OF PCPN TYPES INCLUDING SLEET AND FREEZING RAIN. THE LATEST
GFS FAVORS A WARMER SOLUTION WITH MAINLY RAIN…BUT THE LATEST
GEFS…AND THEIR ASSOCIATED PLUMES SHOW THE POSSIBILITY OF SOME
MIXED PCPN. THE ECMWF DRAGS THE WAVE ALMOST RIGHT OVER CNTRL AND
ERN NY. AFTER COLLABORATING WITH NEIGHBORS WFOS…WILL CONTINUE
RAIN/SNOW TREND AND WORK ON THE FINE PTYPE DETAILS AS WE GET CLOSER
IN TIME. LOTS OF UNCERTAINTY EXISTS IN DAYS 6 AND 7 HERE. OUR
FORECAST TEMPS FOR SUNDAY ARE ABOUT 5 DEGREES WARMER THAN THE WPC
GUIDANCE. HIGHS WOULD BE IN THE MID 40S TO L50S FROM THE CAPITAL
DISTRICT SOUTH AND EAST…AND U30S TO LOWER TO M40S NORTH AND WEST.
A MILDER SOLUTION COULD ALSO MELT QUITE A BIT OF SNOW…AND POSSIBLY
CAUSE SOME HYDRO PROBLEMS.

MONDAY…THE FRONT DROPS SOUTH AND EAST OF THE REGION WITH COLDER
AIR INFILTRATING FROM THE NORTH AND WEST. TEMPS MAY ACTUALLY FALL
ABOUT 5 DEGREES BELOW NORMAL WITH SOME ISOLD SNOW SHOWERS AND
FLURRIES PERSISTING…AS ANOTHER RIPPLE OF LOW PRESSURE MOVES ALONG
THE FRONT…AND A SFC HIGH RIDGES IN FROM SOUTH OF JAMES BAY.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/…
HIGH PRESSURE WILL BUILD IN THIS AFTERNOON INTO THIS EVENING. A
LOW PRESSURE SYSTEM WILL BRING SOME LIGHT SNOW TO MOST OF EAST
CENTRAL NEW YORK AND WESTERN NEW ENGLAND TOMORROW MORNING INTO THE
EARLY EVENING.

MAINLY VFR CONDITIONS WILL PREVAIL THIS AFTERNOON…AND MOST OF
THE OVERNIGHT PERIOD. SOME PATCHY HIGH MVFR STRATOCUMULUS WILL
LINGER AT KPSF FOR A FEW MORE HOURS…BEFORE THE SKIES CLEAR BY
SUNSET. THE SUBSIDENCE FROM THE SFC ANTICYCLONE RIDGING IN OVER NY
AND NEW ENGLAND TONIGHT…WILL YIELD CLEAR/MOSTLY CLEAR CONDITIONS
BEFORE MID AND HIGH CLOUDS MOVE IN FROM SOUTH TO NORTH ACROSS THE
TERMINALS AFTER MIDNIGHT.

WARM ADVECTION SNOWFALL WILL LIKELY COMMENCE BTWN 12Z-15Z FROM
KPOU NORTH TO KGFL. EXPECT -SN TO START AT KPSF AND KALB AT 13Z-
14Z. BASICALLY LOWERED CLOUDS BASES AND VSBYS TO MVFR LEVELS BTWN
12Z-15Z/TUE. SOME IFR CONDITIONS MAY BE POSSIBLE AT KPOU AROUND 14Z.

WEST TO NORTHWEST WINDS OF 10-15 KTS WITH SOME GUSTS AROUND 20-25
KTS AT KALB AND KPSF WILL DIMINISH TOWARDS SUNSET. EXPECT THE WINDS
WILL DECREASE TO LESS THAN 10 KTS BTWN 22Z-01/TUE. THE TREND WILL
CONTINUE FOR LIGHT TO CALM WINDS OVERNIGHT…BEFORE LIGHT AND
VARIABLE WINDS /LESS THAN 5 KTS/ WILL PERSIST IN THE LATE MORNING.

OUTLOOK…
TUESDAY PM-NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF SHSN.
WEDNESDAY: MODERATE OPERATIONAL IMPACT.BREEZY CHANCE OF SHSN.
WEDNESDAY NIGHT: NO OPERATIONAL IMPACT. NO SIG WX.
THURSDAY: NO OPERATIONAL IMPACT. NO SIG WX.
THURSDAY NIGHT: NO OPERATIONAL IMPACT. NO SIG WX.
FRIDAY-SATURDAY: MODERATE OPERATIONAL IMPACT. CHANCE OF RA…SN.

&&

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

A CLIPPER TYPE SYSTEM APPROACHES FOR TONIGHT INTO TOMORROW. THE
PRECIPITATION IS EXPECTED TO BE ALL SNOW WITH THIS SYSTEM. TOTAL
LIQUID EQUIVALENT WITH THIS SYSTEM IS EXPECTED TO RANGE FROM ONE TO
THREE TENTHS OF AN INCH WITH THE HIGHEST AMOUNTS OVER THE ERN
CATSKILLS…W-CNTRL MOHAWK VALLEY…AND WRN NEW ENGLAND. THIS
SYSTEM WILL REDEVELOP SOUTH OF LONG ISLAND…AND QUICKLY MOVE
NORTHEAST OF CAPE COD TOMORROW NIGHT.

SOME LAKE EFFECT SNOW IS POSSIBLE WED-WED NIGHT WITH LIGHT SNOW
AMOUNTS…AND LIQUID EQUIVALENTS GENERALLY LESS THAN A TENTH OF AN
INCH FOR THE WRN DACKS REGION…AND NRN TIER OF THE HSA.

FOR THE MID WEEK…TEMPS WILL CONTINUE TO BE BELOW NORMAL AND ICE
WILL CONTINUE TO FORM AND THICKEN ON AREA RIVERS…STREAMS AND
PARTICULARLY LAKES.

A MODERATING TREND IN TEMPS IS LIKELY THU INTO FRI WITH A FRONTAL
BOUNDARY BRINGING SOME SHOWERS TO CLOSE THE WORK WEEK. SOME SNOW MELT
IS LIKELY THIS WEEKEND. ALSO…A STORM SYSTEM MOVING ALONG A
FRONTAL BOUNDARY NEAR THE HSA MAY BRING SIGNIFICANT PCPN TO THE
FORECAST AREA SAT NIGHT INTO SUNDAY WITH EVEN MILDER TEMPS. THIS
WILL CONTINUE TO BE MONITORED FOR THE UPCOMING 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 WEATHER ADVISORY FROM 7 AM TO 6 PM EST TUESDAY FOR
CTZ001-013.
NY…WINTER WEATHER ADVISORY FROM 5 AM TO 5 PM EST TUESDAY FOR
NYZ054-058>061-063>066.
MA…WINTER WEATHER ADVISORY FROM 7 AM TO 6 PM EST TUESDAY FOR
MAZ001-025.
VT…WINTER WEATHER ADVISORY FROM 7 AM TO 6 PM EST TUESDAY FOR
VTZ013>015.

&&

$$
SYNOPSIS…SND/WASULA
NEAR TERM…SND
SHORT TERM…SND
LONG TERM…WASULA
AVIATION…WASULA
HYDROLOGY…WASULA

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