FXUS61 KALY 151744
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
1244 PM EST TUE DEC 15 2009

.SYNOPSIS...
AN ARCTIC AIR MASS WILL MOVE INTO THE REGION LATER TODAY IN THE WAKE 
OF A COLD FRONT. THIS WILL SET THE STAGE FOR LAKE EFFECT SNOW...MUCH 
COLDER TEMPERATURES AND EVEN COLDER WIND CHILL VALUES AS STRONG WEST 
TO NORTHWEST WINDS WILL PREVAIL FOR THE REMAINDER OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 1135 AM EST...SCATTERED RAIN SHOWERS CONTINUE TO AFFECT 
CENTRAL PORTIONS OF THE REGION...ASSOCIATED WITH AND IMMEDIATELY 
AHEAD OF FIRST COLD FRONT. THIS FRONT IS EXPECTED TO TRACK E ACROSS 
THE REGION OVER THE NEXT 2 HOURS...WITH WINDS SHIFTING INTO THE 
W/NW...AND INCREASING IN ITS WAKE. HOWEVER...THE COLDER AIR WILL BE 
LAGGING FURTHER BEHIND THE WIND SHIFT...AND THUS WE EXPECT AT LEAST 
VALLEY LOCALES TO RISE ANOTHER FEW DEGREES THROUGH EARLY 
AFTERNOON...ESP SHOULD ANY BREAKS IN THE CLOUDS DEVELOP. ACROSS 
HIGHER ELEVATIONS...TEMPERATURES SHOULD BEGIN FALLING SOONER IN THE 
WAKE OF THE WIND SHIFT...WITH ALL TEMPS FALLING MORE RAPIDLY BETWEEN 
3 AND 6 PM.

AS FOR SHOWERS...BASED ON RADAR/SATELLITE TRENDS...EXPECT MOST 
SHOWERS/PATCHY DRIZZLE TO ONLY LINGER ANOTHER 1-2 HOURS IN THE 
VALLEYS AND ACROSS EASTERN AREAS...BEFORE SUBSIDENCE OCCURS IN THE 
WAKE OF THE FRONT...REDUCING SHOWER POTENTIAL. FOR HIGHER 
ELEVATIONS...ESP ACROSS THE SW DACKS...SHOWERS SHOULD PERSIST INTO 
THE AFTERNOON...ESP AS SOME LAKE MOISTURE ASCENDS THE HIGHER 
TERRAIN. AND...MUCH OF THIS SHOULD TRANSITION TO SNOW SHOWERS BY 
EARLY AFTERNOON.

SO...HAVE INDICATED CHC POPS FOR MANY AREAS FROM ALBANY N AND W 
THROUGH ABOUT 1 PM...THEN MAINLY FOR HIGHER ELEVATIONS WITHIN THE 
DACKS THEREAFTER.

OTHERWISE...HAVE TWEAKED HOURLY TEMPS/DEWPTS/SKY COVER BASED ON 
RECENT TRENDS...WITH NO OTHER SIG CHANGES MADE TO FORECAST DATABASE.

PREVIOUS DISCUSSION FOLLOWS...

SHOWER ACTIVITY WITH MIXED PRECIPITATION ALONG THE LEADING EDGE OF
MODEST ISENTROPIC LIFT/WARM ADVECTION HAS LIFTED INTO NEW
ENGLAND WITH ASSOCIATED SURFACE WARM FRONT. MAIN SURFACE LOW WAS
PROGRESSING NORTHEAST ALONG THE ST LAWRENCE VALLEY AS ITS
TRAILING COLD FRONT WAS A BIT SLOWER WITH ITS FORWARD
PROPAGATION. PER THE LATEST HOURLY RUN OF THE RUC13...THIS FROPA
SHOULD OCCUR THROUGH THE HUDSON RIVER VALLEY BY NOON AND CLEAR THE
ADJACENT NEW ENGLAND COUNTIES BY EARLY AFTERNOON. BASED ON
UPSTREAM RADAR MOSAIC...LIMITED SHOWER ACTIVITY WILL ACCOMPANY THE
FROPA AS WE WILL KEEP CHANCE POPS FOR MOST OF THE CWA. THE
EXCEPTION WOULD BE ACROSS THE WESTERN DACKS AS SHOWERS ARE ONGOING
AND IN CLOSE COLLABORATION WITH NEIGHBORING WFOS WE WILL KEEP
LIKELY POPS HERE.  

WITH THE COLD ADVECTION AND WESTERLY FLOW INCREASING THIS
AFTERNOON...LAKE ONTARIO CONTRIBUTIONS ARE EXPECTED TO INCREASE.
THIS WILL KEEP THOSE POPS ON THE HIGH SIDE FOR THE SAME AREAS OF
THE DACKS AND CHANCE POPS ELSEWHERE.  

TEMPERATURES WILL BE RATHER MILD BUT THIS AFOREMENTIONED COLD
FROPA WILL QUICKLY PUT A STOP TO THOSE VALUES WITH A DECREASE IN
TEMPS EXPECTED THROUGH THE AFTERNOON HOURS.

CLOUDS WILL ALSO PROVE TO BE A CHALLENGE AS WE SHOULD SEE SOME
BREAKS OF SUNSHINE...ESPECIALLY IN THE WAKE OF THE FROPA AND
DOWNSLOPING COMMENCES INTO THE VALLEYS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
BY TONIGHT...THE FIRST PIECE OF ARCTIC AIR ARRIVES WITH AN
INCREASING WEST-NORTHWEST WIND MAGNITUDES. IN ADDITION...LAKE
ONTARIO CONTRIBUTION IS EXPECTED TO INCREASE AS DELTA T/S APPROACH
MODERATE/EXTREME THRESHOLDS. BASED ON THE LATEST FORECAST
TRAJECTORIES...SEEMS THE FLOW WILL BE 300-330 DEGREES. THIS FAVORS
PORTIONS OF THE CATSKILLS IN OUR CWA. HOWEVER...UPPER TROUGH AT
THIS TIME WILL BE SHARPENING AS A SHORT WAVE PASSES OVERHEAD AFTER
MIDNIGHT. FORECAST SOUNDINGS REVEAL A STEEPENING LAPSE RATE WITH
EXPERIMENTAL REFLECTIVITIES SHOW A QUICK ENHANCEMENT ACROSS THE
HIGHER TERRAIN OVERNIGHT. HENCE...WE WILL CONTINUE WITH THE HIGHER
POPS FOR LOCATIONS AT AND ABOVE 1000 FEET AND LOWER THOSE VALUES
ACCORDINGLY INTO THE VALLEY LOCATIONS...ESPECIALLY INTO THE MID
HUDSON VALLEY AND NW CT WHERE DOWNSLOPING COMPONENT SIGNAL TENDS
TO BE STRONGER.

THERE WILL BE A PERIOD OF SUBSIDENCE IN THE WAKE OF THE UPPER
TROUGH...BUT THIS IS EXPECTED TO BE BRIEF AS COLD NORTHWEST FLOW
REGIME TAKES FIRM CONTROL. AVAILABLE GUIDANCE ALL SUGGEST A GREAT
LAKE INDUCED THERMAL TROUGH DEVELOPS ON WEDNESDAY. THIS WILL ALLOW
THE BOUNDARY LAYER FLOW TO BECOME A BIT MORE WEST THAN NORTHWEST.
THIS PROVIDES THE WINDOW OF OPPORTUNITY FOR LAKE EFFECT SNOW TO
PROGRESS DOWN THE MOHAWK RIVER VALLEY AND INTO THE CAPITAL REGION
WITH UPSLOPE CONDITIONS INTO THE TACONICS/BERKS. THIS WILL NEED TO
BE MONITORED CLOSELY AS THE COMBINATION OF WINDS AND A
MODERATE/HEAVY BURST OF SNOW COULD PROVE TO BE A CHALLENGE FOR
BOTH MOTORISTS AND AVIATION. DIFFICULT TO ASCERTAIN SNOW
ACCUMULATIONS AT THIS TIME...INITIAL THOUGHTS ARE FOR 1-2 INCHES
FOR THE CAPITAL REGION INTO THE MID MOHAWK VALLEY WITH NEAR TO
BELOW ADVISORY LEVELS SNOWFALL FOR THE WESTERN MOHAWK VALLEY. WITH
WIND GUSTS IN EXCESS OF 20KTS EXPECTED COMBINING WITH TEMPS
RANGING FROM THE TEENS ACROSS THE DACKS AND THE LOWER 30S FOR
PORTIONS OF THE MID HUDSON VALLEY AND NW CT...WIND CHILL VALUES
WILL DROP INTO THE SINGLE DIGITS AND TEENS THROUGHOUT THE DAY.

WEDNESDAY NIGHT...THE LAKE INDUCED TROUGH IS EXPECTED TO SLIDE
SOUTH WHICH WILL ALLOW LAKE EFFECT SNOW TO DRIFT SOUTHWARD INTO
THE CATSKILLS OVERNIGHT. 850MB TEMPS ARE EXPECTED TO PLUNGE BACK
TOWARD -20C OVERNIGHT. TRANSLATION AT THE SURFACE WILL BE BELOW
ZERO TEMPS FOR PORTIONS OF THE DACKS AND WESTERN MOHAWK VALLEY
/ESPECIALLY WITH A FRESH SNOW COVER/...SINGLE DIGITS FOR TERRAIN
ABOVE 500 FEET AND TEENS FOR THE CAPITAL REGION AND SOUTHWARD
THROUGH THE MID HUDSON RIVER VALLEY AND NW CT. SURFACE GRADIENT
AND BUFKIT WIND MOMENTUM TRANSFER SUGGEST WIND GUSTS WILL STILL
EXCEED 20KTS. THIS EQUATES TO WIND CHILL VALUES BELOW ZERO AND
ADVISORY LEVEL CRITERIA BEING MET FOR THE
DACKS...CATSKILLS...SOUTHERN GREENS AND PORTIONS OF THE BERKS.  

THURSDAY...ABUNDANCE OF DRY AIR AS EVIDENT BY THE EXPECTED PWATS
AT OR BELOW ONE TENTH OF INCH SHOULD DRY OUT THE LAKE ONTARIO
CONTRIBUTION AND CLOUD FIELD. OUTSIDE OF SOME STRATOCU...A GOOD
DEAL OF SUNSHINE. THIS WILL NOT AID MUCH IN THE SURFACE
TEMPERATURE RESPONSE WITH TEENS FOR THE HIGHER TERRAIN AND LOW-MID
20S FOR THE VALLEY FLOOR AS 850MB TEMPS REMAIN INTO THE NEGATIVE
TEENS.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AN ARCTIC HIGH WILL DOMINATE OUR WEATHER FOR MUCH OF THIS PERIOD
WITH NORTHWESTERLY WINDS AROUND THE WEST SIDE OF THE 500 HPA TROF
BRING A CONTINUOUS FLOW OF COLD FROM CENTRAL CANADA WHERE 850 HPA
TEMPERATURES ARE CURRENTLY MINUS 25C. THE COLDEST AIR WILL HAVE
MOVED ON...AND SOME WARMER AIR WILL MIX IN FROM THE PLAINS STATES
SO TEMPERATURES WILL MODERATE SOME. THURSDAY NIGHT WILL BE COLD...
NO DOUBT ABOUT IT...WITH LOWS BELOW ZERO ACROSS MUCH OF THE 
ADIRONDACKS AND ONLY IN THE LOWER TEENS FROM ALBANY SOUTH IN 
THE HUDSON VALLEY. BUT UNDER PARTLY TO MOSTLY SUNNY SKIES 
FRIDAY IT WILL WARM INTO THE LOW 20S ACROSS THE ADIRONDACKS
AND SOUTHERN VERMONT...AND INTO THE LOW 30S IN THE LOWER HUDSON
AND HOUSATONIC VALLEYS. ANOTHER COLD ONE FRIDAY NIGHT...WITH
LIGHT WINDS AND MOSTLY CLEAR SKIES PROVIDING NEAR IDEAL CONDITIONS
FOR RADIATIONAL COOLING. STILL NIPPY ON SATURDAY...HIGHS PRETTY 
MUCH THE SAME AS FRIDAY...BUT A BIT MILDER SATURDAY NIGHT...AS
CLOUDINESS PREVENTS RADIATIONAL COOLING. 

THE MODELS BEGIN TO DIVERGE SIGNIFICANTLY OVER THE WEEKEND...
WHICH WILL ADD A LOT OF UNCERTAINTY TO THE FORECAST. BOTH THE
GFS AND THE ECMWF MODELS DEVELOP A COASTAL LOW SATURDAY NIGHT
WITH THE ECMWF PLACING IT JUST SOUTH OF CAPE HATTERAS BY 12Z
SUNDAY...THEN MOVING IT TO ABOUT 300 MILES SE OF CAPE COD
BY 12Z MONDAY.  THE GFS TRACKS IT FARTHER OUT TO SEA PUTTING
IT ABOUT 500 MILES EAST OF CAPE COD BY MIDNIGHT SUNDAY NIGHT.
WHILE EVEN THE CLOSER TRACK WOULD PROBABLY ONLY IMPACT OUR 
ZONES IN CONNECTICUT...A SHIFT FARTHER WESTWARD COULD IMPACT
MUCH OF OUR FORECAST AREA...SO WE FEEL CHANCE POPS ARE 
JUSTIFIED AT THIS TIME. ONCE SUCH A STORM MOVES BY...IT WILL
TEND TO DEVELOP A TIGHT GRADIENT AND BRING ABOUT ANOTHER FLOW
OF COLD OUT OF CANADA ACROSS LAKE ONTARIO...AND THUS THE 
POSSIBILITY OF LAKE EFFECT SNOW SHOWERS ON MONDAY. THEN HIGH
PRESSURE MOVES IN FROM THE WEST AND ALLOWS WINDS TO DIMINISH
AND TEMPERATURES TO MODERATE SOMEWHAT ON TUESDAY.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
FRONT MOVING THROUGH THE AREA CURRENTLY WITH WESTERLY WINDS SOON TO 
MIX DOWN WITH GUSTS INCREASING IN THE MOHAWK VALLEY. WHEN WINDS 
START TO MIX DOWN...VSBYS WILL INCREASE TO VFR AT KALB. OTHERWISE 
VFR CONDITIONS EXPECTED THROUGH THE REST OF THE PERIOD AT ALL 
TERMINALS. 

THE AFOREMENTIONED FRONT WILL FILTER IN COLDER AIR ALLOWING FOR LAKE 
EFFECT SNOW SHOWERS TO AFFECT KALB AFTER 06Z WITH WINDS CHANNELING 
DOWN THE MOHAWK. HAVE INCLUDED VCSH FROM 06Z ON FOR KALB. WINDS WILL 
REMAIN OUT OF THE WEST TO NORTHWEST INCREASING IN SPEED WEDNESDAY 
AFTERNOON.

OUTLOOK...
WED-THU...VFR...SOME SHSN DOWNWIND FROM LAKE ONTARIO. WINDY. 
FRI...VFR...NO SIG WX.
SAT...MAINLY VFR...SLGT CHC -SHSN.

&&

.HYDROLOGY...
RAINFALL ACROSS THE SOUTHERN PORTION OF THE FORECAST AREA 
SUNDAY CAUSED RISES OF ONE TO TWO FEET ON THE RIVERS INCLUDING
THE HOUSATONIC ABOVE LAKE LILLINONAH. RUNOFF INTO THE HEAD
WATERS OF THE SCHOHARIE CREEK ALSO BROUGHT THE RESERVOIR 
LEVEL UP TO THE NOTCH...RESULTING IN SOME OVERFLOW DOWNRIVER.    
NORTH OF THE ALBANY AREA...IT WAS COLD ENOUGH...AND THE SNOW
PACK DEEP ENOUGH...THAT MOST...IF NOT ALL...OF THE RAIN WAS
SOAKED UP.  

WHILE TEMPERATURES HAVE REMAINED ABOVE FREEZING ACROSS MUCH
OF THE REGION SINCE MIDDAY SUNDAY...IN MOST AREAS THERE WAS
LITTLE...OR NO SUNSHINE TO WARM THE SNOW PACK...AND THUS THE 
MELT RATE WAS VERY SLOW. THIS HAS SLOWED THE RECESSION ON 
SOME RIVERS. MOST OF THE RIVERS FROM ALBANY NORTH...INCLUDING
THE MOHAWK...HAVE REMAINED MORE OR LESS STEADY. PRECIPITATION
ACROSS THE REGION THIS MORNING FROM A WEAK CLIPPER TYPE LOW
WILL BE VERY LIGHT...AND THUS NOT AFFECT THE RIVERS. 

MUCH COLDER AIR WILL BEGIN TO POUR INTO THE REGION STARTING 
THIS EVENING. TEMPERATURES WILL DROP BELOW FREEZING BY LATE
AFTERNOON NORTH...AND BY LATE EVENING SOUTH. HIGHS ON 
WEDNESDAY WILL NOT MAKE IT ABOVE FREEZING EXCEPT IN THE 
LOWER HUDSON AND HOUSATONIC VALLEYS...AND ON WEDNESDAY NIGHT
THE TEMPERATURE WILL DIP BELOW ZERO NORTH OF THE MOHAWK 
VALLEY. WITH FORECAST DAILY MEAN TEMPERATURES WELL BELOW 
FREEZING WED-FRI...ICE FORMATION MAY BE EXPECTED ON ALL 
RIVERS...STREAMS...AND LAKES.

&&

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
MA...NONE.
VT...NONE.

&&

$$
SYNOPSIS...BGM
NEAR TERM...KL/BGM
SHORT TERM...BGM
LONG TERM...RCK
AVIATION...KGS
HYDROLOGY...RCK