FXUS61 KALY 120544
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
1245 AM EST SAT DEC 12 2009

.SYNOPSIS...
A DEEP LOW PRESSURE SYSTEM WILL CONTINUE MOVING NORTHEAST ACROSS 
EASTERN CANADA TONIGHT...AS A LARGE ARCTIC HIGH PRESSURE SYSTEM 
SETTLES IN TO THE SOUTH OF THE REGION. THIS WILL RESULT IN THE 
CONTINUATION OF GUSTY WESTERLY WINDS THROUGH TONIGHT. AS THE COLDER 
AIR MOVES ACROSS THE RELATIVELY WARMER WATER OF LAKE ONTARIO...LAKE 
EFFECT SNOW WILL CONTINUE INTO EARLY SATURDAY ACROSS AREAS OF THE 
WESTERN ADIRONDACKS AND WESTERN MOHAWK VALLEY WITH SIGNIFICANT 
SNOWFALL. LATER IN THE WEEKEND...A WEAK LOW PRESSURE SYSTEM WILL 
BRING SOME SNOW AND RAIN TO THE REGION ON SUNDAY AND SUNDAY NIGHT.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
AS OF 940 PM...LARGE SINGLE LAKE EFFECT BAND HAS BEEN SOMEWHAT
DISRUPTED DURING THE LAST FEW HOURS AND HAS SHOWN SIGNS OF
WEAKENING AND ERODING ALONG THE EASTERN EDGE. EXTREMELY DRY
ENVIRONMENT OUTSIDE THE BAND AS WELL AS SIGNIFICANT DIRECTIONAL
WIND SHEAR MAY BE RESPONSIBLE FOR THE DISORGANIZATION. THE 00Z ALB
AND BUF SOUNDINGS REVEAL PWATS OF ONLY 0.09...WHICH IS VERY DRY.
IN TERMS OF THE SENSIBLE FORECAST...THIS IS HAVING IMPLICATIONS
FOR SOUTHERN HERKIMER/NORTHERN FULTON COUNTY WHERE CURRENT
HEADLINES RESIDE. AT LEAST LIGHT SNOW IS FALLING ACROSS SOUTHERN
HERKIMER NEAR ROUTE 8 AND NORTH OF I-90. THERE ARE STILL SOME
SIGNIFICANT REFLECTIVITIES ACROSS THE TUG HILL...SO IT IS POSSIBLE
SOME RE-ORGANIZATION TAKES PLACE AS LAKE-TEMP DIFFERENCES STILL
VERY LARGE AND CAPPING INVERSION HEIGHTS ARE ABOVE 3 KM.
SO...WHILE CONFIDENCE IN 7+ INCHES IN SOUTHERN HERKIMER HAS
DIMINISHED...IT STILL IS POSSIBLE FOR AREAS NEAR ROUTE 8 SO WILL
NOT DROP CURRENT WARNING THERE...OR THE ADVISORY ACROSS NORTHERN
FULTON. THE BAND IS STILL AFFECTING CENTRAL HERKIMER/SOUTHWEST
HAMILTON IN A WEAKENED STATE...BUT A FEW TO SEVERAL MORE INCHES
MAY FALL OVERNIGHT SO WILL JUST KEEP THE WARNING GOING THERE AND
DECREASE SNOWFALL AMOUNTS SOMEWHAT. OUTSIDE OF THE LAKE EFFECT
ONLY A FEW LIGHT SNOW SHOWERS OR FLURRIES WILL OCCUR...MAINLY
ACROSS THE HIGHER TERRAIN.

PREVIOUS NEAR TERM DISCUSSION...

COLD WESTERLY FLOW CONTINUES THROUGH TONIGHT WITH THE HEAVY LAKE
EFFECT SNOW BAND CONTINUING OFF LAKE ONTARIO. THE SNOW BAND IS A
LITTLE FURTHER SOUTH...SO HAVE EXPANDED THE LAKE EFFECT SNOW
WARNING INTO SOUTHERN HERKIMER COUNTY. THE LAKE SNOW BAND WILL NOT
SHIFT MUCH FURTHER SOUTH OVERNIGHT. SO THE HEAVY LAKE EFFECT SNOW
BAND WILL BE CONFINED TO AREAS NORTH OF THE MOHAWK VALLEY AND
THRUWAY. WITH THE MORE SOUTHERN POSITION OF THE LAKE SNOW
BAND...HAVE ALSO ISSUED A LAKE EFFECT SNOW ADVISORY FOR NORTHERN
FULTON COUNTY.

FOR THE REST OF THE REGION...EXPECT PARTLY CLOUDY CONDITIONS WITH 
SCT SNOW SHOWERS IN MOST AREAS. LAKE ERIE LAKE EFFECT SNOW BAND WAS 
EXTENDING AS FAR EAST AS THE CATSKILLS AND PRODUCING SCT SNOW 
SHOWERS THERE. 

WESTERLY SURFACE WINDS WILL CONTINUE QUITE GUSTY...BUT BELOW 
ADVISORY CRITERIA. LOWS WILL BE IN THE SINGLE NUMBERS AND TEENS... 
WITH WIND CHILL READINGS BELOW ZERO AT TIMES.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
ON SATURDAY...THE MEAN LOW LEVEL WIND FLOW WEAKENS CONSIDERABLY 
THROUGH THE DAY...AND THE DEPTH OF THE INSTABILITY AND MOISTURE 
BECOMES TOO SHALLOW BY AFTERNOON TO SUPPORT AN ORGANIZED LAKE EFFECT 
SNOW BAND. SOME WEAK WARM ADVECTION BEGINS BY AFTERNOON AS THE LOW 
LEVEL RIDGE AXIS BUILDS OVER OUR REGION...AND BEGINS TO BUILD EAST. 
HIGHS SATURDAY IN THE 20S TO LOWER 30S. WEAK WARM ADVECTION WILL 
CONTINUE SATURDAY NIGHT...BUT LOW LEVEL RIDGING STILL CLOSE ENOUGH 
FOR LIGHT WINDS AND MOSTLY CLEAR SKIES EARLY IN THE NIGHT. WITH SNOW 
COVER...TEMPERATURES WILL ONCE AGAIN FALL INTO THE SINGLE NUMBERS 
AND TEENS. HIGH CLOUDS WILL SPREAD OVER THE REGION TOWARD SUNRISE 
AHEAD OF THE NEXT SYSTEM.

THERE IS INCREASING CONSENSUS FROM GUIDANCE THAT OUR REGION WILL SEE 
PCPN FROM A WEAK LOW MOVING OFF THE VIRGINIA COAST SUNDAY AND SUNDAY 
NIGHT. EXPECT QPF IN THE QUARTER TO HALF INCH RANGE WITH THIS 
SYSTEM. HOWEVER...MODELS HAVE BEEN TRENDING WARMER WITH THIS SYSTEM 
     ESPECIALLY THE GFS AND NAM...SO ALL SNOW IS UNLIKELY WITH THIS 
EVENT...EVEN ACROSS NORTHERN AREAS. HAVE GENERALLY FORECAST A SNOW 
MIXING WITH OR CHANGING TO RAIN SCENARIO FOR THE ENTIRE FORECAST 
AREA...WITH THE MILDER TEMPS AND LIQUID OR MIXED PCPN REMAINING WELL 
INTO SUNDAY NIGHT. IN GENERAL ONE TO THREE INCHES OF SNOW HAVE BEEN 
FORECAST IN THE GRIDS. HIGHS SUNDAY WILL BE IN THE 30S TO AROUND 
40...BUT THESE HIGHS WILL OCCUR LATE IN THE DAY WITH THE TEMP 
REMAINING STEADY INTO THE EVENING. LATER ON SUNDAY NIGHT...THE TEMPS 
WILL SLOWLY DIP TO BETWEEN 25 AND 35.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
THE PERIOD WILL START WITH A WEAK HIGH PRESSURE RIDGE MOVING 
EASTWARD OVER THE NORTHEAST BEHIND THE COLD FRONT WHICH PASSES 
THROUGH SUNDAY INTO SUNDAY NIGHT. THIS HIGH PRESSURE WILL RESULT IN 
DRYING CONDITIONS DURING THE DAY ON MONDAY BEFORE ANOTHER LOW 
APPROACHES FROM THE WEST MONDAY NIGHT INTO TUESDAY. AT THIS 
TIME...WILL INDICATE CHC FOR SNOW SHOWERS FOR MONDAY NIGHT...BUT 
ENOUGH WARMING BETWEEN 925-850 MB COULD ALLOW FOR SOME POCKETS OF 
RAIN OR EVEN FREEZING RAIN...SO WE WILL NEED TO MONITOR AS EVENT 
NEARS. 

GFS AND ECMWF INDICATE SFC LOW TRACKING NORTH OF NY ON TUESDAY WITH 
SECONDARY TROUGH REINFORCED BY UPPER LEVEL TROUGH BEHIND THE COLD 
FRONT. THIS WILL KEEP PRECIP IN THE FA THROUGH LATE TUESDAY/EARLY 
WEDNESDAY BEFORE HIGH PRESSURE STARTS TO SLOWLY BUILD WITH 
NORTHWESTERLY FLOW PRODUCING LAKE AFFECT SNOW ACROSS THE ADIRONDACKS 
AND WESTERN MOHAWK VALLEY THROUGH THURSDAY. DURING THE DAY 
TUESDAY...TEMPERATURES IN THE VALLEYS WILL BE WARM ENOUGH FOR SNOW 
SHOWERS TO TRANSITION TO RAIN SHOWERS BEFORE COLDER TEMPERATURES 
FILTER IN TUESDAY NIGHT. THE COLDER AIR IN THE WAKE OF THE 
FRONT/STORM SYSTEM SHOULD ALLOW LAKE EFFECT SNOWBANDS TO IMPACT NW 
PORTIONS OF THE REGION. HOWEVER...LOW LEVEL FLOW MAY BE MORE NW THAN 
CURRENT EVENT...WITH POTENTIALLY SHORTER OVER LAKE TRAJECTORY... 
WHICH COULD REDUCE THE INTENSITY SOMEWHAT.

FOR FRIDAY...GFS AND ECMWF DIFFER WITH ECMWF BRINGING HIGH PRESSURE 
ACROSS THE MID-ATLANTIC STATES AND GFS BRINGING A CLIPPER TYPE LOW 
QUICKLY THROUGH ON FRIDAY. ECMWF BRINGS A SIMILAR LOW IN ABOUT A DAY 
LATER. WILL HAVE TO KEEP AN EYE ON THIS TO SEE IF TIMING ISSUES 
RESOLVE AS WE GET CLOSER.

TEMPERATURES WILL START ABOVE NORMAL THROUGH TUESDAY NIGHT WHEN 
COLDER TEMPERATURES FILTER IN BEHIND THE FIRST STORM. MAX 
TEMPERATURES WILL BE AROUND NORMAL THROUGH THE REST OF THE PERIOD 
WITH MIN TEMPS ABOUT 5 DEGREES BELOW NORMAL.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
VFR CONDITIONS WILL PREVAIL ACROSS THE REGION THE NEXT 24 HOURS. 
HOWEVER THERE WILL BE SOME LOCAL AREAS OF MVFR/IFR CONDITIONS IN
LAKE EFFECT SNOW BANDS EXTENDING EAST FROM LAKE ONTARIO INTO THE
ADIRONDACKS. THERE MAY ALSO BE A FEW UPSLOPE ENHANCED BANDS OVER
THE WESTERN CATSKILLS...THE NORTHERN BERKSHIRES...AND THE GREEN 
MOUNTAINS OF SOUTHERN VERMONT. 

WESTERLY WINDS HAVE DIMINISHED DURING THE EVENING AND WILL BE 
5 TO 10 KNOTS DURING THE PREDAWN HOURS. AFTER SUNRISE THEY WILL
INCREASE TO BETWEEN 10 AND 15 KNOTS WITH GUSTS TO 20 KNOTS DOWN
THE MOHAWK VALLEY TO THE ALBANY AREA DUE TO THE TERRAIN. THEY 
WILL THEN DIMINISH TO LESS THAN 5 KNOTS TONIGHT. 

OUTLOOK...
SUN-SUN NGT...MVFR/IFR -RA/-SN LIKELY. 
MON...VFR...NO SIG WX. 
MON NGT-WED...VFR/MVFR. CHC -SHRASN.

&&

.HYDROLOGY...
WE WILL STAY COLD ENOUGH FOR LITTLE OR NO SNOW MELT. SOME LIGHT SNOW 
OR RAIN IS LIKELY SUNDAY AND SUNDAY NIGHT. TEMPS WILL NOT GET WARM 
ENOUGH TO CAUSE ANY SIGNIFICANT SNOW MELT...AND RAIN WILL NOT BE 
HEAVY ENOUGH FOR SIGNIFICANT RUNOFF TO OCCUR...SO NO HYDRO PROBLEMS 
ARE FORESEEN FOR THE NEXT WEEK.

SOME RIVER ICE WILL BEGIN TO FORM EARLY THIS WEEKEND ACROSS THE 
NORTHERN SECTIONS OF OUR HYDRO AREA.

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...NONE.
NY...LAKE EFFECT SNOW WARNING UNTIL 7 AM EST SATURDAY FOR NYZ032-
     033-038.
     LAKE EFFECT SNOW ADVISORY UNTIL 7 AM EST SATURDAY FOR NYZ082.
MA...NONE.
VT...NONE.

&&

$$
SYNOPSIS...GJM
NEAR TERM...GJM/JPV
SHORT TERM...GJM
LONG TERM...KGS
AVIATION...RCK
HYDROLOGY...GJM