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fxus61 kaly 210920 cca 
afdaly 


Area forecast discussion 
National Weather Service Albany New York 
420 am EST Friday Nov 21 2008 


Synopsis... 
the cold weather pattern across the region will continue through the 
weekend...with some moderation to near normal temperatures early 
next week. An upper level disturbance will produce isolated to 
scattered snow showers across the region today and tonight...with 
more widespread and heavier snow shower activity downwind of Lake 
Ontario. 


&& 


Near term /through 6 am Saturday/... 
deepening upper level trough over the region will have little effect 
on most of the region except to continue and even enhance the flow 
of very cold air into the region. 850 mb temperatures will reach as low as 
-16 degree celsius by early Saturday morning. In terms of precipitation nothing 
more than isolated to scattered snow showers expected for most 
areas...but lake effect activity in about a 320 degree orientation 
will produce more numerous snow showers along with the likelihood of 
light snow accumulations from southern Herkimer County to Schoharie 
County and into the southeast Catskills. 


It will be cold with highs today only in the low 20s to middle 30s. 
Lows tonight will be mainly in the teens with some single number 
readings across the higher terrain. Surface winds will be northwest 
at 10 to 15 miles per hour with gusts over 20 miles per hour through tonight. 


&& 


Short term /6 am Friday morning through Sunday/... 
upper level trough axis moves east of the region late tonight or early 
Saturday morning. This will result in the coldest air being over the 
region on Saturday and Saturday night as 850 mb temperatures remain in -14 
to -16 degree celsius range. After the trough passage...northwest surface 
winds will increase to 15 to 25 miles per hour with gusts to 30 to 35 miles per hour. 


Snow shower activity will decrease in areas outside of the lake 
induced snow shower activity...so much of the region is forecast to 
be dry Saturday through Sunday. Lake effect snow showers during this 
period will slowly transition from a 320 degree orientation on 
Saturday...to a 260 to 270 degree orientation by Sunday. The 
intensity of the snow band will also be decreasing as the flow 
becomes more anticyclonic and instability decreases somewhat by 
Sunday afternoon. 


High Saturday will range from around 20 in the Adirondacks...to the 
lower 30s in the middle Hudson Valley. On Sunday highs will be warmer 
as winds switch to southwest as the center of a large surface high 
pressure system moves off the the middle Atlantic coast. The highs 
Sunday will be in the upper 20s to upper 30s. Even though warmer 
than Saturday...these forecast highs are still 5 to 7 degrees below 
normal. 


Lows Saturday night will be in the teens once again with some single 
number readings across the higher terrain. 


&& 


Long term /Sunday night through Thursday/... 
models develop a second 500 hpa trough in central Canada and it 
plunges south across the Great Lakes region into the Middle Atlantic 
States Monday and Monday night...and stalls as a cutoff over the 
region Tuesday. Warm air moves north around the west side of the 
high in the Atlantic and begins overrunning the colder air in the 
region Monday...reaching our forecast area late afternoon. GFS and 
European model (ecmwf) models in fairly good agreement on the features at 500 hpa 
up through Tuesday night...after which the European model (ecmwf) places the cutoff 
low center several hundered miles north of the GFS position...and 
consequently the European model (ecmwf) model lifts the surface low north into 
Canada while the GFS stalls it over the region. HPC seems to be 
going Half Way in between...which might spread some hope that our 
weather for Thanksgiving day could be fairly dry and perhaps even 
the sun might come out of hiding in the Hudson Valley and our 
western New England zones. As for p-type...the latest GFS profile 
suggests snow except for a brief period of rain or mix in the middle 
Hudson region midday Thanksgiving day...but the mref ensembles 
show a multicolored mess of spaghetti...at least for Albany... 
although snow is predominant. The 850 and 925 hpa temperatures on 
the latest GFS and European model (ecmwf) runs are below freezing across the 
region which would lessen the likelihood of sleet or ice. Since 
Thanksgiving day is at the end of the forecast period the best 
news is that a lot can change between now and then...and there 
is not a lot of confidence at this time. Went with the gmos 
guidance through the period...which for Thanksgiving day has 
chance probability of precipitation for the Upper Mohawk valley...Adirondacks...and the 
Lake George region and slight chance probability of precipitation from the capital district 
and southern Vermont south. Temperatures moderate some...for midweek 
they are fairly close to normal...but it is late November after all 
and the normals for Albany for November 27...Thanksgiving day this 
year...are a high of 43 and a low of 27. 


&& 


Aviation /06z Friday through Tuesday/... 
VFR conditions will predominate across most of the region for the 
next 24 hours. The major exceptions will be over much of the 
Adirondacks...Catskills...and western slopes of the Green Mountains 
of Vermont...where MVFR to IFR ceilings may be encountered across 
the higher terrain...and where visibility may decrease below 
MVFR/IFR thresholds for brief periods of time in snow showers. 
Cloud bases over the Hudson...Housatonic...and most of the Mohawk 
valleys should stay above VFR minimums. A clipper type system will 
bring about a possibility of some more widespread light snow later 
today but again most of it will be well to the west of the Hudson 
Valley. During the predawn hours winds will be light from the west. 
They will increase to between 5 and 10 knots from the west/northwest 
later this morning. 


Outlook... 
late tonight-Sat...VFR...isold -shsn. 
Sun...VFR...no sig weather. 
Mon-Tue...MVFR/IFR...chc -sn/-ra. 


&& 


Hydrology... 
no Hydro problems expected for at least the next five days. River 
levels are slowly falling across eastern New York and western New 
England. Current River and Reservoir levels are near to slightly 
above normal for his time of year. Water temperatures on smaller 
streams have fallen into the 30s. Therefore...with cold temperatures 
forecast...some river ice should begin to form late this week into 
the weekend...especially over rivers in the Adirondacks and colder 
valleys of the Catskills and southern Vermont. Water temperatures on 
the larger rivers such as the tidal Hudson are still in the 40s. It 
will probably be another week before water temperatures on the 
larger rivers fall enough so river ice begins to form. 


River flows will continue to diminish the next several days... 
except where affected by Reservoir releases or diversions. Only 
light precipitation is forecast and it will mostly come as snow. 
The southwestern Adirondack basins have snow cover estimated to 
contain around an inch of water over the headwaters of the Black 
River and west Canada creek. There is around three quarters of an 
inch of water in the Sacandaga river basin above hope and a quarter 
to half inch of water in the Indian River basin above Indian Lake. 
Elsewhere...snow water equivalent is negligible. Due to cold 
temperatures...little or no melting may be expected for several 
days. The next chance for significant precipitation...snow north 
and probably a mix south...looks to be this coming Monday and 
Tuesday. 


For details on the rivers...please visit the advanced hydrologic 
prediction service /ahps/ graphs on our website. 


&& 


Aly watches/warnings/advisories... 
CT...none. 
New York...none. 
Massachusetts...none. 
Vermont...none. 


&& 


$$ 


Synopsis...gjm 
near term...gjm 
short term...gjm 
long term...rck 
aviation...rck 
hydrology...rck 

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