712 
fxus61 kaly 210531 cca 
afdaly 


Area forecast discussion 
National Weather Service Albany New York 
1230 am EST Friday Nov 21 2008 


Synopsis... 
the cold weather pattern the region has had lately is expected to 
continue well into next week. A clipper type system will move 
through the region this afternoon and tonight. This system has 
very little moisture associated with it...but it will still produce 
some light snow showers or flurries...mainly to the south and west 
of the capital district. Occasional lake effect snow showers are 
expected downwind of Lake Ontario into the weekend. 


&& 


Near term /until 6 am this morning/... 
issuing update mainly to refresh stale wording but overall forecast 
looks good. Just added a few flurries to the higher terrain to the 
east of Albany as radar echoes occasionally up to about the 10-15 
dbz threshold...just enough to yield a few flakes. Significant lake 
effect should be confined to area well west of our region overnight 
leaving US with a cold and partly cloudy night overall with nothing 
more than scattered flurries (scattered snow showers well west in 
the upslope terrain). Did not tinker with overnight lows as they 
looked reasonable. 






&& 


Short term /6 am Friday morning through Sunday/... 
northern stream upper impulse amplifies as it approaches the 
region...and tracks through the region Friday night and Saturday. 
Deeper cooling takes place once the system exits...as boundary 
layer temperatures cool rapidly. Mean flow through the boundary 
layer is mainly northwest to north-northwest...which suggests that 
lake effect snows will be enhanced by Friday afternoon and 
night...in southern Herkimer...perhaps skirting Schoharie...green 
and extreme northwest Ulster counties. Some flurries and snow 
shower activity is possible in all areas later Friday afternoon 
and night with local dustings. Areas from Herkimer through 
Schoharie and parts of the Catskills could see a couple/few inches 
of snow by Saturday morning. Highs Friday in the middle 20s to middle 
30s...with lows Friday night in the teens most areas...near 20 
southern areas. 


Surface winds become more gusty Saturday...and continue from the 
northwest...so again..parts of the western Adirondacks...and 
western Mohawk Valley...along with western Catskills could see 
more enhanced snow shower activity. Flurries still possible all 
other areas. Highs in the 20s to lower 30s. Surface high pressure 
builds south of the region Saturday night...but it will be at its 
closest proximity...so lows Saturday night single numbers in 
colder spots to teens elsewhere. 


On Sunday...surface high pressure builds offshore the middle 
Atlantic area...and weak warm advection begins. Low level flow 
becomes more west to west-southwest...and boundary layer 
temperatures warm a little. Some high clouds begin to increase 
later Sunday ahead of the next system trying to dive out of Canada 
into the Great Lakes...which could be a bigger story in the 
extended time frame. Highs Sunday in the 30s most areas...some 20s 
in mountains. 


&& 


Long term /Sunday night through Thursday/... 
the big story is the clipper system...which will be tracking across 
the Great Lakes at the start of the extended period. A warm front 
is still expected to develop in advance of the low across western 
New York and central Pennsylvania Sunday night. The low will pass 
through New York state Monday night...with the warm front partially 
lifted through our County Warning Area. A significant difference between this run 
and wednesday's 12z run is that neither the GFS nor the European model (ecmwf) is now 
redeveloping the low off the New England coast. Rather...both lift 
the low out of New York and slowly up through Quebec from Tuesday 
on. The GFS continues to provide relatively low qpf's...but the 
European model (ecmwf) is pointing to a bit more. The warm intrusion aloft is 
showing up as less significant than yesterday...with only the European model (ecmwf) 
drawing in temperatures above 1 degree c at 925 mb. The 850 mb values are all 
below freezing throughout the event...so worst case scenario on the 
icing front would seem to be some sleet or snow pellets in southern 
and eastern zones...otherwise a snow/rain scenario given high temperatures 
forecast around 40 degrees each day...except in the all-snow 
Adirondacks. A relatively streamlined vertical wind profile on the 
backside of the retreating low supports the likelihood for lake 
effect...with the fetch mainly across the western Adirondacks...so 
chance -sn/-shsn is retained there for the daytime periods Wednesday and 
Thursday. It must be stressed that given the big change in the model's 
general tracks from yesterday...a significant degree of uncertainty 
obviously still exists concerning the unfolding of monday's 
storm...particularly since there is still some disagreement between 
them as to the exact track and timing of the system. 


Went with MOS guidance throughout. This means it will be mostly 
cloudy for the vast majority of the period. The good news is 
Thanksgiving day looks like it could well be the best weather 
day...outside of the lake effect belt...but high temperatures won't change 
much from day to day through then...with lows in the valleys 
generally around 40 degrees. Lows will be below freezing every 
night and everywhere...with middle to upper teens in some of the 
normally colder northern locales. Comparing the forecast 
temperature values to the mex...we are being a little more generous 
on the highs over the mex each day. The lows are very close. 


&& 


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






Outlook... 
Sat...VFR...isold -shsn. 
Sun...VFR...no sig weather. 
Mon-Tue...MVFR/chc IFR...chance -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. 


&& 


$$ 
Aviation...rck 
hydrology...rck 

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