575 
fxus61 kaly 030150 
afdaly 


Area forecast discussion 
National Weather Service Albany New York 
850 PM EST Tuesday Dec 2 2008 


Synopsis... 
mainly dry weather is expected tonight into early Wednesday night 
as a ridge of high pressure builds in...then a strong cold front 
will track through the region Thursday with more rain or snow 
showers. Much colder weather is expected Friday through the 
weekend. 


&& 


Near term /until 6 am Wednesday morning/... 
main update to the forecast is to reflect the ongoing trends seen 
in the satellite and radar imagery. Boundary layer flow continues 
to back toward the southwest taking lake effect activity into the 
St Lawrence Valley. So reduced the probability of precipitation for northern Herkimer 
and Hamilton County including an improvement to the sky cover 
grids. Temperatures are in excellent shape at the present time. 


&& 


Short term /6 am Wednesday morning through Friday/... 
warm advection increases through the day Wednesday...but winds 
through the boundary layer should not be all that strong. Still a 
mix of sun and clouds along with the warming boundary layer 
temperatures...and a light south to southwest surface 
wind...should help temperatures climb well into the 30s to middle 
40s. 


Next strong cold front begins to approach Wednesday 
night...associated with a northern stream upper level impulse. 
Boundary layer winds become west to southwest and increase rapidly 
through the night. Clouds will increase through the night...and 
with the strengthening low-level wind fields...mixing should help 
temperatures rise a few degrees by sunrise. Boundary layer 
temperatures surge above freezing by sunrise as well in most areas 
except parts of the Adirondacks. Some scattered snow showers are 
possible along the leading edge of the stronger warm advection in 
the Adirondacks by sunrise. Lows across the region Wednesday night 
in the 20s to lower 30s during the evening...then rising slowly 
through sunrise. 


Continued mostly cloudy Thursday...but strong south to southwest 
winds...shift to northwest after the cold frontal passage later 
Thursday afternoon and toward sunset. Good boundary layer 
frontogenesis along the tight thermal gradient with rapid cooling 
behind the cold front...should support scattered shower 
activity...could be convective with such forcing...and strong low- 
level jet energy. Good mixing through the day with the gusty west 
to southwest low-level wind fields...and based on boundary layer 
temperatures ahead of the cold front...even with cloud cover and 
scattered showers...highs Thursday in the upper 30s to middle 40s. 
Precipitation could end as some snow showers with the rapid 
cooling. The west to southwest deep flow is quite different from 
the east to south wind flow on Sunday which kept the area under 
the influence of cold high pressure at low levels...hence the 
potentially warmer highs Thursday...even with scattered showers 
spreading across the area through the day. 


Thursday Night Lake effect machine begins...and northern Herkimer 
and Hamilton counties will see the best chances...with the west to 
west-southwest wind flow through the inversion level. Should be 
mostly cloudy in most areas Thursday night and Friday...but areas 
of the Hudson Valley from the capital district south...and points 
east should see occasional breaks in the clouds for occasional 
pokes of sun. Lows Thursday night in the upper teens to middle 
20s...highs Friday in the 20s to lower 30s. 


&& 


Long term /Friday night through Tuesday/... 
Friday night will be dominated by a rather chilly airmass. While the 
850 hpa temperatures aren't anything extreme /about -15 degrees c/...they 
still will provide for a below normal night...with teens in most 
areas...except for the dacks where single digits will be possible. 


With the cold airmass sticking around for the weekend...next 
forecast issue will be the timing and quantitative precipitation forecast concerning a clipper type 
system. Both the European model (ecmwf)/GFS show a weak surface feature moving 
through the region /probably across northern NY/...with the 500 hpa 
low tracking over or just south of kalb. The 500 hpa low looks 
rather progressive...although it may close off once it gets east of 
the region /more towards eastern New England/. With 850 hpa temperatures 
plenty cold...this looks to be entirely a light snow event. 
However...with this system coming out of the dry northern 
stream...and not really taping any Atlantic moisture until it gets 
well east of the region...would only expect a fairly light and low 
impact event...and the 12 UTC mref plumes agree with this idea. 
Still...this could be our chance to finally get our official first 
inch of snow storm for the immediate capital region. 


Behind this system...high pressure builds into the region for Monday 
with dry weather. It will remain chilly...although not really as 
cold as over the weekend. The next system to watch has the potential 
to be a higher quantitative precipitation forecast event...as models have indicated some type of 
phasing between the northern and southern stream could occur for 
Tuesday. Still...the ultimate track of the storm will dictate total quantitative precipitation forecast 
and p-type...and every model run seems to be shifting the storm/S 
track about 500 km on either side of kalb. For what it/S Worth...the 
12 UTC mref plumes show primarily a rain event...but my gut would 
lean towards at least some type of snow or especially ice considering how 
cold the airmass ahead of this system will be...along with the 
strength of the departing high /at least 1028 mb/. At this 
point...will keep chance probability of precipitation for rain/snow in the forecast and continue to 
monitor model trends. 


&& 


Aviation /02z Wednesday through Sunday/... 
VFR conditions will continue through the entire taf period. Stratocu 
clouds from lake effect and the last remains of an upper level 
trough over the northeast will diminish this evening as a weak upper 
level ridge begins to build into the region. This should allow for 
skies to go sky clear in the south and just few-scattered clouds in northern 
areas. Some middle/high level clouds will spread into the region during 
the day on Wednesday ahead of the next frontal system which affect 
the area on Thursday. Surface winds will remain fairly light /generally 
less than 10 kts/ through the entire taf period. 


Outlook... 
Thursday...VFR/MVFR. Scattered -shra/-shsn. Windy. 
Friday...VFR/MVFR. Widely scattered/scattered -shsn in the north. 
Sat...VFR. No sig weather. 
Sun...MVFR/IFR. Chance -sn. 


&& 


Hydrology... 
no Hydro problems are expected over the next several days. It 
will turn colder this week and any precipitation should then come 
as snow which will not have any immediate effect on the rivers. 


Starting Thursday night temperatures over the region will 
average well below freezing into the middle of next week with 
highs from the middle 20s to the middle 30s and lows from the middle 
singles to the middle teens. This will be favorable for ice to 
form and thicken on rivers and lakes...especially in the 
Adirondacks and valleys in the Catskills and southern Vermont. 


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...NAS 
near term...bgm/NAS 
short term...NAS 
long term...frugis 
aviation...NAS 
hydrology...NAS 


For the latest updates...please visit our webpage at 
www.Weather.Gov/Albany 

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