526 
fxus61 kaly 200920 
afdaly 


Area forecast discussion 
National Weather Service Albany New York 
420 am EST Thursday Nov 20 2008 


Synopsis... 
the cold weather pattern the region has had lately is expected to 
continue well into next week. A weak clipper type system will move 
through the region today. 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. Otherwise...occasional lake effect snow showers are 
expected downwind of Lake Ontario from late tonight into the weekend. 


&& 


Near term /through today/... 
radar/satellite data/loops indicate that most of the light snow/flurries 
associated with the clipper like system moving through the region 
will stay over the southwest and southern part of the forecast area 
today...and have forecast the highest probability of precipitation for this region (30-40 
percent). For most of the rest of the forecast area have forecast 
only slight chance probability of precipitation. 


With 850 mb temperatures not expected to get above -10 degree celsius and lots 
of cloud cover across the region...temperatures will remain quite cold with 
highs only in the middle 20s to middle 30s. 


&& 


Short term /tonight through Saturday/... 
the clipper like system will usher in even colder air...with 850 mb 
temperatures across the region Friday and Saturday in the -12 to -16 degree 
celsius range. That should result in highs generally in the low 20s 
to low 30s across the region both days. Nightime lows will be mainly 
in the teens. Gusty winds...especially on Saturday when wind gusts 
could reach around 35 miles per hour...will make it feel very winterlike across 
the region during this period. 


With the clipper like system moving through the region today... 
and the deepening upper level trough affecting the region through 
Saturday...have kept slight or low chance probability of precipitation in most areas through 
Saturday. However...the highest probability of precipitation have been forecast for the 
southwest part of the region from southern Herkimer County...into 
Schoharie County and then into the southeast Catskills due to 
expected lake effect activity which should line up in a 310-320 
degree orientation. The lake effect activity will peak on 
Friday...so have forecast the highest probability of precipitation (up to around 50 percent) 
for these areas at that time. 


&& 


Long term /Saturday night through Wednesday/... 
a ridge of high pressure will build in Sat night into sun...bringing 
dry conditions. However...temperatures will still be quite chilly as the 
coldest core of air aloft will not retreat until later sun. So maximum 
temperatures will still be in the 30s in the valleys and 20s in the 
mountains. Sun night the ridge moves east of the area...as a warm 
front approaches from the Great Lakes. Some light snow possible well 
north and west of Albany associated with an initial shot of warm 
advection. 


On Monday...widespread but mainly light quantitative precipitation forecast is possible. A cut-off low 
will advance eastward across the Great Lakes and more substantial 
isentropic lift commences out ahead of the low across our region. 
GFS/European model (ecmwf) still differ with position of the upper low and surface 
cyclone...with the European model (ecmwf) depicting a more southerly track. This has 
greater implications for the Tuesday/Wednesday time frame...but for Monday both 
model solutions still result in a period of widespread light snow 
with mainly minor accumulations. Some rain may mix in the valleys 
during the afternoon as the boundary layer warms somewhat. 


Monday night into Tuesday is when much more uncertainty develops as to the 
evolution of the cut-off low as it moves east...which has major 
implications for the sensible weather across eastern New York and 
western New England. The GFS and most of the gefs ensemble members 
track the cut-off low right over eastern New York as is deepens...with 
coastal development across far eastern mass and Maine. This scenario 
would keep significant precipitation away from US with just scattered snow 
showers and some lake effect by middle week. The European model (ecmwf) cuts off the 
upper low to our south over the middle Atlantic region which results in 
coastal development near New Jersey...with the low gradually lifting 
northward into southern New England on Wednesday and actually retrograding 
into New York by Thursday. This scenario could potentially result in 
significant wintry precipitation. Will keep things somewhat simple for 
now and mention mainly chance probability of precipitation through Tuesday night and keep ptype 
snow/rain based on elevation and diurnal cycle. Overall..less 
confidence than normal for this forecast period. 


&& 


Aviation /06z Thursday through Monday/... 
a clipper type system diving southeast across the eastern Great 
Lakes early this morning will move into central New York/PA later this 
morning into the afternoon. This will result in ceilings lowering at the 
taf sites...with some occasional flurries possible at kalb/kpou. 
Generally VFR conditions should prevail...although some brief MVFR 
visibility/ceilings possible. Omitted from tafs due to low probability of 
occurrence. Farther north near kgfl flurries will be more sporadic. 
Flurries should end by early afternoon...but plenty of cloud cover 
will persist courtesy of an upper level trough settling in across the 
region. Winds will be variable less than 5 kts through much of the 
morning...then becoming northwest around 7-10 knots by this afternoon. 


Outlook... 
Thursday night...VFR. No sig weather. 
Fri-Sat...VFR...isold -shsn. 
Sun...VFR. No sig weather. 
Monday...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. 


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...jpv 
aviation...jpv 
hydrology...jpv 

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