086 
fxus61 kaly 091143 
afdaly 


Area forecast discussion 
National Weather Service Albany New York 
643 am EST Friday Jan 9 2009 


Synopsis... 
weak high pressure will build into the region later today and 
tonight. On Saturday a low pressure system will move from the 
Ohio Valley to the virginias...then off the New Jersey coast 
Saturday night. This system will bring a moderate to potentially 
heavy snowfall...especially south of the capital region. The storm 
system will quickly depart by Sunday morning...with high pressure 
building back in Sunday night. 


&& 


Near term /until 6 PM this evening/... 
a fairly tranquil day expected today. There are still a few very 
narrow and mainly light lake effect snow showers moving across 
portions of the eastern Catskills early this morning with northwest flow 
persisting. Will mention 20-30 probability of precipitation across this area this morning 
with only a few tenths of a inch of accumulation in isolated 
spots. Elsewhere will mention scattered flurries into this 
morning. Inversion heights are forecast to drop to around 900 mb 
today...which should limit the intensity and coverage of snow 
showers...hence the low probability of precipitation. By this afternoon the entire area 
should be dry as high pressure builds in from the west. Most areas 
will see at least some sunshine by this afternoon...with 
mountainous areas hanging onto cloud cover the longest. Maximum temperatures 
somewhat chilly with middle teens to lower 20s across the higher 
elevations and middle 20s to lower 30s in the valleys. 


&& 


Short term /6 PM this evening through Sunday/... 
a Winter Storm Watch has been issued for Ulster...Dutchess and 
Litchfield counties from Saturday afternoon into Sunday morning... 


High pressure building in should ensure a quiet night with mainly 
clear skies early...and high clouds increasing towards morning. 
Winds speeds will also be decreasing...so radiational cooling will 
lead to cold min temperatures. Single digits to lower teens expected from 
the Mohawk Valley and Saratoga region southward...with lower single 
digits to below zero temperatures north. 


On Sat...attention shifts to the next storm system that will be 
affecting the region Saturday afternoon through early Sun morning. 
Models had previously shown a great deal of spread with this system. 
There are still some differences...but overall better agreement 
especially between the GFS/NAM with regards to track/qpf. The European model (ecmwf) 
continues to be the outlier...with a stronger surface low...greater 
quantitative precipitation forecast and a more northerly track. Will lean towards the more 
consistent GFS solution...although quantitative precipitation forecast has increased in latest run. 
Despite agreement with the track...there are still timing issues 
between NAM/GFS...with the NAM much slower with onset of precipitation. 
Will lean towards faster GFS...with warm advection regime typically 
resulting in earlier onset. Will mention likely to categorical probability of precipitation 
south of Albany from Sat afternoon through 00z Sunday...with likely 
to categorical probability of precipitation across almost the entire area Sat night into 
early Sun morning. 


Synoptically...this storm will be a fast-moving system with an open 
upper level wave. However...the surface low is forecast to deepen as 
it lifts northeast from the Ohio Valley...through the middle Atlantic 
region and off the New Jersey coast Sat night. This track favors all 
snow for ptype. A quick but significant period of isentropic lift on 
the 285 k surface is forecast from early evening into the overnight 
hours. The frontogenesis does not really get going until the storm 
deepens well off the coast and is past our region. However...there 
is some overlap of Omega and favored -12c to -18c dendritic growth 
zone as well...so snow ratios will likely exceed climatology values of 
12.5 to 1. Used mainly 14 to 1 ratios through the event. Heaviest 
quantitative precipitation forecast of 0.50 to 0.75 forecast across Ulster...Dutchess and Litchfield 
where the Winter Storm Watch has been issued. Based on expected snow 
ratios...this is where snow accumulations of 7 or more inches is 
expected to fall. Advisories may eventually be needed for the Mohawk 
Valley and capital region southward through green...Columbia and 
Berkshire counties...where 3 to 7 inches is possible. At this time 
only light snowfall amounts expected across the southern Adirondacks. 
Snow should start to diminish around or shortly after sunrise from 
west to east across the area. Dry conditions expected Sunday 
afternoon. 


&& 


Long term /Sunday night through Thursday/... 
region remains under a long wave trough through the period. The 
pattern is expected to amplify by middle week as Arctic air plunges 
southward and a deep broad trough covers the Continental U.S. East of The 
Rockies. On Thursday 850 mb temperatures across the local area are 
forecast to drop to -20 to -25 degrees celsius. The low which will 
bring snow to the region over the weekend will head northeast up the 
New England coast Sunday night and weak surface ridging will build 
in. The high's visit will be brief as more energy dives into the 
long wave trough and spins up another low pressure system which will 
move across the region early in the week. Arctic air will begin to 
pour into the region in the wake of this system Tuesday. 
However...yet another low pressure system will spin up as more 
energy dives into the long wave trough. This time the low is 
forecast to pass to our south Wednesday night or Thursday then 
even colder air will be ushered into the region. 


&& 


Aviation /12z Friday through Tuesday/... 
VFR conditions expected at taf sites through taf period...12z/Sat. 
West-northwest winds 10 to 15 knots will become gusty this morning with 
gusts around 25 knots especially at kalb. The winds will diminish 
Friday evening. Scattered to broken stratocumulus clouds expected 
today with skies clearing early this evening. High level cirrus 
clouds overspread the region late tonight in advance of an 
approaching low pressure system. 


Outlook.... 
Sat...VFR-MVFR...snow overspreading during the afternoon. 
Sat night...MVFR-IFR in snow. 
Sun...improving conditions with snow ending. 
Sun night...VFR...no sig weather. 
Monday...VFR with MVFR possible...slight chance to chance snow showers. 
Monday night-Tue...VFR- MVFR...chance snow. 


&& 


Hydrology... 
few...if any...hydrology related problems are expected through the 
weekend and into the coming week. 


Seasonable temperatures into early next week with an Arctic airmass 
expected for middle week. Ice will form and thicken especially early 
next week as temperatures plunge well below freezing and it may get 
cold enough across the Adirondacks and southern Vermont for some 
isolated freeze up river ice jams to form by Tuesday. Housatonic 
flow has had only a slight increase...so little if any ice movement 
may be expected. 


Snow water equivalent data from field surveys show 3 to 7 inches 
of water over much of the Adirondacks...with 2 to 4 inches of 
water in southern Vermont. Our initial 08-09 winter Spring flood 
potential outlook will be issued on Friday Jan 9th. 


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


&& 


Aly watches/warnings/advisories... 
CT...Winter Storm Watch from Saturday afternoon through Sunday 
morning for ctz001-013. 
New York...Winter Storm Watch from Saturday afternoon through Sunday 
morning for nyz063>066. 
Massachusetts...none. 
Vermont...none. 


&& 


$$ 
Synopsis...jpv 
near term...jpv 
short term...jpv 
long term...iaa 
aviation...iaa 
hydrology...iaa 

National Weather Service Glossary of Abbreviations

Non-Expanded Version (with abbreviations)