836 
fxus61 kaly 140137 
afdaly 


Area forecast discussion 
National Weather Service Albany New York 
835 PM EST Sat Mar 13 2010 


Synopsis... 
a Nor'easter will impact the region through the weekend with 
abundant moisture and windy conditions. Temperatures are expected 
to vary greatly from the valley floor into the higher terrain with 
a variety of winter precipitation types expected. This storm will 
exit the East Coast early next week with drier and seasonable 
conditions. 


&& 


Near term /through Sunday/... 
as of 830 PM...impressive downsloping continues thanks to an 
easterly wind averaging about 30 miles per hour...higher across the higher 
terrain. Very little if any rain has fallen in the Hudson Valley 
north of Kingston since the afternoon. Meanwhile...Doppler estimated 
radar has indicated over an inch of rain has fallen across portions 
of the Housatonic basin...and just to the west of the Hudson Valley 
floor...in the upslope areas. Our soundings indicate that if 
precipitation were to fall hard enough...it would cold enough for 
snow. We suspect snow is now falling across many areas over 1000 
feet. Had some minor wind damage across portions of the 
Berkshires...but observation indicate than winds are not even close to high 
wind thresholds. Will continue with the Wind Advisory. 


Temperatures generally running 40-45 in the Hudson Valley...30s 
higher terrain. These values should drop a few degrees overnight. 


No changes to headlines anywhere. Just touched up grids. Did lower 
the quantitative precipitation forecast in the Hudson Valley north of Kingston. No impressive 
reports of snow or rain yet but will likely run a public statement 
before news time. 




****************Previous near term discussion*************** 




Quite impressive downsloping event and is quite evident in the 
local radar representation. The Hudson River valley has seen 
little in the way of precipitation with upslope conditions for the 
Berks...northwest CT...helderbergs...Catskills and the dacks. Based on 
spotter reports and hourly rtma analysis...seems the wet bulb zero 
heights are near 1000 feet as this should continue through the 
balance of the near term. Meanwhile...impressive short wave was 
rotating northward from the Outer Banks of NC with an equally 
impressive baroclinic Leaf that evolved. Radar mosaic shows high 
reflectivity's across the state of New Jersey and advancing northward 
through the lower Hudson Valley /there is even some suggestion of 
a Gravity wave propagating/. This will be our trend into tonight. 


&& 


Short term /Sunday night through Monday/... 
NCEP model suite all point toward a moderate to significant event 
for the County Warning Area tonight into Sunday. Increasing wind field and some 
drier boundary layer air to the north will advect southward per 
the low level ageostrophic flow. This seems to be impacting the 
elevations above 1000 feet than the valley. This is where we have 
a variety of headlines with winds...snow...sleet...fzra. The 
heaviest precipitation amounts will likely occur outside of the 
Hudson River valley as strong easterly winds will result in 
downsloping and breaks in the precipitation field. The 850mb and 
925mb Standard deviations of these aforementioned winds are on the 
order of 3 to 5...which all suggest this will be a unique and 
significant event. Overall confidence in this forecast is less 
than ideal with respect to winter headlines as the hires 
NAM/WRF/ruc13 were utilized for thermal profiles tonight. 


A middle level dry wedge approaches during the day Sunday with a 
reduction in the precipitation shield. Although terrain enhancement will 
likely contribute to higher concentration of precipitation. But the 
boundary layer temperatures should climb sufficiently to change most of 
the precipitation into a liquid variety. 


Deformation axis will be the next issue Sunday night into Monday. 
The atmospheric column is expected to cool off further which will 
result in another elevation winter precipitation type issues. Wet bulb 
zero heights are expected to drop back to around 1000 feet /could 
be a little lower/ and will have at least likely probability of precipitation with near 
categorical probability of precipitation for the higher terrain. 


This deformation axis along with the potential for a Mohawk Valley 
convergence mesoscale phenomenon will hang in there Monday as this 
storm slowly tracks away from the middle Atlantic coast. This will 
keep the clouds and the chance for additional accumulating 
precipitation. 


&& 


Long term /Monday night through Saturday/... 
the storm that will have plagued the eastern Seaboard will drift to 
our east by Monday night and slowly get replaced with high 
pressure...not only at the surface but aloft. 


As a result...dry weather will return along with above normal 
temperatures Tuesday through Thursday. Forecast confidence is pretty 
high with scenario. Expect temperatures well into the 50s each 
day...dipping down into the 30s at night with a mostly clear sky. 


By Friday...a backdoor cold front looks to slip south from Canada. 
This feature has limited moisture with it...so for now...went with a 
slight chance on Friday with partial sunshine. Any shower activity 
will be very light and isolated at best. Slightly cooler weather 
will follow for Saturday...but temperatures could still be running a 
tad above normal. With a northwest and somewhat cyclonic 
flow...there might be just enough moisture to trigger some upslope 
isolated showers of rain or snow. Placed 20 probability of precipitation across elevations 
higher than 1000 feet for Saturday. Again...any of these would be 
very light. 


&& 


Aviation /02z Sunday through Thursday/... 
have decided to remove all mention of low level wind shear. Kenx VAD winds indicated 
winds at the 2000 foot level only around 30kts from the east. All 
the tafs were experiencing winds from similar directions and speeds 
less than 25kts compared to the 2000 foot winds...thereby not 
reaching the low level wind shear threshold. 


Downsloping easterly winds holding tough and thus far preventing all 
tafs from going down to IFR. Earlier we though the wind would back 
more to the northeast. There now indications that since the storm 
has become occluded...it will not move much further north and 
therefore the winds will remain more easterly...slowly becoming 
northeasterly by tomorrow. For now...will keep all tafs above the 
IFR/MVFR threshold throughout tonight. Will drop the ceiling below 2000 
feet at kpou by 04z (occasionally before that with a tempo group). 
Still think some sleet will mix the rain at kgfl. 


The east-northeast surface wind will continue around 15kts...gusting to 
25kts...slowly diminishing later tonight into Sunday as the wind 
backs to the NE. 


Look for MVFR/IFR conditions persisting through Sunday. 


Outlook... 
Sun night...improving conditions with decreasing chances for 
precipitation. 
Monday...MVFR-VFR with scattered light rain showers. 
Monday night-Thu...VFR...no sig weather. 


&& 


Hydrology... 
a Flood Watch remains in effect for the southern half of the forecast 
area...including Schoharie...Albany...Rensselaer and Berkshire 
counties southward. 


A complex and fairly long duration rain event will continue through 
the weekend...with the heaviest rain expected late this afternoon 
into Sunday. 


Current quantitative precipitation forecast projections show liquid equivalent precipitation 
amounts will range from around a half an inch across the western 
Adirondacks to up to four inches across portions of Ulster...Dutchess 
and Litchfield counties. 


There are 4-10 inches of water equivalent remaining in the snowpack 
across the Catskills...Adirondacks...greens...and Berkshires...with 
the highest values in the Catskills and southern greens. 


This expected rainfall...along with some snow melt...will likely 
cause some flooding on rivers and streams by Sunday and possibly 
into early next week...mainly for areas south of the capital region. 
Complex temperature profile will result in snow/sleet/freezing 
rain and even a little rain expected over the higher terrain. 


For details on specific area rivers and lakes...including 
observed and forecast river stages and lake elevations...please 
visit the advanced hydrologic prediction service /ahps/ graphs on 
our website. 


&& 


Aly watches/warnings/advisories... 
CT...Flood Watch through Sunday evening for ctz001-013. 
Wind Advisory until 8 PM EDT Sunday for ctz001-013. 
New York...Flood Watch through Sunday evening for nyz047-051>054-058>061- 
063>066. 
Wind Advisory until 8 PM EDT Sunday for nyz032-033-038>040-042- 
047-048-051-054-058-061-063-082. 
Winter Storm Warning until 8 PM EDT Sunday for nyz047-058-063. 
Winter Weather Advisory until 8 PM EDT Sunday for nyz033-042- 
048-051-082. 
Massachusetts...Flood Watch through Sunday evening for maz001-025. 
Wind Advisory until 8 PM EDT Sunday for maz001-025. 
Winter Storm Warning until 8 PM EDT Sunday for maz001. 
Vermont...Wind Advisory until 8 PM EDT Sunday for vtz013>015. 
Winter Storm Warning until 8 PM EDT Sunday for vtz013-014. 


&& 


$$ 
Synopsis...bgm 
near term...bgm 
short term...bgm 
long term...hwjiv 
aviation...hwjiv/kgs 
hydrology... 

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