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Area forecast discussion 
National Weather Service Upton New York 
751 PM EST Tuesday Dec 2 2008 


Synopsis... 
high pressure along the middle Atlantic coast will control the weather 
on Wednesday before moving east on Thursday. A cold front will 
move across the local area Thursday afternoon followed by cold 
Canadian high pressure building over the region for Friday and 
Saturday. An Alberta clipper will pass over the region on Sunday 
followed by more cold high pressure on Monday. 


&& 


Near term /until 6 am Wednesday morning/... 
the strato cumulus will gradually dissipate this evening with the 
loss of day time heating and the cirro status will advect out of 
far eastern portions of the region shortly. Thus expect a good 
view of The Crescent moon with Venus and Jupiter in the southwest 
sky this evening. 


A mainly clear night forecast as the upper trough lifts out and 
the winds subside. This results in good radiational conditions 
across the region and temperatures from MOS is accepted - near freezing 
in the city - 20's elsewhere. 


Forecast on track...with just some minor tweaks to grids based on 
latest observation/Sat/mod data. 


&& 


Short term /6 am Wednesday morning through Thursday night/... 
12z deterministic NCEP model runs and 09z sref are very consistent 
with a cold frontal passage for Thursday afternoon. Probability of precipitation are lowered based 
on latest guidance to slight chance along the coast. 


Temperatures on Thursday expected to reach 50 in most locations in mild 
southwest flow just ahead of the cold front - though clouds from 
warm advection aloft limits sunshine. Temperatures again are from blended 
MOS. 


Breezy too on Thursday especially across Long Island with gusts 
to 30 miles per hour - gales possible on the waters. 


Cold advection prevails Thursday night in wake of the cold front. 
Will carry scattered flurries over the interior...as downslope 
should kill most flurry activity down on the coastal plain. 


&& 


Long term /Friday through Tuesday/... 
main focus of the extended is on the late weekend period. 


1045 hpa high currently over Alaska will be located over the central 
Continental U.S. 12z Friday. Mslp 1035 hpa or so. Cold air advection on Friday with temperatures blw 
climatology. Blend of men and gmos used. Synoptic subsidence and dry low 
levels despite moisture at the -12 to-15c level. Perhaps a flurry but 
will not include in the grids at this time. 


GFS ensembles/operational GFS and 12/00z European model (ecmwf) forecast waves of low 
pressure developing offshore through the weekend as 500 mb trough digs southeastward 
into the region. High amount of uncertainty with the details. All 
models do keep the surface lows offshore so precipitation type will generally be 
snow...exception may be parts of Li and eastern CT. Forecast reflects 
increasing chances Sat night into sun...ending Sun night. Could see 
a MDT band but this will be dependent on where and if a weak low 
develops and is able to transport a bit more moisture into the County Warning Area 
to go with the strong upper level dynamics. 


High pressure then builds in for Monday with gusty winds diminishing late. 


Model solutions all over the place for Tue/Wed...but there looks to 
be some activity in store. At this time some fz precipitation may develop ahead of a 
mostly rain event. 


&& 


Aviation /01z Wednesday through Sunday/... 
VFR through 00z Thursday. 


Shortwave slides NE of region overnight as high pressure builds 
from the south with skies clearing. High cloudiness moves over 
the terminals after 12z Wednesday today as the ridge axis moves east. 


Light west-southwest flow...becoming southerly late Wednesday afternoon into Wednesday 
night as high pressure slides offshore and ahead of approaching 
cold front. 


Outlook for 00z Thursday through Sunday...cold front moves 
through late Thursday night into Friday morning. Some flurries may 
accompany the front with local and brief MVFR to IFR visibilities. 
Strong and gusty northwesterly winds behind the front Friday will 
impact area terminals. Otherwise...VFR until late Saturday night 
into Sunday when a clipper system moves through the area bringing 
light snow with MVFR to IFR conditions. 


&& 


Marine... 
winds have diminished to below small craft levels on all waters, 
but seas remain in the 5 to 9 feet range on the ocean. Thus, small 
craft on the ocean is continued for hazardous seas. Based on 
latest wave watch...seas on eastern ocean don't fall below 5 feet 
(hazardous seas criteria) until late Wednesday morning. 


Winds quickly increase in the warm advection early on Thursday ahead 
of the next cold front. It appears that we may approach gales and 
thus have highlighted this in our hazardous weather outlook. 


Cold advection in the wake of the cold front Thursday night is 
expected to remain in the small craft criteria range. 


Long term...possible Small Craft Advisory winds diminish during the day Friday. Chance 
of shsn over the ocean Friday night into Sat with cold air advection. Waves of low 
pressure will develop well offshore over the weekend. A strong system 
will drop southeastward late sun resulting in possible gales Sun night into 
Monday. 


&& 


Hydrology... 
no significant precipitation expected through Saturday. 


&& 


Okx watches/warnings/advisories... 
CT...none. 
New York...none. 
New Jersey...none. 
Marine...Small Craft Advisory for hazardous seas until midnight EST 
tonight for anz355. 
Small Craft Advisory for hazardous seas until 11 am EST 
Wednesday for anz350-353. 


&& 


$$