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fxus61 kbtv 211441 
afdbtv 


Area forecast discussion 
National Weather Service Burlington Vermont 
941 am EST Sat Nov 21 2009 


Synopsis... 
a low pressure system continues to move east through the Canadian 
Maritimes...and will give way to high pressure right into Monday 
before moving offshore. A couple of low pressure systems will affect 
the region Tuesday...and again towards the end of next week. 


&& 


Near term /through tonight/... 
as of 941 am EST Saturday...quick update to the today and tonight 
period...mainly to reflect much slower erosion of pesky cloud cover 
across the region. Current acars data from cyul this morning showing 
impressive synoptic ll inversion near 900 mb...which is acting to 
trap residual ll moisture across much of the area. With 
orographically...albeit light norhwesterly flow persisting across 
our area today...hard to disagree west/NAM BUFKIT sounding forecasts 
showing ll stratocu hanging tough for most of the day...especially in the 
northern mountains thus have opted for more pessimistic chances of 
sunshine today in these areas. Some peeks of sun more likely by 
later in the day in the lower elevations and portions of SC Vermont. By 
tonight...cloud cover should slowly thin/erode as high pressure and 
deep layer drying continue to push into the area. Rest of forecast in 
excellent shape in regard to wind/temps...so other than sky cover 
adjustments noted above no other changes needed at this time. 


Prior discussion... 
remnants of exiting system continue to pinwheel down across the County Warning Area 
this morning...as ll cloud cover blankets the County Warning Area. This exiting low 
over the Maritimes will give way to broad surface ridge...which is 
currently over the Midwest. Expecting inversion to develop during 
the day as ridge builds east. As a result...ll clouds will remain over 
much of the County Warning Area before breaking late in the day. Enough moisture will 
be left over for mention of --rw over hir terrain. Temperatures will be 
constrained from extensive clouds...so have stayed close to guidance. 
Going into the evening hours...skies will clear out allowing for temperatures 
to drop west/radiational cooling. 


&& 


Short term /Sunday through Monday/... 
as of 312 am EST Saturday...nice weather continues into Sunday as ridge 
crests over the region. Inversion will remain for much of the County Warning Area 
during Sunday. This is evident in latest 850 temperatures that work up 
and over broad upper ridge in Great Lakes region...and down upon the 
northeast. Diff is only a few degrees so will only etch up hir 
elev...mainly in nny...high temperatures for Sunday than in adjacent 
valley locales. Surface ridge will begin to slide offshore late 
Sunday. Still expect clring skies overngt for radiational 
cooling...but less than previous night. Weak southerly flow will 
slowly work into western portions of County Warning Area towards morning. This 
will translate to rest of County Warning Area during the day Monday. Clouds on the 
increase Monday as low works up along southeast coast. Ridge in place over 
the NE will keep system at Bay for Monday...W/ only southern zones 
seeing sl chance for --rw on northern edge of approaching system. 


&& 


Long term /Monday night through Friday/... 
as of 411 am EST Saturday...as the above mentioned system moves 
up the Atlantic coast the potential for showers in southern zones 
increases Monday night...with showers possible in eastern Vermont and 
even central/eastern dacks Tuesday. For middle week there remains 
considerable disagreement of guidance with handling of shortwave 
over the Heartland. More specifically...with the fujiwhara effect 
between the primary upper low and Pacific energy that enters the 
broad trough. The GFS offers a much more progressive 
solution...though has been much more inconsistent from run to 
run. The ecmwf's less progressive solution has been more 
consistent and is therefore favored. Under the European model (ecmwf) solution the 
potential for widespread precipitation Tuesday night and 
Wednesday is markedly less than MOS guidance indicates...as the 
ridge of high pressure tries to remain over the region. Through 
differing solutions...both GFS and European model (ecmwf) eventually bring 
precipitation into the northeast around the Holiday...especially 
late Thursday into Friday. Both also bring the first true 
seasonal airmass into the northeast toward the end of the work 
week. Given the uncertainty in placement of surface features and thus 
placement of the cold air...have maintained the rain/snow 
forecast...except at higher elevations which should be cold 
enough for all snow. 


&& 


Aviation /15z Saturday through Wednesday/... 
through 12z Sunday...abundant low level moisture remains over the 
forecast area. Expect MVFR ceilings at most taf sites through the 
morning with 
IFR at kslk. Expect ceilings to gradually improve during 
around 18z...improving to VFR eventually scattered late this afternoon. 
Higher terrain will be obscured in clouds through 18z. Some areas 
of surface wind gusts of 20 kts or greater this morning...notably 
at kmpv...but will diminish by 14z. Otherwise winds will be west to 
northwest around 10 kts...diminishing to light and variable after 02z 
Sunday. Look for the potential for fog to form after 05z Sunday at 
prone locations like kmpv and kslk with MVFR visible. 


Outlook 12z Sunday through Wednesday...MVFR visible posslible at kmpv 
and kslk with br through 14z Sunday. Otherwise VFR conditions 
anticipated for much of the period. Some scattered showers and 
periods of MVFR are possible Tuesday in terraine of southeast Vermont Tuesday. 


&& 


Btv watches/warnings/advisories... 
Vermont...none. 
New York...none. 


&& 


$$ 
Synopsis...jn 
near term...jmg/jn 
short term...jn 
long term...amf 
aviation...amf/rjs