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fxus61 kbtv 211917 
afdbtv 


Area forecast discussion 
National Weather Service Burlington Vermont 
217 PM EST Sat Nov 21 2009 


Synopsis... 
high pressure across the Great Lakes and Ohio Valley states will 
build slowly east tonight and settle across the northeast on Sunday 
into Monday. Therefore...outside any lingering clouds across the 
area this evening...expect generally fair and dry weather during 
the period as temperatures remain on the mild side. The next chance 
of significant precipitation will occur by the middle to later 
portions of next week as low pressure tracks east from the Central 
Plains. 


&& 


Near term /through tonight/... 
as of 217 PM EST Saturday...quiet conds on tap for tonight as broad 
high pressure builds slowly eastward into the area along with dry 
weather. Only problematical question in the forecast for tonight will be how 
long pesky ll stratocumulus deck persists across portions of the 
area. Current acars data out of Montreal (cyul) continues to show 
very sharp subsidence inversion near 900 mb this afternoon...and 
along with orographically favorable though weak northwesterly flow 
clouds have hung tough across many areas today. Given these factors 
have trended toward idea of some brief clearing early this 
evening...then more clouds later tonight along with some patchy 
br/fg. With the clouds...light winds and overall lack of advective 
processes...min temperatures will hold fairly mild overnight by late 
November standards ... out generally in the upper 20s to 
lower 30s most locales. 


&& 


Short term /Sunday through Monday night/... 
as of 217 PM EST Saturday...tranquil and mild late Fall weather then 
continues through the remainder of the short term as aforementioned 
high pressure builds atop the northeast during Sunday/Monday time 
frame. Therefore expect fair and dry conds through the period along 
with a fairly wide diurnal range in temperatures. With shallow nature of 
planetary boundary layer this time of year daytime temperatures will be rather uniform... 
slightly milder perhaps at the higher elevations where shallow planetary boundary layer 
mixing may be able to tap into warmer 925 mb temperatures aloft. Nighttime 
lows will be near seasonal norms...though with at least some 
radiative effects expected...have undercut MOS mins temperatures slightly 
during overnight periods. 


By Monday night...some disagreement begins to creep into the models 
as deeper moisture across the southeast/western Atlantic attempts to 
creep northward beneath western extension of departing ridge axis. 
At this time believe any deeper moisture will have a tough time 
reaching this far north given placement of ll ridge axis...and with 
broad support from this mornings op European model (ecmwf) run and GFS mean 
ensembles have kept sensible conds essentially dry through 12z 
Tuesday. Middle to upper level clouds will likely be on the increase 
however in upper anticyclonic flow...thus have kept overnight min 
temperatures slightly milder than prior counterparts. 


&& 


Long term /Tuesday 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 /19z Saturday through Thursday/... 
through 18z Sunday...low clouds have been hanging in across most 
of the region today...especially over the higher terrain...as a 
low level inversion has trapped this moisture in the lower levels. 
Conditions range from VFR conditions in valley locations to MVFR 
over the higher elevation. Expecting some of this cloud cover to 
become scattered after 00z Sunday...except over the Adirondacks 
and portions of the Green Mountains. Expecting some fog and mist 
to develop tonight...mainly after 05z Sunday...with some MVFR 
ceilings as a high pressure area builds into the region from the 
Ohio Valley. Any fog or MVFR ceilings will dissipate by 14z 
Sunday...with skies becoming mainly clear. 


Outlook 18z Sunday through Thursday...mainly VFR conditions 
expected from 18z Sunday through 12z Tuesday as a ridge of high 
pressure will be over the region. 


Mainly VFR conditions expected from 12z Tuesday through 18z 
Wednesday...as a weak ridge of high pressure will be over the region. 


18z Wednesday through 12z Thursday...areas of MVFR in showers. 
12z Thursday through 00z Friday...mainly VFR. 


&& 


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


&& 


$$ 
Synopsis...jmg 
near term...jmg 
short term...jmg 
long term...amf 
aviation...wgh