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Area forecast discussion 
National Weather Service Burlington Vermont 
252 am EST Sat Nov 22 2008 


Synopsis... 
below normal temperatures will continue across the north country 
through next week. An upper air disturbance will bring snow 
showers or flurries to the region through Saturday. Gusty 
northwest winds are also expected across the region on Saturday 
as an intensifying low pressure area moves into the Canadian 
Maritimes on Saturday. A weak ridge of high pressure will build 
into the region on Sunday. A low pressure area moving southeast 
across the Great Lakes on Monday will bring more precipitation to 
the north country next week. 


&& 


Near term /until 6 am this morning/... 
as of 915 PM EST Friday...quick update to this evenings 
forecast...mainly to reflect current and expected coverage of shsn 
activity across the area this evening...and to tweak sky cover per 
latest satellite/surface observations. Latest synoptic map showing 
coastal cyclogenesis well underway south of the 40n/-70w benchmark 
this evening...with moist cyclonic flow persisting across northern New 
England/SC Canada. As this system pushes quickly northward later 
tonight...digging upper trough and associated middle/upper level height falls 
should build southward into northern New York/New England. This combined with a 
general increase in middle level moisture advection should allow scattered to 
occnly numerous shsn activity to increase in areal coverage after 
midnight...especially in the northern mountains where some minor/light accumulate likely. 
Have tweaked pop/weather grids based off latest radar/surface observation and 
new model guidance...showing highest coverage this evening across 
the northern greens...with activity then building into the northern dacks and 
southward into the southern greens by later tonight. Other than these 
changes and some small sky cover adjustments inherited forecast in good 
shape and no other changes needed at this time. Enjoy the evening. 


&& 


Short term /6 am this morning through Monday/... 
as of 355 PM EST Friday...gusty winds during the day Saturday as 
pressure gradient increases and surface low pressure which passed 
off the coast of New England overnight will move north into the 
Canadian Maritimes. Cold air advection continues across the region and gusty northwest 
winds will affect the region. Upslope snow showers 
continue...especially the western slopes of the Green Mountains. 
Have continued to use the NAM 12 bias corrected numbers for 
temperatures...which has done a better job with maximum and min temperatures 
the past couple days as the other models are much too high. A 
weak ridge of high pressure will build into the region Saturday 
night. Have gone warmer than guidance for min temperatures Sunday night 
as warm air advection begins to edge into the area ahead of approaching low 
pressure system...thicknesses will increase and 850 temperatures respond 
as well. 


&& 


Long term /Monday night through Friday/... 
as of 252 am EST Saturday...a digging upper trough pushing through 
the Great Lakes/Ohio Valley region Monday is expected to deepen 
significantly and become a closed low Monday night over the middle 
Atlantic and northeast. Upper level forcing increases significantly 
by Tuesday morning as surface low pressure continues to deepen. 
GFS has shown good continuity with this system thus far and have 
weighted the forecast heavily towards this solution. 


Deep-layer cyclone cuts off to our south on Tuesday...and position 
of the low will and subsequent isentropic lift will determine 
ptype and potential for locally high winds. Based on current 
guidance...it appears that mixed precipitation will move east to 
west across Vermont into the eastern Adirondacks with surface temperatures 
increasing to the middle-upper 30s. Meanwhile across western 
portions of the northern Adirondacks and Saint Lawrence valley 
ptype looks to remain all snow with possibly some sleet mixed in 
late in the day. Moderate snow accumulations certainly look 
possible at this tie...but too early to tell. Other concern is for a 
downslope wind event along the western slopes of the Green Mountains. 
The 00z GFS continues to indicate 60+kt winds at 850hpa and 50kts 
at 925hpa Tuesday which could result in a potentially damaging 
wind event along portions of the western slopes...but its too 
early to have high confidence in this until the intensity and 
position of the easterly jet can be better determined. Stay tuned 
for further details on potential impacts from this system. 


Deep-layer low eventually lifts away from the region during the 
middle-late week period though continued cyclonic flow regime will bring 
abundant cloud cover and periods of snow showers to the north 
country through the remainder of the week with temperature 
remaining slightly below normal. 


&& 


Aviation /08z Saturday through Wednesday/... 
through 06z Sunday...overnight conditions will continue to vary 
from Vermont to northern New York through morning. Energy from 
coastal low combined with approaching upper trough has enhanced 
snowfall across the Champlain Valley of Vermont and into central 
Vermont tonight on northwest flow. Expect these conditions to continue 
overnight before northwest flow increases after 12z and pushes snow 
activity east of the Green Mountains. For northern New York 
not much to worry about over the next 24 hours with generally 
4-5kft VFR overcast deck with only exception at kslk where continued 
MVFR conditions should continue through 15z with on and off snow 
showers. As with Vermont...winds will become gusty out of the northwest after 
14-15z with surface wind gusts up to 25kts. For Vermont...expect MVFR 
conditions to continue through 10-15z with on and off snow showers 
and brief periods of IFR cigs/vsby. After 15z northwest flow increases to 
15-25kts and will push snow activity east of The Greens where only 
site affected after this time will eb kmpv where IFR conditions 
will prevail after 18z through the remainder of the period. 


06z Sunday through Wednesday...ridge of high pressure brings 
mainly VFR weather conditions for Sunday with middle-upper level clouds 
only. Should see a break in snow shower activity on Sunday. A warm 
front lifts across the area Sunday night...which may bring some 
light snow along the international border...with periods of MVFR conditions. 
Significant storm possible Tuesday with widespread mixed wintry 
precipitation and IFR conditions. May also have to contend with a 
downslope wind event along the west slopes of the Green Mountains with 
strong gusty east-southeasterly winds. Details are yet to be determined at this 
time range and will ultimately depend on the track and intensity 
of the low pressure system. Will continue to monitor this 
potential. 


&& 


Equipment... 
computer specialists have rectified the local server problem that 
had limited data flow to specific web-based and phone recorded 
products over the past 48 hours. All data flow problems appear to 
have been corrected at this time. We apologize for any inconvenience 
this has caused. 


&& 


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


&& 


$$ 
Synopsis...neiles 
near term...jmg 
short term...neiles 
long term...lahiff 
aviation...lahiff 
equipment...weather forecast office btv 

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