Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 241100

Area Forecast Discussion
National Weather Service Burlington VT
700 AM EDT Mon Oct 24 2016

The North Country will remain in cyclonic flow with variable
cloudiness and cooler than normal temperatures through most of
the week. A secondary trough moving into the region from the
northwest late Monday will bring a chance of light rain showers,
with snow showers possible across the northern Adirondacks and
northern Green Mountains through Tuesday night. A more significant
wave of low pressure approaching from the Great Lakes and Ohio
Valley will bring the next chance for rain, generally late
Thursday into early Friday.


As of 700 AM EDT Monday...Low clouds persist in cold air
advection with water vapor imagery showing increase in moisture
over the North Country. Prevailing westerly flow continues to be

Overall quiet weather to start the period with variable clouds
and increasing W-NW winds becoming gusty by midday. As we remain
in broad cyclonic flow expect low- level cold air advection to
increase low level clouds today. Water Vapor imagery showing weak
shortwave embedded in 500mb flow that looks to affect the North
Country with slight to low chance for rain showers, especially in
upslope and higher terrain areas of Green Mtns and Adirondacks
this afternoon but more so overnight. Areas above 1500 feet likely
to see snow showers mixing with mostly snow expected above 2000ft.
With dewpoint temps in the 20s overnight, can`t rule out a couple
wet flakes in the valleys. Light snowfall accumulations expected
this afternoon and overnight...generally a dusting to 2 inches in
the highest elevations of the Northeast Kingdom.

Temperatures today look to peak today in the low 40s to around 50
for most areas. Overnight lows will range from the upper 20s to
mid 30s.


As of 400 AM EDT Monday...A 1 to 2 STD below normal mid/upper
height field associated with a trof across the northeast CONUS
will continue to provide our region with below normal temps
through midweek. The combination of favorable 925mb to 850mb
upslope flow and ribbons of deeper layer moisture associated with
cyclonic circulation will continue to produce terrain focused
precipitation through Tuesday. The associated low level wind
fields are between 20 and 30 knots on Tuesday result in limited
low level forcing from upslope component...but weak embedded vort
at 500mb and some low level cold air advection will be enough to
produce light qpf across the mountains. Will mention likely pops
for Tuesday...with qpf generally 0.20 or less across the northern
dacks and western slopes...with only a trace to couple hundredths
in the valleys.

Thermal profiles show both 925mb and 850mb temps below 0c...with
850mb temps near -10c by 00z Weds...supporting mostly
snow...except the valleys and near the warmer Lake. Speaking of
Lake Champlain...some enhanced precipitation is possible on the
east side of the lake with moderate instability created between
the air/water temp difference...especially on Tuesday.
Also...noted with boundary layer heating and cold air
aloft...lapse rates steepen on Tuesday afternoon...supporting some
convective elements with potential graupel in the valley. Thinking
any snow accumulation below 1000 feet will be difficult during the
daytime...but some minor accumulation above 1000 feet between a
dusting to several inches is likely across the northern dacks and
mountains of central/northern VT. Its never too early to start
building the snow pack. Thermal profiles support about a 20 degree
difference between lower/mid 20s mountains summits to lower/mid
40s valleys on both Tuesday and Weds...with lows mainly upper
teens to lower 30s.


As of 400 AM EDT Monday...Active pattern continues for days 4
thru 7 with additional chances for rain and snow on Thursday into
Friday and another system next weekend. Overall...given the
progressive west to northwest flow aloft...temps will stay below
normal thru the period with additional chances to increase snow
pack across the mountains...especially Thursday Afternoon.

GFS/GEM and ECMWF in good agreement with potent 5h energy in the
northern jet stream crossing the Great Lakes and NE CONUS on
Thursday into Friday. Meanwhile...initial surface low pres tracks
across the central Great Lakes with weak secondary development
over southern New England by 12z Friday. The combination of 1036mb
high pres over eastern Canada and developing secondary low
pres...suggests warmer air will have difficulties advecting into
our region...supporting potential for additional snow
accumulations in the mountains. Sea level pres fields show a cold
air damming signature. Latest ECMWF only briefly increases the
850mb temps to 0c around 06z Friday...before winds shift to the
northwest and colder air follows. Current thinking a band of
rain/mixed with wet snow flakes develops from southwest to
northeast on Thursday...associated with moderate to strong warm
air advection. The combination of evaporational cooling and
progged 925mb to 850mb profiles below 0c initially supports even
some wet flakes in the valley with no accumulation...before
quickly turning over to rain. Meanwhile...cold air remains locked
east of the greens and across the northeast kingdom with a longer
duration of snow...with several inches of wet snow accumulation
possible Thursday afternoon/evening...before changing over to
rain. Mountain thermal profiles are tricky as progged 850mb temps
stay near 0c...but warm nose around 5000 feet associated with
southerly jet...supports some freezing rain possible near the
summits of the dacks and greens on Thursday Night. It shall be
interesting to see what the picnic table on Mansfield receives.

Otherwise...the potential for gusty downslope southeast winds
will have to be latest GFS shows 850mb winds of 40 to
50 knots. The strongest winds are collocated when precip will be
falling and difficult to determine how much mixing will
occur...but something to watch along the western slopes on
Thursday afternoon/evening.

Next system arrives late Saturday into Sunday with additional
chances for precipitation and once again thermal profiles support
mainly rain valleys and a mix in the 850mb 0c line
bisects the area. Temps during the period mainly in the 30s
mountains and 40s valleys with lows in the 20s to mid/upper 30s.


.AVIATION /12Z Monday THROUGH Friday/...
Through 12z Tuesday...Prevailing VFR conditions with brief MVFR
ceilings at SLK this morning. Westerly winds increasing at 10-15
with gusts up to 25 knots during the day.

Chances for showers increase tonight as embedded pieces of energy
in the midlevel cyclonic flow move over the North Country. MVFR
conditions may develop overnight at SLK and MPV.

Outlook 12z Tuesday through Friday...

12z Tuesday through 00z Wednesday: VFR ceiling with possible MVFR
showers and higher elevation snow snow showers as a broad upper
trough remains over the region. Increasing chances for MVFR
ceilings at MPV/SLK later Monday night through Tuesday, with
periods of light precipitation and MVFR cigs/vsby conditions.

00Z Wednesday through 00Z Saturday: Next low pressure system
approaching from the Great Lakes/Ohio Valley brings chances for
widespread showers and periods of MVFR conditions late Thursday
through the first half of Friday.


AS OF 420 AM EDT MONDAY...A Lake Wind Advisory goes into effect
for Lake Champlain this afternoon.

Winds out of the west at 10 to 20 knots today will shift
northwest and increase to 15 to 25 knots this afternoon. This will
result in choppy waters as wave heights increase to 2 to 4 feet
with the highest waves along eastern shores exposed to a greater
fetch on northwest winds; specifically those locations adjacent to
the open waters north of the Charlotte Ferry and south of Valcour
Island. Expect these strong winds and waves to continue into




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