Area Forecast Discussion
Issued by NWS Burlington, VT
FXUS61 KBTV 251827
Area Forecast Discussion
National Weather Service Burlington VT
227 PM EDT Tue Oct 25 2016
Low pressure over the Canadian Maritimes will maintain cloudy
conditions and a few snow showers across the higher terrain of the
Adirondacks and northern Vermont through tonight. High pressure
building in from the west will yield lighter wind speeds and some
additional sunny breaks during the day Wednesday. It will remain
seasonably cold with afternoon highs in the upper 30s to lower
40s in most areas. A widespread precipitation event is expected
later Thursday into Friday as low pressure approaches from the
Great Lakes and Ohio Valley region. Precipitation type will be
predominantly rain in the valleys, but some snow accumulation or
mixed precipitation is likely in the mountains at times Thursday
night into Friday morning.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 200 PM EDT Tuesday...Continue to see some weak reflectivity
returns associated with shallow instability showers in NW flow
across nwrn and n-central VT. At 18Z, boundary layer is warm
enough to generally yield rain in the Champlain Valley (38-42F),
but seeing some intermittent light snow in surface obs across
n-central into nern VT in sfc obs and available wx cams. Road
surfaces are above freezing, so not anticipating any travel issues
through this evening. Freezing levels this afternoon generally
around 1500ft, and will gradually fall to around 500ft by 06Z
tonight. Will see continued chances of upslope snow showers thru
the first half of tonight, with a dusting to 0.5" possible in
communities east of the Green Mtns. Could see a max of 1-2" at the
higher summits of the nrn Greens, including Jay Peak and Mt.
Mansfield. Thereafter, anticipate some low-level drying, and
majority of mesoscale models indicate decreasing precip chances
per simulated reflectivity fields. Moderate NW winds this
afternoon (10-15kt with gusts around 20kt), will generally
decrease overnight to 5-10kt, with little change in direction.
Combination of continued stratus/stratocu and winds will keep
temps from dropping too significantly; looking at overnight lows
upr 20s to lower 30s, warmest near Lake Champlain.
Generally going with a dry forecast Wednesday as surface high
pressure builds ewd into nrn NY by afternoon. May see a few
flurries far nern VT. Weaker p-gradient will also result in
lighter winds, mainly 6-10mph. Decreasing low-level RH fields
suggest we`ll see some additional sunny breaks, especially away
from the higher terrain areas. 850mb temps at 18Z Wed still -9C
to -10C, so will remain colder than normal for late October.
Valley highs mostly 40-44F, with a few upr 30s far nern VT and
across the nrn Adirondacks.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
As of 411 AM EDT Tuesday...Wednesday and Wednesday night will
likely be the quietest 24 hours of the next 7 days as a brief area
of high pressure both at the surface and aloft swing through the
North Country. The day will begin fairly cloudy across the higher
terrain with perhaps a few mountain snow showers lingering, while
in the deeper Saint Lawrence and Champlain Valleys some breaks in
the clouds will be developing. By the afternoon low/mid level
moisture will be decreasing with cyclonic flow aloft trending to
anti-cyclonic as an upper trough exits to our east and high
pressure builds in. Strong cold air advection remains in place on
brisk northerly flow so expect highs to continue to run well below
normal in the low 40s across the deeper valleys to upper 30s
elsewhere. Wednesday nights temps follow suit, running about 5-10
degrees below normal, mainly in the 20s to locally around 30 in
the Champlain Valley along Lake Champlain, to upper teens in the
coldest hollow of the Northeast Kingdom and northern Adirondacks.
.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 411 AM EDT Tuesday...Thursday onward through the weekend
the pattern becomes quite active again with mean troughiness
redeveloping aloft across the eastern CONUS and 2 clipper-like
systems bringing mixed precipitation to the North Country.
The first and more robust system comes Thursday mid-day through
Friday as low pressure develops out of the Great Lakes/Ohio River
Valley region and tracks northeast to the Maine coast by Friday
night. Precipitation along a warm frontal boundary works its way
into the area fairly quickly by mid-day on the nose of a strong
40- 50kt 925-850mb south-southeasterly jet with thermal profiles
initially supporting a mix of rain and snow in the valleys and
snow at the higher summits, but by the afternoon and overnight the
ptype forecast become a bit more tricky. Latest trends in NWP
guidance indicate a warm nose slightly above 0C at 925-850mb works
in after 00z and this coupled with marginally warm boundary layer
temps supports rain in the deeper valleys and a mixed bag of
rain/snow with possible brief periods of sleet and/or freezing
rain across the Adirondacks and eastern Vermont. As the low pushes
east on Friday, temps aloft support a transition back to snow for
the summits, but the boundary layer remains too warm at the
surface supporting showers/rain as precip becomes more orographic
in nature on developing northwest flow. Early thoughts on storm
totals through Friday show the highest elevations the big snow
winners with 6-8" along the Green Mountain spine, to 8-12" across
the high peaks of the Adirondacks. Below 1500 feet, a dusting to
perhaps 2" is possible outside of the Champlain and St. Lawrence
The strong jet mentioned above also presents the potential for
gusty downslope winds along the Green Mountain spine Thursday
night, but currently coincides with the bulk of precipitation
falling which limits mixing potential. While I think winds will be
gusty across the southeast downslope communities along the western
slopes, overall impacts should be minimal with gusts peaking only
in the 20- 30mph range.
Next system looks to swing through Saturday through Saturday
night, taking a more northern track than its predecessor, offering
even warmer thermal profiles, enough to produce mainly rain
showers with highs pushing into the mid/upper 40s. Behind it, high
pressure looks to return for Sunday night into Monday.
.AVIATION /18Z Tuesday THROUGH Sunday/...
Through 18z Wednesday...BKN-OVC areawide through tonight.
Ceilings generally around 4kft (VFR), but will see MVFR ceilings
redevelop this evening thru overnight at SLK/MPV. Also included
VCSH at SLK/MPV for passing flurries or light snow showers, which
are most likely to occur thru the first half of tonight (04Z Wed).
Not expecting any impact to airport ground ops. Decreasing clouds
and becoming VFR all areas after 15Z Wednesday. Winds still
W-NW...12-15kt through 00Z, then decreasing...5-10kts tonight
Outlook 18z Wednesday through Sunday...Primarily VFR through 15Z
Thursday with high pressure in place. Low pressure approaching
from the ern Great Lakes and Ohio Valley will bring prevailing
MVFR with intervals of IFR possible later Thursday thru early
Friday. Will see valley rain, and possible snow/mixed pcpn at
times for SLK/MPV during the event. After a brief break Friday
aftn/night, a warm front approaching from the WSW could bring
additional showers Saturday into Saturday night.
As of 1055 AM EDT Tuesday...northwest winds have been gusting 25
to even 30 knots this morning, and this is expected to continue
well into the evening. There may be a little bit of a decrease of
the gusty winds during the early/mid afternoon, however another
increase is expected during the late afternoon into mid-evening
hours. These winds will produce rough/choppy conditions, with
waves 2 to 4 feet. Winds will decrease to 15 knots or less late
tonight and Wednesday.