Area Forecast Discussion
Issued by NWS Burlington, VT
FXUS61 KBTV 252256
Area Forecast Discussion
National Weather Service Burlington VT
656 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 /THROUGH WEDNESDAY/...
As of 655 PM EDT Tuesday...Regional composite radar mosaic
continues to reveal weak reflectivity returns associated with
light rain or snow showers in the prevailing deep northwest flow.
Due to wet- bulb cooling effects, there has even been some
flurries (9 SM visibility) observed in Burlington, marking the
first flakes of the 2016-2017 cold season in Burlington. High-
resolution mesoscale model output continues to depict periods of
isolated to scattered snow showers through a good part of the
overnight; with that in mind, I`ve opted to introduce areal
coverage wording (isolated/scattered) to the Wx grids with this
update, and also introuding some flurries in parts of the northern
Champlain Valley as well. While snow levels do fall from 1500` to
around 500`, the greatest likelihood of accumulations of 1-2"
still to be comfined the higher summits of the northern Greens.
While snow levels drop, BTV-4km WRF BUFKIT soundings reveal an
increasingly unsaturated dendrite snow growth layer and a portion
of the cloud-ice layer by the early morning hours. So it`s
possible that the guidance is indicating more riming than actual
snowflakes at that point and will be considered in the later
evening update. Aside from that minor wording adjustment to the Wx
grids, no significant changes were made. Lows a few degrees around
freezing still appear on track.
Previous near-term discussion issued at 200 pm Tuesday follows...
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 /WEDNESDAY NIGHT THROUGH THURSDAY/...
As of 331 PM EDT Tuesday...Wednesday night will remain quiet as a
brief area of high pressure will move through the North Country.
Clouds cover will be slowly decreasing with a few breaks likely
working in but we will stay partly to mostly cloudy throughout.
Cold air advection will remain in place and overnight lows will be
on the chilly side will low 20s in the typical cold locations of
the Northeast Kingdom and northern Adirondacks. Along Lake
Champlain and the nearby locations temps will be in the upper 20s
to low 30s.
Thursday clouds will thicken as a low pressure system begins to
dig in to the north country. Cold air will remain in place over
the eastern portion of the forecast area as we will be in cold air
daming situation with the high pressure over eastern Canada and
the deepening low over the Great Lakes. The system looks fairly
strong as a warm front will bring some warm advection snow
Thursday morning before switching over to rainfall for all
locations below 2500`. Above 2500 expect a mix of snow and mixed
precip for the duration as the max t aloft hovers right at 0C or
below. Guidance continues to show a strong 850mb southerly jet
that develops during the day on Thursday however the max winds
will coincide with the heaviest precip so mixing wont be all that
strong. Downslope winds on the northern facing mountains will
likely be in the 20-30mph range.
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
As of 359 PM EDT Tuesday...Overnight Thursday the ptype forecast
become a bit more tricky. Guidance shows 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/sleet/freezing rain across
the Adirondacks and eastern Vermont. As the low pushes east on
Friday, thermal profiles become more supportive of a transition
back to snow elevations above 1000ft, 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 with the highest snow totals in the 6-8" range along
the spine of the Green Mountain with 8-12" across the high peaks
of the Adirondacks. Elsewhere expect between a dusting to 2
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 /00Z Wednesday 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.