Area Forecast Discussion
Issued by NWS Burlington, VT
FXUS61 KBTV 261839
Area Forecast Discussion
National Weather Service Burlington VT
239 PM EDT Wed Oct 26 2016
Partial clearing and light winds are expected tonight as high
pressure briefly settles over North Country. This will lead to
chilly temperatures tonight, with lows generally in the 20s. The
next low pressure system will approach from the Great Lakes later
Thursday, with the primary low tracking into the St. Lawrence
Valley before a secondary low takes over closer to the New England
coast during Thursday night. After increasing cloudiness Thursday
morning, looking for precipitation to develop Thursday afternoon
and continue through Thursday night into Friday morning. After a
brief rain/snow mix, precipitation will be predominantly rain at
elevations below 2000 feet. Several inches of wet snow
accumulation is possible at the higher summits. Total rainfall
amounts generally a half inch to one inch, highest along the
eastern slopes of the Adirondacks and Green Mountains.
.NEAR TERM /THROUGH THURSDAY NIGHT/...
As of 138 PM EDT Wednesday...Mostly cloudy to cloudy conditions
persist in NW flow, with lingering inversion near 5kft (per RAP
soundings) helping to trap moisture and stratocu layer. Sfc ridge
axis across sern Ontario will gradually shift ewd this evening
into tonight. Effect will be for winds to become light and
variable, and should see some partial clearing during after
sunset. Depending on amount of clearing and radiational cooling,
should be a chilly night. Certainly lows in the 20s for most
sections. If skies can become mostly clear, may see a few readings
in the teens for the nrn Adirondacks. Other than a lingering
flurry across n-central into nern VT late this aftn, expecting dry
Dry conditions will be short-lived as next wave of low pressure
approaches from the Great Lakes region on Thursday. Surface low
will shift across Lake Erie/nwrn PA late Thursday morning, with
increasing mid-upr clouds across our area. Leading surge of
850-700mb warm advection and associated precipitation arrives
around 18Z across s-central VT and into the Adirondacks of NY.
Precipitation will overspread the remainder of the North Country
late in the afternoon...early evening for far nern VT. In terms of
precipitation type, PBL will have a chance to warm out ahead of
the arriving precipitation, generally into the low 40s.
Anticipate some wet-bulb cooling with precip onset as column
saturates, allowing for wet snowflakes as low as 500ft elevation
mid- afternoon Thursday, but thereafter, looking at mainly a rain
event below 1500ft with continued WAA and strengthening S-SE
flow. Generally no snow accumulation at all below 1500 ft. May see
a slushy coating to an inch 1500-2500ft. Above 2500ft, temps will
hold on below freezing longer, and could see 4-8" across the
highest summits of nrn NY and central/nrn VT through Thursday
night. With a 50-kt sly low-level jet, there is a warm (above
freezing) layer that comes in above summit level, so may see some
periods of sleet as well into Thursday night. So, not expecting
any impact for population/roadways, but the highest summits could
see a moderate accumulation of wet snow based on current trends.
Highs on Thursday generally in the low-mid 40s, and near freezing
across the highest summits of VT and nrn NY.
One other issue will be moderate winds on the western slopes of
the Green Mtns, and across all of the higher terrain. SE winds
peak during Thursday evening, and should see 15-25 mph with a few
gusts 30-35mph possible along the immediate western slopes, as
primary surface low tracks into the St. Lawrence Valley. Later
Thursday night, gradient slackens as secondary low development
takes place across sern new England...and should see sfc winds
weaken. Stable low-level conditions will limit areal coverage of
gusty winds to the immediate wrn slopes. Winds at summit level
could reach 50mph consistent with model soundings closer to
In terms of total QPF, looking for some precipitation enhancement
along the ern slopes of the Greens and into the ern slopes of the
Adirondacks given low-level sely (upslope) conditions. Total
rainfall amts ranging from 0.6" across the St. Lawrence and
Champlain Valleys, but locally around 1" in aforementioned upslope
flow areas, from Ludlow up to Bethel, and across portions of
Essex/Clinton Counties in NY.
.SHORT TERM /FRIDAY/...
As of 418 AM EDT Wednesday...Overall idea from the previous
forecast and mine before that remains in place for the end of the
work week as low pressure pulling out of the Eastern Great Lakes
and Ohio Valley will bring mixed precipitation mainly in the form
of rain and snow to the North Country. Main change with this
morning`s forecast is to offer a slower arrival time of the onset
of precipitation, and adjust temps warmer for the bulk of the
event. Consensus amongst the latest NWP guidance is that deeper
layer moisture doesn`t really arrive until at least mid-day as the
parent surface low tracks northeast through northern New York.
Precipitation at the onset will mainly be in the form of rain for
most locations with boundary layer temps in the 40s, but across
the Adirondacks temps will likely wet-bulb down to support snow.
As we move into Thursday evening and night, a developing 925/850mb
southeasterly jet of 40-50kts will usher in above freezing
temperatures aloft transitioning ptype to a rain/snow mix for the
Adirondacks and portions of eastern Vermont, and eventually all
rain area-wide after midnight. Thereafter, potent shortwave energy
rounding the base of an upper trough swinging to the area develops
a weak surface low along the frontal wave and eventually the
aforementioned parent low transitions its energy to this new low
over southern New England by Friday morning. Wrap- around moisture
combined with developing northwesterly flow on Friday will keep
precipitation going, especially across the upslope regions of the
Adirondacks and northern Greens but remains mainly rain as
surface/boundary layer temps remain mild.
All in all impacts from this event are very limited at the
surface, with any snow on the front side of the system only a
dusting to perhaps 2", and any downslope winds along the western
slopes Thursday night limited to 20-30 mph as the timing of max
winds aloft coincide with the heaviest precipitation occurring.
That said, it will be a different story across the higher peaks
above 2000 feet where thermal profiles still support storm total
accumulations in excess of 6" to up to as much as a foot of heavy
wet snow through Friday.
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 418 AM EDT Wednesday...In general, the long term period
from the weekend into early next week has begun to trend more
quiet than what we`ve seen the past few days. Trends are for
another northern stream clipper to track north of the BTV CWA
Saturday offering a return to above normal temperatures and just
some light rain showers. Behind that, high pressure builds in and
dominates for Sunday and Monday before a strong low develops out
of the northern Plains and tracks well to our northwest on
Tuesday. A weak front traverses the forecast area Tuesday
afternoon, but with limited moisture to work with, we`re not
expecting a whole lot of precipitation. Temperatures though sky-
rocket well above freezing aloft supporting highs pushing back
into the mid-40s to low 50s on Monday, and further into the
mid/upper 50s for Tuesday.
.AVIATION /18Z Wednesday THROUGH Monday/...
Through 18z Thursday...Localized MVFR ceilings at SLK this
afternoon, but otherwise VFR at the TAF sites with cigs generally
3.5-5kft. HIR TRRN will remain obscd into tonight with prevailing
stratus/stratocu. Anticipate partial clearing and light winds
overnight, with VFR conditions. Approaching low pressure from the
Great Lakes will bring increasing clouds above 10kft Thursday
morning, lowering to near 8kft SLK/RUT toward 18Z Thursday. Most
of the precipitation should hold off until after 18Z Thursday, but
did include VCSH at RUT/SLK in line with 30-50percent chance of
toward the end of the TAF period.
Outlook 18z Thursday through Monday...An active pattern with
changeable flight conditions expected during this time period.
Mainly a rain event beginning Thursday aftn. However, initial
precipitation will be a rain/snow mix, especially at MPV/SLK, and
snowfall could result in some IFR conditions for several hours
Thursday aftn. A slushy accumulation possible at SLK (coating to
0.6"), but no snow accumulation expected at the other TAF
locations. Rain continues at the TAF sites Thursday night with
widespread MVFR, and intervals of IFR. SE wind gusts in excess of
25kts possible at KRUT 22Z Thu thru 04Z Fri. In addition...strong
low level jet of 50 knots around 5000 feet will produce areas of
turbulence and wind shear during this time period areawide. Low
pressure departs across the Gulf of Maine during the day Friday,
with winds shifting into the NW. Will see diminishing
precipitation chances from west to east through the day. Next
system with breezy southwest winds arrives late Saturday into
Sunday with additional precip and potential impacts to aviation.