Scientific Forecaster Discussion
fxus61 kbtv 231947
Area forecast discussion
National Weather Service Burlington Vermont
247 PM EST Thu Nov 23 2017
surface high pressure across the north country on Thanksgiving
day will slide eastward tonight, allowing for mainly cloudy
skies tonight with scattered snow showers across the
Adirondacks and northern Green Mountains. Friday will be milder
with increasing south to southwest winds. Highs Friday will
generally be in the low to mid 40s. A low pressure system
passing to our north on Saturday will bring a trailing cold
front across the north country allowing for periods of rain or
snow showers Saturday into Saturday night. Overall, temperatures
will be trending above seasonal levels over the next 5 to 7
Near term /through Friday night/...
as of 111 PM EST Thursday...relatively quiet weather through
Friday night. Chilly air mass in place Thanksgiving afternoon
in association with sfc ridge axis extending from central PA
newd across New York and northern New England. Highs generally
reaching the upr 20s to lower 30s this aftn...roughly 10deg
below seasonal averages for late November. Meanwhile, a weak
700-500mb shortwave trough is moving ewd across sern Ontario and
nrn NY, and this feature is bringing widespread mid-level
clouds across our region despite the sfc ridge.
This evening, it continues to appear that some lake effect snow
showers will develop off of Lake Ontario as sfc ridge slides ewd
and deep-layer SW flow develops. This is reflected especially in
NAM-3km and btv-4kmwrf forecasts showing a brief period of lake
effect snow 00-06z across the Route 3 corridor from Star Lake
wwd across srn St. Lawrence County. Maintained a period of
likely snow showers, with possible snow accumulations around 1"
across srn Franklin New York and St. Lawrence counties. May also see a
few flurries ewd across the Champlain Valley and especially into
the Jay Peak area overnight with trajectories favoring east-northeastward
advection of the lake moisture mainly 06-12z tonight. Low
temperatures won't be as cold as last night, generally in the
mid-upr 20s with abundant cloud cover and above mentioned light
snow shower or flurry activity.
On Friday, strengthening p-gradient will bring breezy
conditions, with S-SW winds 10-20 mph, with a few gusts to 30
mph in vicinity of Lake Champlain. Expecting a good moderation
in temperatures, with friday's highs generally in the low-mid
40s. Should also see mostly sunny conditions.
South winds continue Friday night as next shortwave trough moves
ewd into the Great Lakes region. Shouldn't see much direct
impact from that system and attendant cold front until the
daylight hrs Saturday, but the south flow will keep our temps
mainly in the low 30s for overnight lows, except upr 20s across
the nrn Adirondacks and mid-upr 20s for ern Vermont where some of the
deeper valleys may decouple with stable planetary boundary layer conditions.
Short term /Saturday through Saturday night/...
as of 245 PM EST Thursday...models remains consistent in
showing a shortwave trough and attendant cold front approaching
the area during the day on Saturday, then passing east and south
by Saturday night. Have largely maintained persistence in
showing increased chances of rain showers through the day as
skies trend mainly cloudy. Highest coverage should occur across
the northern mountains, especially in the Adirondacks as
southwest boundary layer flow transports lake moisture
downstream. Overall quantitative precipitation forecast will remain light however, and generally
less than a tenth of an inch. Temperatures to remain mild -
mainly 40s under modestly gusty south/southwest flow. Rain
showers then transition to snow showers from north to south and
higher to lower elevations over time Saturday night while waning
in overall coverage as cold front exits east and synoptic flow
trends northwesterly. Some minor accumulations of a dusting to 2
inches will be possible by sunrise Sunday, mainly across the
northern mountains. Lows near seasonable late November norms
from the mid 20s to lower 30s.
Long term /Sunday through Wednesday/...
as of 245 PM EST Thursday...much of next week will continue to
favor a progressive synoptic flow pattern across the northern
tier of the nation with several weak shortwave features bringing
periodic light rain/snow shower chances interspersed by brief
interludes of high pressure and quiet weather. Any threat of
Arctic air will remain bottled well north of our area with near
seasonable temperatures expected under an average airmass of
eastern North Pacific and southern Canadian origin. This is in
contrast to what the moderately negative ao and nao indices
would typically predict (i.E. Much colder). The best threat of
additional light precipitation will occur Sunday into Sunday
evening, and again by next Wednesday with passage of
aforementioned shortwave energy. Again any precipitation or snow
accumulations will be light. High temperatures to range through
the 30s during Sunday/Monday and in the upper 30s to mid 40s
from Tuesday Onward. Lows mainly in the upper teens to mid 20s
Sunday night/Monday night, moderating into the 25 to 35 range on
Aviation /19z Thursday through Tuesday/...
through 18z Friday...mainly VFR with prevailing mid-level
(8-12kft) overcast. Will see some moisture from Lake Ontario
00-06z resulting in MVFR ceilings at slk and periods of 3sm in
light snow showers with intervals of brief IFR possible. May
also see brief MVFR at mpv during the overnight hrs and hir terrain
obscured across the central/nrn green mtns and across the northern
Adirondacks. Ceilings at pbg/btv may lower to 4-5kt tonight,
but generally expecting to maintain VFR. Improving back to VFR
areawide after 12z Friday. Winds generally continuing S-SW
5-10kts, with localized gusts to 18kts at kmss with valley
channeled low- level flow.
Friday: VFR. No sig weather.
Friday night: VFR. Chance rain showers.
Saturday: mainly VFR, with areas MVFR possible. Chance shra,
Saturday night: mainly MVFR, with local IFR possible. Chance
shra, chance shsn.
Sunday: mainly MVFR, with local IFR possible. Chance shsn.
Sunday night: mainly MVFR, with local VFR possible. Slight chance
Monday: mainly VFR, with areas MVFR possible. No sig weather.