Scientific Forecaster Discussion
fxus61 kbtv 200537
Area forecast discussion
National Weather Service Burlington Vermont
1237 am EST Wed Nov 20 2019
pockets of patchy drizzle or snow flurries will be possible this
evening. Areas of light flurries and light snow showers will
develop Wednesday morning through early Thursday morning.
Mostly dry conditions and a warming trend will take place
Thursday. The next weather system of interest will come through
on Friday with a rain and snow mix turning to just rain. As the
cold front advances across the region, a transition back to snow
showers with a few signals for some moderate wet snow behind
the front. Temperatures will then return to below normal values.
Near term /until 1 PM this afternoon/...
as of 1235 am EST Wednesday...current forecast remains in good
shape, only minor tweaks to current temps to capture latest
Previous discussion...wintry mix has come to an end for most
areas, though there are still some pockets of rain/snow mix or
drizzle across the northern Champlain Valley and Northeast
Kingdom. Temperatures are currently sitting near 32 into the mid
30s, and these are expected to only fall slightly overnight.
Some patchy drizzle and flurries are expected for portions of
the Champlain Valley and in Essex County, New York where low-level
moisture will remain trapped beneath blocked northerly flow. An
Special Weather Statement has been issued for this potential, as pockets of this area
could fall to around 30 degrees and glaze elevated surfaces.
Elsewhere, low- level moisture thins somewhat, and do not
anticipate as much drizzle or flurry potential.
For Wednesday, high res models continue to develop scattered to
numerous snow showers over the region as another upper shortwave
trough enters the region. The low-level convergence is excellent
with northwest winds across northern New York and northeast winds
across Vermont funneling into the Champlain Valley. With the very
low Froude numbers forecast, the lower valleys and mountain bases
should see much of shower activity. The poorly saturated dendritic
growth zone will keep most showers limited to light flurries or
small dendrites, keeping amounts down to a dusting to an inch at
most. Highs will be in the lower to mid 30s. Overnight lows should
fall into the 20s.
Short term /1 PM this afternoon through Thursday night/...
as of 341 PM EST Tuesday...brief ridging will move in during
the day Thursday, then quickly shift east of the area by
Thursday evening. This ridging will keep the north country dry
and partly sunny during the day, then support warming
temperatures through the night as southwesterly return flow
develops behind the ridge. Thursday night, a low pressure system
will lift out of the Great Lakes region and move into western
Quebec. The system's warm front will move through Thursday night
into Friday morning, allowing for the development of some warm
air advection showers. Magnitude of moisture advection into the
north country along and behind this warm front is not overly
impressive - forecast precipitable water values peaking around 0.75 inches are
only about one Standard deviation above climatological daily
norms. The limited moisture coupled with the lack of deep ascent
(main lifting mechanism will just be isentropic ascent in the
mid-levels) will keep overall quantitative precipitation forecast amounts relatively light
Thursday night/early Friday morning...generally under a tenth of
an inch. Precip will start during the early overnight hours as
some brief snow/rain-snow mix, then quickly transition to a cold
light rain overnight as temperatures warm. Winds will be breezy
from the south overnight, but lack of instability overnight
will keep the stronger flow associated with the cyclone off the
surface. The exception will be higher terrain and Lake
Champlain, which will see some gusty southerly winds overnight.
Long term /Friday through Tuesday/...
as of 341 PM EST Tuesday...a cold front will push through from the
northwest Friday. The cold air advection along and behind the
boundary will support a changeover from rain to snow as the
predominant precipitation type during the afternoon hours. The
frontal passage will be accompanied by some show showers and
gusty winds, and a few snow squalls can't be ruled out given the
progged low-level instability, sharp temperature gradient, and
45kt + low-level jet. Once the front clears the area, expect
some residual upslope northwesterly showers over higher terrain
through Saturday morning, then drier weather for the weekend.
The next storm that we will be watching closely is a low
pressure system tracking from the mid-Atlantic coast to near
benchmark (40n 70w) during the day Sunday. At this point, both
the GFS and the European model (ecmwf) keep the system south and east of the
area, but will be watching it closely. Have kept the forecast
mainly dry for this time frame for this forecast package, but
this is assuming the system does indeed stay further off the
Aviation /06z Wednesday through Sunday/...
through 06z Thursday...mainly a mix of MVFR/IFR/LIFR through
the period with lots of low level moisture/clouds/fog lingering
across the north country. Ceilings will generally be between
200-2000ft, with locally lower ceilings possible due to fog,
such as at mpv. Periods of -fzdz/fzfg are possible at rut and
mpv overnight. After 09z, light snow showers will be likely
across the area with mainly MVFR visibilities expected. These
snow showers will continue through the afternoon hours across
Vermont, especially for the Champlain Valley where low level
flow remains strongly blocked. Winds for all terminals will be
light out of the north around 5 kt or less.
Thursday: mainly VFR, with local MVFR possible. No sig weather.
Thursday night: mainly VFR, with areas MVFR possible. Likely
shra, chance shsn.
Friday: mainly MVFR, with local IFR possible. Likely shra, chance
Friday night: mainly VFR, with areas MVFR possible. Chance shsn.
Saturday: VFR. No sig weather.
Saturday night: VFR. Slight chance shsn.
Sunday: mainly MVFR, with local IFR possible. Slight chance shra,
slight chance shsn.