Scientific Forecaster Discussion
fxus61 kbtv 182325
Area forecast discussion
National Weather Service Burlington Vermont
625 PM EST Mon Nov 18 2019
patchy drizzle or freezing drizzle this evening, then a mix of
freezing rain and sleet moving into western Vermont and northern
New York during the evening and overnight hours. This mix of
precipitation will change over to snow prior to sunrise on
Tuesday and will gradually taper off during the afternoon hours
on Tuesday. Quieter weather is expected on Wednesday and
Thursday but another storm system will move into the region on
Friday. This system will likely bring a mix of rain and snow to
the north country.
Near term /through Tuesday night/...
as of 332 PM EST Monday...Winter Weather Advisory continues for
Rutland, Orange, and Windsor counties in Vermont and will take
effect at 6 PM for the rest of Vermont and much of northern New
York. The forecast remains on track with minor tweaks. The first
is the expectation for more a drizzle or freezing drizzle at
the onset favoring areas east of The Greens where easterly 850mb
flow will advect low to mid-level moisture from a coastal
system passing east of the benchmark. As flow turns more
northerly and more moisture expands over the rest of the
advisory area later this evening, we should see additional
drizzle/freezing drizzle reports. A second system crosses the
region during the pre-dawn areas of Tuesday with an additional
bout of a wintry mix and briefly moderate wet snow.
Light radar returns are starting to sneak up the Champlain and
Connecticut valleys. Given the drizzle will be low to the ground,
anticipate this will make it hard for the radar to Sample east of
The Greens. Temperatures warmed a bit further than expected reaching
the mid to upper 30s. They have since leveled off and should begin
to fall once cold air advection begins to take effect in the next
hour or so. As temperatures cool tonight, the concern will be
intermittent freezing drizzle leaving a glaze across untreated
surfaces as temperatures fall into the mid 20s to lower 30s. The
bulk of the precipitation occurs during the pre-dawn hours on
Tuesday as a compact shortwave rounds the base of an upper trough
positioned along the Great Lakes. The north country will be
positioned in the left exit region of a jet streak along this
compact embedded trough with a narrow area of strong ascent.
Overall, sharp fgen/deformation remains south of the region before
lifting northeast and weakening as it grazes our eastern areas. It
remains a challenging forecast though, with a handful of models
placing the strongest forcing over our region instead. Anticipate a
sharp quantitative precipitation forecast gradient with this shortwave. One of the potential
predicaments with missing this strong forcing is the lack of any
dynamical cooling it would yield. The 12z GFS and a few hrrr runs
have come in with little to no transition to snow as the warm nose
remains in place. In general, the forecast still reflects a glaze to
a tenth of an inch of ice accumulation, and wet snow adding a
dusting to 1" over much of the north country, and then 1-3
inches in the Northeast Kingdom.
Precipitation comes to an end Tuesday afternoon/evening. There is
not much of a change in air mass overnight, and there will be some
high-level clouds keeping temperatures in the 20s overnight. Yet
another upper trough begins to lift northward overnight. Without
much moisture, anticipate mainly upslope showers along northwestern
slopes to begin developing into Wednesday.
Short term /Wednesday through Wednesday night/...
as of 332 PM EST Monday...Wednesday will be mostly cloudy with
some light snow showers around the area. An upper-level low will
lift over coastal New England during this time frame, enhancing
synoptic-scale ascent and marginally increasing low-level
instability. With limited moisture however, accumulations will
be limited to a dusting if anything for lower elevations, and up
to a couple tenths of an inch for higher elevations of northern
Vermont. High temperatures will again be in the 30s, lows in
Long term /Thursday through Monday/...
as of 332 PM EST Monday...a low pressure system will track
northeastward through Quebec Friday, dragging a series of fronts
through the north country as it progresses northeastward.
Friday morning, the system's warm front will move through,
supporting some spotty morning shower activity. The system's
cold front won't move through until sometime late Friday
afternoon through early Friday night. At this point, nothing
looking too concerning about the system impact-wise, looks to
for the most part just a be run-of-the-mill system typical of
fall in New England. Early indications looking like an inch or
less of precipitation, but this will be dependent on low track
and other factors that could change. Still too early to nail
down precipitation type, but at this point thinking it'll start
as rain (highs Friday currently forecast in the 40s) and then
transition to some snow on the back side of the system. Will see
some Post-frontal clearing Saturday with some gusty winds
developing and cooler temperatures. From Sunday Onward, models
differ quite significantly in the evolution of the next low
pressure system to move out of the southeastern US.
Aviation /00z Tuesday through Saturday/...
through 00z Wednesday...deterioration to mainly MVFR/IFR over
the next 24 hours as upper low pressure and light mixed
precipitation moves through the region. Winds light and less
than 10 kts through the period. Precipitation type quite
tricky, with patchy -ra/-fzdz from 00-04z transitioning to a
general -fzra/pl mix, then light snow/pl in the 04-12z time
frame. Light mixed precipitation lifts out of the area in the
14-18z time frame. Only exception will be kmss where pcpn will
be patchy/intermittent at best so only vcsh there.
Given higher confidence of at least some patchy -fzdz/-fzra
later tonight into tomorrow morning, runway treatment and de-
icing operations will be likely where applicable.
Tuesday night: MVFR/IFR conditions possible. No sig weather.
Wednesday: mainly MVFR, with local IFR possible. Slight chance
Wednesday night: MVFR/IFR conditions possible. Slight chance
Thursday: mainly VFR, with local MVFR possible. No sig weather.
Thursday night: VFR. Definite shra, likely shsn.
Friday: mainly MVFR, with areas IFR possible. Likely shra, likely
Friday night: mainly MVFR, with local VFR possible. Chance shra,
slight chance shsn.
Saturday: mainly VFR, with local MVFR possible. Slight chance
Vermont...Winter Weather Advisory until 1 PM EST Tuesday for vtz001>012-
New York...Winter Weather Advisory until 1 PM EST Tuesday for nyz027-028-