Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kbtv 171201 
afdbtv

Area forecast discussion
National Weather Service Burlington Vermont
701 am EST Wed Jan 17 2018

Synopsis...
light to moderate snow will continue today with
additional snow amounts generally up to 2 inches expected, with
up to 4 inches expected in southern and eastern Vermont. As a
developing coastal low retreats further up the New England coast
this evening, expect widespread snow to taper off later today.
Some light snow showers will develop through the end of the
week along with a general warming trend going into the weekend.

&&

Near term /through Thursday/...
as of 650 am EST Wednesday...Winter Weather Advisory remains
in effect for Rutland, Windsor, and Orange counties of Vermont
until 100 PM today. Light warm air advection snow continues
over southern/eastern Vermont in the pre dawn hours, with areas
further north seeing more sporadic localized snow showers.
Expect snow to become more widespread once again within the next
few hours as heights fall aloft in advance of an upper level
open wave and a developing coastal surface low tracks inside of
benchmark (40n 70w). Southern and eastern Vermont will see some
influx of Atlantic moisture this morning as southwesterly flow
briefly takes on more of a southerly/southeasterly component
ahead of the approaching low. This will result in slightly
higher snow fall accumulations in the southern and eastern part
of the state.

Overall, expect to receive generally 3 to 5 inches of snowfall
out of the system through this evening in southern and eastern
Vermont. Northern New York and northern Vermont will pick up
lighter amounts (generally up to 3 inches) as the best moisture
transport and lift associated with the surface cyclone will
stay further south and east.

As the surface low tracks further northeast up the New England
coast, flow will quickly Switch Back to westerly and the stratiform
snow will taper off from west to east this afternoon through
early evening. Low level lapse rates will steepen in response to
cold air advection behind the departing low this evening,
supporting the development of some light lake effect snow east
and northeast of Lake Ontario tonight through tomorrow. Southern
Saint Lawrence and Franklin counties in New York could pick up
a dusting to 2 inches out of the band by Thursday night.

Temperatures will remain fairly seasonal through Thursday night
with highs generally in the 20s and lows in the high single
digits to teens tonight under partly clear skies.

&&

Short term /Thursday night through Friday night/...
as of 417 am EST Wednesday...the short-term forecast period
will maintain a moderating temperature trend, which will last
through the weekend and early next week. Still appears that sfc
anticyclone across the Tennessee River valley will be associated
with low-level ridge axis extending newd into PA and the srn
tier of New York Thursday night into Friday. Combination of west-southwesterly low-
level flow from Lake Ontario (on nrn periphery of ridge axis),
and modest mid-level shortwave trough crossing New York/northern New
England Thursday night into Friday, will bring about sufficient
moisture and ascent for light snow shower activity, mainly for
the nrn adironacks into the nrn green mtns. Pops peak at 40-50%
during the pre-dawn hrs on Friday, with snowfall amts of a
dusting to 1" generally possible for the nrn Adirondacks and
northern green mtns (little or no snow accumulation expected in
the valleys). Will see partial clearing in the wake of this
shortwave trough by Friday afternoon, and developing S-SW flow
will result in continued warming trend. Looking for overnight
low generally in the teens - except lower 20s in the St.
Lawrence Valley - for Thursday night. Temperatures warm into
the lower 30s for Friday, and then generally falling back to the
low-mid 20s for Friday night, under variably cloudy skies.

&&

Long term /Saturday through Tuesday/...
as of 417 am EST Wednesday...will see the development of weakly
anticyclonic flow in the mid-levels over the weekend with
gradual height rises as deep-layer ridge builds across the sern
Continental U.S.. not expecting much in the way of precipitation during the
weekend as a result, though the GFS shows a developing frontal
zone just north of the Intl border, especially during the day
Sunday. Can't rule out some light precipitation, but overall
activity along the developing quasi-stationary front should
mainly occur across srn Quebec. Carried just 20 pops across nrn
sections. Should see temperatures rising into the upr 30s to
lower 40s on Saturday and Sunday, again with expectation that
frontal zone sets up just to our north.

Differences between the European model (ecmwf) and GFS are greater thereafter into
early next week, and have increased for the 00z model cycle. Frontal
system is still expected to pass to our west across the Great Lakes
and Ontario, with the GFS a bit faster in the overall synoptic
evolution. The European model (ecmwf) is slower and a bit further east, with
potentially secondary low development during the day Tuesday across
central New England. The 00z European model (ecmwf) suggests the bulk of
precipitation would occur during the day Tuesday, whereas the GFS
suggests moderate precipitation (mainly rain) for Monday night.
European model (ecmwf)-MOS also suggests less of a warmup with this potential
evolution than does the GFS mex-MOS. With both timing/vertical
temperature profile uncertainty larger than normal, have limited
precipitation types to rain or snow attm. Certainly, with
overall low-lvl warm advection regime, some threat of freezing
rain and/or sleet also exists, but a skillful forecast of those
p-types is difficult given current model spread. Would generally
expected mixed wintry precipitation changing to plain rain in
advance of cold front, with precipitation ending as rain/snow
showers later Tuesday night into Wednesday. Official temperature
forecast is closer to GFS scenario, with highs in the upr 30s
to lower 40s for Monday into Tuesday, potentially falling late
with cold frontal passage.

Will need to continue to monitor this system, as moderate
precipitation and above freezing temperatures may affect existing
ice jams across the region. That said, extent of thawing degree
hours and overall precipitation/moisture not nearly as significant
as what occurred last Thursday/Friday. Thus, Hydro impacts should be
comparatively minor and exist mainly as a function of existing ice
jams and modest increases in river levels into those local
areas.

&&

Aviation /12z Wednesday through Sunday/...
through 12z Wednesday...currently experiencing mixed MVFR to LIFR
conditions this morning with some in response to light snow
moving through the north country. Steadiest snow remains over
southern/eastern Vermont with IFR to MVFR conditions expected
to continue at rut/mpv through 22z, with gradual improvement to
VFR expected after. More sporadic snow showers and lingering low
clouds will make conditions more variable at mss/slk/pbg/btv
through the morning and early afternoon, however expect general
improvement to VFR conditions at all sites by 00z. Winds will
generally be under 10 knots through the period.

Outlook...

Thursday: mainly VFR, with local MVFR possible. Slight chance
shsn.
Thursday night: mainly VFR, with areas MVFR possible. Slight
chance shsn.
Friday: mainly MVFR, with areas VFR possible. No sig weather.
Friday night: VFR. Slight chance shsn.
Saturday: mainly VFR, with areas MVFR possible. Slight chance
rain showers.
Saturday night: mainly VFR, with local IFR possible. Slight
chance shsn.
Sunday: mainly MVFR, with local IFR possible. Slight chance shra,
slight chance shsn.

&&

Btv watches/warnings/advisories...
Vermont...Winter Weather Advisory until 1 PM EST this afternoon for
vtz010>012-019.
New York...none.

&&

$$

National Weather Service Glossary of Abbreviations