Scientific Forecaster Discussion
fxus61 kbtv 171341
Area forecast discussion
National Weather Service Burlington Vermont
941 am EDT Thu Oct 17 2019
strong low pressure will slowly pull away to the east today
with periods of heavy rain and windy conditions slowly abating
later this afternoon and especially tonight. Breezy conditions
and lingering higher elevation rain and snow shower activity
continue into Friday, though lower elevations largely trend dry
as high pressure begins to build into the region. This high
pressure will settle atop the area for the upcoming weekend with
seasonably cool and quiet weather expected.
Near term /through Friday/...
as of 930 am EDT Thursday...no changes needed to ongoing Flood
Watch or Wind Advisory (in the Champlain valley) attm. That
said, did increase wind speeds east of the Green Mountains for
the remainder of today. Noted a recent gusts to 38mph at
Springfield,VT (vsf), and continued gusts 30-38 mph should be
common through sunset on wrn periphery of strong low pressure,
as center drifts ewd into Maine this afternoon. Dry slot and
downsloping effects have limited rainfall across the Northeast
Kingdom. However, still seeing moderate rainfall rates in
deformation zone further west, affecting much of northern New York
into western Vermont. Still seeing some rainfall rates 0.10-0.20"/hr,
including 0.16" this past hour at kslk. This will maintain a
threat of minor river flooding, including on the ausable, Otter
Creek, and Mad River during the next 12-18 hrs, based on
current trends. In addition, downed leaves and clogged storm
drains will maintain poor drainage/street flooding throughout
the day. With low overcast and windy conditions in place,
temperatures will not change significantly with highs mainly in
the upper 40s to lower 50s. Noted 30f at the Whiteface Summit,
and snow accumulations are underway above 3500-4000ft in the
Adirondacks. Higher Summit level snowfall in the Adirondacks
could exceed 6" by this evening.
windy and inclement weather continues today as deep sub-980 mb
low pressure occludes across the southern Vermont/New Hampshire border and pulls
east into far eastern New England tonight. A sharp pressure
gradient will exist across our area and as winds back to
northerly gusts into the 25 to 35 mph range will be likely in
most areas. Stronger gusts into the 35 to 45 mph range with
localized gusts to 50 mph are expected across the Champlain
Valley due to enhanced channeling effects. Areas closer to Lake
Champlain, especially in the southern Champlain Valley will
likely see the strongest gusts, which should peak in the 6 am to
2 PM time frame. In these areas a Wind Advisory remains in
effect through early evening for scattered limb damage and
isolated power outages. Temperatures should hold fairly steady
from the mid 40s to lower 50s.
Rainfall will be steady and occasionally heavy at times, especially
across the Champlain Valley of New York and the Adirondacks in proximity
to best deformation and frontogenesis. Further east the character of
rainfall will be more of the light to moderate variety, especially
across eastern Vermont with a distinct dry slot edging westward as system
occludes. Overall rainfall from this event was adjusted slightly to
incorporate more cam quantitative precipitation forecast output which highlights more enhanced
shadowing effects in the eastern Champlain Valley/western Green
Mountain slopes/northeastern Vermont (see Hydro section below). Based off
blended 850 mb thermal profiles a changeover to wet snow is also
likely across the Adirondack high peaks which will continue, albeit
lighter into tonight. Here totals should average from 2-5 inches in
the 3500-4500 foot range with the highest peaks above 5000 feet
possibly seeing totals nearing 1 foot. Further east totals will be
less given milder easterly Atlantic trajectories - perhaps an inch
or two on the very highest summits.
By later this afternoon and especially tonight steadier rainfall
gradually takes on a more showery character and lessens in
intensity/coverage as deep occlusion begins to trundle slowly
eastward. Winds and wind gusts also abate to more tolerable levels
with p-gradient slowly relaxing over time. Low temperatures to
average generally from 37 to 43.
Conditions continue to slowly calm down into Friday as occlusion
pulls further away into the Maritimes and low to mid level ridging
edges east from the Great Lakes. It will remain breezy as northwest
wind gusts average from 15 to 20 mph and shower activity remains
confined largely across higher elevations of the northern mountains
where additional light quantitative precipitation forecast is expected. High temperatures a blend of
bias-corrected MOS guidance - mid 40s to lower 50s.
Short term /Friday night through Saturday/...
as of 336 am EDT Thursday...for Saturday, broad surface high
pressure sets up to our south. Some lingering showers will be
possible in the Northeast Kingdom during the overnight hours,
but will quickly scour out towards dawn. Overnight lows should
be coldest in northern New York, where partial clearing will
allow lows to fall between 25 and 32. The Champlain Valley and
eastern Vermont should remain in the mid to upper 30s. With
skies clearing on Saturday, it will be a pleasant fall day with
highs in the 50s.
Long term /Saturday night through Wednesday/...
as of 336 am EDT Thursday...a warming trend will take place as
ridging builds through the long term with the next impactful
weather system coming in either Tuesday or Wednesday with
details on the timing still being sussed out.
On Sunday, a weak shortwave trough will northeastward, but it will
do little in the face of the ridge that is over the region. With
little moisture advecting in and with the parent low of surface cold
front so far north, this will have no more impact than some
increased cloud cover.
For Monday, deep layer ridging will reamplify in response to an
upstream trough digging across our west. Thus, a pleasant day is
expected. Deterministic models have slowed the speed of the next
system, which seems reasonable given the size and strength of the
upper trough over the Great Lakes. Monday should remain dry with
highs above seasonal norms, topping out in the 60s. The question
then becomes whether the front arrives Tuesday or Wednesday. The
latest 00z European model (ecmwf) forecast does not have the trough approaching until
overnight Tuesday into Wednesday morning and has a low developing
along the coast near a strengthening baroclinic zone. The 00z CMC
agrees. Looking at ensemble guidance though, it looks like "the
blend is your friend" approach will be best for now with a few GFS
ensemble members showing a solution like the ec forecast. It
certainly seems to be the favored set up as of late, but there are
not enough members in support among the GFS and CMC ensembles to
have ME lean further towards the ec. We should be back around
seasonal norms behind the departing upper trough.
Aviation /14z Thursday through Monday/...
through 12z Friday...flight conditions range from MVFR to IFR
at this time. Period of widespread precipitation is expected to
continue through about 00z before becoming more scattered.
Visibilities could drop in heavier showers, generally between
3sm and 8sm. Ceilings are currently between 500 and 1500ft agl.
Not much in the way of improvement is expected today, though by
00z, we should see a steady rise at most terminals to
Strong winds are currently channeling down the valleys,
impacting kmss, kbtv, and kpbg. Anticipate 15 to 25 knot
sustained north to north-northwesterly winds with 30 to 35 knots
gusts expected. An isolated 40 knot gust will be possible at
kpbg. Winds will begin to subside to 5 to 15 knots and become
northwesterly beyond 00z. Still anticipate periods of northerly
low-level wind shear across all terminals from now through about
00z, except at kmss.
Friday: MVFR. Chance rain showers.
Friday night: mainly VFR, with areas MVFR possible. No sig weather.
Saturday: mainly VFR, with local MVFR possible. No sig weather.
Saturday night: VFR. No sig weather.
Sunday: VFR. No sig weather.
Sunday night: VFR. No sig weather.
Monday: VFR. No sig weather.
as of 336 am EDT Thursday...storm total rainfall will be quite
variable with this event and exhibit classic orographic
character given strong low to mid level flow. Highest totals
will occur across the Adirondacks and southern Green Mountains
where 24-hour amounts should average from 2-3 inches. Totals in
the St. Lawrence, Champlain and CT river valleys should average
from 1-2 inches with areas across northeastern Vermont seeing the
least (0.5 to 1.5 inches) with enhanced white mtn. Shadowing
effects. With this rainfall all river should see fairly sharp
rises, though given current near base-flows most should remain
within their banks. Of most concern is the ausable basin and to
a lesser extent the Otter Creek and Winooski basins. The ausable
tends to overperform during strongly forced northerly wind
regimes such as this and the current forecast crest of near 9.0
feet, or higher-end minor flood level still looks reasonable.
All other rivers should crest near or below bankfull. Some
minor, poor drainage flooding will also be possible as falling
leaves will tend to inhibit storm water flows. As such, our
current Flood Watch for the southwestern 2/3rds of Vermont and much
of northern New York will remain in effect through Friday morning.
as of 336 am EDT Thursday...a Wind Advisory remains in effect
today. Strong northerly winds from 25 to 35 kt and gusts from 40
to 50 kt are expected on Lake Champlain today. This will create
hazardous conditions with a rough chop and significant wave
heights into the 4 to 7 foot range in open water and bays/inlets
with northerly exposures. The highest winds/waves will occur
across the southern half of the Broad Lake this morning and this
afternoon before slowly abating tonight. Those with
recreational plans on the lake today should strongly consider
postponing plans until Friday or the upcoming weekend when
conditions will be significantly better.
Vermont...Flood Watch through Friday morning for vtz002-005-006-008>012-
Wind Advisory until 8 PM EDT this evening for vtz001-002-005-
New York...Flood Watch through Friday morning for nyz028>031-034-035.
Wind Advisory until 8 PM EDT this evening for nyz028-035.