National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBTV 160756
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
356 AM EDT Mon Apr 16 2018

.SYNOPSIS...
Strong and damaging southeast wind gusts in excess of 60 mph still
expected today along the western slopes, especially across eastern
Addison and Rutland Counties. Elsewhere, winds will generally be 15
to 30 mph with localized higher gusts, as temperatures slowly climb
into the 30s and 40s by this afternoon. Periods of rain with pockets
of freezing rain east of the Green Mountains will continue with
minimal additional ice accumulation expected. Cooler air developing
aloft overnight Monday into Tuesday will produce a mix of rain and
snow showers, with some wet snow accumulation possible in the
mountains. Unsettled and cool weather continues most of the upcoming
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 351 AM EDT Monday...High wind warning continues for the western
slopes for gusts 50 to 60 mph eastern Chittenden/eastern
Franklin counties and near hurricane force wind gusts (75 mph)
expected across eastern Addison and Rutland Counties. Wind
advisory for gusts up to 50 mph continues for eastern CPV and
parts of the northern/western dacks today. No change in speeds
or timing from previous couple of forecast, with highest
confidence southern/central western slopes.

The combination of these winds with saturated soils and some ice
accumulation on trees/power lines will result in scattered to
numerous power outages, especially the southern/central western
slopes of VT.

Already seeing a spike in outages early this morning with Mendon and
Goshen gusting to 55 mph and 48 mph at Bread Loaf (before losing
power) and temp of only 23f.  This event will not be like the Oct
2017 windstorm, as areal coverage of winds >60 mph and associated
power outages will be less and mainly confined to the western
slopes/parts of the eastern cpv and western dacks, as low levels
will remain stable across eastern/central VT with limited mixing of
winds aloft to the surface.

Little overall change noted in magnitude of 925mb to 850mb low level
southeast jet of 65 to 80 knots lifting from south to north across
our region. BTV2km and 4km soundings still show an impressive jet of
65 to 70 knots at the bottom of sharp inversion over eastern
Addison/Rutland Counties, which is below ridgetop...supporting
localized gusts up to 70 mph. BTV 2km shows 62 knots at 500 feet
above ground at Ripton, while BTV 4km is 55 knots, similar values
are indicated at Rutland around 14 to 15z this morning.
Meanwhile...both the HRRR and NAM nested shows sfc gusts between 60
to 65 knots during this time period, which looks very reasonable for
the southern portion of the western slopes. Impressive MAVRUT of 41
knots for 10 meter winds at 18z today.

Still some uncertainty on strength of wind/amount of mixing across
eastern Chittenden and eastern Franklin Counties, as soundings show
best wind field above inversion/ridgetop and less potential for
mixing/breaking mountain waves. However...isolated gusts from
Huntington to Underhill Center to Montgomery of 50 to 60 mph still
possible as 2km/4km show some enhanced wind couplets on lee side of
the northern western slopes.

Next question will be how warm does the eastern cpv get today with
southeast downslope compressional warming as this will impact how
far downwind waves of gusty winds travel. Does strong downslope wind
component create breaks in the overcast and combined with high April
sun angle do we quickly warm into the 40s/lower 50s per latest
MAVBTV which shows a high 53, with a 10 meter wind speed of 36
knots. Water vapor does show deep moisture feed with limited drying
in the mid/upper level, so any breaks in the overcast will be
difficult today. Also, thinking 53 might be hard to reach, given
easterly winds and cold trajectory coming from high pres to our
northeast. Given above factors thinking localized gusts of 40 to 50
mph looks reasonable in advisory for the eastern cpv...with highest
gusts toward Richmond/Williston to East Middlebury areas.

Meanwhile...wind advisory looks good for western/northern dacks from
near Star Lake to Malone to Ellenburg. Sounding data at Star Lake
shows bottom of mixed layer around 45 knots at 16z...supporting
localized gusts 45 to 50 mph. Isolated power outages in advisory
over northern NY still looks good.

Have extended winter weather advisory until 16z for all zones, but
hoping to re-configure advisory this morning when temps increase
above freezing across parts of the CPV, northern Dacks, and SLV.
Given temps in the l/m 20s across portions of the higher trrn of
central/southern VT and crnt radar trends, an additional 0.10 to
0.20 inches of ice possible, adding to the potential power issues as
winds increase. Areas of slick travel expected this morning, but
with high April sun angle, thinking conditions will quickly improve
by 12z most locations, except higher terrain east of the green
mountains.

Core of strongest low level winds will be north of our cwa by 02z
this evening, with decreasing wind speeds expected. Temps mainly in
the 30s east of the Greens today to mid/upper 40s cpv/slv and
western dacks...with mid 30s mountains.

A period of rain expected with occluded front this
aftn/evening...which will change to snow in the mountains toward
Tuesday morning as cooling aloft develops behind boundary. As temps
cool aloft we actually may warm up several degrees in the valleys,
as winds shift from east/northeast to west/southwest.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
As of 351 AM EDT Monday...Mid/upper level trof lifts slowly toward
northern New England on Tuesday with modest 925mb to 850mb cold
air advection. Expect additional rain/snow showers to prevail
with some snow accumulation likely in the mountains on Tuesday.
Temps will fall back into the 20s mountains and 30s
valleys....with westerly winds at 10 to 20 mph. Have continued
to mention likely to cat pops during this time period. Cool and
unsettled weather with lots of clouds prevail for Weds...with
little change in thermal profiles. Have trended toward the
cooler guidance given thermal profiles and expected cloud cover.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
-- Changed Discussion --
As of 355 AM EDT Monday...It`s tough to find a dry day in the
forecast as we`ll be under the influence of multiple low
pressure systems through the rest of the week. Wednesday night
we may see a brief lull in between the low pressure system that
is currently impacting the North Country and a clipper type low
that will track through the Saint Lawrence Valley. That clipper
then occludes and dumbbells around leading to more chances for
rain and mountain snow showers. Finally by Friday night we`ll
see high pressure pushing in and we should see a 24-36 hour time
period with little chance for precip.

At this point giving the pattern aloft we`ll be hard pressured
to see anything but below normal temperatures. I undercut MOS
guidance by a good margin as the feeling is MOS is trending to
much towards climo in the extended. Expect highs in the mid to
upper 40s through the rest of the work week with a chance of
getting to 50 over the weekend. Normal for this time of year is
mid 50s so we`ll be looking at 5-10 degrees below normal highs.
-- End Changed Discussion --

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
Through 06Z Tuesday...Expect widely varying conditions with
periods of VFR and a mix of MVFR/IFR in a mix of sleet and
freezing rain. Scattered freezing rain continues across the
North Country and when a shower moves through a TAF site
conditions rapidly fall to MVFR ceilings with 2-3SM visibility.
Expect by 09z the precip to continue to become more scattered
in nature and so VCSH is mentioned in the TAFs from 09 through
around 21z today.

Wind becomes a significant concern before day break as a very
strong low level southeasterly jet moves into the region. Cross
barrier flow will see downsloping winds at RUT/BTV/MPV/SLK in
the 30 to 40 kt range. At MSS winds will gust in the 25 to 35kt
range due to channeled northeasterly flow. Confidence in gusts
in the 40-50kt range is highest at RUT where significant low
level turbulence is expected as mountain waves will likely break
developing rotors on the western slopes. Due to the strong winds
in the boundary layer low level wind shear and turbulence can be
expected almost anywhere near and west of both the Greens and
Adirondacks.

Rainfall will begin to overspread the North Country from the
south by 21Z Monday as the winds begin to ramp down but it
still looks like VFR conditions will persist. LLWS will still be
a concern especially at KMPV and KSLK as the winds begin to
diminish at the surface but remain in the 40 to 50 kt range at
2kft around 22Z.

Outlook...

Tuesday: Mainly MVFR, with local IFR possible. Chance SHRA.
Tuesday Night: Mainly MVFR, with areas VFR possible. Chance SHSN,
Chance SHRA.
Wednesday: Mainly MVFR, with local VFR possible. Chance SHRA,
Chance SHSN.
Wednesday Night: MVFR/IFR conditions possible. Chance SHRA,
Chance SHSN.
Thursday: Mainly MVFR, with local IFR possible. Likely SHRA.
Thursday Night: Mainly IFR, with local MVFR possible. Chance
SHRA, Chance SHSN.
Friday: Mainly MVFR, with local IFR possible. Chance SHRA.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Winter Weather Advisory until noon EDT today for VTZ001>012-
     016>019.
     Wind Advisory until 11 PM EDT this evening for VTZ002-005-009.
     High Wind Warning until 11 PM EDT this evening for VTZ011-
     016>019.
NY...Winter Weather Advisory until noon EDT today for NYZ026>031-
     034-035-087.
     Wind Advisory until 11 PM EDT this evening for NYZ029>031.

&&

$$
SYNOPSIS...Taber
NEAR TERM...Taber
SHORT TERM...Taber
LONG TERM...Deal
AVIATION...Clay/Deal