Area Forecast Discussion
Issued by NWS Burlington, VT

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459
FXUS61 KBTV 271504
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1004 AM EST Thu Feb 27 2020

.SYNOPSIS...
Low pressure system continues to track northward into the Saint
Lawrence valley today. Widespread rainfall this morning will
change to snow showers this afternoon as colder air moves into
the north country. Strong downslope winds are ongoing along the
western slopes of the Green Mountains, with localized gusts up
to 60 mph possible. Gusty westerly winds behind this front will
lead to areas of blowing snow as lake effect snow continues from
tonight through Friday.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 1004 AM EST Thursday...Rain continues to transition to
snow across portions of the region this morning while gusty
downslope winds have subsided below advisory levels. Going
forecast remains generally intact for the day, but did drop the
winds advisory for the region except across the NEK where a few
more hours of gusty winds up to 50 mph are possible. That will
end early this afternoon and plan to drop it fully by then.

Previous discussion...Strong downslope winds are occurring as
expected along and just west of the spine of the Greens. 850 mb
jet will intensify as it lifts north across our area this
morning, so strongest wings are yet to come. Rain is lifting
north into our area as low pressure lifts into the Saint
Lawrence valley. As a secondary low moves from the Hudson Valley
eastward, precipitation will change to snow across the north
country. Forecast continues to be very challenging due to
marginal surface temperatures. Strong frontogenesis between 2
surface lows places our region under heavy precipitation this
morning. The threat for thunder continues to remain non-zero. An
update for this morning`s forecast was to lower snow amounts
across much of the area as temperatures have warmed into the
lower 40s this morning, and it will take some time for the
change over to snow. As rapid cyclogenesis begins, these strong
dynamical processes could effect these rain/snow levels. QPF
through 7pm will range from just about a quarter of an inch in
Northeastern Vermont affected by downsloping and shadowing off
the whites, to a little over an inch long the spine of the
Greens and in the Dacks. Could see some hydrology concerns with
combination of heavy rain and snowmelt, especially in the Otter
Creek basin of Southern Vermont. Current RFC forecast shows
Otter Creek at Rutland reaching action stage. At this time,
hydro concerns remain isolated with the potential for localized
ice jams where ice is thin. Current indications show ice
thicknesses highly variable around a foot or less. Will continue
to monitor this in the coming forecast cycles.

For tonight into Friday, temperatures will drop quickly and
flow becomes westerly off the Great Lakes bringing a period of
lake effect snow to the region. Have issued a lake effect snow
warning for southeastern St Lawrence County, mainly south of
Route 3 where the lake effect snow will pile up a bit. Will also
have strong wind gusts out of the west during this timeframe,
though should stay below advisory criteria. Blowing and drifting
snow is anticipated.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY/...
As of 343 AM EST Thursday...Westerly flow continues as the
upper low lingers just to the north, providing cloudy skies and
continued chances for precipitation Friday night. Favorable wind
direction combined with cold air advection will allow lake
effect snow showers off of Lake Ontario to persist Friday night
across northern New York and possibly northern Vermont as well.
During this time, a surface boundary will slowly advance
southward across the North Country, providing a narrow zone of
low level convergence along which the lake effect band will be
focused. Heavy snow can be expected where the lake effect band
sets up, though by Friday night, it will most likely shift to
the south of our forecast area. Chances for precipitation will
diminish throughout the day Saturday. Cold temperatures are
anticipated for the weekend as flow aloft becomes northwesterly
and the upper low pivots eastward. Saturday morning lows are
expected to be in the low teens and single digits, with
afternoon highs in the upper teens to low 20s.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 343 AM EST Thursday...Next week will begin with a warming
trend as an upper level ridge moves across the region, inducing
southwesterly flow aloft. We may even see some break in cloud
cover Sunday afternoon into Monday morning as weak surface high
pressure weak settles across the North Country. High
temperatures will warm to upper 30s for Monday and continue to
rise mid week. Several passes of shortwave energy aloft will
bring ongoing chances of widespread precipitation to the area
beginning late Monday and continuing throughout the week. The
first bout of precipitation Monday night has the potential to
bring a mix of precipitation types as mid level warm air
advances from the south. However, temperatures are expected to
rise to mid 40s Tuesday thus changing any frozen precipitation
entirely to rain. Chances for precipitation will continue for
the remainder of the week, though the forecast proves to be a
challenge as model guidance provides differing solutions
regarding the evolution of upper level features.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
Through 12Z Friday...Low level wind shear will be an issue
through about 18z as strong southeast winds at 2000 feet in the
40 to 60 knot range move across the entire area. This strong low
level jet will lift northeast of the area after 18z. Strong and
gusty surface winds will develop during this time mainly from
the south and southeast...but northeast at KMSS. Surface gusts
will be in the 20 to 40 knot range. After 18z surface winds will
become more west and southwest...but still looking at gusts in
the 20 to 30 knot range for the remainder of the period. Expect
a burst of moderate to heavy precipitation...mainly in the form
of rain and snow through 16z...which will result in visibilities
down into the 1 to 3 mile range. After 16z visibilities will
gradually improve into the MVFR and VFR categories for the
remainder of the period as the steadier precipitation lifts
north of the area, but lake effect snow showers move into the
region after 00z. KSLK will have the best chance after 06z to
see IFR/MVFR conditions due to the lake effect snow.

Outlook...

Friday: VFR. Windy with gusts to 30 kt. Chance SHSN.
Friday Night: VFR. Chance SHSN.
Saturday: Mainly VFR, with local MVFR possible. Slight chance
SHSN.
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. NO SIG WX.
Sunday Night: VFR. NO SIG WX.
Monday: Mainly MVFR, with areas VFR possible. Slight chance SHRA,
Slight chance SHSN.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Wind Advisory until 1 PM EST this afternoon for VTZ003-004.
NY...Winter Weather Advisory until 4 PM EST this afternoon for
     NYZ026-030-031-034-087.

&&

$$
SYNOPSIS...Neiles
NEAR TERM...Lahiff/Neiles
SHORT TERM...Hammond
LONG TERM...Hammond
AVIATION...Evenson



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