387
FXUS61 KBTV 131733
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1233 PM EST Tue Nov 13 2018

.SYNOPSIS...
Low pressure moving along the East Coast will produce a mix of rain
and wet snow across the North Country today. Snow accumulations will
range from an inch or two in the Champlain and Saint Lawrence
Valley to 3 to 6 inches in the mountains of Vermont and northern New
York. Blustery and colder conditions follow this system tonight into
Wednesday, with highs mainly in the upper teens to upper 20s.
Another coastal system will impact our region on Friday into
Saturday with a mix of rain and snow likely.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 1015 AM EST Tuesday...Overall forecast mainly on track
for the first widespread snow event of the season. Radar imagery
shows a well-defined back edge of the precipitation quickly
moving eastward through northern New York. Webcams from the
Saint Lawrence Valley show bare grass...concurrent with some
null snow reports. Have adjusted forecast to account for the
sharp precip gradient as areas further east have picked up
considerable measurable snow. The heaviest snowfall is being
reported over portions of the Northeast Kingdom where some
bands of snow continue to be observed on radar. Areas of
southern Caledonia County and southern Essex County (in VT) have
reported around 4-8 inches thus far, so Winter Storm Warning
remains in effect for northeastern VT.

On track for precipitation to end from west to east through the
early afternoon. Lower elevations will likely see some rain
mixed in with the snow before precipitation ends. Timing the
back edge of the precip...expecting precip to end in the
Champlain Valley by noon, Montpelier/Barre area by 1 PM, and
then finally in the Northeast Kingdom by around 4 PM. Could see
some light upslope showers this evening as flow becomes
northwesterly, but main even will be finished this afternoon.

Previous discussion below:
Winter storm warnings continue for northern Vermont, including
the Northeast Kingdom for 4 to 8 inches of wet snow. Meanwhile,
winter weather advisories continue for the central/southern
Green Mountains in VT and northern Dacks in NY for 3 to 6 inches
of wet snow. Meanwhile, a dusting to an inch or two of slushy
wet snow is possible across the cpv/slv. Given timing of
expected heaviest snowfall, a difficult morning commute is
likely with poor visibilities along with snow covered and
slippery roads, especially above 1000 feet. The heavy wet snow
will have the potential to cause isolated to scattered power
outages.

An extremely challenging snowfall forecast continues across our cwa
today, especially in the valleys below 1000 feet where current
temps are holding in the mid 30s. Little overall change in
forecast occurred with this package, other than to sharpen west
to east qpf gradient and trim back snowfall amounts over the
slv/western dacks. Fast/progressive system with open circulation
will result in qpf ranging from 0.10 to 0.20 slv/western dacks
to 0.30 to 0.50 cpv to 0.50 to 0.75 for eastern VT. These type
of open wave and fast moving systems typical under perform in
the qpf department across our cwa, especially western sections.

Current thinking is a band of moderate to briefly heavy precip
will lift from south to north across most of VT and the eastern
Dacks btwn 10z-16z this morning, per latest radar trends. This
band of precip will have enough dynamics to cool the column just
enough to produce a period of wet snow, even into parts of the
cpv. Albany, NY started at 42f, but heavier precip arrived and
sfc temp cooled to 34f with snow falling, expect similar
scenario to occur at Rutland/Middlebury/BTV. The tricky part for
the cpv, including the BTV area how much accumulates given warm
sfc temps. Thinking very little near the water front, but a
quick slushy inch or two is possible near the airport into the
Essex/Williston/ and Jericho areas.

However, if this strong band stays south, then little snow
accumulation would be anticipated in this area. The northern
dacks and mountains of central/northern VT should stay cold
enough for all snow above 1000 feet. The best 850 to 700mb fgen
forcing and associated uvv`s lifts from south to north across
our central/eastern cwa btwn 10-16z today. Once this better uvv
couplet lifts northeast of our fa, expect temps to warm back
into the mid/upper 30s with a mix of light rain/snow depending
upon elevation. As precip tapers off expect snow levels to climb
around 1500 feet, before winds shift to the west/northwest by
21z and cold air advection develops. Given the progged 925mb to
850mb 0c line bisects our southern cwa during the event, the
heaviest axis of qpf/snowfall should occur 25 to 50 miles north
of this line, over central VT.

Given very fast/progressive flow aloft with no closed 7h/5h
circulation to advect deeper Atlantic moisture on the backside,
thinking precip ends quickly from west to east btwn 18z-21z today. A
brief period of upslope snow showers are possible as strong low
level caa occurs and squeezes out remaining moisture in the column
this evening. However, moisture within the favorable snow growth
region is limited, which will minimize additional snowfall amounts.

Strong low level caa develops on brisk west/northwest winds tonight,
as 925mb to 850mb temps crush into the -10c to -16c range by Weds
morning. Lows will range from the single digits summits to l/m 20s
cpv. Expect wind chill values near 20 below summits to single digits
and teens on Weds morning. A cold and dry day is anticipated on
Weds. However, soundings show lake instability to be extreme off
Lake Champlain, so anticipate clouds downwind in the BTV area, along
with maybe a few flurries/light snow showers. The missing element
for snowfall is moisture. Highs teens to mid/upper 20s with brisk
northwest winds prevailing.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/...
As of 400 AM EST Tuesday...High pressure will be cresting
overhead Wednesday night into Thursday and this will lead to
some rather cold temperatures Wednesday night. 925mb temps will
be in the -11C to -14C range and that supports lows in the
single digits to low teens. The challenge will be that if we do
get that cold, then with a lake water temperature in upper 40s
we should see a significant lake response. So I`ve added some
cloud cover directly over Lake Champlain and just to the east as
light winds should push some of those clouds into the eastern
Champlain Valley. Once the high crests over the North Country
on Thursday the flow will be light enough that I believe we`ll
see some tea kettling effect where there are clear skies across
most of the North Country with mostly cloudy to overcast skies
right next to Lake Champlain.

Temps should warm into the upper 20s to low 30s in the valleys
under clear skies and no chance for precip on Thursday.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 400 AM EST Tuesday...Heading into the weekend we`ll see
another round of moderate snow moving into the region. An upper
level cutoff low pressure system will end up phasing with a
developing coastal low on Friday morning. Consensus guidance
continues to be in fairly decent agreement with the low track
moving just off Cape Cod but west of the benchmark. The 700mb
closed low tracks south of the region which should push quite a
bit of moisture into the atmosphere before the precip starts to
fall. Expect the snow to start falling early Friday morning and
we should get a quick burst of some moderate snowfall Friday
morning as the surface low deepens to our east. I`d anticipate
the eastern slopes seeing the highest totals initially as the
easterly flow should enhance the surface lift.

The temperature profile continues to be on the marginal side in
the valleys but the 00z suite trended colder with more snow. We
could be looking at another significant system bringing a round
of heavy wet snow. Its too early to have specific snow totals
but if trends continue, the entire region should see plowable
snow. Additionally snow ratios are on the lower side of climo
meaning we`ll need to monitor for potential impacts from heavy
wet snow.

After the low pressure system pushes out of the region the
upper level pattern shifts to fast nearly zonal flow with
modest high pressure at the surface. Temps will start out the
weekend on the mildish side with highs in the upper 30s to low
40s but will quickly drop down below normal for Sunday into
Monday.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Through 18Z Wednesday...Ceilings will slowly improve, as well as
visibilities as light snow ends across our area. Winds will
shift to the northwest this afternoon and become breezy at
times this evening at 15 to 25 knots. Expect vfr conditions by
00z, except lingering mvfr cigs at mpv/slk. A few mountain snow
showers are possible this evening. As colder air moves over the
relatively warmer Lake Champlain waters, anticipate additional
clouds with potential mvfr cigs to develop at btv after 06z this
evening.

Outlook...

Wednesday Night: VFR. NO SIG WX.
Thursday: VFR. NO SIG WX.
Thursday Night: Mainly VFR, with local MVFR possible. Chance SN.
Friday: Mainly MVFR and IFR, with areas VFR possible. Definite
SN.
Friday Night: Mainly MVFR, with local VFR possible. Chance SHSN.
Saturday: Mainly MVFR, with areas VFR possible. Chance SHRA,
Chance SHSN.
Saturday Night: Mainly VFR, with areas MVFR possible. Chance
SHSN.
Sunday: Mainly VFR, with local MVFR possible. Slight chance SHSN.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Winter Weather Advisory until 6 PM EST this evening for VTZ008-
     010-012-016>019.
     Winter Storm Warning until 6 PM EST this evening for VTZ003-
     004-006-007.
NY...None.

&&

$$
SYNOPSIS...RSD/Taber
NEAR TERM...Taber
SHORT TERM...Deal
LONG TERM...Deal
AVIATION...Neiles