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  Sunday January 26, 2020

 

NWS Area Forecast Discussion


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000
FXUS61 KBTV 251744
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1244 PM EST Sat Jan 25 2020

.SYNOPSIS...
A complex weather system will bring wintry mixed precipitation
to the North Country this afternoon through Sunday. A Winter
Weather Advisory is in effect from 1 PM today to 4 AM Sunday
for portions of northern New York and Vermont. Ice accumulations
of a trace to two tenths are expected, with locally higher
along the spine of the Green Mountains. Locally gusty winds
upwards of 40 mph will also be possible this afternoon along
the western slopes of Green Mountains. Any mixed precipitation
will transition to rain or snow showers by Sunday afternoon.
Snow showers will linger through Tuesday morning with additional
accumulations of several inches likely. Quiet weather returns
by mid-week with seasonable conditions expected.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 1006 AM EST Saturday...Forecast remains on track, with
localized areas of freezing rain/sleet expected this afternoon
across ern VT and far nrn NY. Remaining areas of the CWA should
be warm enough for plain rain this afternoon into tonight.
Winter Weather Advisories remain unchanged at this time.

At 15Z, deep-layer moisture and precipitation axis extends from
the Delmarva Peninsula and srn NJ NWWD across ern PA/central NY
to just east of Lake Ontario. With the deep closed and slow-
moving low across the central Great Lakes region, the NNWWD
advection of moisture and low- level WAA will continue. In fact,
850mb sely jet is expected to increase to 60-70kt across srn VT
into the Adirondacks by 00Z this evening as moisture axis
translates newd. Still looks on track for 30-40 mph gusts along
the western slopes of the Green Mtns late this morning through
this afternoon, but onset of precipitation and stable low-level
conditions should keep peak wind gusts below wind advisory
criteria, consistent with previous forecasts. The summit of
Whiteface is already 36F with ssely winds gusting to 40kt, so
that warm layer aloft will continue to be well- supported by the
strong sely flow. As precipitation axis makes a slow newd push
into our region this afternoon, there is ample time for most
locations to warm above freezing at the surface, with a couple
of exceptions. Areas of freezing rain and sleet should be most
focused across the St. Lawrence Valley and along/east of the
Green Mtns in VT. Road temperatures are also starting out below
freezing, so the idea of some icy travel on untreated surfaces
in the above mentioned locations remains on track as well. Could
see up to 0.1" freezing rain accumulation through midnight
across the St. Lawrence Valley, and perhaps a max of 0.1 to 0.2"
freezing rain in vicinity of eastern Rutland and wrn Windsor
counties, where pockets of sub-freezing air are expected to
remain east of the spine of the Green Mountains. Overall
forecast is on track, with just minimal changes at this time.

Previous Discussion...Overall, no significant changes made to
the forecast with no substantial changes in 00z guidance suite.
Winter Weather Advisories remain in effect beginning 1PM today
through 4AM Sunday.

Current surface observations show highly variable temperature
readings across the area. Valleys across the Northeast Kingdom and
northern Adirondacks, as well as the northern Champlain Valley, have
fallen into the mid to upper teens overnight. More widespread
temperatures in the mid to upper 20s exist across much of Vermont
and the St Lawrence Valley of New York, while the western slopes and
higher terrain of the Adirondacks and Green Mountains currently
range from the upper 20s to upper 30s. These early reading
temperatures, along with cloud cover, have a real bearing on
expected warming today and thus precipitation type and impacts. Have
settled on a blend of the NAM/ECMWF using the top-down method, along
with high-res models for surface temperatures, all of which seem to
be capturing the current trends well. This largely lead to mainly
rain across the broader valleys, with a mix of freezing rain and
sleet for the Northeast Kingdom and northern St Lawrence Valley as
temperatures warm today into the low to upper 30s.

Radar imagery as of 345 AM shows precipitation slowly beginning to
spread eastward into central New York. Precipitation should begin to
overspread our far western areas of northern New York towards 18z,
before spreading to the east and north with everywhere seeing
precipitation by 01z. This shot of essentially warm air advection
precipitation will be rather quick as dry slot moves in by 09z.
Expect precipitation to taper off outside the confines of the higher
terrain & Northeast Kingdom with mainly dry weather during the first
part of Sunday. Colder air will begin to work its way back in
towards Sunday morning as upper level low moves overhead. Any
lingering mixed precipitation should transition to snow or rain
showers by Sunday afternoon.

QPF amounts are between 0.50-0.75", with locally lower amounts
between 0.25-0.30" due to downsloping along the western slopes of
the Adirondack and Green Mountains, as well as across the northern
CT River Valley (due to shadowing off the White Mountains). Although
a few ice jams exist along the St Regis and Winooski Rivers we are
not expecting any hydro concerns with this system. Snowfall totals
(including sleet) through Sunday evening are less than 0.50". Ice
accumulations between a trace and 0.20" are expected across the
Advisory area with locally higher amounts up to 0.40" along the
spine of the southern Green Mountains.

Lastly, the threat for gusty winds remain for portions of the
Adirondack and Green Mountains as 30-40 kt 925mb southeasterly
jet sets up across this area. Model soundings show best timing
for mixing will be between 15-20z before precipitation saturates
and stabilizes the low levels. Expect gusts between 30-40 mph
for locations in western Addison and Rutland counties, such as
Bristol, Goshen, Brandon and Rutland. Localized gusty winds will
be likely across the Adirondacks including Saranac Lake and
Lake Placid. These values remain sub- criteria, however very
isolated power outages may be possible.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 419 AM EST Saturday...Low pressure will pull away from the
region through the first part of next week, but a series of upper
shortwaves will rotate over the region. This with the continued
northwest flow will allow mountain snow showers to linger through
Tuesday. Mixed rain/snow showers will possible in the wider valleys,
particularly Sunday night and Monday. Additional snow accumulation
of a few inches will be possible during this time frame.
Temperatures will warm into the mid and upper 30s Monday afternoon,
but then turn slightly cooler on Tuesday with everyone near or below
freezing.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
As of 419 AM EST Saturday...Quiet weather prevails through the last
half of the week as high pressure settles across the region. This
also means it`ll trend a little colder, especially overnight when
mostly clear skies and light winds will allow for good radiational
cooling. Our next chance for precipitation arrives next weekend when
low pressure will move from the southern Appalachians northeastward.
Not a lot of agreement between the GFS and ECMWF on where this low
tracks, and a fair amount of spread in the GFS ensemble members as
well, so have stayed with just low chance PoPs for now.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
Through 18Z Sunday...Occulded low will slowly approach from the
Great Lakes region this afternoon and evening, yielding deteriorating
aviation weather conditions. Axis of moderate intensity precipitation
in advance of the occulded front will move newd into all the
TAF locations, beginning 18-19Z at SLK/MSS and 19-21Z elsewhere.
In terms of precipitation type, there will be periods of
freezing rain at both MSS and MPV where 2-m temperatures are the
closest to freezing. Elsewhere, looking at plain rain with temps
in the mid 30s to near 40 at times. All sites will also see a
period of moderate precipitation 23-03Z with strongest portions
of the frontal precipitation band, along with LLWS as sely 850mb
jet strengthens to 60-70kt. Core of strongest winds remains
aloft. That said, KRUT will see occasional mixing to the surface
with sely winds 15-20kt and gusts to 30kt through 22Z this
aftn. Ceilings and vsby will be highly variable. Have already
seen MVFR ceilings develop with sely upslope flow at MPV, and
HIR TRRN OBSCD generally throughout the period expected.
Elsewhere, will generally see ceilings slowly fall this
afternoon with VFR to MVFR conditions. Once the occulded front
swings through around 03-05Z, then most sites will trend IFR
with intermittent periods of very light rain (and rain/snow mix
at MSS/SLK). Not much change expected into Sunday AM, with a
moist SW low-level flow regime in place. Should see most sites
holding onto 2-3kft ceilings through 18Z Sunday, along with SW
winds at 5-10kts and periods of 4-5SM BR and intermittent very
light rain or snow.

Outlook...

Sunday Night: Mainly VFR, with local IFR possible. Chance SHSN.
Monday: Mainly MVFR, with local VFR possible. Chance SHSN, Chance
SHRA.
Monday Night: Mainly MVFR, with local VFR possible. Slight chance
SHSN.
Tuesday: Mainly MVFR, with local VFR possible. NO SIG WX.
Tuesday Night: VFR/MVFR conditions possible. NO SIG WX.
Wednesday: VFR. NO SIG WX.
Wednesday Night: VFR. NO SIG WX.
Thursday: VFR. NO SIG WX.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Winter Weather Advisory until 4 AM EST Sunday for VTZ003-004-
     006>008-010-012-018-019.
NY...Winter Weather Advisory until 4 AM EST Sunday for NYZ026-027-
     030-031-034.

&&

$$
SYNOPSIS...LaRocca
NEAR TERM...Banacos/LaRocca
SHORT TERM...Hastings
LONG TERM...Hastings
AVIATION...Banacos



 
 
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