Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
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FXUS61 KBTV 191507
Area Forecast Discussion
National Weather Service Burlington VT
1007 AM EST Thu Jan 19 2017
As surface high pressure and an a ridge aloft build into the region
today, areas of morning drizzle should dissipate through the day,
but a developing low level inversion will keep skies cloudy right
through Friday and into the weekend along with above normal
temperatures. A storm system shifting out of the southeastern states
Monday will bring the potential for a wintry mix Monday night,
changing to all rain for Tuesday.
.NEAR TERM /THROUGH FRIDAY/...
-- Changed Discussion --As of 1004 AM EST Thursday...Forecast in great shape this
morning as mid/upper level ridge across the central great lakes
shifts into our cwa and high pres builds at the surface.
Unfortunately...plenty of low level moisture is trapped below
developing subsidence inversion resulting in plenty of clouds
and areas of br. This will continue this afternoon with little
change in temps and light south winds. All covered well in
Mid/upper level shortwave trough shifting through the Northeast
this morning continues to provide areas of low clouds and
drizzle to the North Country through mid-day before surface high
pressure and an upper ridge building east from the Ohio Valley
brings an end to precipitation this afternoon. Moving forward
into tonight and Friday, despite strong subsidence building in
aloft, a developing low level inversion will trap abundant
moisture below 925mb with very light winds in the boundary
layer. This combination isn`t good for any clearing, except at
the mountain top level, so will continue to highlight cloudy
skies through Friday morning before the inversion possibly
breaks Friday afternoon with some peaks of sun possible towards
sunset. Should be interesting to see what the summits look like
Friday morning as I suspect they`ll be above the clouds. With so
much cloud cover through the period, temps will have a hard
time warming much today and falling off tonight so think highs
will mainly run in the mid/upper 30s and lows only in the mid
20s to low 30s. Light wind fields and warm air moving over fresh
snowpack will also enhance the potential for fog to develop
tonight, and feel it will be fairly widespread after sunset
reducing visibility below a mile at times. Not much airmass
change for Friday either so temps should be similar to Thursday,
but with the hope of a little afternoon sun could see some low
40s out there, mainly in the Champlain Valley.
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.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY/...
As of 311 AM EST Thursday...Relatively quiet weather continues
into the Friday night/Saturday time frame. A quick perusal of
this morning`s data suggests a fairly consistent theme showing
blocking upper ridging across New England will act to dampen an
approaching shortwave trough advancing northeast from the Ohio
Valley/Mid-Atlantic during this period. With light warm thermal
advection rippling in aloft expect a return to mainly cloudy
skies with perhaps some spotty very light rain and/or snow
arriving from the southwest over time and weakening in coverage
as we progress into Saturday. Any snow accumulations will be
negligible and generally less than an inch - mainly across
elevated terrain. Temperatures will continue very mild with lows
Friday night from the mid 20s to lower 30s and Saturday maxes
from the upper 30s to lower 40s.
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 311 AM EST Thursday...As we progress into the extended
portion of the forecast the one certainty is a continuation of
unseasonably mild weather with daily mean departures averaging
from +10 to +20 degrees. This has been a very consistent signal
among varying ensemble output over the past 10 days or so. Our
most notable weather will occur during the Monday/Tuesday time
frame as a rather potent southern stream system phases with
northern stream energy across the northeast before exiting into
the maritimes by mid-week. Examination of model thermal profiles
suggests at least a threat of some light sleet or freezing rain
in customary areas of northern New York and eastern VT into
Monday evening before boundary layer warming transitions p-type
to rain in all areas by Tuesday. For the Champlain Valley this
will primarily be a light rain event. Any icing threat appears
rather marginal at this time given such mild boundary layer
temperatures but a light glaze can`t be ruled out, at least at
this point. Other minor concern will be the potential for gusty
southeasterly downsloping winds, especially along the western
slopes of the Green Mountains later Monday afternoon into Monday
night as mean 925-850 mb flow may exceed 40 knots. This will
eventually predicate some adjustment of model qpf fields as
valley/terrain shadowing/enhancement effects will be magnified.
Higher-res guidance will certainly provide more detail as we
draw closer in time.
Behind this system mean lower to mid level flow remains
southwesterly, so little cooldown/airmass change is expected
through Thursday at this point. With several additional
shortwave impulses crossing the area the idea of a daily threat
of scattered rain/snow shower activity also appears reasonable
as progress into Wed/Thu. Afternoon highs should from the mid
30s to lower 40s with overnight lows averaging in the upper 20s
to lower 30s - more typical of March than January.
.AVIATION /15Z Thursday THROUGH Monday/...
Through 12Z Friday...Mainly offering a persistence forecast in
regards to ceilings as a developing low level inversion will
trap current moisture/clouds beneath it with little overall
airmass change expected through the next 24 hours. This
highlights mainly IFR cigs at KMSS/KSLK and MVFR elsewhere,
exception being VFR at KPBG through the daylight hours. VFR
vsby through the day trends to a mix of MVFR/VFR in fog after
00z with some spotty IFR. Winds light and variable through the
Outlook 12Z Friday through Monday...
12z Friday - 00Z Sunday - Inversion layer looks to possibly
break Friday but could continue to see prolonged stretches of
MVFR ceilings, and perhaps IFR at times for SLK/MPV. In addition
to low clouds, patchy BR/FG also possible.
00Z Sunday through 00Z Tuesday - Generally VFR Sunday. Moisture
laden low pressure approaching from the south brings potential
for widespread precipitation (mostly rain) for Monday with MVFR
and intervals of IFR conditions. SE gusts in excess of 25kts
possible at KRUT late Monday.