Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
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FXUS61 KBTV 231906
Area Forecast Discussion
National Weather Service Burlington VT
306 PM EDT Thu Mar 23 2017
-- Changed Discussion --Clear skies will give way to increasing clouds and the threat of
light snows by tomorrow morning as a warm front pushes into the
area. Mixed precipitation or rain will be likely on and off into the
coming weekend as this front waffles south and north across the
region. Temperatures will moderate back toward more seasonal late
March values through the period.
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.NEAR TERM /THROUGH FRIDAY NIGHT/...
-- Changed Discussion --As of 306 PM EDT Thursday...A nice rebound in temperatures
under full sun has occurred this afternoon as northwesterly flow
slowly diminishes with modifying arctic high pressure sprawled
across the eastern seaboard. KBTV has hit 32F as of 230 pm. For
tonight clear skies will slowly give way to thickening and
lowering mid and upper level clouds as we progress after
midnight as winds trend light. An approaching warm frontal
system will be approaching from the south and west during this
time frame and the leading edge of its precipitation shield will
begin to encroach into our far western counties toward sunrise
Friday in the form of light snows. Temperatures will bottom out
early given the clear skies (5 to 15 above in the
mountains/teens to lower 20s valleys) but will trend steady or
slowly rise overnight as clouds arrive and light southerly
return flow develops.
A messy day then on tap for Friday as the warm front marches into
the region under strengthening southerly flow and widespread mixed
precipitation. Some channeling effects likely in the Champlain
Valley where gusts to near 30 mph look plausible at this point.
Boundary layer to mid level thermal profiles will be critical in
determining eventual p-type as widespread light snows slowly
transition to a mix of snow/sleet and eventual rain from the
Champlain Valley west. P-type should hold more in the form of snow
and/or a mix of snow/sleet across much of east central and
northeastern VT where mid level warming will be less and colder near
surface layers will be harder to scour out. Mixed precipitation top
down methodology using a variety of model output continues to
support the idea of little in the way of freezing rain with this
feature, which appears reasonable seeing the primary mid-level warm
layer generally runs in the 0-3C range through 21Z. Experience would
suggest however at least some patchy -fzra may occur here and there
through the morning hours. Front end snow totals should generally
run in the 0.5 to 2 inch range, with slightly higher totals from 1.5
to 4 inches likely across east central and northeastern VT. Given
the front end light snows will inhibit any pavement icing and only
low probabilities of a few hundredths of ice accumulation are
suggested (if any) will hold off on issuing any advisories at this
point. Late day high temperatures should range from the lower to mid
30s east and north, and the upper 30s to lower 40s elsewhere.
By Friday night widspread light rains (or mixed precipition north
and east) will gradually wane over time as best warm thermal
advection lessens. Later at night models continue to suggest
building high pressure to our north will push the front back
southward into the area with flow transitioning to a light northerly
regime by daybreak Saturday. This will tend to shunt the
precipitation shield southward as well as coverage/intensity
lessens. Some lingering light rains/mixed precipitation/light snows
will remain possible though settle generally into our southern
counties by morning. Lows a bit tricky though with expected
abundance of clouds upper 20s to lower 30s looks reasonable for most
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.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
As of 200 AM EDT Thursday....High pressure shifts east of our
longitude overnight and into the Gulf of Maine by 09-12z Friday.
This will allow for a light S-SW return flow to develop. Aloft,
will see a warm front approaching from wrn NY and sern Ontario,
and increasing 850-700mb WAA will result in thickening mid-level
overcast. These factors will keep overnight temperatures
generally in the mid teens to lower 20s, with a tendency for a
slow rise in temps toward daybreak Friday, especially west of
the Green Mtns.
Moderately strong 850-700mb WAA with approaching warm front
brings developing stratiform precipitation beginning during
Friday morning from SW-NE. It appears thermal profiles will
initially support snow, with a transition to sleet/rain as the
day progresses. Subfreezing thermal profiles will persist
longest across central/ern VT and in the nrn Adirondacks, where
1-3" of wet snow/sleet are forecast. Should see generally 1" or
less wet snow in the Champlain Valley as PBL temperatures warm
more quickly thru the 30s. Could see some minor impacts to
travel especially around the time of onset of the mixed wintry
precipitation (and especially away from the Champlain Valley),
and will continue to highlight in the Hazardous Weather Outlook.
Afternoon highs on Friday generally 36-39F, except 33-34F
across portions of ern/nern VT.
First wave of low-level WAA passes to our east Friday
evening/night, but E-W oriented low-level frontal zone will
become quasi-stationary across nrn NY/nrn VT. May be a tendency
for a shallow nly wind shift after midnight with strong high
pressure building into wrn Quebec, so we`ll need to monitor
trends with the frontal position overnight with possible shallow
CAA near the intl border. Anticipate continued overcast skies,
but with just very light rain/drizzle or isolated pockets of
snow/sleet/freezing drizzle across far nrn areas. Temperatures
will generally hold in the low-mid 30s.
.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 309 AM EDT Thursday...Interesting forecast with rather
active period expected and above normal chances for mixed
precipitation. Large high builds down from Canada on Saturday
and pushes surface boundary southward out of the area...which
will help bring precipitation to an end during the morning
hours. Highs will range from the mid 30s along the Canadian
border to the upper 30s and mid 40s elsewhere. Northwest flow
aloft Saturday night continue to bring colder and drier air into
the region. An upper trough will move east from the Ohio Valley
and this will allow the boundary that moved out of our area on
Saturday to return northward into our region and enhance the
potential for precipitation...especially Sunday afternoon and
night. Thermal profile suggests mixed precipitation with surface
cold air holding in the longest across eastern Vermont Sunday
night into Monday. Precipitation should become rather widespread
Sunday night into the first part of Monday as the trough moves
across the area. Will have to monitor this situation closely in
case there will be a need for a winter weather advisory. There
will be a brief respite in precipitation Monday night into the
first part of Tuesday...but another trough of low pressure will
move toward the region later Tuesday into Wednesday and bring
more precipitation to the area. Still cannot rule out some mixed
precipitation...but at this time looking at either rain or snow
with this system. The precipitation should be fairly widespread
as well given the strength of the upper trough moving into the
.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
Through 18Z Friday...VFR through 12Z as high pressure gives way
to approaching warm front and associated pcpn. SKC expected
through 00Z, then slowly thickening/lowering VFR OVC in the 00Z
to 12Z time frame. Winds light/modest northwesterly through 00Z,
trending light overnight. After 12Z Friday widespread snow
overspreads all terminals, likely transitioning to a
snow/sleet/rain mix from Champlain Valley terminals west toward
the end of this forecast cycle. Winds trending southerly 5 to 15
knots, most pronounced at KBTV/KPBG where valley channeling
effects may push gusts near 25 kts.
Outlook 18Z Friday through Tuesday...
18Z Friday through 18Z Saturday...widespread light mixed pcpn
likely, slowly settling southward and lessening in coverage by
Saturday afternoon affecting mainly southern terminals at that
point. Highest threat of mix to occur at northern terminals.
18Z Saturday through 12Z Sunday...trending mainly VFR/pcpn-free
as Canadian high pressure noses briefly southward into the area.
12Z Sunday through 12Z Tuesday...widespread mixed pcpn and/or
rain return to the region.
12Z Tuesday onward...light and spotty mixed pcpn transitions
toward a period of steadier rains by Wednesday.