Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
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FXUS61 KBTV 201420
Area Forecast Discussion
National Weather Service Burlington VT
1020 AM EDT Mon Mar 20 2017
A ridge of high pressure will bring dry and seasonable weather
conditions to the North Country today, with just some advancing
high level cloudiness from the west this afternoon. A weak upper
level trough will bring a chance of snow showers late tonight
into Tuesday, especially across the northern mountains. A strong
cold front moving in from Quebec will bring additional snow
showers or possible snow squalls to the area during the first
half of Tuesday night. Seasonably cold and dry weather will
follow Wednesday and Thursday. Temperatures will warm back above
normal Friday, but a warm front will bring chances for
.NEAR TERM /THROUGH TUESDAY/...
-- Changed Discussion --As of 1020 AM EDT Monday...Other than some tweaks to sky
cover...essentially slowing down timing of thicker mid and high
level clouds...going forecast in real good shape. Continued
tranquil weather today with sfc ridge extending SW-NE across the
nern CONUS and clear skies at daybreak across the North
Country. Early AM temps are starting chilly, mainly in the
teens, but locally below zero (-4F at SLK and -2F at Island
Pond, VT), but will warm quickly under full sun. A weak upper
level trough evident on early morning IR imagery across the
central Great Lakes and sern Ontario will spread mid-upr level
clouds ewd across our region this afternoon and evening. Thus,
will trend toward filtered sunshine as the day progresses. Light
winds and 850mb temps about 2C warmer today compared to Sunday.
Thus, should see highs reaching the low-mid 40s this afternoon
in most areas. Leaned toward the higher end of MOS guidance.
Will continue to see some snowmelt, especially with the
relatively high sun angle (vernal equinox at 629am this
Will see 500mb ridge axis breakdown tonight with increasing
zonal flow and weak mid-level trough moving in from the west.
While PBL moisture is limited, good upr diffluence in 300mb jet
exit region and PWs increasing to near 0.5" per 00z GFS suggest
a few snow showers are possible late tonight and into the day
Tuesday. Shouldn`t be a big deal, and kept PoPs in the 20-40%
range, highest across the nrn Greens and nrn Adirondacks.
Overall liquid equiv. amts only a few hundreths, and could see a
dusting to an inch of snow in spots across the higher terrain.
Mostly cloudy to cloudy skies will keep low temperatures warmer
than recent nights...generally 25-30F tonight. Highs on Tuesday
should reach the upr 30s to lower 40s, so may see a few
sprinkles with any light pcpn in valley locations.
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.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 309 AM EDT Monday....A strong arctic cold front will be
swinging through the North Country Tuesday night. Ahead of the
front there will be decent surface based instability across the
Saint Lawrence Valley which combined with strong 925mb F-gen
could be enough to develop snow squalls. Based on the sharpness
of the wind shift there will also be nice convergence along the
line so while the overall threat appears to be limited, we
certainly can`t rule out squalls especially over the northern
tier of counties and in the Saint Lawrence Valley. By Wednesday
afternoon the snow will be confined to the high terrain as we
are under cyclonic northwesterly flow. RH is limited so any
snow/flurries will need some orographic help.
Equally as impactful, the thermal gradient will be very sharp
behind the front. Temps ahead are -1C to 0C at 925mb and behind
the front rapidly cool to -12C to -17C. This will likely cause
a flash freeze across the North Country which could develop icy
and hazardous road conditions.
The temperatures represent a difficult forecast because as we
start the evening Tuesday temps will be in the mid 30s but
behind the front cold air advection will drive in that arctic
airmass. Expect our lowest low to be right around 12z in the
single digits above zero. Then expect a non-diurnal range as the
cold air advection continues to surge in. We`ll likely warm a
degree or two but mainly holding steady in the teens for our
daytime highs. Overnight on Wednesday it will be quiet as we see
radiational cooling and well below normal temperatures.
.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 309 AM EDT Monday...High pressure continues midweek as we
sit under the upper level ridge. We`ll start to trend back to
normal temperatures by the end of the week with highs back in
the 40s. Towards the end of the week a northern stream system
increases our moisture feed, and should bring some precipitation.
The question is what kind? There is considerable spread in the
guidance and neither solution offers up something I feel
confident in. The GFS brings a warm front through and then just
as the warm front clears a cold front sweeps through so we`d be
looking at rain switching to snow, and the EC never gets the
warm front to the region so there`d be the potential for some
mixed precip. Either way we`ll continue to monitor this but I`ve
opted to run precip much down the middle leaning slightly
towards the warmer GFS.
.AVIATION /14Z MONDAY THROUGH FRIDAY/...
Through 12Z Tuesday...Ridge of high pressure will bring VFR
conditions and light winds. Will see increasing high cloudiness
this afternoon, with ceilings falling to 4-5kft by the pre-dawn
hours on Tuesday as a weak trough approaches from the west. May
see a few snow showers toward the end of the period, mainly
across the higher terrain. Carried VCSH after 08-09Z/Tue, except
-SHSN at SLK.
12Z Tuesday through Friday...
12Z Tuesday - 12Z Wednesday...An upper trough will bring mainly
VFR ceilings during the day Tuesday, but could see some
flurries/sprinkles during the daylight hrs. A strong cold front
will bring scattered snow showers and possible snow squalls
00-06Z Wednesday. May see a "flash freeze" situation for airport
ground ops with rapidly falling temps causing some icy spots on
runways and taxiways during Tuesday night. Brief IFR conditions
possible for 30 minutes or less. Will see a NW wind shift with
gusts 25-30kts possible Tuesday night following frontal passage.
12Z Wednesday through Friday...Flurries possible on Wednesday
morning. Otherwise, gradual clearing and mainly bcmg VFR. High
pressure will crest over the region Thursday with lighter winds.
A warm front approaching from the SW on Friday will bring
additional chances for rainfall, along with gusts S-SW winds and