Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
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FXUS61 KBTV 240805
Area Forecast Discussion
National Weather Service Burlington VT
405 AM EDT Mon Oct 24 2016
A departing low pressure across eastern Quebec will allow for
continued clearing this evening, along with diminishing wind
speeds. A secondary trough moving into the region from the
northwest late Monday into Monday night will bring a chance of
light rain showers, with snow showers possible across the northern
Adirondacks and northern Green Mountains. A more significant wave
of low pressure approaching from the Great Lakes and Ohio Valley
will bring the next chance for rain, generally late Thursday,
Thursday night, into early Friday.
.NEAR TERM /THROUGH TONIGHT/...
As of 149 AM EDT Monday...Shortwave trough embedded in mid level
flow passing to our south with an increase in clouds through the
next few hours. These clouds along with W to WSW wind flow of
5-10kts keeping temperatures from dropping. Therefore, have
increased the morning lows to low 30s mainly in the northeast
kingdom and Adirondacks where fresh snowpack will help with
cooling. In the broad valleys, expect temperatures to remain in
Generally quiet weather expected Monday. Broad cyclonic flow
remains in place aloft, and it appears we`ll have another surge of
low-level CAA and possible passage of weak mid-level shortwave
trough. Shallow instability layer will produce clouds by afternoon
and possible light upslope precipitation into the Adirondacks and
nrn Green mtns. Freezing levels generally 2000-2500ft, so can`t
rule out some flurries down to about 1000ft in elevation Monday
aftn, especially wrn slopes. May see passing sprinkles in the
valley locations, and kept PoPs generally less than 20%. High
temps generally low-mid 40s, except upr 40s near Lake Champlain
and with downslope warning effects across ern Windsor county/VSF
area. Winds will be W-NW winds 8-15kts with gusts developing in
the afternoon with presence of steeper lapse rates.
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
-- Changed Discussion --As of 400 AM EDT Monday...A 1 to 2 STD below normal mid/upper height
field associated with a trof across the northeast CONUS will
continue to provide our region with below normal temps through
midweek. The combination of favorable 925mb to 850mb upslope flow
and ribbons of deeper layer moisture associated with cyclonic
circulation will continue to produce terrain focused precipitation
through Tuesday. The associated low level wind fields are between
20 and 30 knots on Tuesday result in limited low level forcing
from upslope component...but weak embedded vort at 500mb and some
low level cold air advection will be enough to produce light qpf
across the mountains. Will mention likely pops for Tuesday...with
qpf generally 0.20 or less across the northern dacks and western
slopes...with only a trace to couple hundredths in the valleys.
Thermal profiles show both 925mb and 850mb temps below 0c...with
850mb temps near -10c by 00z Weds...supporting mostly
snow...except the valleys and near the warmer Lake. Speaking of
Lake Champlain...some enhanced precipitation is possible on the
east side of the lake with moderate instability created between
the air/water temp difference...especially on Tuesday.
Also...noted with boundary layer heating and cold air
aloft...lapse rates steepen on Tuesday afternoon...supporting some
convective elements with potential graupel in the valley. Thinking
any snow accumulation below 1000 feet will be difficult during the
daytime...but some minor accumulation above 1000 feet between a
dusting to several inches is likely across the northern dacks and
mountains of central/northern VT. Its never too early to start
building the snow pack. Thermal profiles support about a 20 degree
difference between lower/mid 20s mountains summits to lower/mid
40s valleys on both Tuesday and Weds...with lows mainly upper
teens to lower 30s.
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.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
-- Changed Discussion --As of 400 AM EDT Monday...Active pattern continues for days 4 thru 7
with additional chances for rain and snow on Thursday into Friday
and another system next weekend. Overall...given the progressive
west to northwest flow aloft...temps will stay below normal thru
the period with additional chances to increase snow pack across
the mountains...especially Thursday Afternoon.
GFS/GEM and ECMWF in good agreement with potent 5h energy in the
northern jet stream crossing the Great Lakes and NE CONUS on
Thursday into Friday. Meanwhile...initial surface low pres tracks
across the central Great Lakes with weak secondary development over
southern New England by 12z Friday. The combination of 1036mb high
pres over eastern Canada and developing secondary low
pres...suggests warmer air will have difficulties advecting into our
region...supporting potential for additional snow accumulations in
the mountains. Sea level pres fields show a cold air damming
signature. Latest ECMWF only briefly increases the 850mb temps to
0c around 06z Friday...before winds shift to the northwest and
colder air follows. Current thinking a band of rain/mixed with wet
snow flakes develops from southwest to northeast on
Thursday...associated with moderate to strong warm air advection.
The combination of evaporational cooling and progged 925mb to
850mb profiles below 0c initially supports even some wet flakes in
the valley with no accumulation...before quickly turning over to
rain. Meanwhile...cold air remains locked east of the greens and
across the northeast kingdom with a longer duration of snow...with
several inches of wet snow accumulation possible Thursday
afternoon/evening...before changing over to rain. Mountain thermal
profiles are tricky as progged 850mb temps stay near 0c...but warm
nose around 5000 feet associated with southerly jet...supports
some freezing rain possible near the summits of the dacks and
greens on Thursday Night. It shall be interesting to see what the
picnic table on Mansfield receives.
Otherwise...the potential for gusty downslope southeast winds will
have to be watched...as latest GFS shows 850mb winds of 40 to 50
knots. The strongest winds are collocated when precip will be
falling and difficult to determine how much mixing will
occur...but something to watch along the western slopes on
Next system arrives late Saturday into Sunday with additional
chances for precipitation and once again thermal profiles support
mainly rain valleys and a mix in the mountains...as 850mb 0c line
bisects the area. Temps during the period mainly in the 30s
mountains and 40s valleys with lows in the 20s to mid/upper 30s.
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.AVIATION /08Z Monday THROUGH Friday/...
Through 06z Tuesday...VFR conditions persist with potential for
intervals of MVFR ceilings at SLK for the next few hours. Westerly
winds continue at 5-10kts til mid morning, when winds shift a
little more NW at 8-12kts with gusts up to 25 knots during the
day. Generally VFR conditions prevail, but some low level clouds
develop in the cold air advection between 3500-5000 ft after 15Z.
Chances for showers to develop increase late in the period as
embedded pieces of energy in the midlevel cyclonic flow move over
the North Country.
Outlook 06z Tuesday through Friday...
06z Tuesday through 00z Wednesday: VFR ceiling with possible MVFR
showers and higher elevation snow snow showers as a broad upper
trough remains over the region. Increasing chances for MVFR
ceilings at MPV/SLK later Monday night through Tuesday, with
periods of light precipitation and MVFR cigs/vsby conditions.
00Z Wednesday through 00Z Saturday: Next low pressure system
approaching from the Great Lakes/Ohio Valley brings chances for
widespread showers and periods of MVFR conditions late Thursday
through the first half of Friday.