Area Forecast Discussion
Issued by NWS Burlington, VT
FXUS61 KBTV 211130
Area Forecast Discussion
National Weather Service Burlington VT
630 AM EST Tue Feb 21 2017
A weak disturbance and associated ribbon of mid level moisture will
produce scattered rain showers late this afternoon across northern
New York. This threat of showers will spread into Vermont
overnight...with a few pockets of light freezing rain possible in
the deeper valleys. Very minimal ice accumulation if any is
anticipated...with temperatures in the upper 30s to mid 40s today. A
big warming trend is expected for most of the week with more showers
anticipated on Thursday Night into the weekend.
.NEAR TERM /THROUGH WEDNESDAY/...
As of 621 AM EST Tuesday...Update to capture latest temps
associated with sharp thermal inversion across our region.
Currently Saranac Lake is 6F while atop Whiteface is
39F...indicating the warming aloft. Thinking deeper valleys will
slowly mix out this morning as gradient increases between
departing surface high pres and weak front approaching our
region from the west. Otherwise...rest of forecast in good
1031mb high pres centered over eastern VT this morning will
shift east...while decaying short wave energy and associated
ribbon of 850 to 500mb moisture approaches our western cwa by
00z Weds. Latest trends have been for this moisture to weaken as
it encounter mid/upper level ridge across the ne CONUS and
limit the overall qpf output over our forecast area. GFS/NAM and
local WRF show up to 0.10 for mountain zones...with a trace to
0.05 most other locations. Developing 850mb southwest winds of
20 to 25 knots will produce modest low level warm air advection
today with 925mb temps ranging from near 0c NEK to +6c western
dacks/slv...so anticipating a large spread in highs today.
Also...playing a factor will be amount of sunshine and how
quickly clouds spread from west to east across our cwa...but
thinking highs range from the mid/upper 30s NEK to mid/upper 40s
SLV/Western Dacks with maybe a few lower 50s near
Tonight...soundings show deep dry layer between 925mb and 700mb
becoming saturated as moisture advection occurs on south to
southwest winds. Thinking temps fall early as some evaporational
cooling occurs...but with clouds and developing southerly flow of 10
to 20 knots...especially cpv/slv temps hold mainly in the mid/upper
30s to near 40f most of the night. East of the greens still looking
at some pockets of <0C temps in the protected valley with the
potential for some spotty freezing rain. Given the marginal temps
and scattered precip/very light qpf...not anticipating widespread
coverage of freeze rain and very minor ice accumulation. If needed
will handle with a sps.
Wednesday...low to mid level warm air advection continues with
progged 925mb to 850mb temps climbing between 2c and 4c.
However...soundings especially the nam shows plenty of low level
moisture trapped below thermal inversion between surface and 850mb.
Is this overdone again or do we see lots of low clouds and limited
sun on Weds...keeping our temps on the cooler side of guidance with
some areas of light precip. Soundings show this moisture mixing
out...especially during the afternoon hours as top of the mixed
layer winds increase between 15 and 20 knots and drier air aloft is
advected toward the surface. Will trend toward the warmer side of
guidance and keep forecast mainly dry at this time...with highs
mainly lower 40s northeast kingdom to near 50f cpv/slv and western
.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 358 AM EST Tuesday...Thursday will see another low pressure
system from the Great Lakes region pass to the north of the
CWA. Light showers, mainly in the northern half of the forecast
area, are expected with the system passes north of the border
and into northern Maine. QPF is minimal with this system with
the Adirondacks seeing a couple tenths of an inch, the Northern
Vermont counties seeing around a tenth and the rest of the state
seeing only a few hundreths of an inch.
Southerly flow will continue to boost temps well above seasonal
norms for Thursday with highs in the 50`s for the majority of the
area and overnight lows in the mid to upper 30`s.
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 358 AM EST Tuesday...Friday sees low pressure tracking north
and west of our region from the Great Lakes Friday through
early Sunday morning. Models are in general agreement of a warm
front lifting through the region Friday afternoon/evening with
precipitation ramping up through the day Saturday with the peak
Saturday afternoon/evening just ahead of the passage of a cold
front. Winds out ahead of the front could lead to gusty
conditions and potential advisory level winds especially across
the Champlain Valley as the 00Z GFS indicates 850mb winds to
reach 65 knots Saturday afternoon. After frontal passage, rain
will switch over to snow showers Saturday night with the strong
cold air advection. Very warm temperatures are expected Saturday
ahead of the cold frontal passage. Temperatures overall look to
be in the 50s with the Champlain Valley pushing a record
breaking 60. A sharp cold front will drop temps quickly back
into the 20s Saturday night. Possible flash freeze issues are
possible with temperatures dropping so sharply after a moderate
rainfall. Moving into next week, more seasonable weather will
return for Sunday through Tuesday.
.AVIATION /12Z Tuesday THROUGH Saturday/...
Through 12z Wednesday...Clouds increase from west to east across
our taf sites today with cigs trending toward mvfr conditions
between 03z-06z tonight. Expecting a brief period of light
rain...possibly mixed with a few pockets of freezing rain at
mpv/slk. Winds increase from the south/southwest this afternoon
at 5 to 15 knots with a few localized higher gusts. Soundings
show plenty of low level moisture developing from snow melt and
precip...especially at slk/mpv after 06z tonight...which may
support some ifr cigs toward sunrise Weds. Have mention cigs
between 1500 and 2000 feet and will monitor moisture trends.
Outlook 12z Wednesday through Saturday...
Challenging aviation forecast with regards to low level moisture
and potential mvfr/ifr cigs weds into thursday. Thinking mostly
vfr/mvfr with pockets of mvfr/ifr in our mountains sites. A warm
front lifting from southwest to northeast on Friday will produce
additional showers along with some enhanced southerly winds. The
turning wind profiles and rapid increase in speed with height
will cause some areas of turbulence and shear on Friday Night
into Saturday. Widespread gusty southerly winds likely on
Saturday with areas of rain showers...producing localized
mvfr/ifr cigs/vis in the heavier elements.