Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 210902

Area Forecast Discussion
National Weather Service Burlington VT
402 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.


As of 401 AM EST Tuesday...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/ 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 Potsdam/Edwards.

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


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.


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 /09Z Tuesday THROUGH Saturday/...
Through 06z Wednesday...High pressure across area bringing
mostly clear skies and VFR conditions to the region through
overnight period. Will see increasing clouds above 15kft after
12Z Tuesday as high clouds advance from W-E ahead of the next
trough across the Great Lakes. Precipitation arrives in St.
Lawrence Valley near 00z Wed and eventually sweeps east.
Activity is light with showery rain or freezing rain in eastern
VT with MVFR cigs due to pcpn.

Light and variable winds overnight but as high pressure system
shifts to the east, will see winds developing from the south
toward daybreak Tuesday, increasing to 10-12kts with gusts to
20kts at BTV by 18z Tuesday.

Outlook 06z Wednesday through Saturday... A weak trough will
bring periods of light rain, with pockets of freezing rain east
of the Green Mtns during Tuesday night. Brief MVFR conditions
are possible with this system, mainly during the pre-dawn hours
Wednesday. Generally returning VFR with high pressure Wednesday
afternoon through Friday morning. Warm front approaches from the
southwest Friday afternoon with increasing chances for rain and
periods of MVFR/IFR conditions. Will also see possible sfc wind
gusts locally in excess of 25kts with low-level turbulence and
wind shear late Friday through Saturday as deep low pressure
passes to our west across the Great Lakes and Ontario.




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