Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 201109

Area Forecast Discussion
National Weather Service Burlington VT
609 AM EST Fri Jan 20 2017

Relatively quiet weather will persist across the region through the
upcoming weekend with mainly cloudy skies and very mild
temperatures. A more significant weather maker is looking more
likely to affect the region Monday night into Tuesday with potential
significant accumulations of snow or mixed precipitation. Behind
this system continued mild temperatures with on and off chances of
rain and snow shower activity are expected by the middle to later
portions of next week.


As of 609 AM EST Friday...Overall forecast remains in decent
shape as of 600 am. Did tweak hourly temperatures and dewpoints
and also made some adjustments to sky cover through the
morning/afternoon, leaning more heavily toward WRFARW/WRFNMM
output which is capturing current trends well. Again, sky cover
and the degree to which we can achieve some spotty afternoon
partial clearing will be the biggest near-term forecast
challenge. Have a great day.

Prior discussion...
Quiet conditions continue today as pronounced and blocking
upper ridge remains parked across the northeast. With lingering
moisture trapped beneath a semi- permanent subsident inversion
the timing and coverage of any partial clearing today will
remain the biggest forecast challenge. Background flow does
trend southerly over time however, and with the inversion
weakening slightly the prior idea offering at least some breaks
in the overcast still appears reasonable by afternoon in many
spots. Time will tell though as we`re still near the annual
bottom in regard to weakness in insolation. As has been the case
over the past few days temperatures will remain remarkably
steady, climbing only some 4 to 6 degrees from our overnight
lows - generally from 35 to 41.

By tonight into Saturday we`re still advertising a weakening impulse
and associated spotty light precipitation to arrive from the
southwest over time. Mid-level warm thermal advective processes are
rather unimpressive and with the described weakening trend as system
runs into our blocking ridge I expect rather scant, very light QPF
at best across the area. Some minor concern that where surface
temperatures do drop near or slightly below freezing some spotty
very light -fzra and/or -fzdz will be possible. Indeed FRAM model
output does show a light glaze of a few hundredths of an inch here
and there across the SLV into portions of the Dacks and Vermont
later tonight into the morning hours on Saturday. However, given the
expected spotty, light QPF coverage will only mention in our
Hazardous Weather Outlook at this point. As boundary layer
temperatures warm by late morning on Saturday any threat of spotty
light icing will end. With little airmass change very uniform
temperatures will continue with overnight lows in the upper 20s to
lower 30s (mid 20s northeast VT) and highs on Saturday in the upper
30s to lower 40s.


As of 345 AM EST Friday...Model guidance showing plenty of low
level moisture will be over the region Saturday night and Sunday
which will trapped below a low level temperature inversion,
with a weak upper ridge over the region. Expecting mostly cloudy
skies for Saturday night and Sunday.


As of 345 AM EST Friday...GFS and ECMWF models showing a ridge
of high pressure at the surface and aloft over the region Sunday
night, so have lowered superblend pops Sunday night and will
keep the region dry Sunday night. Plenty of low level moisture
still will be present over the region Sunday night, so expecting
skies to be cloudy Sunday night.

Models continue to show a prolonged period of unsettled weather
from Monday through Thursday. Models continue to show a surface
low over the mid Atlantic states on Monday, underneath a closed
upper low. Models bring this moisture slowly northward into the
region mainly Monday afternoon, as a ridge of high pressure at
the surface and aloft will be over the Canadian maritimes. This
moisture will spread northward by a negative upper trough closed
upper low over Pennsylvania late Monday night and Tuesday.
Models continue to hint at a mixed precipitation event from
Monday through Tuesday, with chances for rain, sleet and snow
across the region from Monday through Tuesday. Expecting
precipitation to wind down late Tuesday night, as an upper ridge
builds into the region.

The region will see a brief break early Wednesday, before
another system approaches from the Great Lakes by late Wednesday
bring more chances for rain or snow across the region
Wednesday and Thursday.

Temperatures expected to remain above normal in the long term
portion of the forecast.


.AVIATION /12Z Friday through Tuesday/...
Through 12Z Saturday...BKN/OVC MVFR/VFR cigs and light winds
generally expected over the next 24 hours though some partial
clearing in the 18Z-06Z time frame will be possible. Difficulty
lies in degree to which synoptic inversion and trapped moisture
can thin over time. Confidence only modest that partial
clearing will occur at any given terminal. After 06Z weakening
system approaching from the southwest may spark a spotty light
shower or spotty light freezing rain where surface temperatures
are near freezing. Coverage of pcpn quite scant so have omitted
discrete mention at this point.

Outlook 12Z Saturday through Tuesday...Areal coverage and cigs
heights associated with plenty of low level moisture continues
to be the aviation focus for Friday night into Saturday. A few
sprinkles or flurries possible Saturday with general mvfr
mountains to vfr valleys. Next system spreads a wintry mix
across our taf sites late Monday into Tuesday with widespread
mvfr to ifr conditions likely...along with breezy southeast
downslope winds possible at Rutland.




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