Area Forecast Discussion
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FXUS61 KBTV 300240
Area Forecast Discussion
National Weather Service Burlington VT
1040 PM EDT Thu Sep 29 2016
Fair and dry weather continues as high pressure over Quebec
builds over the North Country through Friday. A closed upper low
over the Ohio valley will linger there through Saturday. This low
will move northward into the Great Lakes Saturday night into
Sunday. Moisture from the closed upper low will bring increasing
chances for rain showers to the North Country this weekend through
.NEAR TERM /UNTIL 6 PM FRIDAY EVENING/...
As of 1040 PM EDT Thursday...Same as earlier...going forecast in
real good shape with no real changes needed at this time other
than a few tweaks to current temperatures and dew points. Clouds
will generally be on the increase as the night wears on helping to
limit the threat of fog.
The North Country stays dry through Friday as a ridge of high
pressure resides over Quebec keeping a cutoff low over the Ohio
River Valley. Models continue to indicate 500mb heights increasing
over the North Country with mid-high level clouds pushing northward
over northern New York. Any rain showers associated with deeper
moisture over western and central New York dissipate in the drier
air over the St Lawrence Valley and Adirondacks as dewpoints
generally in the low to mid 40s. The cutoff low meanders a little
southward around the Ohio Valley, likely seeing a brief retreat in
clouds overnight, but Friday afternoon will see deeper moisture
spread northward into southern portions of the forecast area. With
PWATs increasing to around 1 inch late in the day, lower clouds
and possibly some late period showers begin to edge in from the
south. Have included slight to low chance POPs near southern CWA
border late Friday.
Min temps tonight ranging from the mid 30s to upper 40s. Friday
max temps will vary on cloud cover and cloud depth; with overall
less sunshine, expect temperatures to be a few degrees cooler than
.SHORT TERM /6 PM FRIDAY EVENING THROUGH SATURDAY NIGHT/...
As of 307 PM EDT Thursday...
The North Country will still be under the influence of two main
weather features during the short-term period: a lingering ridge
of high pressure extending from Maine into the eastern half of the
North Country, and the very slow-evolving upper low centered over
the Ohio Valley and its associated northward feed of Atlantic
moisture on its extreme eastern periphery. The main forecast
challenges in this period will be on temperatures and identifying
a period when PoPs may be more focused. Specific to the latter
point, there remains little clarity on when there may be a more
widespread period of rain as dry surface to 850 mb air should
limit areal coverage. The 12z NAM is the most aggressive in
showing QPF across our area on Friday into early Saturday. Feel
this is more overdone as compared to the 09z SREF and the 12z GFS
which is a lot more spotty. Through Friday night and early
Saturday morning, PoPs are kept generally under Chance except for
the extreme southern part of Vermont. Precipitation would also
likely show a good component of southeasterly upslope with highest
precip chances along the eastern spines of the Greens and
Adirondacks and lower in the Champlain and St. Lawrence Valleys on
the lee side. PoPs then begin to increase into the Chance/low
Likely range for the second half of Saturday into Saturday night
as mid-upper flow becomes more diffluent and might be just enough
to spark a greater coverage of light showers.
Temperature trends through the short-term period will be largely
governed by mostly cloudy to overcast skies, with milder than
normal lows but below-normal highs. Lows Friday night are
generally coolest north (in the low 40s) to the mid/upper 40s
south and in the valleys. Clouds and off-and-on light showers
keeps highs Saturday a rather raw upper 50s to lower 60s east to a
somewhat milder mid 60s for the St. Lawrence Valley. Little change
to lows from daytime highs Saturday night in the 40s to mid 50s.
.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 307 PM EDT Thursday...
Upper low through the previous period undergoes a deamplifying
trend into more of an open wave Sunday into Monday. Focus for
highest PoPs would generally be Sunday into Monday but it`s worth
pointing out that precipitation would be more showery in nature,
meaning that not everyone would see rain and it would not amount
to very much. Still some lingering slight chance PoPs on Tuesday
but the weaker open wave then merges with a northern stream trough
with a dry trend then offered for Tuesday night. A good stretch of
dry weather looks to be the case with a broader diurnal range in
temps for the mid-week period. Temperatures stay generally a few
degrees above normal through the period, though expect to see more
cooler nights Wednesday and Thursday with more clear skies.
.AVIATION /03Z Friday THROUGH Tuesday/...
Through 00Z Saturday...Largely a persistence forecast over the
next 24 hours. VFR conditions expected throughout with BKN-
OVC100-150 across nrn NY, and SCT-BKN120-150 generally across the
VT terminals. Can`t completely rule out a bit of 2-3SM BR at MPV
during the pre-dawn hours, but it appears there will be just
enough mid-level cloud cover (and impedance to radiative cooling)
that patchy fog/mist formation is a low probability tonight.
Otherwise, region is on nern fringe of cyclonic circulation
associated with cutoff low over the Ohio Valley. This will
generally keep a light easterly component to the winds across the
North Country. Locally channeling effects in the St. Lawrence
Valley will result in somewhat stronger winds at KMSS, generally
NE 10-12kts overnight.
Outlook 00Z Saturday through Tuesday...
00Z Sat though 12Z Saturday...Mid-level cloud cover continues in
place, with increasing chances for light rain showers, especially
12z Sat - 12z Tue: Mix of VFR/MVFR in scattered rain showers,
mainly from 00z Sun onward.
12z Tue onward: Generally VFR as rain showers depart eastward and
surface high pressure builds into the North Country.