Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
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FXUS61 KBTV 241440
Area Forecast Discussion
National Weather Service Burlington VT
1040 AM EDT Sat Sep 24 2016
A high pressure system moving down from Canada will bring dry
weather to the area this weekend. Expect plenty of sunshine and no
precipitation along with below normal temperatures. Highs will
only be in the mid 50s to lower 60s. More importantly...low
temperatures tonight and Sunday night will get cold enough for
frost to develop over the Northern Adirondacks of New York...the
west slopes of the Green Mountains...and north central and
.NEAR TERM /THROUGH SUNDAY/...
-- Changed Discussion --As of 1040 AM EDT Saturday...Going forecast is in great shape
with only a few tweaks need to hourly datasets to match current
observational trends. Fog continues to slowly scatter out, though
some lingering low stratus will still hold tough for about another
hour. Thereafter, that stratus deck will lift into some fair
weather cumulus for the remainder of the day. Temps on track to
top out in the mid 50s to low 60s, about 5 degrees below normal
for late September. Enjoy!
Frost Advisory in effect from 2AM to 8AM Sunday for the Northern
Adirondacks of New York...the west slopes of the Green Mountains
in Vermont...and north central and northeast Vermont. Temperatures
will fall into the lower to mid 30s across this area...which
should be sufficiently cold to develop frost and potentially have
an impact on vegetation sensitive to cold temperatures.
Otherwise...looking at quiet weather today through Sunday with
high pressure building down from Canada. We`ll have fog early this
morning...but will burn off by mid-morning. Plenty of sunshine
today and Sunday...but cold air advection will lead to below
normal temperatures with highs generally in the mid 50s to lower
60s both days. Steepening lapse rates by midday will lead to
better mixing and northwest winds will pick up in the 10 to 20 mph
range before gradually tapering off after sunset. There may be
enough wind in the mountains overnight to limit the areal coverage
of frost at the highest elevations...but temperatures will
definitely be cold enough.
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.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY/...
As of 451 AM EDT Saturday...Biggest challenge in the short term
period is how low will the temperatures go Sunday night. Very good
setup for radiational cooling as surface ridge moves across the
forecast area for near calm winds. Low RH, below 30 percent in the
1000-500 mb layer, will produce cloud free skies. Superblend was
several degrees warmer this run that previous official forecast,
apparently the raw model output used in the consensus group is not
handling the radiational cooling very well. Additionally the bias
applied will be based on past day`s warm bias, but now that we`re
in a cooler than normal regime will take a day or two for that to
catch up. So bottom line have adjusted superblend heavily back
toward previous forecast. This results in area of below freezing
in the Adirondack portions of St. Lawrence, Franklin, Clinton, and
Essex Counties NY and Essex County VT. Frost producing temps 33-36
possible over much of the remaining area except areas close to
Lake Champlain where warmer waters moderate temperatures. If this
forecast holds will need Freeze Warning for Adirondacks and
Northeast Kingdom, and Frost Advisory elsewhere.
On Monday the surface ridge will shift east, allowing light
southerly flow to begin. Rising heights and low level warm air
advection will bring 850 mb temps from a couple degrees below zero
Sunday night +5 in northeast VT to +9 northern NY by Monday
afternoon. This will yield temps a little higher than blend of
models offers, so nudged gridded max temps upward based on 850 mb
temp reduction. Otherwise sunny skies for much of the day, then high
clouds move in from west to east late in advance of approaching low
from the west.
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 451 AM EDT Saturday...Guidance still in agreement that we
saw come together yesterday with upper low driving through Great
Lakes into the forecast area, and slowly moving across the region
through mid week. At the surface a frontal system will move
through Monday night and Tuesday, with a narrow band of showers
along the front. Good upper level support with this feature with
diffluent flow on the east side of the 500 and 300 mb low, and a
45 knot 850 mb southerly jet translating west to east Monday night
across northern NY and Vermont. Moisture feed with this is
impressive for this time of year with Precipitable Water around
1.3 inches according to the GFS, which puts it in the 90th
percentile. Despite moisture feed and dynamics producing 75 knots
of 0-6 km shear, temps remain much too cool to support any
instability that would produce thunder, and kept precip type as
Expect a scenario where showers along the surface front will move
west to east Monday night and Tuesday. Upper low then settles in
over the eastern US for continued chances for showers under the cold
pool aloft, aided by westerly low level upslope flow. The upper low
will slowly move east and fill, with low level ridging moving in,
and decrease POPs through chance category Tuesday night and
Wednesday, with a dry forecast from Wednesday night onward.
After the initial warmup at the start of the extended period there
will be little airmass change. Temperatures will trend near normal
with highs in the 60s and lows in the 40s.
.AVIATION /15Z Saturday THROUGH Wednesday/...
Through 12Z Sunday...IFR to VLIFR conditions will exist through
13z or 14z at all locations due to low clouds and fog with the
exception of KPBG where no fog exists. Once the fog burns off VFR
conditions will exist everywhere for much of the remainder of the
period as no clouds are expected. After 08z there may be some
brief periods of IFR at KSLK and KMPV due to fog and low clouds
forming. Light winds will become northwest after 14z with speeds
increasing into the 10-15 knot range...then taper off after 00z.
Outlook 12z Sunday through Wednesday...
12z Sun through 12z Tue: Mainly VFR. Overnight IFR with patchy
12z Tue onward: Potential MVFR with showers.
VT...Frost Advisory from 2 AM to 8 AM EDT Sunday for VTZ003-004-
NY...Frost Advisory from 2 AM to 8 AM EDT Sunday for NYZ029>031-034.