Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
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FXUS61 KBTV 221055
Area Forecast Discussion
National Weather Service Burlington VT
655 AM EDT Thu Sep 22 2016
One more day of above normal temperatures is expected across
northern New York and Vermont as high pressure gradually moves
east of the area. Clouds will be on the increase this afternoon
and tonight ahead of a cold front moving down from Canada. This
feature will increase precipitation chances after midnight tonight
through much of Friday. The front moves south of the area Friday
night and behind it colder air will move in for the weekend.
.NEAR TERM /THROUGH FRIDAY/...
-- Changed Discussion --As of 655 AM EDT Thursday...Other than a band of mid clouds over
parts of northern New York and Vermont this morning...overall
forecast in good shape. Have adjusted the sky grids to account for
these clouds to persist over the next few hours before eroding.
More mid and high level moisture will eventually move into the
region later today on westerly flow aloft. Warm 925 mb temperatures
remain in place across the area and this will give us another day
of above normal temperatures with highs in the mid 70s to lower
Cold front north of the border tonight will not move down into our
area until after midnight and looks to exit the area during the
afternoon hours. Most of the precipitation is along and behind the
surface front...thus will not bring the bulk of the precipitation
into the area until after midnight. Highest probabilities should
be between 09z and 18z with total amounts ranging from a tenth to
a half inch by late in the day on Friday. With the clouds and
precipitation on Friday...high temperatures will generally be in
the 60s...but around 70 over southern Vermont with the later
timing of the cold frontal passage. Gusty north winds are also
expected behind the front which will be the start of noticeable
cold air advection for the weekend.
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.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 423 AM EDT Thursday...Post frontal conditions in the short
term period, with northerly flow, cold air advection, and drying
in the mid and upper levels. 500 mb flow is a nearly blocked Omega
pattern. A sharp ridge along the Mississippi River separates a
closed low over the Canadian maritimes from a low lifting
northeast through the intermountain west. Low to east and ridge to
west will keep northerly flow over the forecast area, although
ridge will slowly build east and relax the pressure gradient by
the end of the period. Moisture trapped below frontal inversion
Friday night will dry out through Saturday night with a decreasing
trend in cloud cover.
Temperatures to drop a few degrees below normal Friday night, and 5-
10 degrees by Saturday night. Lows Friday night in the 30s to low
40s except upper 40s near Lake Champlain where water temp remains
around 70. Some wind Friday night will keep frost formation at bay.
Odds are better for frost Saturday night as pressure gradient
slackens and drier air allows temperatures to radiate down to
solidly in the 30s. Have patchy frost Saturday night in the
Adirondacks and Northeast Kingdom. 850 mb temps around 0 to +1
Saturday support max temps in the 50s to near 60 in the Champlain
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 423 AM EDT Thursday...Model differences become apparent in
the latter part of the extended period and reduced confidence in
Tuesday and Wednesday forecasts. 00z ECMWF has completely flipped
from previous run. Prior 12z run had slower moving ridge with
cutoff low over the southern plains, and resembled the GFS. The
latest 00z ECMWF run is much more progressive, and the ECMWF
brings in rain as early as Monday night to a previously dry
forecast. GFS is more consistent, although GFS ensemble mean is a
little more progressive but not to the degree the ECMWF is. For
now will go with a persistence forecast until model difference
resolve themselves. This means a dry forecast until
Wednesday/Wednesday night when the slow moving upper low moves out
of the Great Lakes and into the northeast US.
Patchy frost Sunday night, then a warming trend back to near normal
temperatures in this period with the ridge shifting east and
southerly return flow. Highs generally in the 60s and lows in the
.AVIATION /12Z Thursday THROUGH Monday/...
Through 06Z Friday...VFR conditions are expected through the
period. Expecting only mid and high level clouds to move into the
region through 00z before clouds slowly begin to lower...but still
remain above 5000 feet. Dry conditions are expected for much of
the period...but as a cold front begins to move down from
Canada...the threat for showers will increase at KMSS after 04z.
The bulk of precipitation will not move into the entire area until
after 06z. Light winds this morning will increase from the south
and southwest by midday and persist through the period...but
speeds will generally be under 15 knots.
Outlook 06Z Friday through Monday...
06z Fri to 00z Sat: MVFR with scattered showers associated with a
00z Sat through 00z Tue: Mainly VFR as a ridge of high pressure
builds into the region.