Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 261752
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
152 PM EDT Thu Apr 26 2018

.SYNOPSIS...
Scattered showers are expected this afternoon across mainly
northern sections of New York and Vermont as an upper level low
pressure system moves through. As it gets east of the region
tonight, dry weather moves in. The dry air will be short lived
as a low pressure system moves into the region from the
southwest on Friday and spreads more showers back into the
region... especially during the afternoon and evening hours.
Unsettled weather and cooler temperatures are expected for the
weekend.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 150 PM EDT Thursday...improving conditions across most of
the region as drier air at mid levels is moving into the
region. Upper level low is now centered over the Adirondacks and
continues to move steadily ENE. A few showers are circulating
around the upper low, but are generally on the lighter side.
Higher chances for these showers will be in the vicinity of
where the low tracks across northern parts of NY and VT for the
remainder of the afternoon. Otherwise westerly flow is resulting
in breaks in the cloud cover, especially downwind of the
Adirondacks and Green Mountains. The early afternoon update did
not feature much in the way of significant changes for the
remainder of the afternoon. Could see a few spots, especially
where they get some sun, make a run at 60F, otherwise highs in
the 50s look good.


Previous discussion from 10am...
only subtle changes to the forecast for today, mainly to fold
in latest observations and nudge hourly PoPs toward the latest
HRRR hi-res models for the evolution of the rain showers for the
remainder of the day.

Water vapor imagery shows a well defined upper low just east of
Lake Ontario and moving to the ENE. The bulk of the deep
moisture is now across northeast Vermont, with a sharp cut-off
(again seen via water vapor) to a much drier airmass steadily
pushing east. With the colder temperatures associated with the
upper low, there is some convective showers, but the last few
hours have seen a decrease in coverage and deeper moisture. Thus
the idea that the most concentrated area of rain showers will
be across far northern VT for the next few hours looks good,
with precipitation chances decreasing everywhere as the day goes
on. Lots of low level moisture, so it will remain cloudy, but
breaks in the cloud cover will occur, especially on the east
side of the Adirondacks and southern Vermont as a developing
westerly flow brings downsloping conditions.

With the relatively high dewpoint air over the still cold Lake
Champlain, fog is pretty thick over the lake, but with westerly
flow developing by early afternoon bringing in some drier air,
some better mixing will cause that fog to dissipate.

Watching rivers closely, but no additional flooding is
anticipated. See the Hydro section.


Previous Discussion from 430am...
Plenty of low level moisture continues to linger over the area
early this morning. This has led to the development of
fog...which has been producing reduced visibilities at times.
Have added this to the forecast through about mid-morning. This
is when we should start to see some mixing with increasing west
to southwest winds and increasing precipitation chances as upper
low moves slowly east across the area. Based on the track of
the low northern New York and the northern half of Vermont will
have the best chance for precipitation...with an additional
quarter to half inch of rain expected. This should help promote
additional rises on area waterways with some higher level
snowmelt taking place. High temperatures will range from the
upper 40s to the mid 50s.

Upper low is east of the area tonight and with more favorable
dynamic support east of the region as well...precipitation will
quickly come to an end by midnight with lows expected in the mid
30s to lower 40s. The dry weather will not last long...Friday
morning will be dry...but a shortwave trough moving northeast
toward the region will bring rain back into the area Friday
afternoon...especially across Vermont. Highs will be in the
upper 50s to lower 60s.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY/...
As of 434 AM EDT Thursday...Friday night and Saturday an upper
level trough will remain anchored to our west, and upper level
shortwaves passing through the southwesterly flow will bring
several chances for showers to the area. Highest chance for
showers will be right at the start of the short term, 00z
Saturday, with a potent shortwave passing along our Eastern CWA
border. A low pressure system will also track along the Southern
New England coast while another low approaches from the
Northwest. Lots of moisture and dynamics in place, therefore
have gone with categorical rain showers for Eastern Vermont
Friday night. There will be a brief break in the precipitation
Saturday morning as shortwave exits to our Northeast, and the
Northern stream low pressure system gets a bit hung up to our
Northwest. Another vort max will enter Western New York area
later in the day on Saturday, and will be the next focus for
precipitation going into Saturday night.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 434 AM EDT Thursday...Active weather pattern continues
headed into the long term portion of the forecast. Upper level
trough and low will slowly creep eastward and upper level low
will be centered over Northern New York by early Sunday morning.
As pieces of upper level energy rotate around base of upper
level trough our region will experience scattered light rain
showers. These features are difficult to time this far out, but
details will become more clear as we get closer to the weekend.
Currently models are indicating that the upper level low in the
base of the trough will finally push east of our region Sunday
night into Monday. Monday should be the end of the active
weather period, with surface and upper level ridging expected
from Monday night through early Thursday.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Through 18z Friday...wide ranging conditions across the region,
primarily due to the varying ceilings. Lowest ceilings remain
across the St Lawrence Valley and in the higher terrain of
northern NY and Vermont. VFR conditions have developed in
portions of the Champlain Valley and in south-central/southeast
VT. Still a few showers, but they don`t appear too heavy nor
long lasting. As such, maintained VCSH at most TAF locations
for the next few hours just to acknowledge their existance.
Otherwise expecting conditions this evening and the first part
of the overnight to slowly improve as ceilings lift and clouds
dissipate.

Some uncertainty in the various guidance for the 06-11z
timeframe and fog development. It appears we`ll have enough
clearing and relatively light winds to give a window for fog to
develop. Some guidance suggests LIFR conditions at spots, other
guidance says no fog at all. It`s not really fog season, but
given the rain we just had, it seems quite plausible patchy fog
will develop. So have mention for those more fog prone
locations.

Tomorrow morning should be VFR area wide, but by mid-day clouds
will overspread most of the region, with light rain starting to
move in from the south.

Outlook...

Friday Night: Mainly VFR, with local IFR possible. Chance SHRA.
Saturday: Mainly VFR, with local MVFR possible. Chance SHRA.
Saturday Night: Mainly VFR, with local IFR possible. Chance SHRA.
Sunday: Mainly MVFR, with local IFR possible. Chance SHRA.
Sunday Night: Mainly MVFR, with local IFR possible. Chance SHRA,
Slight chance SHSN.
Monday: MVFR/IFR conditions possible. Slight chance SHRA.
Monday Night: Mainly VFR, with local MVFR possible. NO SIG WX.
Tuesday: VFR. NO SIG WX.

&&

.HYDROLOGY...
As of 1000 AM Thursday...combination of some pretty decent
rainfall totals across parts of northern NY last evening into
the overnight (3/4 to 1") and snow melt from the highest
elevations of the `Dacks combined to push the Ausable River into
minor flood for a few hours. But with the rain having ended,
the river has peaked and is quickly coming down. Watching other
rivers across northern VT as well as they too have seen decent
amount of rises overnight and this morning. Not expecting any
other rivers to rise above flood stage however.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.

&&

$$
SYNOPSIS...Evenson/Nash
NEAR TERM...Evenson/Nash
SHORT TERM...Neiles
LONG TERM...Neiles
AVIATION...Nash
HYDROLOGY...Nash



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