Area Forecast Discussion
Issued by NWS Burlington, VT

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928
FXUS61 KBTV 210551
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
151 AM EDT Tue Aug 21 2018

.SYNOPSIS...
Other than some patchy early morning fog another beautiful day
is expected across much of the North Country. Conditions will
begin to deteriorate Tuesday evening as an upper level trough
displaces the high pressure over the region and brings the
return of rainfall to the region. Rain will continue through
Wednesday afternoon before exiting to the east. Skies will clear
heading into Thursday and will continue to remain mostly clear
through the first half of the weekend. Temperatures will remain
near normal with temperatures a degree or two with each passing
day.

&&

.NEAR TERM /UNTIL 3 PM THIS AFTERNOON/...
As of 151 AM EDT Tuesday...Going forecast in real good shape
and no big changes are needed at this time.

.PREVIOUS DISCUSSION...
Afternoon satellite imagery shows a plethora of fair weather
cumulus across the North Country. Based on the Albany RAOB at
12Z, a stout inversion has capped these cumulus clouds and these
clouds should dissipate with the lack of diurnal heating this
evening. This will allow for another true radiational cooling
night with temperatures dropping into the upper 40s at Saranac
Lake to the lower 60`s in the Champlain Valley. Crossover temps
for favorable fog locations tonight are in the lower to mid 50`s
which means that there is once again a decent chance of fog
across northern New York and the Connecticut River Valley with
forecast lows in these areas in the upper 40s to lower 50`s. Any
fog that does develop late night into Wednesday morning will
quickly dissipate after sunrise.

Tuesday will largely be another beautiful summer day across the
North Country as temperatures once again warm into the mid 70`s to
lower 80`s. Throughout the day, the upper level ridge and surface
low pressure will begin to be displaced eastward as a deepening
upper level trough over the Great Lakes Region tracks northeastward.
As we shift from the upper level ridge to the upper level trough,
southwesterly flow aloft will tap into a very moisture rich air mass
which will allow dewpoints to quickly rise into the lower to mid
60`s on Tuesday as PWAT values increase to about 2 inches. Contrary
to previous model runs, the main moisture axis is now expected to
come through with the main upper level support which will favor some
heavier rain amounts. Rainfall is expected to move into the St.
Lawrence Valley late Tuesday afternoon into the evening hours and
ultimately into Vermont just before midnight. However, a strong
southwesterly LLJ of about 35 to 40 kts will develop at the same
time as the strongest upper level support pushes through which will
likely initially downslope rainfall across the Champlain Valley while
the western slopes of the Adirondack and Green Mountains. This will
limit values across the Champlain Valley while the western peaks
could receive a bit more rainfall than is currently forecasted.

In addition to rainfall, some gusty winds are expected across
portions of the North Country Tuesday afternoon. A decent gradient
wind will set up as a surface low tracks of the Great Lakes Region
into the Ottawa Valley Tuesday afternoon and ultimately into the
Canadian Maritimes. Models are also picking up on a decent
isallobaric couplet just north of the international border which
should help even more with the gusty winds. Overall, the strongest
winds are expected over the higher terrain with winds in the 30 to
45 knot range and over Lake Champlain with winds in the 15 to 25 kt
range.

&&

.SHORT TERM /3 PM THIS AFTERNOON THROUGH WEDNESDAY NIGHT/...
As of 309 PM EDT Monday...Rainfall is expected to continue through the
afternoon hours on Wednesday. A cold front will come sweeping
across the North Country during the late morning and afternoon
hours which will help bring an end to rainfall during the
afternoon and evening hours on Wednesday. A few rumbles of
thunder are possible from early Wednesday morning through the
afternoon as colder air aloft helps to increase mid- level lapse
rates and instability. Still, no strong thunderstorms are
expected as the atmosphere still remains saturated and stable
(mainly moist adiabatic lapse rates through the column). Skies
will begin to clear behind the cold front Wednesday night which
will likely lead to another bout of fog across a good portion of
the North Country.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 338 PM EDT Monday...A dry upper level trough will be
tracking through the North Country thursday pushing out through
the region as high pressure builds in over the North Country.
Anticyclonic flow will bring southwesterly winds to the region
bringing slightly milder temperatures back in for Friday.
Thankfully however the moisture will still be near normal as
relative humidities will be in the 35-40% range. Given the long
string of warmer days it should feel like a nice refreshing
day.

Heading into the weekend quiet weather continues as heights
continue to build through Saturday morning. Our next chance for
showers begins sometime over the weekend as a weak shortwave
slowly creeps in from the west. With the strength of the high
pressure system the shortwave may end up pushing up and over
the ridge and so for the time being I`ve only offered up 20-30%
chance for showers over Northern New York with 10-20% across the
Champlain Valley and areas south and east. Temperatures will
remain fairly steady, with highs in the upper 70s/low 80s and
lows in the 50s to mid 60s Friday through Sunday.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Through 06z Wednesday...Looking at VFR conditions through 00z
with mainly only mid and high level clouds expected to move
across the area. The only exception to this will be some early
morning fog at KSLK and KMPV...which will result in some MVFR to
LIFR conditions for brief periods between 07z and 12z. South to
southwest winds will be increase today with gusts in the 10 to
20 knot range. Lower ceilings should move in after 00z with MVFR
conditions expected. Rain showers will also start to move in
after 00z...but visibilities will generally be in the VFR
category. Lower ceilings and visibilities are expected after
06z.

Outlook...

Wednesday: Mainly VFR, with local IFR possible. Chance SHRA,
Slight chance TSRA.
Wednesday Night: VFR. Slight chance SHRA.
Thursday: VFR. NO SIG WX.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. Slight chance SHRA.

&&

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

&&

$$
SYNOPSIS...Clay
NEAR TERM...Evenson/Clay
SHORT TERM...Clay
LONG TERM...Deal
AVIATION...Evenson



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