Area Forecast Discussion
Issued by NWS Burlington, VT
FXUS61 KBTV 310230
Area Forecast Discussion
National Weather Service Burlington VT
1030 PM EDT Tue Aug 30 2016
Clouds will be on the increase across the north country overnight,
as a cold front approaches from Ontario. There will be a chance
of showers after midnight across northern Vermont and northern New
York. On Wednesday, a cold front will move south from Canada and
will bring rain showers to the region, along with a chance for
thunderstorms, especially during the afternoon hours. A high
pressure area over Ontario and the western Great Lakes on Thursday
will build slowly east and bring fair and dry weather to the north
country from late Thursday through Labor Day.
.NEAR TERM /UNTIL 6 PM WEDNESDAY EVENING/...
As of 1017 PM EDT Tuesday...Surface cold front extends from
southwestern Quebec swwd across Georgian Bay and Lake Huron at
0215Z. Attendant mid-level closed low appears fairly vigorous on
IR imagery, and is located west of James Bay, along with band of
60kt mean flow in the 500-300mb layer across nrn Ontario. Will see
gradual height falls overnight in advance of this system as it
translates esewd in prevailing wnwly flow regime. Widespread mid
and upper level clouds in place across all but s-central VT late this
evening. These clouds should preclude fog formation, and keep
temps mild overnight (mainly in the 60s). Adjusted temps upward a
couple of degrees above the MOS consensus for most areas
(including a low of 67F at BTV).
With mid-level height falls occurring during the pre-dawn hrs,
some remnant shower activity may reach nrn NY into nwrn VT
toward/after midnight. PoPs increase to 30-40 percent across nrn
CWA during the pre-dawn hours.
Question on Wednesday will be how much surface heating/destabilization
can take place as surface and mid-level trough sharpens across
sern Ontario during the afternoon hours. With S-SW winds in place,
should see 2-M dewpoints climb into the low to mid 60s, but
prevailing cloudiness should keep temps mainly mid 70s to around
80F for afternoon highs. With 700-500mb lapse rates generally <
6C/km, it appears SBCAPE values will be limited to below 1000
J/kg. Will see moderate 0-6km bulk shear (20-30 kts), and can`t
rule out a few stronger storms with locally gusty winds, if
sufficient PBL heating can occur. Otherwise, precipitable water
values reach 1.5" or so, suggesting some locally heavy downpours
are possible with embedded convective elements.
.SHORT TERM /6 PM WEDNESDAY EVENING THROUGH THURSDAY NIGHT/...
As of 407 PM EDT Tuesday...chance for showers persists as cold
front progresses from NW to SE across the North country Wednesday
night into early Thursday. Showers will become less numerous
during the day Thursday as the surface front exits SE VT during
the morning. 500mb trough will continue to provide some lift with
plentiful clouds and slight to low chance for showers. Otherwise
NW flow will filter into the area with gradually drying
conditions. Expect the base of the mid level trough to move across
the region Thursday night with continued clouds.
Temperatures Wednesday night will be near normal to slight above
with cooler air more evident as max temps on Thursday peak in the
60s to mid 70s. Cooler temperatures expected Thursday night with
mins in the mid 40s to mid 50s.
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 407 PM EDT Tuesday...Mid level trough exits south and east
on Fridays with an isolated shower possible. After that, N to NW
flow persists into Saturday as high pressure at the surface and
aloft affect the region. This will result in mostly clear skies
and dry weather with below normal temperatures moderating into the
weekend. Overnight min temperatures Friday night and Saturday
night will fall into the low 40s to low 50s as the surface ridge
crests over the region and 850mb temps fall to 7C-8C.
This ridge will also help keep a tropical system offshore Sunday
into Tuesday, but run to run consistency is lacking at this time
with regard to track. Will have to continue to keep an eye on this
.AVIATION /02Z Wednesday THROUGH Sunday/...
Through 18Z Wednesday...Mainly VFR conditions expected through the
Tonight there could be a shower or sprinkles tonight, mainly at
SLK/MSS as convective debris heads east but diminishes with time.
These showers are not expected to cause any visibility
restrictions at this time. With all the clouds tonight, the
chances of the usual fog is low, so do not have any mention in the
Wed a.m. some chance of MVFR cigs especially MSS as additional
moisture is advected NE up the St. Lawrence valley and can`t rule
out a shower.
A cold front moving through the region Wed p.m. brings the best
chance of showers and thunderstorms during maximum daytime heating
from noon to 8 pm. There may be brief MVFR/IFR in scattered
showers and thunderstorms along and ahead of the front. For now
have left out mention of thunderstorms until it becomes more
certain when and where they form.
Outlook 00Z Thursday through Sunday...
Wed night: LCL MVFR/IFR in showers and thunderstorms tapering off.
Thu-Fri: A few light showers/sprinkles possible with local MVFR
cigs but confined mainly to the mtns on Fri.
Sat-Sun: Mainly VFR with building surface high pressure.