Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
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FXUS61 KBTV 310534
Area Forecast Discussion
National Weather Service Burlington VT
134 AM EDT Wed Aug 31 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 THIS 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 THIS 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 /06Z Wednesday THROUGH Sunday/...
-- Changed Discussion --Through 06Z Thursday...Mainly VFR through 14Z with sct/bkn cigs
from 050-100 AGL at most terminals. A few showers may encroach
toward KMSS/KSLK toward 12Z per output from a few of the hi-res
models. However, paucity of current activity upstream across
southern Ontario leaves low confidence of occurrence and will not
include in the forecast at this point. After 14Z surface trough
will swing into the area with scattered showers and a few storms
expected. Mainly VFR continues, though brief MVFR/IFR possible
and turbulence with any heavier convective cores. Severe weather
is not expected at this point. Given scattered nature of
convective coverage, only VCSH mentioned in forecast at this point
and we`ll be able to fine tune this better later today once
activity develops. Surface trough departs south by 00Z with cold
front approaching from the northwest late. General coverage of
shower/storm activity should wane over time with loss of heating,
but enough dynamic support aloft to continue mention of VCSH.
Winds light through 12Z, then trending south to southwesterly 6 to
12 knots thereafter.
Outlook 06Z Thursday through Sunday...
Wed night: LCL MVFR/IFR in showers and thunderstorms tapering
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.
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