Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
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FXUS61 KBTV 251936
Area Forecast Discussion
National Weather Service Burlington VT
336 PM EDT Mon Jul 25 2016
Above normal temperatures are expected today along with
increasing chances for showers and thunderstorms this afternoon
and evening. Some of the storms may contain gusty winds...small
hail...and heavy downpours. Quieter weather is expected on Tuesday
and Wednesday with maybe a few showers up near the Canadian Border
both days. The above normal temperatures will continue through
midweek as well.
.NEAR TERM /UNTIL 11 PM THIS EVENING/...
-- Changed Discussion --As of 336 PM EDT Monday...Have lowered the chance for showers and
thunderstorms for today until after 21z when we may get into the
clearing and get some convection started.
Potential for showers and thunderstorms still exists for this
afternoon and evening, with strong storms possible in the St
Lawrence Valley and portions of Central and Southern Vermont.
Previous discussion follows. Today...going forecast in good shape
with increasing clouds and weakening convection moving into the
Saint Lawrence River Valley. Convective debris clouds and or some
convection will continue to move across the North Country this
morning. Moisture advection will be taking place and this will be
needed to raise dew points into the 60 to 65 degree range. Warmer
925 millibar temperatures also moving into the region will combine
with clearing skies to raise temperatures into the 80s to around
90. This should create CAPE values in the 750-1500 J/kg range with
the lower of this range in the Northeast Kingdom of Vermont and
the higher values of the range over south central Vermont and the
far southern portions of the northern Adirondacks. Where this
greater instability will develop there will also be increasing
flow aloft and this deep layer shear should allow for storms to
become organized and reach strong to severe levels. Essentially
this will be south of a line from Ogdensburg to Middlebury to
White River Junction. North of that line the potential for strong
storms will exist. Thus will maintain enhanced wording in the
forecast of gusty winds and small hail and include heavy downpours
as higher precipitable water values develop. Potential for these
stronger storms will exist between 18z and 03z. The increasing
deep layer shear this afternoon is the result of an approaching
shortwave trough moving into the eastern Great Lakes late in the
day. Dynamic support will be increasing with the trough and upper
diffluence in advance of the trough suggests synoptic scale lift
will be sufficient to have the showers and storms be fairly
widespread in nature. Thus like the idea of likely precipitation
chances just about everywhere this afternoon and into the first
half of the night.
Tonight...as mentioned above any potential threat for stronger
storms will exist until about midnight but precipitation will be
ending from west to east as the evening wears on. No precipitation
is expected after midnight. Clouds and low level moisture will
linger tonight and this will help to keep low temperatures in the
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.SHORT TERM /11 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
As of 409 AM EDT Monday...Fairly tranquil mid-summer weather
expected for the period. On Tuesday we`ll see some daytime heating
cumulus develop across the region (a little more so over the
higher terrain). Can`t rule out a lingering sprinkle/light shower
across the higher terrain of northeast Vermont due to slightly
deeper moisture and the relative nearness of the upper trough.
We`ll still be an overall west/northwest flow aloft, so the
airmass will continue to be warm as we remain on the far fringes
of the massive heat across the center of the country. 925mb
temperatures Tuesday will generally be in the range of 18C (north)
to 21C (south). This would support high temperatures in the 80s
everywhere, and perhaps pushing 90F in some of the southern
valleys. Decent amount of boundary layer mixing, so by afternoon
we should tap into some slightly stronger winds up at 4000-5000ft.
We should see some gusts in the 20-25mph range in spots.
Clear and calm Tuesday night. High pressure at the surface and
weak ridging aloft will ensure a clear night. Looks like we`ll
have patchy fog develop in those typical areas across the `Dacks
and Eastern Vermont as overnight lows are expected to drop below
the crossover temperature (dewpoint value midday Tuesday). Lows
across the region will range from the 50s to lower 60s.
Wednesday should be a very warm to hot summer day. With the
continued westerly flow aloft, a little bit more of that heat off
to our west will advect in. Guidance is pretty solid in showing
925mb temperatures of 23-24C. This suggests high temperatures in
lower elevations will top out in the upper 80s to lower 90s. For
whatever reason, the suite of guidance we can look at had a number
of members that only indicated mid-80s for highs, so I ignored all
but the warmest guidance. There will be a weak front lurking north
of the US/Canada border that should spark a few t-storms up there.
We`ll stay dry for the day. That front may ooze a bit south during
the evening, so a rogue t-storm along the border is a possibility
Wednesday night. Have kept PoPs only in the 15-25% range however.
Should be a relatively warm night with most of us seeing
temperatures only bottoming out in the 60s. A little muggy as
.LONG TERM /THURSDAY THROUGH MONDAY/...
-- Changed Discussion --As of 336 PM EDT Monday...Surface ridge building in from south
central Canada with light north-northwest flow will coincide with
500mb troughing providing a low chance for showers on Thursday.
Continued ridging at the surface and slight ridging aloft will
keep Friday dry before low pressure system develops to the
south/west and brings a chance for precipitation late Friday.
Model guidance diverges on evolution of this system associated
with two areas of vorticity embedded in the 500mb flow. 12Z ECMWF
develops these features into a double barrel surface low pressure
system late in the week into the weekend. While 12Z GFS keeps mid
level vorts along more southerly route and surface high pressure
over southwestern Quebec and the northern New England. High
uncertainty in the pattern beyond early Friday. Both models show
mid level troughing across the Northeast late Saturday with the
GFS much broader than the ECMWF. With these differences noted,
have stuck with Superblend with chances for precipitation through
Temperatures generally expected to be near normal, but highly
dependent on variability of cloud cover and precipitation.
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.AVIATION /20Z Monday THROUGH Saturday/...
Through 18z Tuesday...VFR conditions will exist through much of
the period. However...between 18z and 03z we are expecting
scattered showers and thunderstorms to move east across the area
resulting in periods of MVFR/IFR conditions along with the
potential for gusty winds...small hail...heavy
downpours...frequent lightning... and moderate to severe
turbulence. At this time the locations likely to see these lower
flight categories are SLK...PBG...BTV...MPV... and RUT. Light
winds becoming south and southwest this afternoon at speeds in the
5 to 15 knot range.
Outlook 18z Tuesday through Friday...
18z Tue - 00z Fri: Mainly VFR under high pressure. Isolated
showers possible Wed/Thu afternoons.
00z Fri - Sat: Increasing chances for widespread MVFR showers and