Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 251429

Area Forecast Discussion
National Weather Service Burlington VT
1029 AM 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.


As of 1025 AM EDT Monday...No significant changes for 1030 am
update. Showers moving into Northern New York have been very light
so far.

Potential for strong to possibly severe
storms will exist across the area this afternoon and evening.

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. 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


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


As of 409 AM EDT Monday...00z guidance suite in okay agreement
Thursday and Friday, but then start to diverge rapidly for the
weekend and even more so early next week. The 00z GFS has made the
biggest changes from earlier runs, while the ECMWF has been more
consistent, so perhaps that is a signal that the GFS solution is
not as robust? At this point, not too sure, so as typical, kept
with a model blend for the forecast. Some specifics:

Thursday/Friday: Looks like some height falls across the northeast
US as an upper trough settles in across eastern Canada. Models also
show moisture pooling into the region from the west and southwest.
So can`t rule out a few showers. Doesn`t look like a lot of
instability, so t-storms might be limited (but don`t hold me to
that). With the slight lowering of heights, temperatures aloft will
also cool down a bit. Looking more like 925mb temperatures of 18-20C
Thursday which would support low-mid 80s for highs and then even a
bit cooler Friday.  Went with the model blend for PoPs, so I`ve got
a good amount of 20-30% chance of showers both days. Could be that
one of those days ends up totally dry, but too much variability in
the models to have high enough confidence in that.

Saturday/Sunday: As we go into the weekend, the ECMWF swings a
shortwave through on Saturday night and then parks it just to our
northeast, keeping us in slight troughiness into early next week. At
face value that would mean showers/t-storms over the weekend and
then slightly cooler than normal temperatures. The GFS on the other
hand, departs from previous runs, and does not have that shortwave
any more. In fact by early next week it is building the heat wave
ridge north and east across the Great Lakes and into the northeast.
Not sure if I buy that right now. So the forecast features a blend
that turns out to be pretty much a climatological normal forecast.
Highs in the 70s to lower 80s with a chance of showers.  Don`t
cancel outdoor plans at this point, as that weekend forecast is
bound to change between now and then as we gain clarity.


.AVIATION /15Z Monday THROUGH Friday/...
Through 12z 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 KSLK...KPBG...KBTV...KMPV...
and KRUT. Light winds this morning becoming south and southwest
this afternoon at speeds in the 5 to 15 knot range.

Outlook 12z Tuesday through Friday...

12z Tue - 00z Fri: Mainly VFR under high pressure. Isolated
showers possible Wed/Thu afternoons.

00z Fri - 00z Sat: Increasing chances for widespread MVFR showers
and isolated thunderstorms.


The threat for thunderstorms will exist this afternoon into early
evening across Lake Champlain. Storms will move west to east
across the lake and as has been the case with the last three
weather events...any storms will have the potential to produce
gusty winds...small hail...heavy downpours...and frequent
lightning. Boaters should keep an eye on the sky this afternoon
and evening and have a plan in place to seek safe harbor at the
first sign of threatening weather. Stay tuned to our latest
forecasts and any lake thunderstorm advisory that gets issued.




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