Area Forecast Discussion
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FXUS61 KBTV 222235
Area Forecast Discussion
National Weather Service Burlington VT
635 PM EDT Fri Jul 22 2016
Scattered showers and thunderstorms are expected this evening...
largely across Northern New York but especially Northern Vermont.
More scattered showers and thunderstorms move across the North
Country on Saturday and yet another possibility of showers and
thunderstorms late Monday. Meanwhile Sunday still looks dry and
.NEAR TERM /THROUGH SATURDAY/...
As of 628 PM EDT Friday...Finally a few showers/storms have fired
up but very weak. The main activity is across Maine and ahead of
shortwave just NW of Ottawa where both locations have numerous
thunderstorms. There is some convective activity in an
extrapolated line between both features just north of
international border ad believe this will fire up within the next
few hours but given the trend in expectations has been lowered
feel isold svr threat only...thus have taken out enhanced wording.
Combination of BTV4 and HRRR has highly been used through 06z sat.
Previous discussion...A HOT afternoon with temperatures at
mid-afternoon in the mid 80s/ low 90s across the region with
dewpoints in the 60s. As of 3 pm...BTV has reached 94 degrees.
Last occurrence was just 9/7 of last year(2015).
Despite SFC based CAPES in the 1500-2500+ J/KG range enough drying
at mid-levels and lack of a lifting mechanism has kept things in
check. A strong vort across Quebec has fired up some storms
headed for far northern Maine thus SVR WATCH has been posted there.
As advertised the last day/two our triggers were mainly expected
this evening and that still holds.
Plenty of Low level instabilty...shortwave trough approaching as
well as nose of 300mb and 500mb jets moving into area by 00z Sat
enhancing any lift. Also..Northern VT/NY will be on the tail of the
Quebec system moving across Maine. Models are in general agreement
of tstm activity between 21z Fri-00z Sat largely across the northern
areas with eventual shift into nrn VT only.
Dry air aloft....decent 30-40kts 0-6km shear still could account for
isold/sct damaging winds and large hail.
Later tonight...Any shower/thunderstorm activity wanes after
midnight but still can`t rule out a few showers across NC-NE
Vermont. There will be enough breaks across area that some patchy
fog around especially where it rains this evening. lows mainly in
Saturday: A potent shortwave expecyed to move across our area in the
afternoon. The dynamics are expected to kick off thunderstorms
(actually, there will likely be a cluster of thunderstorms as well
with that shortwave that will move southeast out of Quebec and into
our region). Each model has a differing evolution of the convection,
and is again a symptom of just how sensitive the models are to this
type of weather pattern that is driven by mixed layers, elevated and
low level instability and boundary layer details.
Taking a blend of the models suggests that we`ll have CAPE values
perhaps up to 1000 J/kg which is decent enough to drive convection.
NAM has 30-40kts of shear, GFS is less than 30kt. Suppose we can`t
totally rule out a stronger storm with gusty winds here or there.
Looks like the highest chances for storms will be from mid-day
through the evening and more so from the `Dacks and points eastward.
SPC has this same region marked with "Marginal Risk" and at this
point, that seems like a good assessment.
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 310 PM EDT Friday...Scattered showers/storms (a few
possibly strong early) then wane and exit east fairly quickly
Saturday evening as upper trough swings through the region and is
replaced by building high pressure. Will carry 30/40 pops through
about 900 pm or so to account for timing uncertainties, then trend
conditions largely dry from midnight onward. Low temperatures near
seasonal mid-summer norms in the 50s to around 60 for most
Ideal weather then expected by this coming Sunday with surface high
pressure bridged by dry and zonal westerly flow aloft. Mean 925-850
mb thermal profiles support highs in the 77 to 83 degree range under
light west to northwesterly winds and ample sun. This definitely
will be the better day of the two weekend days.
By Sunday night our next shortwave trough in the pipeline begins to
approach from the Great Lakes with mid to high level cloudiness
advecting into the region later at night as flow backs to
southwesterly and warm thermal advective processes begin aloft.
There could be a stray shower or isolated storm in developing mid-
level instability as lapse rates aloft steepen and heights begin to
fall, but drier air in lower levels should preclude anything
widespread. Will carry a nominal 20/30 pop across our western
counties to account for any activity that may occur. Low
temperatures a blend of available guidance supporting values
generally in the 55 to 65 degree range.
.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 310 PM EDT Friday...The shortwave trough then swings
quickly through the area Monday into Monday evening with a good
threat of showers and storms. Some parameters support a few
stronger storms but early indications suggest plenty of mid/high
level moisture around that could limit boundary layer
destabilization ahead of the associated surface trough. Time will
tell how this all pans out. For now have maintained continuity
offering solid pops in the 40-60 percent range. Temperatures
should average slightly above seasonal levels with highs in the
80s and lows Monday night in the 60s.
Behind this system our typical mid-summer pattern continues with the
region largely on the south edge of the westerlies and deeper heat
and humidity off to our south and west. Temperatures should average
slightly above seasonal levels with daily highs generally in the 80s
and overnight lows in the 55 to 65 degree range. Additional
shortwave energy riding through the mean flow may affect the area by
next Thursday or so, but timing and strength differences in this
morning`s global models support capping pops below 40 percent at
.AVIATION /00Z Saturday THROUGH Wednesday/...
Through 00z Sunday...mainly VFR with a round of showers/thunderstorms
this evening...largely across northern 1/3 of area...in response
to upper level short wave. This will producing mvfr vis in
scattered rain showers perhaps some very brief IFR in
Showers and storms will wind down by midnight. Some patchy fog or
mist possible where it rains, but for now just put in at MPV where
climatology favors it.
Aft 15z Sat...VFR, with scattered brief MVFR/IFR in showers and
thunderstorms. Some thunderstorms may contain strong winds and
Outlook 00z Sunday through Tuesday...
Sat Ngt...VFR but some localized MVFR/IFR due to patchy fog.
Sun...Mainly VFR under weak high pressure.
Mon/Monday night...VFR with scattered brief MVFR/IFR in showers
and thunderstorms with frontal passage.