Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KBTV 220235
Area Forecast Discussion
National Weather Service Burlington VT
1035 PM EDT Thu Jul 21 2016
Periods of showers and thunderstorms are expected after midnight
tonight through Saturday as a frontal system moves slowly through
the region. Some of the storms will have the potential to become
strong or severe. Another round of thunderstorms is possible on
Monday. Meanwhile Sunday looks dry and seasonable.
.NEAR TERM /THROUGH FRIDAY NIGHT/...
-- Changed Discussion --As of 1035 PM EDT Thursday...A few showers trying to make it into
the Saint Lawrence River Valley tonight, but its been a struggle.
More potent shortwave near Hudson Bay is enhancing convection...
but trends have been for the convection to be weakening and
shortwave is moving more east than south and may not impact the
area at all overnight. Have thus slowed down the onset of any
overnight convection. Remainder of forecast in good shape.
Given the general consistency and thinking of the larger features
discussion is largely borrowed from previous shifts with slight
editing for current model runs and thinking.
.This Evening...Generally fair skies with high clouds from
gradually weakening MCS upstream across Great Lakes. Light south-
southwest winds but they will be increasing well ahead of surface
cold front and approaching shortwave along with increasing humidity
and thus will will result in low temps only dropping into the mid
60s to lower 70s.
.Tonight...Ring of Fire activity (last night/this morning) that
is typical in these synoptic patterns was largely missed by models
and was on the leading edge of strong elevated mixed layer...
moisture pooling along boundary and shortwave. The shortwave and
EML associated with that feature moves into eastern Great Lakes
overnight and eventually North Country early Friday morning. This
activity has continued across the Great Lakes today and could see
some of it holding together and moving into our area after
Friday: The initial shortwave and likely decaying MCS will shift
east across area for temporary stabilization along with some
shortwave ridging. Sounding data brings in decent dry air advection
that should allow for plenty of sun to develop and thus heat up for
high levels of surface instability (GFS has CAPE around 2000
J/kg, and still some remnants of elevated mixed layer and waiting
on a trigger..perhaps a pre-frontal trof in the early-mid aftn
Very dry mid-levels and strong CAPES...surface and aloft support
some downward momentum for winds and large hail given wet bulb
zero levels drop below 10K.
Otherwise the main trigger should be toward evening hours. Low level
instability still prevalent early and area in closer proximity to
approaching stronger nrn stream shortwave...surface front as well as
nose of 300mb and 500mb jets moving into area by 00z Sat enhancing
any lift. The elevated mixed layer is in question again...it`s been
back and forth with models if we had it I`d feel more confident
about this period but even without it still should be enough support.
Any shower/thunderstorm activity wanes after midnight but still
influenced by northwest cyclonic flow which will keep shower threat
especially across NC-NE Vermont.
-- End Changed Discussion --
.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
As of 303 PM EDT Thursday...By Saturday another potentially
active weather day is in store as secondary and fairly robust
northern stream shortwave drops southeast through the region.
Reasonably steep mid-level lapse rates and boundary layer
instability along with 35 to 50 kts of deep-layer shear all
support this idea. Thus prior forecast of scattered to numerous
showers/storms, a few strong to perhaps severe, still appears
reasonable and have leaned toward a blend of consensus and WPC
progs for timing of pops/weather. High temperatures in the 78 to
86 range and rather humid.
Evening convection then wanes fairly quickly from midnight onward if
not sooner Saturday night as shortwave energy pulls across the area
and is replaced by building heights and surface high pressure by
Sunday morning. Again, a few of the storms could be on the strong
side early. Low temperatures in the 50s to around 60. There could be
some patchy fog here and there but given lingering wind fields aloft
confidence is on the lower side at this point.
.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 303 PM EDT Thursday...High pressure then builds atop the
region on Sunday providing for an ideal mid-summer day with plenty
of sun and moderate humidity levels. After a partly cloudy and
seasonably mild night on Sunday focus then turns to the next
shortwave and attendant surface front approaching from the Great
Lakes and southern Canada. Global models suggest another
potentially active weather day with several favorable factors
coming into play. Time will tell but the idea of another round of
scattered to numerous showers/storms still appears reasonable at
Behind this system dry and seasonable mid-summer weather is expected
from Tuesday onward into next Thursday as surface high pressure is
bridged aloft by zonal/westerly flow. Temperatures should
average within a few degrees of seasonal norms with daily highs
in the upper 70s to mid 80s and overnight lows generally in the upper
50s to mid 60s.
.AVIATION /03Z Friday THROUGH Tuesday/...
Through 00z Saturday...VFR through 08z with ceilings lowering to
060 agl for much of the area. High confidence in the first 8 hours
of the forecast. Band of showers and thunderstorms forecast to
move into the region toward sunrise with passage of upper trough
and approaching surface front. Forecast period of mvfr vis with
passage of storms, but low confidence in exact timing and
intensity. Another round of showers/thunderstorms in the afternoon
with another wave, again producing mvfr vis in rain. These storm
coincide with daytime heating and may produce gusty winds and
small hail. Lull between rain episodes with no precip a few hours
ahead and after 18z, trying to indicate relative minimum in
Some minor southwesterly LLWS concerns to 40 kts in the pre-dawn
hours ahead of the potential convection, and included LLWS in KSLK
for a brief time in the morning, otherwise mean southerly flow 6
to 12 kts.
Outlook 00z Saturday through Tuesday...
Fri night-Sat...VFR, with scattered brief MVFR/IFR in showers and
thunderstorms. Some thunderstorms may contain strong winds and
Sun...Mainly VFR under weak high pressure.
Mon/Monday night...VFR with scattered brief MVFR/IFR in showers
and thunderstorms with frontal passage.