Area Forecast Discussion
Issued by NWS Burlington, VT-- Remove Highlighting --
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FXUS61 KBTV 221152
Area Forecast Discussion
National Weather Service Burlington VT
752 AM EDT Fri Jul 22 2016
scattered showers and thunderstorms, some possibly severe, are
expected through Saturday as a frontal system moves slowly through
the region but there will be partly sunny rain free periods as
well. It will be hot today with high temperatures in the mid 80s
to lower 90s. Another round of thunderstorms is possible on
Monday. Meanwhile Sunday looks dry and seasonable.
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --As of 751 AM EDT Friday...The shortwave and scattered early
morning showers/storms have exited the area and some shortwave
ridging is resulting in some temporary stabilization.
Model soundings mix down decent dry air advection that should
allow for plenty of sun to develop and thus heat up for high
temperatures reaching the mid 80s to lower 90s especially where
westerly to southwest winds downslope into the valleys.
Surface instability should start to return this afternoon but will
depend on how much dry air gets mixed down to the surface and what
the resulting dew points are. Right now it looks like low to mid
60s should do it which will give us CAPES around 1000 J/kg, some
of the models suggest dew points will be peaking into the upper
60s later in the day when CAPE may rise to 1500 to 2000 J/kg. It
will probably end up somewhere in between.
Very dry mid-levels support downward momentum for potentially
damaging winds and hail given wet bulb zero levels drop below 10K.
0-6km shear values are around 40 kts which also support the severe
potential. SPC outlook has us in the slight chance category for
The main trigger for thunderstorms should be toward late afternoon
and 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.
Tonight...Any shower/thunderstorm activity wanes after midnight
but still influenced by northwest cyclonic flow which will keep
shower threat especially across NC-NE Vermont. Could be some
patchy fog around especially where it rains this evening. lows
mainly in the 60s.
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.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 414 AM EDT Friday...00z guidance suite still inconsistent
with some of the details for Saturday, especially with respect to
the coverage and specific timing of convection. Synoptically, a
potent shortwave, currently moving into the far reaches of western
Ontario will move east- southeast over the next 36 hours and
should be reaching into our area sometime Saturday 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. Not seeing any strong signals with other convective
indices to suggest additional severe t-storms. GFS hints at a bit
of an elevated mixed layer (EML) but not the NAM. 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.
Storms come to an end during the evening. An upper ridge moves over
the region for Sunday. If you want a day with no weather worries for
outdoor activities, Sunday will be the day.
Temperatures both days will probably be within a couple of degrees
of normal. Upper 70s to lower 80s. A bit humid on Saturday, but in
the wake of the upper trough, drier air will come on in as flow
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 414 AM EDT Friday...No huge changes with the overall
synoptic pattern depicted by the 00z guidance. In general our
area will be underneath westerly flow. One moderately strong
shortwave comes across somewhere in the late Monday/early Tuesday
timeframe. Some instability depicted in the models, as well as
decent 0-6km shear (GFS has 40-50kt), however the big question is
timing. If all of this comes together with peak heating time
Monday afternoon, we would have the chance for strong/severe
t-storms. If it comes through at night, then it`s nothing much
more than showers with embedded rumbles of thunder. 00Z GFS is a
little slower than it`s previous runs and suggests a Monday night
passage. 00z ECMWF is quicker and suggests Monday could be
somewhat active. At this point, trying to pin this feature down to
within 6 hours is beyond my skill level. Thus have maintained a
more broadbrush forecast indicating roughly 50% chance of t-storms
Monday and Monday night. With the westerly flow, temperatures
aloft do warm a few degrees so we should be a bit warmer than
normal (lower- mid 80s).
Depending on the timing of the Monday/Monday night system, there
could be some residual showers around first thing on Tuesday.
Otherwise Tuesday will be the beginning of a stretch of some fine
mid-summer weather. With westerly flow, temperatures won`t vary much
from day to day and will top out several degrees above normal.
Looking for widespread lower/mid 80s into Thursday. At this point it
looks dry for Wednesday, and pretty much Thursday. Couldn`t rule out
an isolated t-storm Thursday however as at least the ECMWF
indicates some moisture around with moderate levels of instability.
Looks like the next system will be coming in sometime Thursday night
.AVIATION /12Z Friday THROUGH Tuesday/...
-- Changed Discussion --Through 12z Saturday...mainly VFR cigs through 15z with some
stratocumulus MVFR at KSLK. expect all VFR by 15Z with daytime
heating. Expecting another possible round of showers/thunderstorms
in the late afternoon or evening with another upper level short
wave and surface trough, again producing mvfr vis in scattered
rain showers perhaps some very brief IFR in thunderstorms. These
storm coincide with daytime heating and may produce strong gusty
winds and hail. Lull between rain episodes with no precip through
much of midday. Confidence low on thunderstorm occurrence and
location, so didn`t put in the TAFs until it becomes more certain.
Best guess is northern NY and VT in the 21-03Z period.
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.
South to southwest winds will be 10-15G23KT today, perhaps
veering more to west by afternoon.
Outlook 12z Saturday through Tuesday...
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.
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