Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 202332
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
732 PM EDT Wed Jul 20 2016

.SYNOPSIS...
Ridge of surface high pressure will remain over the North Country
through Thursday, providing the region with sunny and dry weather.
Temperatures will warm above seasonal normals again towards the
end of the week. Periods of showers and thunderstorms are expected
Thursday night through Saturday as a frontal system moves slowly
through the region. Some of the storms will have the potential to
become strong or severe.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 732 PM EDT Wednesday...Going forecast in good shape with no
changes needed at this time. Previous discussion...Large ridge of
surface high pressure will remain over the region right through
Thursday. Dry weather is expected. Tonight`s minimum temperatures
will be slightly cooler than seasonal normals with another good
radiational cooling night in place. Then highs on Thursday will be
warmer than normal with ample sunshine and warming aloft. Could
have some fog form overnight in the typically fog prone spots, but
if any high clouds make it into the area this could be hampered.
Believe Thursday will remain dry with any convection holding off
till after midnight with next approaching system.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 320 PM EDT Wednesday...An active period with several rounds
of strong to severe storms possible.

Thu Ngt/Early Fri Morning: A surface front in Ontario/Northern Great
Lakes will be slowly approaching. Deep low-level layered moisture
with with PWATS >1.5 inches advecting ahead of front...instability
aloft with increasing presence of elevated mixed layer...a
shortwave trough and exit region of 300mb jet approaching should
have mesoscale convective complex in northern Great Lakes/Ontario
moving into FA during late Thursday night/early Friday morning.

Friday:  As advertised...an Interesting day. SPC Day 3 (issued
earlier today) is uncommon across FA. At times during the past few
days models suggested that various ingredients didn`t quite come
together all at the same time especially an elevated mixed layer.

However...latest guidance is showing potential elevated mixed layer
being present thus helps support the other parameters that have
already been discussed in previous discussions.

Surface instability (temperatures well into the 80s, resulting in
CAPE values pushing 2000 J/kg. there still remains some questions on
the low-level instability due to previous convection or debris
clouds stabilizing atmosphere but feel enough dry air aloft and
breaks will allow for substantial recoup of llvl instability. A
shortwave skip through at some point during the day.

Deep WNW shear of 35-45kts along with model soundings also indicate
high equilibrium levels and semi-low wet bulb zero (10-11k ft)
levels which suggest a wind and hail threat.

Timing...After some recoup time from early morning activity...llvl
destabilization and upper level shortwave activity in late
morning/ aftn for some activity and perhaps enough drying
afterwards for more late aftn/evening with surface front and
another shortwave.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 320 PM EDT Wednesday...Some residual influence from
departing trough on sat will yield a chance of showers...esp vt
with decreasing west to east and temperatures still seasonable or
above by a few degrees.

Some shortwave ridging sat ngt/sun before approach of another
northern stream shortwave mon. Max T on Sunday a few degrees milder
than sat with more sun. Some showers move into late sunday
night/early monday morning but the main focus will be on Monday.

Very similar Monday to Friday`s set-up with approach of strong
shortwave...strong wind dynamics...a bit more amplified and stronger
surface cold front with decent cold air advection and falling
heights associated with it. Strong to severe storms possible again
and already some mention in SPC Day 4-8 discussion.

Some differences with ECMWF/GFS about Tue/Wed forecast with ECMWF
more amplified thus a bit more wet on Tues. Similar to Sat...best
chance across VT..esp NE Mtns and drying trend into Wed.
Temperatures near seasonable with lower humidity.

&&

.AVIATION /00Z Thursday THROUGH Monday/...
Through 00z Friday...VFR clear through the period except LIFR vis
in FG at KMPV and MVFR vis in BR at KSLK. Both sites approach
their temp/dewpoint crossover temperature but its been a couple
days now since the last rainfall. Any fog that develops will
dissipate around 11z. Low confidence in the FG/BR forecast for
both sites. Light wind for much of the period turning light south
on Thursday. KMSS could see some gusts during the day in tighter
pressure gradient and channeling up the St. Lawrence Valley.

Outlook 00z Friday through Monday...

Thu night-Sat...VFR, with scattered MVFR in showers and
thunderstorms.

Sun...Mainly VFR under weak high pressure.

Mon...Scattered MVFR in showers and thunderstorms.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.

&&

$$
SYNOPSIS...Sisson
NEAR TERM...Evenson/Neiles
SHORT TERM...SLW
LONG TERM...SLW
AVIATION...Hanson


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