Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
1039 PM EDT sun Aug 2 2015
weak high pressure will exit this evening. Clouds will increase
tonight in advance of a warm front...which may produce a few showers
or storms across northern New York. An upper level trough and
surface cold front will bring more widespread showers and
potentially strong thunderstorms to the region Monday afternoon into
Monday night. Unsettled weather with the chance for a few showers
or thunderstorms will continue through midweek.
Near term /until 8 am Monday morning/...
as of 1032 PM EDT Sunday...mesoscale convective system north and
west of Lake Ontario at 0230z will continue eastward motion around
25-30 kts into less unstable air currently across northern New York. Already
seeing some infrared cloud top warming during past hour or so across
Ontario with mesoscale convective system. However...it appears that prognosticated increase in
low- level jet (50kts at kmss at 900mb by 10z) will potentially
lend some dynamic support and low-level warm air advection during the pre- dawn
hours as mesoscale convective system continues eastward. NAM model soundings do maintain marginal
elevated cape up to 500 j/kg...so maintained chance of thunder as
decaying mesoscale convective system moves into the St. Lawrence Valley by 06z and then
dissipates across the Adirondacks and Champlain Valley toward
daybreak. Across Vermont...generally dry and may see a bit of patchy
fog in the most favored valleys of central and eastern Vermont. Overall fog
potential limited by anvil convective debris streaming eastward and
limited radiative cooling effects.
Min temperatures will range mostly from the upper 50s to the middle 60s
across the area...with the coolest readings being east of The
Short term /8 am Monday morning through Tuesday night/...
as of 339 PM EDT Sunday...active weather anticipated Monday through
Tuesday as upper level trough and series of shortwaves rotating
through this feature and the associated surface frontal
boundaries/troughs move eastward across the area. Some differences
remain regarding timing of cold front and how much instability
will be present however.
Chances for showers and thunderstorms will increase on Monday across
the entire area. Outflow boundary from convective complex moving up
through southern Ontario into Quebec tonight into Monday appears as
if it will be the focus for thunderstorm development during Monday.
SBCAPE values expected to range from 500-1500 j/kg across the area
during the afternoon...hampered a bit by surface dewpoints which are
expected to be only around 60 degrees. Plenty of shear however with
0-6km bulk shear values of around 50 knots expected. Storm Prediction Center has entire
forecast area in slight risk for Monday. Have included some enhanced
wording. Expect thunderstorm development to begin early to middle
afternoon over Adirondacks and translate east across Champlain
Valley and rest of Vermont late Monday afternoon into Monday evening
with greatest chance for strong/severe storms in the 20z to 03z
timeframe with potential for damaging winds and large hail. Will
also have to monitor the potential for some locally heavy rainfall
and flash flooding...especially across central and northern Vermont
with precipitable water values peaking between 1.5 and 1.75 inches
and possible training of echoes in southwest flow regime. Maximum temperatures
Monday expected to range from the lower 80s west to upper 80s to
near 90 eastern Vermont.
Shower and thunderstorm activity will diminish later Monday evening
and overnight...but with upper trough axis still west of the region
and position of actual surface cold front difficult to
determine...there will be a chance for more showers and
thunderstorms Tuesday. More instability indicated for Tuesday than
on Monday...but shear less. Expect decent coverage of showers by
afternoon once again...and cannot rule out the risk for some locally
strong storms depending on position of cold front and yet another
shortwave rotating around upper trough. Temperatures Tuesday near
seasonable levels with highs in the upper 70s and lower 80s.
Lingering showers Tuesday night with thunderstorm threat diminishing
during the evening. Low temperatures mostly in the 50s to around 60.
Long term /Wednesday through Sunday/...
as of 252 PM EDT Sunday...the period will start active as large
middle level trough resides over Quebec, bringing a few shortwaves
through the region and producing clouds and showers. Overall
drying trend expected late in the work week as the middle level
trough shifts eastward. As the trough moves east, 500mb heights
increase and some slight surface ridging will move over the north
country for mostly dry conditions on Thursday and Friday. Models
show this ridging keeps a surface low moving up the Ohio River
valley to our south to close out the work week. Another middle level
trough may bring widespread chances for scattered showers on
Saturday. Temperatures will be about five degrees below normal
throughout the period.
Aviation /03z Monday through Friday/...
please see equipment section below for krut data outage
Through 00z Tuesday...VFR conditions overnight for most stations
with the lone exception being a couple hours at kmss with passing
showers potentially bring down visibility to MVFR conditions
Approaching frontal boundary may spark scattered showers and
thunderstorms across the St Lawrence Valley and Adirondacks
between 13z-20z Monday. After that shower and thunderstorms should
move into the Champlain Valley and eventually the entire region
bringing widespread activity for the afternoon. These
thunderstorms could bring periods of IFR conditions if they pass
over any of the terminals.
A strong low level jet moving into the St Lawrence Valley, ahead
of the front, will bring low level wind shear to kmss and kslk starting between
05z-10z out of the SW at 40-45kts. These winds will begin to mix
to the surface after sunrise, resulting in all terminals
experiencing south to SW 10-20kts gusts 20-30kts. Clouds will
lower and increase, but expected to stay VFR Monday morning and
Outlook 00z Tuesday through Friday...
00z Tuesday - 12z Tuesday...scattered showers and thunderstorms
expected with cold frontal passage. Brief MVFR ceilings and IFR
visibilities possible beneath heavier convective cores. Gusty
winds/turbulence also possible.
12z Tuesday - 12z Thursday...mainly VFR...scattered afternoon
showers/thunderstorms with brief MVFR/IFR possible. Patchy IFR in
br/fog possible 06-12z each morning, mainly at kmpv/kslk terminals.
12z Thursday Onward...mainly VFR as surface high pressure tries
to build in over the Great Lakes region.
a lake Wind Advisory has been issued for later tonight through
Monday morning. South winds from 5 to 15 knots this evening will
increase to 15 to 25 knots towards and after midnight tonight. The
strong south winds will continue into Monday morning before
turning southwest and slightly decreasing to 10 to 20 knots
Monday afternoon. The strongest winds will be felt over the Broad
Lake and along southern facing shorelines where gusts to 30 knots
are likely. Waves 1 to 2 feet this evening will build to 2 to 4
feet late tonight and on Monday morning.
In addition...strong to possibly severe thunderstorms are
forecast for Monday afternoon and evening. These storms will be
capable of producing heavy rain with significantly reduced
visibilities...strong gusty winds...frequent lightning...and hail.
Please remain weather aware if planning to be out on the lake
AWOS observational data from the Rutland/southern Vermont
regional Airport (krut) remain unavailable at this time. For
aviation partners current observations may be accessed via telco.
Please reference FAA krut notam 07/007 for more information.