Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
732 am EDT sun Jul 5 2015
a ridge of high pressure both aloft and at the surface
will slowly build into the north country today and continue
through early this upcoming week. This will result in clearing
skies and warming temperatures to above normal levels. A spot
shower is possible across northern Vermont today...however the next
chance for widespread showers and thunderstorms will be Tuesday
Near term /until 6 PM this evening/...
as of 720 am EDT Sunday...minor update to increase clouds through
15z this morning and match grids based on current observation. Infrared Sat shows
some clouds across our region this morning...along with patch fog.
The fog should dissipate quickly this morning with clearing skies.
Still expecting some fair weather cumulus clouds to develop this
afternoon...as convective temperatures are reached and weak updrafts develop
over the higher terrain. Temperatures will warm into the M/u 70s mountain towns
to lower 80s cpv/slv.
Water vapor shows middle/upper level trough directly overhead with final
500 mb vorticity and weak ribbon of enhanced middle level moisture across
northern New York at this time. This energy and moisture will move east into
northern Vermont today...resulting in some sprinkles/light showers over
the nek. Otherwise...given plenty of boundary layer moisture and
temperatures reaching convective values expect diurnally driven fair
weather cumulus clouds to develop. These clouds will have limited
vertical growth due to dry air aloft and building heights
associated with ridge. Prognosticated 850 mb temperatures warm between 12-14c today
and will support highs middle/upper 70s nek/mountain towns to lower 80s
cpv/slv with a few warmer readings in the middle 80s possible near
btv and mss.
Short term /6 PM this evening through Tuesday/...
as of 400 am EDT Sunday...mid/upper level ridge builds
overhead for tonight through Monday...with large scale subsidence
expected. This deep dry layer and warming thickness values will
support above normal temperatures on Monday with mostly sunny skies and
south winds. Prognosticated 850 mb temperatures warm another degree or two with
values between 14-16c...supporting highs well into the 80s. On Monday
night into Tuesday...moisture now located over the MS valley and
associated 500 mb circulation is expected to lift toward the NE Continental U.S. Ahead
of next trough. Both GFS/NAM agree on quickly advecting 850 to 500mb
moisture into our region on middle level southwest winds of 30 to 40
knots. Models also in good agreement with development of showers and
embedded storms on Tuesday morning across our County Warning Area...ahead of
approaching cold front and digging middle/upper level trough.
For Tuesday afternoon it extremely challenging to determine areal
coverage/intensity of storms...given the potential pre trough moisture
and showers...combined with delayed arrival of actual surface cold front
and dynamics aloft. As in many cases already this Summer...best
dynamics and convergence associated with boundary looks to occur after
00z Wednesday...when instability is minimal. In addition...best 0 to 3 and
0 to 6 km shear values lag behind the actual front and are closely
tied to the middle/upper level trough over southern Canada late Tuesday
afternoon. My thinking is that we will some some showers/embedded storms
with initial surge of 850 to 500mb moisture and embedded vorticity between
15z-20z Tuesday...followed by some clearing as our County Warning Area will be between
systems. This will help to destabilize the region with surface based cape
values approaching 1500 j/kg by 00z...but better forcing/front is
still west of the slv. As front pushes across the region between 03z-
09z surface instability will be limited and the best deep layer shear is
located to our north...supporting a broken line of showers with
embedded storms. Given scenario not expecting any severe...but a few
stronger storms with gusty winds and heavy down pours will be
possible. Have noted precipitable water values surge ahead of boundary between 1.60 and
1.80". Temperatures on Tuesday will be tricky with clouds...but 925mb temperatures
warm to near 20c...supporting highs in the middle/upper 80s...with
increased dewpoints...making if feel muggy/Summer-like.
Long term /Tuesday night through Saturday/...
as of 400 am EDT Sunday...numerical models are
coming around to a consensus through the entire period thus making
an increasing forecast confidence that has been lacking as of late.
There is general consensus that short wave and surface front move
north and across region Tuesday night/Wednesday for rain showers/thunderstorms and rain threat sliding
east as Wednesday progresses. Thereafter...models have merged to a
similar solution of predomiant zonal flow with any potential short
waves in the flow minor with a disconnect to any moisture to the
south. Therefore...do I Dare say it a dry period for Thursday-Friday and
possibly Sat before another rain showers/thunderstorms and rain threat Sunday.
After a warm Tuesday...seasonable temperatures in the longer term with
highs in the 70s/80 and lows in the 50s/60s.
Aviation /12z Sunday through Thursday/...
through 12z Monday...VFR conditions are expected through the
period with the exception of localized IFR/LIFR in fog/br between
06-12z Monday at kslk/kmpv.
Westerly winds less than 10 knots today becoming calm to
Outlook 00z Monday through Thursday...
12z Monday - 12z Tue: VFR.
12z Tuesday - 00z Thu: VFR west/scattered MVFR thunderstorms and rain possible.
00z Thursday - 00z Fri: VFR. Early morning IFR fog possible at
ktyx radar will be out of service until Tuesday or later.
equipment...weather forecast office btv