Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KBTV 250712
Area Forecast Discussion
National Weather Service Burlington VT
312 AM EDT Thu Aug 25 2016
High pressure will provide another nice evening across the region
with mainly clear skies and seasonal temperatures. An approaching
surface trough will bring increasing clouds and the threat of
showers across northern counties by Thursday morning, and a few
thunderstorms across the entire area by Thursday afternoon into
Friday morning. Behind the front a return to seasonably mild and dry
weather is expected for the upcoming weekend.
.NEAR TERM /THROUGH TONIGHT/...
As of 105 AM EDT Thursday...Overall forecast in good shape with
only tweak being the onset of any showers across northern New
York early this morning. Looks like it will be a bit closer to
sunrise and have slowed everything up by about two hours.
Otherwise...no other changes needed.
By Thursday we continue to advertise an increasing threat of
scattered showers and a few thunderstorms as weak surface trough
will interact with mid-level energy and nominal instability. Height
falls remain negligible and given rather meager mid level lapse
rates severe weather is not expected. However, latest AMSU/SSM-I
PWAT analysis does show the northern periphery of a very moist
airmass currently residing across the Upper Ohio Valley and Great
Lakes (1.6 to 2.0 inches). It is this airmass that will advect east-
northeast and reside across our area during the day, so the idea of
brief tropical-like downpours in scattered convective cores still
appears reasonable at this point. Mid-level flow looks strong enough
to keep activity moving however, so from a hydrological standpoint
I`m not overly concerned. With higher coverage of clouds I did trend
maximum temperatures downward just a tad and in closer agreement
with blended bias-corrected output offering readings in the 78 to 84
range. Dewpoints will be rather high though (65 to 72F) so it will
feel rather muggy.
.SHORT TERM /FRIDAY THROUGH SATURDAY/...
-- Changed Discussion --As of 253 AM EDT Thursday...Forecast challenge continues to be
areal coverage of potential precip on Friday morning across our
eastern forecast area. NAM/GFS are in good agreement with best 850
to 500mb moisture at 12z from the Champlain Valley
eastward...while ECMWF shows a moderate band of qpf from eastern
Lake Ontario into central VT around 12z. This seems to be related
with some convective feedback issues...therefore will trend toward
chance pops from Champlain Valley eastward through 15z...then
taper to <14% by afternoon. Soundings show deep dry layer and
associated subsidence between short wave energy building...as pw
values fall from 1.75 to 0.75 inches by 00z saturday. This drying
will support mostly sunny skies by afternoon with temperatures
warming into the 80s...with only weak cold air advection behind
boundary. By 12z saturday a 1025mb surface high pressure is
building into the North Country with dry north winds continuing.
A seasonably cool day with low relative humidity values are
expected on Saturday...with temps mainly in the 70s. Winds will
generally be from the north/northwest at 5 to 15 mph.
-- End Changed Discussion --
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
-- Changed Discussion --As of 253 AM EDT Thursday...Overall large scale pattern supports
building ridge across the Mid Atlantic States with moderately
fast westerly flow aloft over the NE CONUS. Both ECMWF and GFS
show next short wave energy and ribbon of enhanced mid level
moisture approaching our western zones by 00z Monday...and quickly
spreading eastward overnight into Monday. Will continue with
previous forecaster idea and mention chance pops during this time
period. Instability looks minimal with surface based CAPE values
<500 J/kg and lis around -1c. Thinking best window for showers
will be between 21z Sunday into 06z Monday...based on 850 to 500
moisture and progged position of 5h vort associated with trof
lifting across southern Canada. Surface high pressure redevelops
across the region for Tuesday into Wednesday with dry conditions
anticipated. Surface analysis shows breezy southwest winds are
likely on Sunday ahead of boundary with gusts to 30 mph possible
Saint Lawrence and Champlain Valley. Progged 850mb temps warm to
16c by 18z Sunday...supporting upper 70s mountains to mid 80s
valleys. If clouds arrive sooner than anticipated temps will be 4
to 8 degrees cooler on Sunday...based on this have stuck very
close to superblend numbers. On Monday very weak low level cold
air advection develops behind front with progged 850mb temps
dropping back between 12c and 14c...supporting highs l/m 70s
mountains to upper 70s to lower 80s valleys. Warmer temperatures
build by the midweek with progged 850mb values around 18c by 12z
Thursday. This will support highs well into the 80s with lows
mainly in the 50s mountains to 60s valleys. Overall...rh values
will remain in the comfortable zone through midweek...before
increasing toward next weekend. Next chance of showers/storms
arrives late next week.
-- End Changed Discussion --
.AVIATION /07Z Thursday THROUGH Monday/...
Through 06Z Friday...Overall looking at VFR conditions through the
period. Expecting scattered showers and isolated thunderstorms to
move across the area mainly between 16z and 00z...but again
looking at VFR conditions with some MVFR ceilings and visibilities
in and near any of the showers or storms. Winds will be increasing
from the south and southwest this morning with gusts in the 15 to
25 knot range...especially this afternoon...before gusts taper off
NOTE: Rutland AWOS (RUT) is now operational.
Outlook 06Z Friday through Monday...
06Z Friday through 18Z Friday...VFR with scattered MVFR/brief IFR
in scattered showers/thunderstorms. Brief heavy downpours with
reduced visibility and turbulence in stronger convective cores.
18Z Friday through 00Z Monday...VFR/high pressure.
00Z Monday onward...VFR with scattered showers/MVFR possible.
As of 0730 PM EDT Wednesday...The AWOS (automated weather
observing system) at the Rutland-Southern Vermont Regional Airport
(KRUT) is now back in service and operational.