Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
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FXUS61 KBTV 241900
Area Forecast Discussion
National Weather Service Burlington VT
300 PM EDT Wed Aug 24 2016
-- Changed Discussion --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
thundestorms 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.
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.NEAR TERM /THROUGH THURSDAY/...
-- Changed Discussion --As of 300 PM EDT Wednesday...Another quiet evening is expected
across the area as high pressure progresses offshore while a few
high clouds filter in from the north and west. Dry weather is
expected as temperatures fall into the 70s, bottoming out in the
60s to around 70 by morning as clouds slowly increase north and
west with the approach of a weak surface trough. Latest CAM output
suggests at least a nominal threat of a few light showers or
sprinkles far west toward morning, but most areas should remain
dry under continued light southerly flow.
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.
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.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/...
As of 301 AM EDT Wednesday...Timing of energy and associated
moisture continues to be the challenge in developing fast westerly
flow aloft. Models continue to show system coming in several
different pieces...making the exact window for predicting the
highest pops difficult. Initial 5h vort over the northern plains
will shear out in flow aloft and weaken across our region on
Thursday morning. This energy...along with increasing 850 to
500mb moisture will result in chance pops across northern NY. This
feature will quick exit our region by 18z...before more energy and
moisture arrives around 00z Friday. Higher surface dewpoints from
earlier showers...along with surface heating will produce surface
based CAPE values up to 800 J/kg across the Saint Lawrence Valley
around 00z. Have mention chance of thunder with likely rain
showers for the combination of instability and dynamics. The
actual surface boundary crosses northern NY overnight and is
located in the Champlain Valley on Friday morning. Will continue
to mention chc to likely pops overnight Thursday into
Friday...before tapering from west to east by Friday afternoon.
I realize we will have 12 to 18 hours of pops for only a 2 to 4
hour window of precip...but timing of multiple short waves in fast
flow aloft is difficult. PWS surge to 1.75 ahead of
boundary...supporting some isolated heavier downpours...especially
in the stronger convective elements over northern NY/VT on
Thursday evening/night. Still thinking qpf will range between 0.25
and 0.75...with some downslope on breezy 850mb southwest winds of
35 to 40 knots. These winds and pressure analysis support some
localized surface gusts to 30 mph across the saint lawrence and
champlain valleys on Thursday afternoon/evening. These winds shift
to the west and much drier air arrives on friday afternoon...with
cooler temperatures by the weekend. Progged 925mb temps between
22-24c...support highs well into the 80s on Thursday...with maybe
a spot 90 in the warmer valleys...expecting clouds to limit
surface heating some. Temps will be slightly cooler on
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 301 AM EDT Wednesday...1026mb surface high pressure will
build into the north country on saturday and continue for sunday.
This will result in plenty of sunshine with mild days and cool
nights. Given the very dry profiles...expect large diurnal swings
in the temps from mid 40s to lower 50s to mid 70s to lower 80s.
Next system in the fast westerly flow aloft approaches our region
late sunday night into monday with a chance of showers. Progged
instability parameters are minimal so no mention of thunder thru
16z monday. Better surface heating and weak surface boundary on
Monday afternoon may produce a few rumbles of thunder. Will
mention chance pops with best chance of thunder based on surface
based cape values of 500 j/kg will be over central/eastern vt.
Progged 850mb temps range between 12-14c for monday into
tuesday...supporting highs mid 70s mountains to lower 80s valleys
with lows mainly in the 50s to lower 60s depending upon elevation.
.AVIATION /19Z Wednesday THROUGH Monday/...
Through 18Z Thursday...VFR under light to moderate southerly flow
and SKC-SCT250 through 06Z Thursday. After 06Z thickening cloud
cover to BKN/OVC 060-150 AGL with scattered showers/isolated
thunderstorms arriving from the west with approach of cold front.
Activity should be scattered with highest coverage generally
toward the end of the TAF forecast cycle at northern/western
NOTE: Rutland AWOS (RUT) is not operating. Because of the lack of
disseminated observations, we continue our suspension of
amendments for the RUT TAF. Once the communication problem has
been resolved, and we again get routine observations automatically
transmitted, we will lift that restriction.
Outlook 18Z Thursday through Monday...
18Z Thursday 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 118 PM EDT Wednesday...The AWOS (automated weather
observing system) at the Rutland-Southern Vermont Regional Airport
(KRUT) remains out of service at this time. The FAA has advised us
that a new computer is on order to fix the problem at the KRUT
AWOS. There remains no estimated return to service at this time.