Area Forecast Discussion
Issued by NWS Burlington, VT

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962
FXUS61 KBTV 241959
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
359 PM EDT Wed Aug 24 2016

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH THURSDAY/...
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.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 350 PM EDT Wednesday...more consensus with the hi-res, and
even global models regarding thursday night into friday morning.
Deep west-southwest flow with moist airmass (precipitable water
values around 2.0") will be in place. Models all pretty consistent
that a little ripple in the flow will spark a round of
precipitation overnight. Elevated instability remains in place all
night, so can`t rule out isolated t-storm at any point. Based on
latest model guidance, it looks like the better chances for these
showers will be 05-09z across northern New York, and 09-14z across
Vermont. Though the atmosphere will be moist, the showers/t-storms
will move along rapidly enough that we aren`t concerned for any
flooding issues. However when it rains, the downpours will be
heavy albeit brief. High dewpoints (upper 60s to lower 70s)
Thursday night will mean it will be a tough sleeping night.

Showers quickly push off to the east by late morning Friday, with
quickly clearing skies. 925mb temperatures will range from around
19C in the north to 22C in the south. That suggests it will be a
warm day, with highs in the 80s areawide -- with some southern
valleys pushing into the upper 80s. Decent boundary layer mixing
should result in some afternoon wind gusts of 15-20 mph or so.

Friday night, quiet and drier and cooler (at least compared to
Thursday night) with lows in the 50s to lower 60s.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 350 PM EDT Wednesday...in general, the forecast period is
rather quiet, with only 1 weather system to bring any
precipitation. 12z GFS and ECMWF are in okay agreement, but do
have some differences with their 00z counterparts (especially with
the ECMWF). Stuck pretty close with the model blend for the
forecast, and thus the forecast doesn`t offer too much change to
the previous version.

Daily details:

Saturday: sunny and dry. 925mb temperatures range from 14C (north)
to almost 20C (south). So look for 70s north to lower 80s in the
south (perhaps approach the mid 80s in southern valleys).

Sunday: starts dry, but upper level trough and associated front
will be approaching the region by late in the day. Looks like the
system will be moving across overnight. Models do indicate minimal
instability, so can`t rule out isolated t-storms embedded within a
band of showers that should move eastward across the area. Ahead
of the system, temperatures aloft warm a couple of degrees, so
Sunday will be a couple of degrees warmer than Saturday in most
places. Should be a good outdoor activity for most of us as the
precip mostly holds off until late.

Monday: 12z suite of guidance does indicate Monday will be mostly
dry as the upper trough and surface front pushes east of the
region by morning. However, previous model runs were a little bit
slower, so as a result have maintained some small PoPs for Monday.
Given all the tropical activity well to our south, the models will
struggle with the overall large scale synoptics as well. Cooler
airmass (compared to Sunday) should come in on Monday, however it
will still be a couple of degrees above normal. Primarily 70s for
highs, with lower 80s in southern valleys.

Tuesday & Wednesday: High pressure should be in control. So high
and dry. Continues to stay above normal on the temperatures,
looking at 70s to lower 80s each day. However confidence isn`t all
that high, given that there could be some sort of tropical
activity well to our south that could have some sort of feedback
into the placement of mid-latitude troughs and ridges.

&&

.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
terminals.

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.

&&

.EQUIPMENT...
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.

&&

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

&&

$$
SYNOPSIS...JMG
NEAR TERM...JMG
SHORT TERM...Nash
LONG TERM...Nash
AVIATION...JMG
EQUIPMENT...WFO BTV



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