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Current conditions from King Hill
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  Thursday September 20, 2018

 

NWS Area Forecast Discussion


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284
FXUS61 KBTV 190707
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
307 AM EDT Wed Sep 19 2018

.SYNOPSIS...
A few showers are possible this evening as a strong cold front
pushes south through the area. Behind this front, variable
clouds and cooler, more seasonable weather is expected tonight
into Thursday. The next chance of showers comes Thursday evening
ahead of a warm front which will pass through the region by
Friday morning. It will be windy and warm Friday before another
strong cold front brings another chance of showers or a
thunderstorm by Friday night. A much cooler Canadian airmass and
its associated high pressure moves in for Saturday.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 1043 PM EDT Tuesday...Late evening update included adding
patchy fog across s-central VT, promoted by the shower activity
occurring mainly 23-01Z. May see the fog become more intermittent
as cold front settles southward into Rutland/Windsor counties
next 1-2 hrs, with developing northerly wind shift and increased
mixing potential.

Previous Discussion...We did it again. Another 80 degree day at
BTV which puts us at 82 for the year and second place all time
behind 86 back in 2016. In fact, we`ve hit 86 at BTV and close
to our record high of 87 set last year.

Shallow cold front continues to progress swd across the forecast
area this evening, draped across the Northern Adirondacks into
the southern Champlain Valley and newd across central/nern VT.
Much of the low-level cold advection appears to be originating
from the Gulf of St. Lawrence and St. Lawrence Valley, with
strong nely flow noted across srn Quebec. In fact, temperatures
are only in the mid 40s in the Quebec City area and nwrn ME...so
definitely a marked air mass change overnight. Winds shift to
northerly and increase to 10 to 20 mph locally a bit stronger
indicated around lake Champlain with good mixing as cooler air
moves over the unseasonably warm lake waters in the lower 70s.
Temps will fall back through the 70s to around 60 by sunset in
the the far northern higher terrain.

A few lingering showers across southern Rutland county will
depart to the south late this evening. Based on satellite trends
to the north, will see an increase in low cloudiness overnight
as frontal inversion sharpens. May even see some patchy drizzle
across far n-central into nern VT late given maritime origin of
the air mass. Some patchy drizzle may also be possible in the
higher terrain. Overnight lows tonight should range from the
upper 40s to mid 50s north and mid to upper 50s south.

Morning stratus in most areas early Wednesday will slowly lift
and break up by afternoon as mixing processes deepen and the
aforementioned inversion weakens as high pressure moves eastward
across southern Quebec and heights rise aloft. With 925 temps
ranging from 10 to 14C looking for highs in the mid 60s to lower
70s.

High pressure ridging down into the area from Canada and the upper
level shortwave ridge crests of the region Wednesday night it should
be mainly clear and cool leading to dense valley fog in the usual
places but it could be more widespread. Expect lows in the upper 40s
to low 50s in Vermont, and upper 30s to upper 40s in northern New
York.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 300 AM EDT Wednesday...A low pressure system will track from
the northwestern Great Lakes Region to central Quebec Friday,
pushing a series of fronts through New England that will control the
short term forecast. Plenty of baroclinicity associated with
the early fall system, so should see some impressive temperature
advection over the area Friday. The cyclone`s warm front will
cross the forecast area Thursday night through Friday morning,
spreading some rain through the North Country as it does so.
Very little dynamic support in the upper-levels over our area
(much more impressive further north...), but a broad area of
synoptic-scale ascent from isentropic lift will ensure that most
areas see at least some measurable rain. Given the strength of
the impressive 50+ kt LLJ within the warm-sector of the cyclone,
QPF will vary greatly with terrain. The Saint Lawrence Valley
should see the most precipitation under this setup, while much
of the Champlain Valley will get rain- shadowed, resulting in
significantly lower QPF amounts. Overall for many areas, should
be a higher PoP/lower QPF scenario. Some marginal (<500 J/kg)
elevated CAPE will be present over northern New York, so an
isolated rumble of thunder Friday morning can`t be ruled out.

Winds Friday will be quite gusty from the south/southwest. Strongest
winds will be at highest elevations and in channeled valleys.
Areas of the Saint Lawrence Valley and the Champlain Valley will
see gusts in excess of 25 mph during the afternoon hours as
higher momentum air within the LLJ is mixed to the surface.

High temperatures Friday will be highly variable across the CWA.
Strong warm air advection will allow temperatures to climb into
the low 80s in the Saint Lawrence Valley. The Champlain Valley
should also warm up quite a bit, with highs near or at 80
degrees not out of the realm of possibilities with strong
downsloping southwesterly winds in place. Areas east of the
Green Mountains, however, will be noticeably cooler, topping out
in the upper 60s to low 70s.

Friday night, the system will sweep a strong cold front through
the area, reinvigorating shower activity. Better dynamics aloft
associated with this frontal passage, however best upper
support does lag quite a bit behind the frontal passage. Given
the overnight timing of the frontal passage and the subsequent
lack of much instability, along with the offset of surface
forcing and upper-level support, not overly impressed at this
point with thunderstorm potential. If any thunderstorms are able
to develop along the front however, the strong shear/flow aloft
could support some gusty winds reaching the surface. Once
again, best chances of an isolated thunderstorm or two would be
in the Saint Lawrence Valley, where the earlier timing of the
frontal passage would line up with better instability.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 300 AM EDT Wednesday...Weather turns more benign, but
noticeably cooler, this weekend as we settle into fall-like
conditions behind the cold front. Highs Saturday and Sunday will
only be in the low to mid 60s. Saturday night will be the
coolest night in quite some time with temperatures in the mid
30s to mid 40s expected. Areas of the Northeast Kingdom and
northern Adirondacks will be the coldest, and should see a frost
or possibly even a freeze Saturday night.

Monday night, high pressure will shift offshore and return southerly
flow will advect in some warmer air. Temperatures will
gradually climb back towards seasonal values towards the middle
of the week. The next chance of precipitation looks to be in the
Tuesday/Wednesday time-frame as another low tracks
northeastward through Canada, sending a warm front through the
northeastern US.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
Through 06Z Thursday...Widespread IFR/MVFR cigs expected
through the 12-14Z time frame as post-frontal low stratus
settles slowly south and west across the region. Some patchy
drizzle possible with higher terrain obscured. Only exception
will be KPBG where mainly VFR is expected. After 15Z cigs lift
to VFR at all terminals and trend SCT from 035-040 over time.
Winds generally north to northeasterly 5-10 kts through the
forecast period.

Outlook...

Thursday: VFR. Slight chance SHRA, Patchy BR.
Thursday Night: Mainly VFR, with local MVFR possible. Likely
SHRA.
Friday: Mainly MVFR, with local VFR possible. Likely SHRA.
Friday Night: Mainly MVFR, with areas VFR possible. Likely SHRA.
Saturday: Mainly VFR, with local MVFR possible. NO SIG WX.
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. NO SIG WX.

&&

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

&&

$$
SYNOPSIS...Sisson
NEAR TERM...Banacos/Sisson
SHORT TERM...RSD
LONG TERM...RSD
AVIATION...JMG



 
 
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