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  Monday August 21, 2017

 

NWS Area Forecast Discussion


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FXUS61 KBTV 181810
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
210 PM EDT Fri Aug 18 2017

.SYNOPSIS...
This afternoon, we`ll have areas of sunshine, however the
increasingly humid airmass will result in a few showers or
thunderstorms late in the day and into the evening. Some storms
could produce heavy downpours. Any showers and storms come to
an end later tonight. On Saturday expect a chance for showers in
the afternoon...but the areal coverage will be scattered in
nature. Highs on Saturday will be in the mid 70s to lower 80s.
Drier air will begin to move into the region on Sunday with
highs once again in the mid 70s to lower 80s.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 1005 AM EDT Friday...late morning refresh is primarily to
sync the forecast up with the latest radar/satellite/surface
observation trends. The bulk of the widespread steady showers
are mostly east of the region at this time. Mid-level water
vapor from GOES-16 shows quite a bit of dry air across the St
Lawrence Valley (although low level moisture remains, thus still
a deck of lower clouds out there), with deeper moisture east
half of the forecast area. The previous forecaster`s concept of
a lull for mid-day with a just a few showers/t-storms
developing later this afternoon still looks good. The latest
runs of the HRRR, and the 06z BTV 4km WRF show this scenario.
Have folded their outputs into the PoP forecasts to show the
mid-day lull and late afternoon slight uptick in shower
coverage. Given precipitable water values this afternoon and
evening will still be 1.5" or so, especially eastern sections,
any t-storm we do see will have a decent downpour with it.
Otherwise, ingredients for stronger/organized t-storms don`t
look all that great at this point.

Bottom line -- much of the rest of the day won`t be too bad. The
sun will eventually break out for most of the area, and
showers/t-storms will only be scattered about.


Previous Discussion...
Low level warm air advection is enhancing showers across
northern New York this morning and Showalter Index values are
slightly negative for indications of elevated instability. We
have seen some lightning with this activity and given the
continued existence of elevated instability through about 800 am
this morning...will continue to mention isolated thunderstorms
over northern New York. The showers will move across Vermont
this morning with noticeable clearing/drying moving into
northern New York during the morning hours. There will likely be
a lull in precipitation around midday with dry weather expected
through about 500 pm before instability develops from the
Champlain Valley westward in advance of an approaching cold
front. Deep layer shear will also be increasing over the Saint
Lawrence Valley but at the same time dry air aloft will move
into that area. So feel that area remains dry late in the
day...but from the northern Adirondacks into the Champlain
Valley can see scattered showers and isolated thunderstorms
developing. Not the most favorable instability and shear in this
area...but enough for the convective threat. Dew points will be
well into the 60s at that point and can see heavy downpours
with any of the convection. At this time will not put in any
enhanced wording...but will need to keep an eye on the wind gust
potential. Feel best threat for strong to severe storms will
remain south of our area...from the Albany area down into
eastern Pennsylvania/northern New Jersey where deep layer shear
and instability are aligned with each other and are sufficiently
strong. High temperatures today will be interesting with
readings in the upper 60s to lower 70s in the east to the lower
80s in the west.

For tonight scattered showers and isolated thunderstorms should
end by midnight as cold front moves east of the region. Lows
will be in the upper 50s to upper 60s and would not be shocked
to see fog develop with higher dew points and additional low
level moisture from Friday`s precipitation.

On Saturday main upper trough is still to the west of our area
and will be approaching by late in the day. Can see the chance
for some afternoon showers as this feature approaches and
enhances dynamic support over the region. West to southwest flow
aloft will allow for slightly above normal temperatures with
highs in mid 70s to lower 80s.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/...
As of 454 AM EDT Friday...Chance for showers Saturday night as
upper level trough and short wave energy passes overhead. Dry
weather returns for Sunday with surface high pressure ridge
building into the north country. Temperatures Saturday night
will be slightly warmer than normal with clouds and chance for
precipitation, then back to near normal values on Sunday with
dry and seasonable weather expected.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 454 AM EDT Friday...Our weather will be dry from Sunday
night through early Tuesday with surface high pressure remaining
the main synoptic feature. On Tuesday a weak low will pass
north of our area and we will have a chance for some showers
from Tuesday afternoon through early Wednesday. Upper level
trough will linger a bit behind this system, and bring a chance
for showers through the end of the period. Monday and Tuesday
will be the warmest of the week ahead of approaching cold front,
max temps reach the mid to upper 80s. Temperatures will be a
bit cooler than normal towards the end of the week with upper
level trough bringing clouds and precipitation to our area.
Highest pops will be Tuesday night and early Wednesday with the
actual frontal passage.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
Through 18Z Saturday...a mix of conditions across the region,
with VFR across most of northern NY, and MVFR across
eastern/southern Vermont. A few showers are also near RUT as I
type. Trends should be toward VFR, except eastern Vermont where
MVFR ceilings will likely hang on. During the evening we expect
scattered showers to redevelop and move across the region.
However the confidence in exact timing and location are such
that "VCSH" is the best that can be placed into the TAFs right
now. Expect MVFR ceilings to also redevelop across much of the
area, along with at least a "light" (4-6sm) fog. Guidance
suggests that IFR due to visibilities of 1-2sm and ceilings
under 1000ft will develop in locations east of the Green
Mountains (eg: MPV), with some as well across the `Dacks.
Conditions will start to improve after 13z Saturday.

Outlook...

Saturday Night: VFR. Chance SHRA.
Sunday: VFR. NO SIG WX.
Sunday Night: VFR. NO SIG WX.
Monday: VFR. NO SIG WX.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. Chance SHRA...Slight Chance TSRA.
Tuesday Night: VFR. Chance SHRA...Slight Chance TSRA.
Wednesday: VFR/MVFR. Likely SHRA.

&&

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

&&

$$
SYNOPSIS...Evenson
NEAR TERM...Evenson/Nash
SHORT TERM...Neiles
LONG TERM...Neiles
AVIATION...Nash



 
 
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