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  Monday August 21, 2017

 

NWS Area Forecast Discussion


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000
FXUS61 KBTV 201853
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
253 PM EDT Sun Aug 20 2017

.SYNOPSIS...
A good deal of sunshine is expected for this afternoon with high
temperatures in the mid 70s to lower 80s. Dry weather continues
tonight and Monday as high pressure moves across the area. A
warming trend will take place with highs in the 80s and
continued sunshine. Above normal temperatures continue on
Tuesday with highs in the 80s...but an approaching trough of low
pressure will enhance the potential for showers and
thunderstorms Tuesday afternoon and night.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 138 PM EDT Sunday...No updates need for near term forecast
with this update. Water vapor imagery showing the upper trough
is retreating to the east with weak high pressure building
across the region. Noticeable drying is taking place upstream
across southeast Ontario and thus we should be able to see
increasing amounts of sunshine as the day wears on. On track for
highs in the 70s to around 80.

For tonight and Monday...high pressure builds in tonight and
gradually exits the area on Monday. Dry weather is expected
during this time period with little in the way of cloud cover as
well. Flow in the low and mid levels becomes west and
southwest...which will allow for warm air advection to take
place. Based on increasing 850 mb temperatures all areas should
easily get into 80s with a few spots in the Champlain Valley
getting into the upper 80s. Solar eclipse viewing on Monday
still looks good with little in the way of cloud cover.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 455 AM EDT Sunday...Monday night should mainly remain dry
ahead of approaching frontal system which will bring showers
and thunderstorms to the area later Tuesday and Tuesday night.
Warm air advection continues on warm southwesterly flow,
temperatures will only drop into the 60s across the North
Country. Could see a couple isolated showers in the Saint
Lawrence valley. On Tuesday, a low pressure system will move
Northeastward from the Northern Great Lakes into Southern
Quebec. Warm air advection on moist southwesterly flow continues
on Tuesday and max temps will edge into the upper 80s, with
perhaps a couple 90 degree readings in the warmer spots. Looks
like surface cold front will still be west of our forecast area
by 00z Wed. Think that by Tuesday afternoon we could have some
surface based instability, especially in the Saint Lawrence
valley and Northern Adirondacks, enough for some thunderstorms
to pop up ahead of the approaching cold front. Have increased
pops after 18z in our western zones to likely. Pretty strong
upper level jet dynamics, so think that storms that do form
could have strong gusty winds and heavy rainfall with pwats
nearing two inches by Thursday evening. Have not added enhanced
wording yet, but may need to as we get closer to Tuesday
afternoon.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 253 PM EDT Sunday...The extended forecast will feature large scale pattern change as
deep full latitude trof develops across the eastern Conus and ridge
builds out west. This will result in temps returning to at or below
normal values with much less humidity. The forecast challenge will
be timing individual short waves in the southwest to eventually
northwest flow aloft and potential areal coverage of showers.
Overall...the atmosphere will have much less available moisture as
pw values drop below 1.0 and instability is very limited.

On Wednesday...first embedded 5h vort arrives around 18z... along
with secondary surface convergence line with some additional weak
low level cold air advection behind boundary. Instability is driven
off sfc heating and developing cool pool aloft with deepening
trof...so 30 to 40% chance of showers with maybe a rumble or two of
thunder...but cape values are weak. Soundings show high cloud bases
with deep dry layer so areal coverage of showers will be
limited...but some localized gusty winds possible based on sounding
profiles. Progged 850mb temps around 10c support highs upper 60s
mountains to upper 70s warmest values. Low level cold air advection
continues overnight into Thurs with progged 850mb temps dropping
btwn 5-7c by 12z Thurs. The gradient flow will limit fog development
and keep temps from completely bottoming out with lows mainly 40s
mountains to mid/upper 50s valleys.

Thursday...another embedded 5h vort in the west/northwest flow aloft
and associated pocket of -20c air moves across our cwa. This energy
will limited moisture will help to produce isolated/scattered
showers during on Thurs aftn. Once again areal coverage and amount
of showers will be limited...because of pws around 0.50 to 0.70.
Progged 850mb temps near 6c support highs upper 50s/lower 60s
mountains to lower 70s warmest valleys.

Friday into next weekend...will feature building 1025mb surface high
pres while aloft remains active with embedded 5h vorts in the
northwest flow. Each piece of energy will have less impact with
limited moisture...so will keep Friday dry at this time... with temps
mainly 60s mountains and lower/mid 70s warmer valleys. Lows mainly
in the mid 30s to upper 40s depending upon locations...with coldest
values at SLK/NEK...especially on Saturday morning. Next weekend is
looking mainly dry with slightly below normal temps and low humidity
values. Highs in the 60s mountains and 70s valleys with lows ranging
from the lower 40s to mid 50s.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
Through 12Z Monday...Scattered clouds throughout the aerodrome
in daytime heating and moisture left in the boundary layer. For
KSLK/KMPV fog is possible but highly uncertain, and included
just a temp 2sm br and sct012. Temps tonight will likely hit the
dewpoint crossover temp, however working against that is lack of
recent rainfall and still relatively low dewpoints in the 50s.
Northwest to west winds to continue through overnight, then
become more southerly after 12z Monday has surface ridge shifts
to the east. Very little cloudiness on Monday.

Outlook...

Monday Night: VFR. Chance SHRA.
Tuesday: VFR/MVFR. Breezy. Chance SHRA...Slight Chance TSRA.
Tuesday Night: VFR/MVFR. Likely SHRA.
Wednesday: VFR. Slight Chance SHRA.
Wednesday Night: VFR. NO SIG WX.
Thursday: VFR. NO SIG WX.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.

&&

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

&&

$$
SYNOPSIS...Evenson
NEAR TERM...Hanson
SHORT TERM...Neiles
LONG TERM...Taber
AVIATION...Hanson


 
 
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