Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 222315

Area Forecast Discussion
National Weather Service Burlington VT
715 PM EDT Sat Jul 22 2017

An isolated shower or thunderstorm remains possible this evening
across the northern Adirondacks and south-central Vermont.
Otherwise, high pressure across Quebec will bring light north
winds and dry conditions overnight and through the daylight
hours on Sunday. Our chances for showers increase as an upper
level trough will bring widespread showers to the North Country
beginning Sunday night and lasting through Monday and into
Monday night.


As of 709 PM EDT Saturday...At 2305Z, regional composite
reflectivity still showing isold shower activity across Essex
County NY ewd across central/s-central VT. Have adjusted PoPs to
account for this activity, which should generally dissipate
after 02-03Z with loss of daytime heating. Into the overnight
hours, high pressure across Quebec will generally be in control
with light northerly winds. Dewpoints are a few degrees lower
than 24 hrs ago, and will be dealing with some mid-upr level
cloudiness overnight, especially across s-central VT. As a
result, fog should be relatively limited compared to last night.

With high pressure in firm control Sunday expect another quiet
day to start. The upper level trough will still be east of the
the Great Lakes mid day so while clouds should be on the
increase during the day, precip will be slower to arrive. The
flow aloft will be generally northwest with northeasterly
surface flow. The weak cool air advection and increase cloud
cover should only allow the temps to warm to the mid 70s on

Heading into the evening hours the upper level clouds low will
continue to track over the Great lakes and a meso low will
develop over Lake Ontario. That meso low will ramp up shower
activity quickly and should lead to widespread showers over
northern New York late Sunday night.


As of 332 PM EDT Saturday...Low pressure system will bring
showers and possible thunderstorms to the North Country Monday
through Tuesday. Surface low pressure will approach from the
southwest as a mid level trough digs into the eastern Great
Lakes during the day Monday. PWATs will climb to around 1.25" as
low level deformation increases with approaching low. While
moist environment will be in place, CAPE will be lacking over
most of VT and 500-1000 J/kg over northern NY on Monday. Expect
thunderstorms to affect northern NY with just showers over VT.
SE to easterly winds around 925-850mb could result in some
downsloping and slightly less POPs in the leeward valleys.
Overcast skies, rain showers, and decreasing 925mb temperatures
on Monday, expect maxes in the 60s.

Monday night into Tuesday will see surface low near Lake
Ontario translate some of its energy to a coastal low off the
Jersey coast. While this coastal low takes the bulk of moisture
with it ENEwd out to sea, the 500mb trough will move across the
North Country on Tuesday, resulting in more showers.
Temperatures still below normal with Monday nigh min in the 50s
and Tuesday max in the upper 60s to mid 70s.


As of 332 PM EDT Saturday...Expect the 500mb trough to move
east of VT by 00Z Wednesday with high pressure building at the
surface. Clearing skies Tuesday night could lead to areas of
patchy fog. Drier air filters in with PWATs falling to 0.5-0.75
Tuesday night into Wednesday. Wednesday will be dry and warmer
with maxes in the mid 70s to around 80.

Ridge of surface high pressure slides east Wednesday night,
putting the North Country in south to southwest flow. A surface
cold front is progged to move into the St Lawrence Valley for
the latter half of Thursday, producing showers and
thunderstorms. This will continue into Thursday night as the
cold front continues to cross the region.

Model guidance diverges as the ECMWF stalls the frontal
boundary over New England Friday as energy rides along the front
and develops into a surface low. This low strengths and moves
northward over western New England resulting in a wet weekend.
On the other hand, the GFS builds high pressure into northern
New England through the rest of the period.


Through 18Z Sunday...Mainly VFR conditions are expected through
the period. SCT-BKN cirrus deck around 20kft will continue to
stream over the area today with some fair weather cumulus
developing over the mountains. A weak frontal boundary may
provide an isolated shower or storm across southern Vermont
through the evening but the chances remain small so I opted not
include any mention of VCSH. As we lose the diurnal heating, the
fair weather cu will dissipate and we should go back to partly
cloudy skies. IFR fog still remains a possibility for SLK/MPV
and the feeling is that visibility`s will jump up and down with
periods of mvfr/ifr 2-4SM visibility`s generally between 8z-


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




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