Area Forecast Discussion
Issued by NWS Burlington, VT

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247
FXUS61 KBTV 192337
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
737 PM EDT Sat Oct 19 2019

.SYNOPSIS...
Dry weather is expected to persist through Monday night as weak
high pressure remains in control of our weather. As we head
into Tuesday, a strong frontal system will move through the
region and widespread rainfall is expected across the North
Country. Showers will persist through the remainder of the week
but they should be fairly scattered and short-lived. Overall,
after Tuesday the remainder of the week looks pretty nice with
near normal temperatures.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
As of 727 PM EDT Saturday...No changes for 730 pm update this
evening, going forecast is in good shape.

Some pesky low clouds have persisted across the northern
Adirondacks and northern Vermont this morning as some moisture
trapped below a surface inversion has had a difficulty mixing
out. Looking at the most recent satellite imagery, it finally
looks like these low clouds are beginning to mix out thanks to
the increasing sun angle this afternoon. This should yield
mostly clear skies by sunset tonight as some weak dry air
advection is noted in the latest RAP data. Temperatures will be
quick to drop tonight with winds becoming nearly calm after
sunset and clear skies persisting. However, we should see
increasing cirrus clouds ahead of post- tropical storm Nestor
and the upper level trough to our west. The increasing cloud
cover should limit radiational cooling after midnight which
should keep temperatures from bottoming out. Because of this,
have increased overnight lows across much of the forecast area.
Widespread frost is still expected across the Champlain Valley
with nearly calm winds and temperatures in the upper 20s to mid
30s.

In addition to the increasing cloud cover, the latest HRRR, RAP
and NAM3 have begun to show an increasing pressure gradient
across northern New York after midnight. It won`t be a lot of
wind but it should be enough to prevent fog development in fog
prone areas of northern New York. The fog prone areas of eastern
Vermont still look likely to fog in as the increasing flow
aloft shouldn`t make it that far east until after sunrise.

Sunday should be another nice day across the North Country as
afternoon high temperatures will be 5-8 degrees warmer than
those observed today. Even though a blanket of cirrus clouds
will move through the region during the daylight hours, warm air
advection associated with increasing mid-level heights and
thicknesses will drive the warming trend on Sunday. It still
looks like the bulk of the moisture associated with post-
tropical Nestor will remain well to our south and have continued
to decrease PoPs in response to this trend. As we head into
Sunday night, we will find ourself in an area of weak flow with
a sharpening upper level trough over the midwest and post-
tropical Nestor to our east. This could set us up into a
favorable pattern for fog Sunday night but details with this
will be ironed out in the next day. With the southwest warm air
advection regime continuing into the overnight hours, lows on
Sunday night will be warmer than tonight with lows in the lower
30s to near 40 degrees.

&&

.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 314 PM EDT Saturday...Another dry day in store for Monday
as high pressure gradually retreats to the northeast. As the
day progresses, southerly gradient flow will increase ahead of
an approaching system to the west. Highs will generally be in
the low 60s. Monday evening, high clouds will spread over the
region, thickening and lowering through the night. Increasing
warm air advection overnight will limit diurnal cooling, with
lows over northern NY and the Champlain Valley noticeably warmer
than previous nights. Meanwhile further east, eastern Vermont
will be the last to feel the effects of the developing WAA...and
can expect cooler lows in the upper 30s. Winds Monday night are
rather tricky to forecast. A 40+ kt LLJ will move over area,
but for the most part not expecting this momentum to transfer to
the surface with such strong WAA during the overnight hours.
However, any shallow mixing that develops near sunrise could
start to bring down some gusty winds to lower elevations.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 314 PM EDT Saturday...A vertically-stacked low pressure
system centered over western Ontario will push a cold front
eastward through the forecast area late Tuesday into Tuesday
night. At the same time, a fairly robust shortwave will round
the base of the upper-level low, becoming slightly negatively
tilted as it rotates through New England. Ahead of the boundary,
increasing southerly flow will result in some gusty southerly
winds (mainly in the 15 to 25 mph range for gusts) during the
day Tuesday before the rain starts. The increasing southerly
flow/moisture transport ahead of the boundary will feed into a
region of moderate ascent over the North Country, resulting in a
wetting rainfall as the boundary moves through later Tuesday
into Tuesday night. However, low-level convergence along the
front is not overly impressive given the occluding nature of the
boundary with southwesterly flow to the west. In addition,
depending on timing of front, upper jet placement may not be
conducive to the best lift.

One wildcard that will have to be watched closely in this setup
will be the potential interaction of the trough moving in from
the west with the remnants of Nestor to our east. While Nestor
itself will stay well offshore as it tracks northeastward over
the western Atlantic Monday through Tuesday, the system will
steer onshore flow towards New England. This increases the
potential moisture advection into the region ahead of the cold
front , although at this point it`s unclear how much additional
moisture will make it this far north and west of the coast. Will
be keeping a close eye on the interaction between Nestor and
the system approaching from the west, but for now doesn`t look
like Nestor will have much of an impact on the BTV forecast
area.

By Wednesday morning, front will be to our east and post-
frontal southwesterly flow will commence. The upper-level low
will continue to send numerous shortwaves through the
northeastern US Wednesday through Thursday night. This will keep
some clouds and potential for some spotty light showers in
place, especially in the lee of Lake Ontario where moisture will
be locally enhanced. The unsettled, showery pattern will
continue through the week. Chances for more widespread
precipitation return over the weekend as a low pressure system
potentially tracks into the area, although details are murky
this far out.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Through 00Z Monday...All terminals are starting VFR tonight.
Skies are clear and winds mainly light. Fog still looks likely
at MPV and eastern Vermont as the winds won`t make it in until
12Z-14Z. VFR conditions will once again persist on Sunday with
winds shifting to the southeast after sunrise.

Outlook...

Sunday Night: VFR. NO SIG WX.
Monday: VFR. NO SIG WX.
Monday Night: VFR. NO SIG WX.
Tuesday: Mainly VFR, with local MVFR possible. Likely SHRA.
Tuesday Night: Mainly VFR, with areas MVFR possible. Definite
SHRA.
Wednesday: Mainly VFR, with areas MVFR possible. Chance SHRA.
Wednesday Night: VFR. Slight chance SHRA.
Thursday: Mainly VFR, with local MVFR possible. Slight chance
SHRA.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Frost Advisory from midnight tonight to 9 AM EDT Sunday for
     VTZ001-002-005-009.
NY...Frost Advisory from midnight tonight to 9 AM EDT Sunday for
     NYZ028-035.

&&

$$
SYNOPSIS...Clay
NEAR TERM...Clay/Neiles
SHORT TERM...Duell
LONG TERM...Duell
AVIATION...Clay/Neiles



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