Area Forecast Discussion
Issued by NWS Burlington, VT

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493
FXUS61 KBTV 290030
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
830 PM EDT Mon Sep 28 2020

.SYNOPSIS...
Mild and moist weather continues tonight before widespread
rainfall associated with a cold front arrives through the
daylight hours on Tuesday. Steadier, at times heavier, rainfall
will be possible Tuesday night into Wednesday morning as the
front passes. Behind this feature conditions trend cooler with
scattered showers into late week before dry and seasonably cool
weather arrives for next weekend.

&&

.NEAR TERM /THROUGH TUESDAY NIGHT/...
As of 754 PM EDT Monday...Few changes needed to this evening`s
update as the going forecast is in good shape. Slight
adjustments were made to the wind/wind gust forecast in which
winds were decreased along the Champlain Valley and across Lake
Champlain according to observations. However, south winds are
expected to increase again during the early morning hours
Tuesday, increasing to 15-25 knots with gusts in the 25-35
knot range. Otherwise, the forecast remains on track. See
previous discussion below.

Previous Discussion...The forecast remains on track for the
next 36 hours. Mild and moist southerly flow continues tonight
with unseasonably mild lows from the upper 50s to mid 60s, and
locally near 70 at KBTV. Variable clouds along with partial
breaks can be expected, with clouds and rainfall chances
increasing across the SLV toward morning as a cold front
approaches from the west. The front will then track slowly east
into the forecast area on Tuesday into Tuesday night with
widespread rainfall expected. Highest threat occurs Tuesday
night when a fairly robust wave of low pressure rides northward
along the boundary. Excellent upper dynamical support and PWATS
into the 1.5 to 1.75 inch range argue for occasional heavier
downpours. With recent drought/dryness, the threat of flooding
appears minimal at this point (see hydro discussion below).
Highs on Tuesday ease back somewhat given clouds and arrival of
cooling rainfall (mainly 60s west and 70s east). Then seasonable
low in the 50s Tuesday night.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of 319 PM EDT Monday...Heaviest and most widespread rain
will be over Vermont Wednesday morning and move eastward out of
the area during the day. Will remain a bit showery through the
day though, as upper level trough still remains over the north
country and shortwave energy rotating through base of trough
continues but deepest low and mid level moisture moves out of
our area. Temperatures on Wednesday will be very close to
seasonal normals, mainly reaching the lower 60s. Temperatures
will remain pretty mild overnight with clouds still remaining
and some scattered light showers possible, lows mainly ranging
through the 40s to around 50.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 319 PM EDT Monday...Weather will remain somewhat
unsettled through much of the long term portion of the forecast
as upper level trough will be very stubborn to push eastward. It
does finally flatten out towards the beginning of next week. We
start to see cooler air aloft moving into the region on Friday
associated with large upper trough becoming established. This
should lead to instability driven showers and forecast soundings
for Friday show dry adiabatic lapse rates to at least 600
millibars indicating instability will be sufficient for
convective showers. Warming aloft going into the weekend along
with drying of the air mass suggests convective precipitation
threat becomes limited and have either dry conditions or a
slight chance of showers. Temperatures over the weekend should
be a few degrees below normal for this time of year. ECMWF and
Canadian models continue to hang onto solution showing yet
another wave lift up across our area in the Saturday timeframe,
but they`re sort of alone on this feature. Something to keep an
eye on though.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Through 00Z Wednesday...VFR conditions are expected at all
terminals through the overnight hours, with cigs lowering to
MVFR after 12z Tuesday morning as a cold front approaches from
the west. Currently, there is mostly clear skies across the
North Country, though few mid-level clouds (4,000-6,000 ft AGL)
are lingering along the higher terrain. South winds will remain
light (5-10 knots) through 06z, after which time southerly winds
will increase to 10-15 knots. Stronger south/southwest flow
aloft will lead to a period of LLWS up to 40 kts at
KMSS/KSLK/KRUT/KMPV generally in the 00-12Z time frame in
advance of the cold front advancing slowly eastward. The front
will bring an increasing threat of -shras after 12Z to KMSS and
KSLK, and generally around 18Z at eastern terminals. Scattered
MVFR cigs are possible with this activity, beginning around 12z
at KMSS and KSLK, then spreading eastward thereafter.

Outlook...

Tuesday Night: Mainly MVFR, with local IFR possible. Definite RA.
Wednesday: MVFR/IFR conditions possible. Definite RA, Chance
SHRA.
Wednesday Night: VFR. Chance SHRA.
Thursday: VFR. Chance SHRA.
Thursday Night: VFR. Slight chance SHRA.
Friday:  Chance SHRA.
Friday Night:  Slight chance SHRA.
Saturday:  Slight chance SHRA.

&&

.HYDROLOGY...
As of 305 PM EDT Monday...Widespread rainfall on the order of 1
to 2 inches is expected across the region from Tuesday
afternoon into Wednesday morning. Rain may fall heavy at times
but hourly rates are not expected to be excessive. Additionally,
given recent dryness the absorption capacity of upper soil
layers is quite high so the potential for higher runoff is quite
low. This is reflected in the latest ensemble river forecast
guidance showing the threat of mainstem river and small stream
flooding is minimal at this point.

&&

.MARINE...
As of 754 PM EDT Monday...Southerly winds have decreased,
dropping to 10-20 knots across Lake Champlain. For such reasons,
the Lake Wind Advisory has been cancelled. However, south winds
are expected to increase during the early morning hours on
Tuesday, increasing to 25-30 knots with gusts up to 35 knots.
Therefore, another Lake Wind Advisory is anticipated on Tuesday
morning. Ultimately, choppy to rough water conditions are
expected. The gustiest winds and highest waves (3-5 ft) will
occur on the broad lake and in inlets/bays with southerly
exposures. These conditions may prove hazardous to small craft
and inexperienced mariners. Winds will abate by Tuesday
afternoon with the approach of a cold front and the stabilizing
effects of rainfall.

&&

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

&&

$$
SYNOPSIS...JMG
NEAR TERM...Hammond/JMG
SHORT TERM...Neiles
LONG TERM...Neiles
AVIATION...Hammond/JMG
HYDROLOGY...JMG
MARINE...Hammond/JMG



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