000
FXUS61 KBTV 211808
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
208 PM EDT Thu Sep 21 2023

.SYNOPSIS...
High pressure will continue to build across the forecast area
through the end of the week, resulting in warm, sunny days and
clear, chilly nights featuring fog in river valleys and potentially
even some isolated frost in the Adirondacks. A low pressure system
will likely approach the area during the weekend, increasing cloud
cover, but uncertainty remains on whether we`ll receive any rain
showers from this system.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 156 PM EDT Thursday...Minimal changes necessary with the
forecast on track. High pressure is evident with mostly clear
skies and temperatures warming around seasonal averages.
Questions of frost extent remain, but dew points at 2 meters are
rising marginally as soil moisture evaporates. This should set
the stage for cooler sub-2 meter temperatures overnight.
Sheltered valleys in the Adirondacks could see a repeat of frost
formation.

Previous Discussion...Main adjustments were to decrease dew
point temperatures and modify air temperatures to better match
observations trends. The big question for today will be whether
dew points continue to dry as mixing occurs and modifies
boundary layer moisture. There is a case that this will support
temperatures as cold tonight in some locations meaning frost
could be a concern in the Adirondacks again. With high pressure
overhead, persistence usually wins out.

Previous Discussion...No major updates with this update as the
forecast is on track. Some minor tweaks to sky cover where
there`s some very thick fog lifting up. We can anticipate
temperatures rising to the mid-60s to lower 70s today with
plentiful sunshine under high pressure. Previous discussion
below:

Previous discussion...High pressure keeps the region fairly
quiet weather-wise through Friday. Today will feature seasonable
highs in the mid-60s in the Adirondacks and Northeast Kingdom and
lower 70s for the wider valleys with a slight warming trend tomorrow
- highs instead in the upper 60s to lower 70s, warmest in the wider
valleys. Otherwise sunshine will be abundant both days and winds
will be light. Tonight will be chilly with the lack of insulating
clouds and lows should drop into the lower/mid-30s in the cold spots
of the Adirondacks to mid-40s close to the mild waters of Lake
Champlain. It won`t be as chilly as last night, but there could
still be some isolated frost or freezing fog developing in the
Saranac Lake area of Franklin County, NY. Elsewhere, regular fog
will likely be plentiful once more under such clear skies and high
pressure, especially in river valleys.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY/...
As of 402 AM EDT Thursday...High clouds should begin to overspread
the North Country from south to north on Friday night as closed mid-
level low tracks northward from the Carolinas into the mid-atlantic
coast. Per NHC, system may acquire some subtropical characteristics
during this time frame, which should bring a strong poleward
moisture flux and surge of high precipitable water values northward
into southern New England by 12Z Saturday. Where the 00Z NWP
differences is whether this moisture plume can advect further north
into our area later in the day Saturday. The 00Z GFS suggests enough
of a blocking ridge to our north to limit the northward movement of
lower clouds and shower activity. Meanwhile, the 00Z ECMWF and
especially the 00Z Canadian are more aggressive in moving rain into
our region Saturday afternoon into Saturday evening. For now, have
kept the forecast closer to the 00Z GFS and GFS ensemble, which is
also closer to continuity from the previous forecast keeping bulk of
precipitation to our south during the forecast period. This means
just a slight chance of rain showers (20% PoPs) Saturday
afternoon/early evening across Rutland/Windsor counties, with dry
conditions further north.

Should see low temperatures Friday night mainly in the 40s, except
lower 50s in the Champlain Valley. On Saturday, the warmest
temperatures are likely in the northern Champlain and St. Lawrence
Valleys where some filtered sunshine is expected. Highs in these
valleys will generally reach the lower 70s. Meanwhile, thicker cloud
cover should keep highs in the 65-70F range across central and s-
central VT, as well as the nrn Adirondacks.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 402 AM EDT Thursday...Per short-term discussion, main question
will be northward translation of closed, deep-layer low pressure
system and associated moisture along the mid-Atlantic coastline, and
its interaction with a blocking high across Ontario and swrn Quebec.
NWP suite continues to show a variety of solns, with interaction
with a northern stream upper level low also a complicating factor.
Blend of deterministic and ensemble mean solutions appears to be
best forecast attm, which brings light precipitation into
Rutland/Windsor and possibly Orange county in s-central VT, but not
much further north as moisture is shunted to the east. Indicated max
PoPs of 30-40% attm across s- central VT Saturday night, before
decreasing PoPs during the day Sunday with current expectation that
bulk of precipitation shifts to our south and east. We`ll continue
to monitor these trends. Rainfall amounts attm <0.1" across
s-central VT.

Drier/quieter weather returns for Monday/Tuesday with a surface
ridge over Quebec and a dry northerly flow. High temperatures in the
mid-upper 60s are generally expected for Monday/Tuesday.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Through 18Z Friday...VFR conditions under high pressure will
prevail during daylight hours. Fog is expected to reform
overnight as surface radiates out heat. The usual suspects of
SLK/MPV should have no problem fogging in with LIFR conditions
despite being displaced another day from rainfall. However,
chances will be more marginal for fog at EFK/MSS/RUT. BTV/PBG
should stay out of fog, but expect river fog along the Winooski
to be present just north/northeast of the BTV terminal. Another
day or VFR will occur with fog/stratus lifting and scattering by
14-15Z.

Outlook...

Friday Night: VFR. NO SIG WX.
Saturday: VFR. NO SIG WX.
Saturday Night: VFR. Slight chance SHRA.
Sunday: VFR. Slight chance SHRA.
Sunday Night: Mainly VFR, with local MVFR possible. NO SIG WX.
Monday: Mainly VFR, with areas MVFR possible. NO SIG WX.
Monday Night: Mainly VFR, with areas MVFR possible. NO SIG WX.
Tuesday: MVFR. NO SIG WX.

&&

.EQUIPMENT...
The KCXX radar will be down for radome repairs, with a return to
service around September 21st.

&&

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

&&

$$
SYNOPSIS...Storm
NEAR TERM...Boyd/Storm
SHORT TERM...Banacos
LONG TERM...Banacos
AVIATION...Boyd/Storm
EQUIPMENT...WFO BTV