Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 241924
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
324 PM EDT Sat Sep 24 2016

.SYNOPSIS...
High pressure building southward from James Bay will continue to
bring dry weather to the area through Monday, along with
unseasonably cool temperatures. Tonight will be the coldest night
of the young fall season thus far, cold enough for frost to
develop over a good portion of the area. Sunday will feature full
sunshine and lighter winds, although temperatures will be slightly
cooler than Saturday.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 151 PM EDT Saturday...Well fall has certainly arrived with
temperatures struggling today to bump out of the mid 50s to low
60s this afternoon. We`ve seen a good deal of fair weather cumulus
form through the day on modest north to northwesterly flow, but as
high pressure drifting southward from James Bay continues to build
into the area this evening, we should skies trend towards clear
after sunset setting the stage for the coldest night of the young
fall season thus far. Clearing skies, abating winds and temps
aloft falling below 0C will combine to produce low temperatures
tonight into early Sunday morning ranging through the 30s to
locally lower 40s along the Lake Champlain shoreline and Grand
Isle County. For most areas outside of the Champlain Valley, this
setup will support the idea of patchy to areas of frost forming,
enough to continue the previously issued frost advisory, but also
hoist an advisory for the St. Lawrence Valley and all of southern
Vermont. Additionally, temperatures will drop to right around
freezing for portions of Essex County of Vermont, so I`ve gone
ahead and upgraded to a freeze warning there. Those with
agricultural interests in the warned area are advised to harvest
or protect tender vegetation left outdoors.

Fog will also be a good bet in the climo favored river valleys
tonight, which could affect the potential for frost in some areas.
Really tricky to forecast whether the fog or colder temperatures
will win out, or if both will occur. I`ve seen all three scenarios
happen, so for now will just go with both!

For Sunday, the aforementioned area high pressure continues to
build right over the North Country. This should result in lighter
winds than today, along with sunnier skies after any morning fog
burns off. Unfortunately, 925-850mb temps cool slightly, only
supporting highs in the mid 50s to low 60s, a couple degrees
cooler than today. With more sunshine though, it shouldn`t feel
that bad so get out and enjoy those harvest festivals!

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 324 PM EDT Saturday...Ridge of high pressure at the surface
with building ridge aloft will lead to clear skies, light to calm
winds and good radiational cooling conditions. 925mb temps of 3-5C
will result in morning low temps at the surface in the mid/upper
20s to low 30s in the high terrain and low to upper 30s in the
broad valleys. Tricky part of where lowest temps will occur will
be somewhat dependent on fog formation. Expect some areas to see
freezing fog, mainly in portions of the Adirondacks and Northeast
Kingdom. Otherwise, widespread frost/freeze possible.

Large closed mid-level low over the Great Lakes region will
approach, with clouds moving into the North Country ahead of it
during the day Monday. At the same time, 500mb ridge will crest
over the forecast area, keeping conditions dry before the large
mid-level low arrives. Winds will shift out of the south with max
temps in the 60s. Precip arrives from west to east Monday night
with PWATs increasing to over 1 inch and SSW low level jet of
30-40 kts at 850mb. This will likely result in enhancement of
showery activity on SW facing slopes and some shadowing on leeward
side. Also gusty winds esp in the high terrain will result.

Temperatures will be noticeably warmer Monday night with clouds
and winds...expect lows in the 40s to low 50s.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 324 PM EDT Saturday...On Tuesday the 500mb closed low
traverses across the central to southern Great Lakes as it digs
southward with a dry slot moving into the North Country ahead of
this low, behind the cold front which brings showers Monday night
into Tuesday. This will result in bulk of rain showers exiting
east during Tuesday afternoon. Low level jet will also exit east
and PWATs look to decrease late in the day. As the mid level low
digs southward into the Ohio River Valley Tuesday night into
Wednesday, 500mb vort will break off into northern stream and
southern stream. High pressure at the surface and bulk of energy
either far to the south or north, expect mostly dry conditions
Wednesday through Friday night, possibly into Saturday. ECMWF and
GFS differ on the evolution and track of the southern stream
energy. ECMWF has it become a closed low and meanders over the
southern Appalachians late in the period.

&&

.AVIATION /19Z Saturday THROUGH Thursday/...
Through 18Z Sunday...SCT-BKN cumulus around 050-060 this afternoon
will trend towards SKC after 00z with primarily VFR conditions
continuing through the next 24 hours. Exceptions will be the
potential for VLIFR fog at KMPV/KSLK from 05-14z, where I`m more
confident at KMPV whereas at KSLK sub-freezing temperatures may
mitigate fog development. Winds a little gusty from the north this
afternoon will trend light overnight, and pick back up from the
northwest around 8-10kts after 14z Sunday.

Outlook 18z Sunday through Thursday...

18z Sun - 00z Tue: Mainly VFR. Overnight IFR with patchy fog possible.

00z Tue - 00z Wed: VFR trending to a mix of VFR/MVFR in scattered showers.

00z Wed - 00z Fri: Mainly VFR with isolated MVFR cigs.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Freeze Warning from 2 AM to 8 AM EDT Sunday for VTZ004.
     Frost Advisory from 2 AM to 8 AM EDT Sunday for VTZ003-006>008-
     010>012-016>019.
NY...Frost Advisory from 2 AM to 8 AM EDT Sunday for NYZ026-027-
     029>031-034-087.

&&

$$
SYNOPSIS...Lahiff
NEAR TERM...Lahiff
SHORT TERM...KGM
LONG TERM...KGM
AVIATION...Lahiff



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