Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 270727
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
327 AM EDT Sat May 27 2017

.SYNOPSIS...
The low pressure system that brought all the rain to the North
Country over the past 24 to 36 hours continues to move eastward.
This will allow showers to come to an end tonight...but plenty of
cloud cover will exist. Areas of fog are expected to develop as
well. Otherwise...the news is good with respect to the Memorial Day
Weekend as dry weather is expected for Saturday and Sunday along
with a warming trend. At this time it does look like showers will
return to the area late Sunday night into Memorial Day.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 645 PM EDT Friday...Minor update to match current
observational trends and to align pops more in tune with most
recent HRRR/BTV 4km WRF output through the midnight hour or so.
This continues to suggest a gradual tapering off of showers this
evening, leaving a largely dry forecast later tonight. Did opt
to confine threat of fog across mainly the western Dacks into
the SLV overnight where lighter low level wind profiles exist
and some partial clearing may arrive in the pre-dawn hours. The
rest of the forecast remains on track and unchanged. Have a
great evening.

Prior discussion...
Upper low in the Gulf of Maine late this afternoon will
continue to move eastward tonight. This will help to bring
showers to an end later tonight...but based on satellite imagery
see no reason why we do not stay cloudy all night. Plenty of
low level moisture will exist and cannot rule out the
development of some fog and have included in the forecast for
later tonight...mainly after midnight. Lows tonight should be in
the mid 40s to lower 50s.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY/...
As of 328 PM EDT Friday...Will see another pattern change
beginning Sunday night as 700mb shortwave ridge translates ewd into
the Gulf of Maine and broad/closed mid-tropospheric low shifts
slowly ewd across the Great Lakes region and Ontario. Onset of
mid-level height falls and developing cyclonic flow aloft occurs
during Sunday night, though the 00Z ECMWF is about 6 hrs slower
than 00z GFS with arrival of shortwave trough/vorticity max
embedded in swly flow moving into the North Country. Have gone
with more consistent GFS timing for now, which means likely PoPs
(70%) for showers into nrn NY during the pre-dawn hrs Monday,
with chance PoPs (30-50%) across VT. It appears that best
synoptic/QG forcing will occur during Monday morning, with
widespread shower activity associated with strongest 850mb WAA.
Overall QPF generally 0.25" - 0.50". Should see partial clearing
occurring later in the day Monday as 850mb warm front shifts
north and east of the region. Can`t rule out a few additional
late day showers with weak surface based instability possible.
Have included slight chance of thunderstorms late in the
afternoon for the St. Lawrence Valley area and s-central VT. 00Z
GFS SBCAPE values reach 600 J/kg at KMSS at 21Z/Mon. In terms
of temperatures, the increasing clouds will keep overnight lows
mild Sunday night, generally in the low-mid 50s (except upper
50s in the St. Lawrence Valley). There is an increase in S-SW
gradient flow, reaching 10-20 mph after midnight in the
Champlain and St. Lawrence Valleys. This will also help with
low-level mixing, keeping temperatures from dropping
significantly. A lake wind advisory may ultimately be needed for
Lake Champlain later Sunday night into Monday morning
associated with this increase in southerly gradient winds. With
only partial clearing expected later Monday, high temperatures
will range from the low-mid 60s across central/ern VT, the upr
60s in the Champlain Valley, and mid 60s (Adirondacks) to lower
70s (St. Lawrence Valley) across northern NY.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 328 PM EDT Friday...Large mid-upper level low pressure
system will be our controlling weather feature through much of
the long-term period. This vertically stacked system will
drift slowly ewd from the nrn Great Lakes/Ontario Monday night,
ewd into wrn Quebec by Thursday. Northern NY and New England
will be embedded in associated cyclonic flow, with several
shortwave troughs crossing the region from WSW-ENE Tuesday
through Friday. It appears the best chance for shower activity
will generally be during afternoon periods, with combination of
relatively steep mid-level lapse rates and surface heating
resulting in shallow instability and shower development. Have
indicated likely PoPs Tuesday afternoon, followed by 30-50%
chances for Wed/Thu/Fri afternoon. Temperatures will generally
reach the low-mid 70s on Tuesday, followed by upr 60s to lower
70s Wednesday, and mid-upr 60s on Thursday as thermal trough
aloft gradually shifts ewd into our region. Min temperatures
will range from the upr 40s to mid 50s...close to seasonal
averages for late May.

&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
Through 06Z Sunday....Mix of conditions around the area
overnight with stations ranging from VFR down to LIFR. KMSS is
on the bottom end with LIFR vis/cig lasting until about 13Z
before improving to VFR. KSLK/KMPV/KRUT are currently MVFR but
could see periods of IFR through 13Z before also improving to
VFR. KBTV/KPBG are both currently VFR but may experience some
brief MVFR conditions before sunrise.

Winds generally out of the NW but remaining light overnight.
Wind speeds will pick up to 5-10 knots during the day.

Outlook...

Sunday: VFR. NO SIG WX.
Sunday Night: VFR. Breezy. Likely SHRA.
Memorial Day: MVFR. Breezy. Likely SHRA...TSRA.
Monday Night: VFR. Chance SHRA.
Tuesday: VFR. Likely SHRA...TSRA.
Tuesday Night: VFR. Chance SHRA.
Wednesday: VFR. Chance SHRA...TSRA.

&&

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

&&

$$
SYNOPSIS...Evenson
NEAR TERM...Evenson/JMG
SHORT TERM...Banacos
LONG TERM...Banacos
AVIATION...KGM/MV


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