Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 232323

Area Forecast Discussion
National Weather Service Burlington VT
723 PM EDT Tue May 23 2017

Weak high pressure across the northeastern United States brings
tranquil weather conditions across the North Country through
tonight. There may be patchy fog development in some of the
favored river valleys overnight, especially east of the Green
Mountains. A weak upper level disturbance may bring isolated
rain showers or a thunderstorm Wednesday afternoon, mainly
across the higher terrain areas. Temperatures will continue to
moderate Wednesday, with afternoon highs into the mid 70s in
most sections. A more significant low pressure system evolving
across the Ohio Valley and mid-Atlantic region will bring
potential for a more widespread rainfall to the North Country
Thursday afternoon through Friday.


As of 623 PM EDT Tuesday...Minor update this evening to
introduce somewhat more clouds across the northwestern counties
per latest satellite imagery and sfc observations. A very weak
surface trough draped across the SLV is also producing widely
scattered light showers or sprinkles as of 22Z and have
introduced just an outside shot of a shower along the intl
border from the Green Mtn spine west through 8-9 pm or so. Some
higher res output, most notably the BTV 4 km WRF also suggesting
a brief sprinkle/light shower may affect the northern Champlain
Valley in this time frame as well, but given lack of returns
currently have downplayed this scenario. The rest of the
forecast remains in great shape. Have a great evening.

Prior discussion...
Tranquil weather expected tonight with dry conditions and light
winds. Weak high pressure across the mid-Atlantic coast remains
the controlling weather feature overnight. Seeing a mix of sct
fair weather cumulus clouds and some thin cirrus this afternoon.
The cumulus clouds will dissipate with onset of diurnal cooling
this evening. It appears we`ll be within a relatively cloud
free axis tonight extending from wrn PA newd across nrn NY/VT.
As such, could see enough radiative cooling to reach crossover
temps, leading to patchy fog development 06-11Z in the favored
river valleys east of the Green Mtn spine, as well as within the
nrn Adirondack region. Overnight lows generally expected mid-
upr 40s across the ern half of VT, and within the nrn
Adirondacks. Should see lows around 50F in the immediate
Champlain and St. Lawrence valleys.

Low pressure develops east of NJ Wednesday morning, with mid-
level vort axis lifting nwd across NY and New England.
Meanwhile, at low levels, surface heating should generate some
sfc-based CAPE (100-300 J/kg), especially across the higher
terrain. Combination of subtle mid-level forcing and surface
based instability should result in isold showers and perhaps a
thunderstorm across the higher terrain of the Adirondacks and
Green Mtns Wednesday aftn. Mentioned a slight chance across
valley locations (20 PoPs) with PoPs closer to 30% across the
higher terrain. Overall low-mid level flow fields are weak, so
any convective activity that does develop should be relatively
slow moving. A few mountain locations may see 0.10-0.20"
precipitation with this activity. Highs Wednesday generally in
the low-mid 70s. Any diurnal SHRA/TSRA activity should dissipate
toward evening.

Large closed mid-upr level low across the OH/TN valleys will
slowly shift ewd Wednesday night, bringing increasing clouds,
and a slight chance of rain toward daybreak across nrn NY. The
increased clouds will mitigate radiative cooling with lows
50-55F in most sections.


As of 326 PM EDT Tuesday...Brief period of quiet weather ends
on Thursday as the pattern becomes active again to end the work
week. The morning will begin dry with high pressure holding
strong, but as low pressure over the Ohio Valley begins to shift
northeast into the eastern Great Lakes, deep layer moisture
along an approaching warm front will spread showers from
southwest to northeast across the North Country. Rainfall should
be relatively light with daytime amounts only in the 0.10-0.25"
range and temps topping out in the 60s to perhaps low 70s. Late
Thursday afternoon into early Friday night the forecast becomes
a bit more uncertain in regards to precip potential as models
are trending towards a weak mid-level dry slot building over
southern/central portions of the area as the low transfers
energy to the southern New England coastal waters and the deeper
warm frontal moisture shifts northward. During this time a
strong low/mid level east/southeasterly jet of 35-45kts develops
and while the window for mixing these winds to the surface is
narrow, the potential exists for wind gusts of 30-45 mph along
the downslope communities of the western slopes of the Green
Mountains in Chittenden, Addison and Rutland counties. That
window closes quickly towards midnight though and through the
remainder of the night as the upper level and surface low
consolidate and strengthen over Cap Cod advecting a moist stable
marine layer into the region with rainfall becoming prevailing
across the majority of the region right through Friday
afternoon. Additional rainfall amounts of 0.25-0.75" are
expected with mild lows in the 50s Thursday night, and cooler
highs in the 50s for Friday.


As of 326 PM EDT Tuesday...Coastal low pressure exits east
Friday night and in its wake surface high pressure and a
somewhat flat upper ridge build into the Northeast for Saturday
and Saturday night offering dry conditions and seasonal
temperatures. Sunday looks to be mostly dry as well as deepening
upper level low pressure over the northern Plains amplifies the
ridge over the Northeast Sunday morning, but increasing
moisture advection on southwesterly flow combined with bits of
shortwave energy ejecting out of the upper low will renew chance
as for showers and possibly thunderstorms Sunday afternoon.
Best chance for widespread rain during the period comes Sunday
night through Monday as the upper low shifts over the Great
Lakes, with continued chances Tuesday as the low barely moves
east and the region remains unsettled.


Through 00Z Thursday...Generally VFR conditions with light
winds expected throughout the TAF period. SCT/BKN cigs in the
060-090 AGL range expected this evening into tonight with
thickening higher deck above 200 AGL pushing in from the
southwest later tonight. An isolated light shower or sprinkle
will be possible at KMSS/KPBG/KBTV through 01Z, but paucity of
coverage warrants ommision from the forecast at this point.
After 14Z Wednesday SCT/BKN VFR cigs continue with persistent
BKN higher overcast under light wind regime. Isolated to widely
scattered showers and a possible thunderstorm will be possible
after 18Z, but mainly focused across higher terrain. Again, lack
of areal coverage warrants omission from the current terminal
forecasts at this point.


Wednesday Night: VFR. SCHC -SHRA.
Thursday: VFR. Breezy. Chance SHRA.
Thursday Night: VFR/MVFR. Definite RA.
Friday: MVFR. Definite RA.
Friday Night: VFR. Slight Chance SHRA.
Saturday: VFR. Slight Chance SHRA.


The WSR-88D at Burlington, VT (KCXX) will be unavailable from
Tuesday May 23, 2017 through Friday May 26, 2017.

During the outage, radar coverage is available from adjacent
radar sites including Montague, Albany, and Buffalo, NY and Gray

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