FXUS61 KBTV 301125

Area Forecast Discussion
National Weather Service Burlington VT
725 AM EDT Sun Apr 30 2017

Persistent, cool northerly flow along with increasing clouds
will keep max temperatures in the mid 40s to upper 50s across
the North Country today. A large strengthening low pressure
system over the Ohio valley region will lift a warm front
through New England bringing another chance for rain late today
into tonight. This low will continue the unsettled weather
through the mid week. Another low pressure system looks to affect
the region late in the week.


As of 725 AM EDT Sunday...Ridging aloft and at the surface will
start out the day before the ridge axis shifts east of the
North Country and warm front/surface trough moves over the area.
This will result in increased clouds and potential for rain
showers. Expect persistent northerly flow to also keep temps
cool during the day. Models continue to differ on placement of
the warm front...affecting how widespread rain showers will be
over the North Country. Expect best chances for showers will
start in the late morning/early afternoon across portions of
Northern New York. As the frontal boundary lifts north expect
showers to affect the St Lawrence Valley, Adirondacks, around
the international border, and the higher terrain late in the day
and continue to lift north of the international border during
the early evening. NAM and GFS show 500mb heights decreasing
with possible embedded vort bringing precip back southward
tonight...as far south as the Adirondacks, lower Champlain
Valley, and central Green Mountains. Towards Monday morning,
precip will lift northward again...ahead of cold front to our
west. Southerly winds settle in over most of the North Country
being in the warm sector, resulting in some breaks in clouds for
the Champlain Valley, eastern Adirondacks and south central
Vermont. However, NE winds channeling down the St Lawrence
Valley will keep temperatures cooler and more persistent clouds.
Eastern Vermont and the Northeast Kingdom will likely see a
similar situation with cooler temperatures and more stubborn
cloud cover.

The frontal boundary that is associated with closed surface low
around the Great Lakes Region on Monday will near the St
Lawrence Valley Monday afternoon, bringing showers and possibly
thunderstorms to the region as we head into Monday night.
Stronger low level jet looks to enter the southern St Lawrence
Valley towards the end of the period, providing potential for
gusty winds.

Temperatures throughout the period will start cool with near
normal temperatures this morning (low around 40 at BTV), will be
slow to warm today as colder northerly flow is in place and the
aforementioned warm front will be slow to lift into the North
Country and bring with it warming trend. Tonight, temperatures
look to be 5-10 degrees warmer that this morning as the warm
front lifts north and WAA settles in over the North Country.
Monday's max temperatures will vary widely. Areas remaining in
cooler NE flow (NEK and SLV) will reach 50s to low 60s, while
CPV and western slopes of the ADKS could see temperatures in the
upper 60s into the 70s.


As of 322 AM EDT Sunday...Very active period of weather
anticipated with sharp cold front and strong dynamics will
interact with weak low level instability parameters to produce a
fine line of low top convection on Monday Night. Latest
guidance continues to show surface based capes up to 500
j/kg...especially northern NY between 00z and 03z Tues...along
with strong low to mid level wind fields...resulting in 0 to 6
km shear values of 40 to 50 knots. Based on magnitude of low
level winds and height falls associated with approaching
mid/upper level trof...have bumped pops to 90 to 100% on Monday
night...with a line of showers with embedded convective elements
expected. A few localized wind gusts and brief heavy downpours
are likely...especially as pws surge between 1.00 and 1.50 ahead
of boundary. Qpf will range between 0.25 to 0.75...with
isolated amounts near 1.0 across the dacks/slv on Monday
night...where dynamics and instability parameters are the
strongest. Additional showers are likely on Tuesday associated
with mid/upper level trof approaching and embedded 5h vorts.
Thinking mid level dry slot will be impacting our cwa around 12z
Tuesday...but deeper moisture redevelops as mid/upper level
trof approaches by 18z Tuesday...with precip becoming terrain
focused on southwest flow. Have mention likely pops in the
mountains with chance in the valleys for Tuesday with an
additional one to three tenths of qpf possible...especially high
peaks of the dacks. 925mb to 850mb winds of 30 to 40
knots...support some localized gusts up to 30 mph in the
southwest to northeast aligned valleys like the slv on Tuesday.
Some downslope shadowing is likely in the cpv with strong
southwest flow. Temps under modest low level caa on Tuesday will
generally range from the 40s mountains to near 60f warmer
valleys. Upslope terrain focused showers continue into tuesday
night with some mix of snow likely above 2000 feet as progged
850 and 925mb are at or below 0c. Would not be surprised several
inches of snow accumulates on summits by 12z Weds...given
thermal 850mb thermal profiles between -2c and
-5c with favorable upslope precip prevailing.


As of 322 AM EDT Sunday...Little change from previous couple of
days with development of full latitude trof expected across the
eastern conus and several periods of moderate precipitation
expected late Thursday into next weekend. Some lingering upslope
precip will end by Weds afternoon with weak high pres building
into our cwa on Weds into Thursday. This will keep forecast area
dry with near normal temps.

Models still have some disagreement on phasing of northern/southern
stream systems and overall magnitude of trof and associated surface
low pres track. Either solution supports a period of moderate mid
level waa rain on Friday with strong ulvl divergence pattern
associated with dual jet couplet. Have bumped pops into the high
likely to low cat range with widespread qpf anticipated. Both the
gfs/ecmwf show cold pocket of progged 850mb temps <0c as precip
starts...so would anticipated some wet snow/sleet on the summits
Thursday Night into Friday Morning. Initial surge of moisture should
be north of our cwa by Friday afternoon with well established dry
slot developing from southwest to northeast. This will result in
more showery precip Friday Night into Saturday...before additional
steadier precip redevelops on Sat Night into Sunday associated
backside deformation. Latest trends support enough cold air
advection into the system on backside northwest winds for a mix of
rain/snow in the mountains with some accumulating snowfall possible
above 2000 feet. As large scale omega block develops across the
conus...look for a prolonged period of upslope precip to prevail
Saturday Night into early next week. Have mention high chance to low
likely pops. As progged 850mb temps drop below 0c by 00z
Sunday...expect some accumulating snowfall for the northern dacks
into the central/northern Greens on Saturday Night into Sunday.
Several inches is likely above 2000 feet. Temps near normal for
Weds/Thursday...cool to below normal for Friday into the weekend
with highs mainly 30s summits to l/m 50s valleys...which maybe
generous for Sunday given progged 850mb temps near -4c. Overnight
lows will remain in the 30s to m/u 40s because of clouds/precip.


Through 12Z Monday...VFR conditions persist with N-NW winds
generally 10 kts or less throughout the daylight hours.
Increasing clouds from the west will thicken and lower, bringing
with it some scattered rain showers. Have included VCSH at KMSS
and KSLK starting around 15Z but greater potential for rain at
terminals will be this afternoon and overnight. -SHRA will
generally spread west to east starting around 21Z at KMSS...02Z-
05Z for KSLK/KPBG/KBTV...and 04Z-06Z at KMPV. Currently looks
like KRUT may be far enough south to only see VCSH. MVFR
conditions are expected to accompany these showers. KMSS could
see IFR cigs after 06Z.

N-NW winds less than 10kts persists for all but KMSS which will
be NE channeling down the St Lawrence Valley at 10-15kts. Some
gusts may also develop in the afternoon at KMSS. After sunset,
expect winds to shift out of the south for all but KMSS.

Greater confidence for showers and potential IFR/MVFR
conditions exists with activity for tonight, as models show the
boundary during the daylight hours is trending further north.


Monday: VFR. Slight Chance SHRA...TSRA.
Monday Night: VFR. Breezy. Likely SHRA...TSRA.
Tuesday: VFR. Windy with gusts to 30 kts. Chance SHRA.
Tuesday Night: VFR. Chance SHRA.
Wednesday: VFR. Chance SHRA.
Wednesday Night: VFR. NO SIG WX.
Thursday: VFR. NO SIG WX.




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