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Current conditions from King Hill
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  Wednesday December 13, 2017

 

NWS Area Forecast Discussion


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000
FXUS61 KBTV 120803
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
303 AM EST Tue Dec 12 2017

.SYNOPSIS...
Deepening low pressure will cross the region today into
Wednesday with a widespread moderate to locally heavy snowfall
expected. Behind this system chilly temperatures are expected
through the end of the week with periodic chances of flurries
and light snow, with the best chances occurring later in the
weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 303 AM EST Tuesday...The forecast remains on track over
the next 36-hours as clipper energy tracks from the eastern Ohio
Valley through central New England today before exiting into
the Maritimes by tonight. All current advisories and warnings
remain intact with this package. As discussed quite thoroughly
over the last few nights the storm will come in two stages - a
warm advection stage today, and an orographic upslope stage
later tonight into Wednesday. The overall idea advertises steady
light to moderate snow overspreading the entire forecast area
through the morning hours before tapering off somewhat later
today into the first part of this evening as surface energy and
associated isentropic lift exit east. By later tonight into
Wednesday the flow transitions to northwesterly allowing a
general reblossoming of activity across northern counties,
especiallly in favored upslope areas. Snowfall will show
considerable variability over any given 6-hour time frame into
tomorrow with the proximity of the surface low track allowing a
gradual backing of the low level flow over time. That said storm
average totals remain largely unchanged and should generally
range from 3-7 inches in advisory areas, 5 to 8 inches or so in
southeastern VT and the St. Lawrence Valley, and from 6 to 10
inches in the northern Greens. Totals that do fall out of these
ranges should be on the order of just an inch or two in the
lower elevations and well within a typical standard deviation
profile for complex events such as this. Northwesterly winds
will also trend quite gusty on Wednesday as p-gradient tightens
so this will create areas of blowing snow. High temperatures
today should top out in the upper 20s to lower 30s before
bottoming out mainly in the teens overnight. Readings won`t
really recovery too much on Wedneday under strong cold thermal
advection and the aforementioned gusty winds - mainly steady in
the mid teens to lower 20s.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/...
As of 303 AM EST Tuesday...Light snow and snow showers wind
down across the northern mountains Wednesday night before ending
by Thursday as high pressure slowly builds into the region. It
will remain quite chilly under modestly gusty west/northwest
flow with lows Wednesday night in the single digits a highs on
Thursday once again in the teens to locally near 20F across the
southern valleys. Wind chills Wednesday night look to generally
range through the negative single digits to negative teens so
slightly warmer than advisory level thresholds - at least that`s
the way it looks at this point.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 330 AM EST Monday...Large scale picture shows mid/upper
prevailing across the eastern Conus...while energy and moisture
from the Pacific NW ejects into the fast flow aloft every couple
of days. Latest guidance supports the northern tier staying on
the cool side of these systems with several mainly light snow
events possible. Below are my daily thoughts for days 4 thru 7.

Thursday...deep mid/upper level trof across eastern canada will
result in favorable upslope flow...but 1000 to 700mb rh is
progged to slowly dissipate by 18z Thurs. Based on llvl caa and
upslope flow...expecting remaining moisture to be squeezed out
across the northern dacks/greens. Have mentioned chc pops with
only minor accumulation expected. Temps aft a chilly start will
only warm into the single digits/lower teens mountains to
mid/upper teens warmer valleys with brisk northwest winds. Weak
surface high pres builds into our cwa on Thurs Night into
Friday...but next system approaches our western fa by Friday.
Very difficult to determine cloud cover/winds and impacts of
fresh snow pack will have on temps Thurs Night/Friday Morning.
Have trended toward cooler side of guidance envelope with -10f
slk/nek to single digits to around 10f cpv. Some lake effect
clouds could impact temps near BTV.

Friday/Saturday...Both gfs/ecmwf show next weak clipper like
system and associated boundary crossing our cwa. This system
will be weaker and have less impact than current clipper. Still
anticipating a period of light snow activity...given good 5h
energy...some enhanced mid level moisture... and great lake
moisture interaction with approaching boundary. Several inches
likely in the mountains with a dusting to an inch possible in
the valleys. Have continued to mention high chc pops in the
grids. Progged 850mb temps btwn
-14c and -16c...support highs mainly single digits summits to
 teens mountain towns to l/m 20s valleys.

Sunday...weak mid/upper level ridge and associated 1025mb high
pres builds into the ne conus. Extremely difficult to time
systems in fast flow aloft...along with amount of clearing and
impacts on temps. Have lowered pops slightly for Sunday...but
timing of next system could arrive quicker based on fast flow
aloft. Clouds and winds will impact temps...but have kept temps
close to superblend with lows mainly in the teens and highs in
the 20s.

Monday...Guidance supports another clipper like system moving
thru the Ohio Valley into the NE CONUS. Have noted lots of
uncertainty in ensemble data and between 00z/12z guidance in
track of surface low...with some to our northwest... while others
show a system to our south. Have continued on the cooler side
of guidance...thinking surface pres will keep system suppressed
to our south...with another light snow event possible. 12z ECMWF
shows favorable mid level moisture...good deep layer lift... and
moderate llvl waa signature. Plenty of time and
uncertainty...so have mention chc pops for now... with temps
holding in the 20s. Overall pattern will support a net increase
in snow pack across the mountains with cool temps keeping
snowpack fresh.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
Through 06Z Wednesday...Deteriorating conditions as moderate
snow moves into the region associated with clipper system
crossing the area today. Widespread IFR to LIFR develops at
all sites by early Tuesday Morning with significant impacts
anticipated through 04z, before widespread snow develops from
southwest to northeast across our TAF sites between 04z-08z.
Visibility will quickly drop to IFR with locally VLIFR in bursts
of heavier snow expected at all sites between 09z-15z Tuesday.
Ceilings will vary from IFR at MSS to MVFR at
RUT/MPV/BTV/SLK/PBG...with periods of IFR possible. Localized
southeast winds gusts to 25 to 30 knots at RUT on Tuesday
morning with breezy northeast winds at MSS. Conditions will
slowly improve at RUT after 18z. Some low level wind shear
likely at MSS/MPV with change of speed and direction...causing
increased shear and turbulence on Tuesday Morning.

Outlook...

Monday Night: Mainly VFR, with local MVFR possible. Chance SN.
Tuesday: Mainly MVFR, with local IFR possible. Definite SN.
Tuesday Night: Mainly MVFR, with areas IFR possible. Chance SHSN.
Wednesday: Mainly MVFR, with areas VFR possible. Chance SHSN.
Wednesday Night: Mainly VFR, with areas MVFR possible. Slight
chance SHSN.
Thursday: Mainly VFR, with local MVFR possible. NO SIG WX.
Thursday Night: Mainly VFR, with local MVFR possible. Slight
chance SHSN.
Friday: Mainly VFR, with local MVFR possible. Chance SHSN.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Winter Weather Advisory until 7 PM EST Wednesday for VTZ001-
     002-005-009-011.
     Winter Storm Warning until 7 PM EST Wednesday for VTZ003-004-
     006>008-016>018.
     Winter Storm Warning until 7 AM EST Wednesday for VTZ010-012-
     019.
NY...Winter Weather Advisory until 7 PM EST Wednesday for
     NYZ027>031-034-035.
     Winter Storm Warning until 7 PM EST Wednesday for NYZ026-087.

&&

$$
SYNOPSIS...Deal
NEAR TERM...JMG
SHORT TERM...JMG
LONG TERM...Taber
AVIATION...Hastings/Neiles



 
 
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