17.3°F
Current conditions from King Hill
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  Wednesday December 13, 2017

 

NWS Area Forecast Discussion


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000
FXUS61 KBTV 121441
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
941 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 931 AM EST Tuesday...Forecast playing out well this
morning with periods of light to moderate snow moving from
southwest to northeast across our cwa. Snowfall amounts have
ranged from 0.5 to 4 inches so far with highest values over
south-central VT and parts of the SLV. Current radar shows
another moderate band of snow from near KART to KRME to KALB
moving northeast at 15 to 20 mph. Expect this band to produce
another quick 1 to 2 inches btwn 15z-18z across our cwa with vis
around 1/2sm. Water vapor shows baroclinic leaf developing
associated with digging short wave energy and upper level jet
over eastern/central PA...which will impact our central/eastern
sections this afternoon with additional periods of snow. Very
difficult in timing these precip pulses associated with waves of
enhanced lift/moisture moving from south to north across our
cwa. By this evening a sharp wind shift will occur as sfc low
pres jumps to the NH/ME line by 03z. Lots of uncertainty in
synoptic and mesoscale models on how much moisture is advected
back into the developing llvl caa for a period of upslope snow
tonight into weds. We will examine 12z data and make any
necessary adjustments with the complete package this aftn.
Otherwise...all advisories and warnings look good at this time.
Did lower kmss temp by several degrees...associated with ne flow
and crnt value only 18f. Rest of fcst looks good.

Prior discussion...
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, especially 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 Wednesday
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 Tuesday...Weak ridge of surface high pressure
will build over the North country Thursday night and Friday. A
weak low pressure system approaches Friday night into Saturday,
but only light precipitation is expected for our forecast area.
This is another clipper type system, but with less synoptic
forcing than the system impacting the area today and tomorrow.
From that point on GFS and ECMWF diverge quite a bit. GFS shows
yet another clipper system passing north of the area Sun, while
ECMWF lacks this feature entirely. Then the ECMWF shows a system
moving along the New England coast on Monday night. Overall
colder than normal temperatures and active weather pattern is
expected. Timing of the different feature is difficult at this
time with a lack of model-to-model and run-to-run consistency.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
Through 12Z Wednesday...Deteriorating conditions as moderate
snow moves into the region associated with clipper system
crossing the area today. Widespread IFR to LIFR at all sites
with significant impacts through much of the day. Visibility
will quickly drop to IFR with locally VLIFR in bursts of heavier
snow expected at all sites between thru 15z Tuesday. Ceilings
will vary from IFR to MVFR. 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 this
Morning. As low passes overhead this afternoon, winds will be
light and variable before veering to Northwesterly behind the
front. When we have a lull in precipitation ceilings may improve
temporarily.

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...JMG
NEAR TERM...JMG/Taber
SHORT TERM...JMG
LONG TERM...Neiles
AVIATION...Neiles



 
 
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