Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
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FXUS61 KRNK 041821
Area Forecast Discussion
National Weather Service Blacksburg VA
121 PM EST Sun Dec 4 2016
High pressure shifts northeast today. A couple of upper
disturbances will lift northeast across our area today into
tonight. The main system shifts across the Gulf Coast states into
the mid-Atlantic Tuesday. A strong cold front enters the area
Thursday with much colder temperatures expected to end the
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --As of 100 PM EST Sunday...
Enough warm air has entered most of the region for precipitation
to be falling as light rain. The hold-outs for p-type issues still
remain light sleet versus light rain over parts of Floyd County,
VA and also the ridge lines across the Alleghany Highlands of
Virginia and also Greenbrier County, WV. Have bumped forecast high
temperatures up a degree or two across parts of Southside Virginia
and neighboring north central North Carolina. Have made little
change to temperatures elsewhere.
As of 955 AM EST Sunday...
Light precipitation continues to make gradual progression
northeast into and through the region. Temperatures across the
southwest portions of the area are slowly rising into the middle
30s. Pockets of sleet and/or snow are gradually decreasing in
coverage across this portion of the area with plain rain becoming
dominate. However, as the leading edge of the precipitation
saturates the low levels of the atmosphere, and both temperature
and dew point trends towards a sub-zero C wet-bulb, some light
sleet and snow will continue to be possible around and a few hours
after the onset of the precipitation. By the time the leading edge
reaches northern parts of the region this afternoon, most areas
will receive only rain. The exception will be the higher ridges of
the Alleghany Highlands where sleet will be possible.
As of 648 am EST Sunday...
Rain and some snow finally making it into the NC
mountains/foothills, and as far northeast as Smyth County VA.
Weather cams showing a coating of snow at Beech Mountain NC. Have
highlighted the higher elevations from Tazewell to Watauga for
light snow coating the roads. Models still favor mainly rain with
snow/sleet mixture at times. Temperatures/dewpoints show wet bulb
within 32F. Confident that wintry precip will be limited to higher
terrain with some lower elevations along I-81 from Abingdon to
Wytheville potentially seeing some snow/sleet but to no impact.
Bump pops up across the southwest CWA to account for latest radar
and high-res model trends. By lunchtime, precip, mainly rain
should be as far northeast as Bluefield to Radford to Stuart to
Danbury, with more patchy rain to perhaps Roanoke and Danville.
Previous discussion from early this morning...
Have not seen any precip in our local observations but seeing
light rain reported just south of Wilkes County NC over the
Interstate 40 corridor. Airmass will be moistening from top to
bottom right through the day. Models are similar in timing for
precip to move into the mountains/foothills of NC/SW VA by 12z
then isentropic lift and upper forcing accelerate east-northeast
through the afternoon. Main concern this morning is with ptype.
Noticing a bit cooler than earlier forecast, so will lean more
toward snow/sleet southwest then rain, as opposed to freezing
rain. Still amounts will be very light but could see a tenth of an
inch of snow in the higher terrain of NW NC into far SW VA, maybe
even some of the lower elevations may see some light coating.
Still for temperatures and ground/road sfcs there should not
enough to cause any problems.
Expect the precip to chase the cooler air north where the leading
edge will be a mixture of rain/snow/sleet before switching to all
rain. Could still remain wintry mix over the Alleghanys of Bath into
Greenbrier through tonight. Overall will be limited in winter precip
so no headlines planned as amounts and coverage are very
One upper vort moves north this morning, then another wave shifts
from the Southern Appalachians around midday to the Southwest VA
mountains this evening. Appears the southern tier of the forecast
area south of Highway 460 should see occasional rain, while the
northern extent along I-64 to north of Amherst will still have a
fair chance of rain, but not as much.
This will change this evening as northern stream shortwave heads
east and the northern CWA gets into better lift with right entrance
upper jet moving from KY to the Northern VA. Expect likely pops for
rain across the east then shifting to dry solution of the EC/NAM
across the southern tier late, with overnight pops ranging from
slight chance NC foothills into the New River Valley to high chance
to low likely east of a Lynchburg to Greensboro line and also across
the western cwa from Tazewell to Lewisburg with shortwave energy
moving in. By dawn we should be mostly dry with possible drizzle
left over most areas with still some light rain in the piedmont of
VA east of Lynchburg, and across the mountains. Still need to watch
for potential freezing rain and/or freezing drizzle in the higher
terrain/eastern slopes of the Alleghanys of Bath county and
Greenbrier. Forecast temps suggest no lower than 32F expected, so
As for temperatures this period since we are dropping cooler this
morning and with precip coming in this morning, the highs were
trimmed some along and either side of the Blue Ridge. These areas
will be hard pressed to reach above 40f, while further west and east
temps should manage to flirt with mid 40s.
Tonight, as we keep clouds and rain around temps will be dropping
slowly and ranging from the lower 30s Alleghanys and Blue Ridge
north of the James River, to mid to upper 30s elsewhere.
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.SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
As of 430 AM EST Sunday...
High pressure building into the Ohio valley will bring an end to any
lingering precipitation on Monday. This high will then move into New
England and wedge down the east slopes of the Appalachians as a surface
low being driven my an upper trof moving out of Texas approaches from
the southwest. There will be significant isentropic lift with this
system as it moves through and synthetic water vapor imagery continues
to show deep moisture transport in a plume emanating from the tropical
Pacific. These ingredients will combine to spread a cold, soaking rain
across the region from the southwest starting Monday night and
continuing through Tuesday, along with gusty winds at the higher
elevations from the northwest mountains of North Carolina up through
the Mountain Empire of Virginia into western Greenbrier county. Hydro
concerns remain low as total QPF amounts through late Tuesday are
expected to generally be around one inch and the region is still
recovering from a very dry fall season.
As high pressure builds in and northwest winds pick up Tuesday night,
some upslope showers are expected west of the Blue Ridge with some wet
snow mixing in for western Greenbrier county during the predawn hours
of Wednesday. Any lingering upslope rain/snow showers will end
Wednesday morning with improving conditions into the afternoon.
Temperatures are generally expected to be at to a bit above normal on
both Monday and Wednesday, but Tuesday will feature temperatures well
below normal in the heart of the wedge with warmer readings mainly
along the western periphery of the wedge.
.LONG TERM /THURSDAY THROUGH SATURDAY/...
As of 200 PM EST Saturday...
Very strong cold front associated with the 500 mb trough will cross the
region Thursday with some timing differences in models as slightly
faster trends continue. Lobe of deeper moisture right along the front
may bring a band of showers west, with a quick change to snow showers
far west as seen with similar arctic fronts in the past. Some
of this coverage may even spill east of the mountains in liquid
form so running with decent to high chance pops west and slight
coverage east. Pending timing, temps to fall from west to east by
afternoon with the core of the cold air arriving Friday into
Friday night under strong northwest winds, and lingering snow
showers despite very dry air by weeks end. Gradient given depth of
the cold advection perhaps enough to warrant advisory level winds
in spots over the mountains otherwise very cold. Appears highs
wont get out of the 20s to around 30 mountains Friday and 30s east
with lows teens most spots Friday night and even single digits in
the deeper valleys. This should also push wind chills to around
zero if not colder in spots by early Saturday. Thermal trough
including the coldest air aloft will lift out by Saturday but
still highs only 30s to low 40s despite sunshine.
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
-- Changed Discussion --As of 1230 PM EST Sunday...
Ceilings will continue to gradually lower as the afternoon
progresses. IFR/MVFR ceilings are working their way into the
southwest portion of the forecast area and spreading northeast.
Suspect that by 00Z/7PM all terminals will be sub-VFR for
ceilings. It is also likely by that time that at least some of
terminals will have sub-VFR visibilities for light rain and some
mist. Enough colder air aloft may allow for a brief period of
sleet around the KLWB region. As the evening progresses, it is
anticipated that even northern parts of the region will lose the
cold air nose in the lower atmosphere so that a precipitation
falls as light rain.
Light rain will cover most of the region through approximately
06Z/1AM Monday before lifting northeast of the area, leaving area
of light fog in its way. A cold front will cross the region late
tonight into early Monday morning. Look for winds to increase from
the northwest around or little after sunrise. The northwest winds
will bring drier air to the region. Ceilings east of the crest of
the Blue Ridge should scatter by the mid-morning. Cloud cover will
last longer across the mountains thanks to an upslope component
working with residual low level moisture.
Extended aviation discussion...
VFR conditions are expected Monday afternoon and evening.
Our next weather system looks to bring rain to the region staring
late Monday night, and continue through the day Tuesday. IFR/MVFR
ceilings are probably late Monday night through the day Tuesday.
Likewise, sub-VFR visibilities will accompany the precipitation.
Another cold front will head through the area Tuesday evening.
Look for improvement to VFR east of the Blue Ridge, with lingering
sub-VFR ceilings across the mountains, and perhaps some scattered
upslope rain/snow showers between KBLF-KLWB later Tuesday night
into early Wednesday morning.
Anticipate another break in the activity on Wednesday before yet
another cold front crosses the region on Thursday. Look for a
return of sub-VFR conditions and better chance of snow showers in
the west Thursday night into early Friday.
Friday, expect a gusty day across the region with lingering
upslope cloud and snow showers between KBLF-KLWB. East of the Blue
Ridge, VFR is expected.
-- End Changed Discussion --
As of 645 am EST Sunday...
Phone company informed us that broadcast from Wythe County weather
radio transmitter, WZ2500, should be available and the line is