Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Remove Highlighting --
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FXUS61 KRNK 231835
Area Forecast Discussion
National Weather Service Blacksburg VA
135 PM EST Mon Jan 23 2017
A strong area of low pressure over the Mid Mississippi valley
will approach from the west tonight bringing a period of
moderate to heavy rain. This low pressure system will slide
slowly east across across the area Monday before exiting Monday
night. In the wake of the low pressure system, a period of gusty
northwest winds are possible for the North Carolina high country
and the Blue Ridge. Temperatures trend closer to seasonal
levels by later in the week.
.NEAR TERM /THROUGH TONIGHT/...
As of 1130 AM EST Monday...
Radar imagery indicates that the heaviest rain has exited the
area to the north northwest as the upper low and nearly
vertically stacked surface low make a jog from central North
Carolina to the coast. Currently, only areas of light rain
continue to pass across the forecast area.
One of the chief concerns through at least mid afternoon will be
rapid rises along creeks and smaller rivers in the vicinity of
the Blue Ridge, especially in the Roanoke area. Runoff from the
heavier rainfall earlier will continue to push these rivers
higher through early afternoon, in some cases out of their
banks to result in minor flooding. With no organized additional
heavy rain expected today, expect that most rivers and creeks
will crest during early afternoon, and will begin to recede
before the afternoon commute.
The pressure gradient east of the Blue Ridge remain tight enough
to support 25mph to 35mph gusts as of 11 AM...longer than what
weather forecast models have anticipated. Will update the
forecast to reflect stronger gusts through mid afternoon, by
which time winds speeds are expected to diminish as the low
pressure system continues east. Also, with clouds expected to
hold in place through the day, expect that we are already within
a degree or two of or daytime high temperatures, and will adjust
the forecast accordingly.
For Tonight: The rain threat will continue to subside, becoming
more confined to the west, upslope side of the Appalachians.
With lingering precip in the mountains there may be some mix of
snow at the higher elevations north of Bluefield and west of
Lewisburg where temperatures slip into the lower to mid 30s. The
NAM is by far the coldest of the models suggesting an inch or
two for western Greenbrier. Attm think this is overdone and will
go with the slightly warmer GFS which indicates only a coating
to an inch. Elsewhere, the boundary layer appears to be too
warm, so will keep the p-type as rain. On the downslope, east
side of the Appalachians look for partial clearing.
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 400 AM EST Monday...
Upper low near the VA/DE coast Tuesday, will head northeast out
to sea on Wednesday. Cooler air will follow this system
Tuesday, however high temperatures will remain above normal.
Also in the wake of this system, pressure gradient and rises,
subsidence and a 40-50kt low level jet will bring windy and
gusty conditions to the area. These strong winds will start
across the southern Appalachian Mountains in North Carolina
Monday night into Tuesday morning, then across southwestern
Virginia early Tuesday morning into Tuesday evening. Winds will
be their strongest across northwestern North Carolina, enough to
issue an advisory. High pressure and upper level ridging will
move over the region Tuesday night, ending the threat for strong
A disturbance will track east across the Great Lakes Wednesday. The
cold front associated with this disturbance will not cross the area
until Wednesday night. With abundant sunshine and increasing
southwesterly flow ahead of the front, temperatures will warm 20F
above normal Wednesday with widespread 60s across the forecast area
to near 70F across Southside Virginia.
.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 337 PM EST Sunday...
Pattern change to overall broad longwave troughing over the region will
begin to take shape Thursday in the wake of a passing surface cold
front by early in the day. This will lead to a prolonged period of cold
advection under west/northwest flow to the east of the main surface
high situated over the Rockies through next weekend. However appears
the overall scenario to remain on the quiet side with mainly shallow
moisture resulting in upslope driven periodic snow showers espcly
northwest sections into Sunday. Appears amounts to be limited though
given more westerly trajectory and only shallow moisture beneath the
inversion, so overall only chance pops this far out along the western
slopes. Otherwise should see the typical split from mainly sunny/clear
skies east of the ridges per downslope, to clouds far west, and at
times out to the Blue Ridge pending the passage of weak impulses.
With the broad trough becoming rather flat and 850 mb temps roughly
above minus 10C, only expecting a return to normal or slightly below
normal temps with highs 30s/low 40s mountains, to low/mid 40s east, and
lows in the 20s. However will feel quite a bit colder after all the
recent warmth, given a persistent blustery northwest wind under the
lingering gradient between low pressure well north and the high well to
the west. Appears coldest could occur during the weekend when thickness
drop a bit so trended toward the colder earlier EC mos as the GFS MEX
values remain warmer.
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
As of 100 PM EST Monday...
Poor flying conditions will continue across much of the region
and at all TAF sites through early Tuesday morning.
Stacked upper level/surface low pressure systems currently
making their way eastward across central North Carolina. As the
lows progress, winds continue to back increasingly north-
northeasterly. IFR ceilings remain widespread, with visibilities
ranging from IFR to VFR depending on locality and proximity to
rain showers developing under the upper low. Do not expect much
change in these conditions through 24/06Z, by which time winds
will back more northwesterly as low begins to push away.
With the northwest wind shift overnight, expect cloud cover to
decrease from east to west due to downslope flow. Believe that
LYH/DAN/ROA will have scattered to VFR ceilings before 24/12Z
while BCB will linger in low clouds through early Tuesday
afternoon. Do not expect BLF/LWB to break out of MRVF/IFR until
Eastward push of the low pressure system will also cause wind
speeds to increase as the pressure gradient tightens between
the departing low and high pressure along the Mississippi River
Valley. Expect 20kt to 30kt northwesterly surface gusts to be
common areawide beginning Tuesday morning, with as high as 35kt
possible at ROA due to wind channeling in the local terrain.
Extended Aviation Discussion...
Winds will subside Tuesday night. High pressure will finally
spread into the region by Wednesday. A band of MVFR showers is
possible along/behind a cold front Thursday into Thursday
night. Colder west to northwest wind flow will develop behind
this front with mountain snow showers possible for the weekend
associated with MVFR CIGS/VSBYS.
As of 1130 AM EST Monday...
Heavy rainfall has exited the area, with only light pockets of
rainfall expected to remain through the day. Area creeks and
streams will continue to rise through early afternoon, with some
pushing out of their banks in spots for a few hours. Expect all
rivers to begin receding by mid afternoon.
VA...Wind Advisory from 6 PM this evening to noon EST Tuesday for
NC...Wind Advisory from 6 PM this evening to noon EST Tuesday for