Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 152252

Area Forecast Discussion
National Weather Service Blacksburg VA
552 PM EST Wed Nov 15 2017

A cold front will move east across our region tonight followed
by dry weather under high pressure Thursday into Friday. A
strong cold front will then bring more showers and windy
conditions to the region this weekend. Cold high pressure will
build in behind the front for early next week.


As of 550 PM EST Wednesday...

Updated grids with latest observations and adjusted PoPs using
HRRR. Main batch of rain will move across the mountains this
evening, then become scattered moving to and east of the Blue
Ridge by midnight.

As of 230 PM EST Wednesday...

Low clouds associated with the cool wedge eroded or mixed out this
afternoon as high center moved east ahead of the approaching cold
front. The cold front with some showers will travel east across the
Appalachians tonight into Thursday. Any convection will fade east of
the Blue Ridge as front stretches out and loses its deep moisture to
the northeast. A westerly component to the wind will also hinger
showers in the east. Low temperatures tonight will range from the
the lower 30s in the northwest mountains to the mid 30s in the

For Thursday morning expected some lingering upslope morning showers
or drizzle in West Virginia. By Thursday, high pressure over the
midwest moves toward our area with drier air. There is enough
pressure gradient between the high center and the low over New
England to result in a breezy afternoon. Some wind gusts over 30 mph
are possible in the higher ridges of the Blue Ridge. In a familiar
cold advection pattern, temperatures will stay cool in the
mountains and warmer with downslope flow in the east. High
temperatures will vary from the upper 40s in the west to the lower
60s in the east.


As of 200 PM EST Wednesday...

Quiet weather under more seasonal temperatures will return Thursday
night and last into Friday night as surface high pressure builds in
under shortwave ridging aloft. May still see some gusty northwest
winds Thursday evening before the gradient relaxes under building
heights overnight. Lingering upslope clouds may also persist over
the far northwest ridges, otherwise expecting clearing skies
Thursday night with dry weather lasting into Friday night. Decent
late night radiational cooling should allow lows to fall below
freezing Thursday night including some 20s mountains.

High pressure overhead should ensure a very nice Friday with steady
warm advection aloft resulting in highs in the 50s and 60s under
light winds. Moisture pushes east in advance of the next strong
upstream trough later Friday night with mixing on the ridges also
increasing under tightening of the 850 mb jet aloft. Slower timing
again suggests that any showers will primarily remain to the west
overnight. Thus only expecting some increase in clouds including a
possible wide range in lows from the 40s/near 50 ridgetops, to the
30s across the valleys and eastern low spots.


As of 130 PM EST Wednesday...

Timing of the next upper trough and subsequent surface cold front
still remains somewhat in question over the weekend as overall
models continue to trend slower and closer to the earlier ECMWF.
This scenario looks about 6 hours slower than yesterday with
the surface front outrunning a secondary shortwave that looks to
lag back to the northwest until later in the weekend. This now
holds the leading edge of the frontal showers back into the
western mountains until early Saturday afternoon with only isolated
showers within the warm sector elsewhere ahead of the boundary
until late in the day. Increasing southwest jet aloft ahead of
the lead shortwave axis trailing the front likely to make for a
breezy/windy Saturday but warm with highs 50s to mid 60s.

Surface front including the 850 mb boundary finally looks to
surge through Saturday evening/night with most showers in the
early evening to the early morning hours of Sunday timeframe.
Appears will be an associated shot of stronger winds as the
front and/or embedded band of shallow convection slides through
during the evening followed by gusty northwest winds overnight
as the initial shot of cold advection arrives. Models have again
trended weaker with the jet aloft but do show a band of
impressive pressure rises as subsidence works in while
inversion levels lower due to cold advection. This would still
support wind advisory criteria in spots along the Blue Ridge
overnight so keeping mention in the HWO. Otherwise should be
enough showers to warrant a period of likely or higher pops
espcly western half, with thickness cold enough to support a
brief change to snow showers far west overnight as temps cool
toward freezing.

Front quickly exits Sunday allowing high pressure to nose in from
the southwest which now looks to limit upslope given drying but
still enough for snow showers/flurries northwest into Sunday
afternoon. Otherwise continued breezy/windy and quite chilly under
increasing sunshine ahead of a secondary shortwave approaching from
the northwest. This feature may again ramp winds up to advisory
levels Sunday afternoon/evening via aided mixing and arrival of
colder air aloft. Highs mostly 30s/40s mountains to low 50s east.
Lows mostly 20s under continued cold advection within an
increasingly dry airmass.

Winds should slowly diminish Monday as the upper trough lifts out
and high pressure builds in from the southwest into Tuesday.
Another weak mid level feature likely to pass across Tuesday
night into Wednesday before the high weakens and the split flow
begins to tap return flow moisture resulting in more clouds
Day7 but dry at this point. However will stay below seasonal
normals with only a slight boost in highs on Tuesday at this


As of 1247 PM EST Wednesday...

SCT to BKN MVFR clouds this afternoon into tonight. A cold front
approaching from the west this afternoon will rotate east
across the area tonight. The best chance for MVFR showers will
occur across the west at KLWB/KBLF. Will include the mention of
VCSH with frontal boundary tonight at other taf locations.

Possible post-frontal sub-VFR ceilings into Thursday in the
western Appalachians, otherwise VFR conditions.

High confidence in ceilings,visibilities and winds during the
taf period.

Extended Discussion...

VFR conditions anticipated through Thursday evening. A cold
front is expected to cross through the Mid Atlantic region
Friday and Saturday with precipitation and strong winds both
ahead of and behind the front. Gusty winds may continue into
Sunday but there is large spread in the guidance at that time
frame. Dry weather expected Monday into Tuesday. Scattered MVFR
rain and snow showers are possible Tuesday night into West in
the western Mountains.




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