Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 192021

Area Forecast Discussion
National Weather Service Blacksburg VA
321 PM EST Sun Feb 19 2017

High pressure will build over the region tonight and control
our weather pattern through at least Tuesday. A weak cold front
will cross the area Tuesday night and exit the region on
Wednesday. A warm front will move north through the region
Thursday into Friday.


As of 245 PM EST Sunday...

Satellite imagery continues to show cloud cover across the western
portions of the region slowly eroding. While not all cloud cover is
expected to have dissipated by sunset, the trend towards less should
continue. A few locations across the Piedmont experienced a few
diurnally based cumulus development this afternoon, specifically
over and near Buckingham County, VA. Anticipate all of this cloud
cover to dissipate at or just before sunset.

This evening, we are expecting what limited moisture remains in the
lowest couple of thousand feet off the surface to redevelop into
stratus clouds again, across approximately same region of the
mountains experiencing them currently. However, as the drier air
aloft continues to build downward as the night progresses, most, if
not all, of these clouds are expected to dissipate between roughly
200 AM and 500 AM.

Winds will die off quickly at sunset, yielding calm or light and
variable conditions for the entire region.

Low temperatures will range from the mid 30s to near 40 across the
mountains with around 40 to lower 40s across the Piedmont. The
highest ridge tops will be a little milder than their surrounding
valleys thanks to warmer air working its way into the area aloft
above the nocturnal inversion.

On Washington`s Birthday, an upper ridge of high pressure will move
eastward from the Tennessee Valley to over the western portion of
the forecast area. At the surface, the southern axis of a ridge of
high pressure will nose south along the lee of the Appalachians by
the afternoon. With building heights, and at worse filtered sunshine
through advancing thin cirrus clouds, temperatures will trend milder
than those realized today, especially in the west where cloud cover
will be significantly less.

High temperatures will range from the mid 60 to near 70 across the
mountains with lower 70s across the Piedmont. A couple locations may
reach or be very close to setting record high temperature records
tomorrow. Please see the CLIMATE portion of this discussion for


As of 235 PM EST Sunday...

Models continue to advertise long wave upper ridge moving east and
offshore with a weak short wave in the northern stream arriving in
the eastern United States by Tuesday night. Jet support is not very
impressive Tuesday and Tuesday night with much of the upper
diffluence remaining over the Ohio Valley and north. Monday evening
western valleys along with the foothills and piedmont will decouple
early. Then as the surface and 850MB high moves of the coast wind
pick up from the west-southwest so expecting temperatures to rise on
the western ridges overnight.

Axis of deeper moisture crosses the from West Virginia into North
Carolina between 00Z/7pm Tuesday night and 12Z/7AM Wednesday
morning. Will be slowing down arrival of precipitation based on this
timing. Have also trimmed probability of precipitation behind the
front on Wednesday.


As of 235 PM EST Saturday...

Per WPC, not much weight put on the GFS, especially Friday through
Sunday, as it is faster with most of the synoptic scale features
than much of the other guidance. Timing of the cold frontal passage
still similar with the front coming through Saturday morning.

00Z ECMWF had colder air behind the front just brushing through the
Mid Atlantic region, which was not nearly as cold and as far a push
south as previous runs. High temperatures will still drop about 10
degrees but coldest air will start moderating after Sunday morning. A
low level jet and cold air advection will result in strong gusty
winds behind the front into Sunday morning.


As of 1240 AM EST Sunday...

VFR conditions currently prevail east of the crest of the Blue
Ridge. As high pressure continues to build into the region, this
pattern is expected to continue through at least the duration of
the valid TAF period. Winds in this region will be close to 10
kts this afternoon from the northwest, with some gusts in the 15
to 20 kt range. Anticipate calm or light and variable winds
overnight through Monday.

Across the mountains, most areas were experiencing decreasing
coverage of ceilings that ranged from LIFR to MVFR. Drying from
aloft will help to continue to the trend of decreasing coverage
as the afternoon progress with ceiling levels increasing mainly
to MVFR and low end VFR. As the night progresses, moisture that
becomes trapped under the nocturnal inversion will allow
ceilings to redevelop and spread eastward. Levels again will
return to LIFR to MVFR levels. However, drier air will
eventually win with clouds decreasing in coverage towards
daybreak. VFR conditions are expected across the mountains on
Monday. Winds this afternoon in this region will be generally
from the northwest around 10 kts with gusts in the 15 to 25 kt
range. Overnight and on Monday, anticipate calm or light and
variable winds. VFR visibilities are expected for much of the
region. Some late night valley MVFR fog is possible in areas
near and south of KBLF.

No low level wind shear is expected during the TAF period.
No precipitation is expected during the TAF period.

Confidence levels of forecast parameters during the TAF time
period include the following.

Ceiling...Moderate to High.
Low Level Wind Shear...High.

Extended Aviation Discussion...

High confidence of VFR conditions Monday afternoon through
Tuesday morning.

Moderate to high confidence of patchy MVFR conditions across the
mountains Tuesday afternoon into Wednesday with the passage of a
cold front. East of the Blue Ridge, mainly VFR conditions will

Thursday into Thursday night, moderate confidence of patchy
light rain returning to the area, with ceiling and visibilities
remaining mainly VFR. Some patchy MVFR is possible.

Friday, moderate to high confidence of precipitation trending
more showery, as low level jet increases in advance of a strong
cold front. Expect a mix of MVFR and low end VFR ceilings and
mainly VFR visibilities with isolated, brief sub-VFR
visibilities under heavier showers. Surface wind gusts of 20 to
30 kts possible across the higher terrain.


As of 315 PM EST Sunday...

Record High Temperatures and Year of Occurrence

Feb 20
Blacksburg, VA..68 in 1984
Bluefield, WV...67 in 1986
Danville, VA....74 in 1971
Lynchburg, VA...76 in 1930
Roanoke, VA.....75 in 1939




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