Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 241958

Area Forecast Discussion
National Weather Service Blacksburg VA
258 PM EST Fri Nov 24 2017

High pressure across our region will briefly give way to a cold
front that will arrive on Saturday. High pressure quickly regains
control over our weather pattern for much of next week. The
potential exists for a cold front to cross the area on Friday.


As of 200 PM EST Friday...

A ridge of high pressure was centered along a line from Louisiana to
Deleware. Low pressure was positioned east of Florida. A cold front
extended southwest from a low in southern Ontario through Minnesota
and South Dakota. A developing surface trough was in advance of the
cold front, across Nebraska south into Texas.

Over the course of the next 24 hours, the surface ridge of our
region will be shunted to the east in advance of the approaching
High Plains cold front. The front itself will arrive and cross our
region during the day Saturday.

We are expecting dry weather to continue across the entire region
through tonight. On Saturday, isolated showers will be possible in
the afternoon and early evening in association with the cold front,
but only across portions of southeast West Virginia, south into the
Northern Mountains of North Carolina. The remainder of the region
will remain dry. Cloud cover will be on the increase overnight,
especially west of the crest of the Blue Ridge, with the remainder
of the region experiencing and increase in cloud cover as Saturday

As the associated upper trough draws closer and the center of the
ridge axis moves eastward, look for an increase in winds across the
area. Stronger winds will first be noted tonight at the higher
elevations across the mountains. Within the mountain valleys and
across the Piedmont, the influence of the nocturnal inversion will
hinder any notable increase in wind. Anticipate the Piedmont and
mountain valley regions to experience a fairly normal decreasing
trend in temperatures as the night progresses. However, at the
higher elevations, the influence of the stronger winds and warm air
advection will yield steady or slowly rising temperatures during the
night. Lows tonight will range from mid 30s to mid 40s across the
mountains depending up elevation. Across the Piedmont, the middle
30s are expected.

On Saturday, all parts of the region will be milder than readings
realized today, especially across the Piedmont where clouds will
arrive later in the day. Highs will range from the low to mid 50s
across the mountains with readings around 60 to the mid 60s across
the Piedmont.


As of 110 PM EDT Friday...

Saturday evening deeper moisture associated with the front will be
moving east out of the Virginia and North Carolina piedmont. Low
level upslope clouds will already be developing on the western
slopes of the Appalachians. Expect these clouds to remain over
southeast West Virginia through Sunday morning. Enough of a low
level jet from the northwest behind the front to support some gusty
winds, especially at higher elevations Saturday night and Sunday.

Surface high pressure centered over western Virginia and western
North Carolina Monday morning. Conditions will be favorable for
winds to decouple Sunday evening and to have cooler minimums in the
valleys overnight. Warm front crossing the Ohio Valley on Monday
night may spread some high clouds into West Virginia and the
northern half of Virginia. This should have little impact on minimum
temperatures. Staying at or below guidance for lows both Saturday
night and Sunday night.


As of 110 PM EDT Friday...

Operational ECMWF and GFS and the ensembles were in fairly good
agreement with the overall pattern Tuesday and Wednesday. Pattern
remains progressive and weak upper ridging moves across the central
and eastern United States. Seeing typical bias with the slower ECMWF
and faster GFS with a closed low that moves out of the Pacific and
into the southwest United States by Tuesday. Bases more on the ECMWF
timing this feature will reach the Mid Atlantic region around
Thursday. Bigger spread in the guidance for the timing and location
of synoptic features on Thursday and Friday.

Warm air advection and west surface to low level wind on Tuesday so
maximum temperatures will be near or slightly above normal depending
on cloud cover.


As of 1230 PM EST Friday...

High pressure will continue to provide for VFR conditions
through the conclusion of the valid TAF period, 18Z/1PM

Low level winds will be on the increase tonight in advance of an
approaching cold front. While surface winds will remain
relatively light, an increasing low level jet will yield 30 to
35 kt winds around 850mb towards daybreak Saturday. Look for the
development of low level wind shear around this this time over
parts of the area. Currently, none is specifically forecast
within any of the TAFs. However, the area between KBCB and KBLF
will have the best opportunity to experience LLWS.

Extended Discussion...

On Saturday afternoon a cold front will cross the area. It will
be moisture starved for the most part, with at best some
isolated showers across the western sections the area along
with some periods of MVFR ceilings also along western slopes.
Otherwise VFR conditions Saturday afternoon and Saturday night
but with west to northwest winds behind the front of 10-20 kts
with gusts to 30 along highest ridges.

High pressure regains control of our weather pattern Sunday
into Monday with VFR for the entire region.

The next potential chance for sub-VFR conditions is not until
late next week at the earliest.




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