Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 171131

Area Forecast Discussion
National Weather Service Blacksburg VA
731 AM EDT Tue Oct 17 2017

High pressure will remain across the area through Friday.


As of 345 AM EDT Tuesday...

Temperatures at 850 MB rise from around +4 this morning to near +10
Wednesday morning. Long wave trof moves offshore this morning.
Expecting subsidence with little to no cloud cover today and

Cold air over the warmer lakes and rivers has produced fog along the
Bluestone, Clinch, and Greenbrier River this morning. This fog will
dissipate quickly after sunrise as will the frost. Will leave the
Frost Advisory in place through 9AM. Dry air mass will result in a
large spread between morning lows and afternoon highs. Blend of
MET/MAV guidance is reasonable for maxes today.

More frost and potentially freezing temperatures are expected
tonight. The surface high will be centered over western Virginia
with little change in this pattern through morning. This will lead
to calm to light and variable wind. Coldest air will be out of the
region but conditions are ideal for radiational cooling. Have gone
toward the cooler MET/National Blend guidance for overnight lows.
Will issue a Frost Advisory for areas west of the Blue Ridge for
tonight. Advisory may need to be expanded east based on a final
look at the 12Z model cycle today.


As of 240 AM EDT TUESDAY...

High pressure will be centered over the mid-Atlantic region
Wednesday and Thursday promoting dry weather, light winds and mainly
clear skies.  Large nocturnal/diurnal temperature swings are
anticipated with lows in the 30s/40s and highs in the 60s/70s.
Persistent subsidence will allow some very dry air to work its way to
the surface from aloft, especially across the highest elevations
where dewpoints may dip into the single digits and teens for
elevations above 3500 feet by 12Z/8AM Thursday. This will likely
promote minimum humidity readings in the 15-25% range, 5-10% below
MOS guidance.


As of 217 PM EDT Monday...

Amplified upper ridge over the southeast will keep us on the warmer
side of normal and dry heading into the weekend. By Saturday night,
the ridge axis begins to get kicked east of our area by a deepening
trough  pushing into the middle of the country. Models are
disagreeing on the depth of the trough with GFS weaker than the
Euro, as it closes off a southern low over southern TX. The Euro on
the other hand closes to low off further north closer to the
northern TX. Since both show low closing off, and upper flow turning
more southwest, influx of moisture should bring increasing chances
of showers by early next week. Should be a dry weekend followed by a
good chance of showers Monday. Temperatures staying above normal
during this period.


As of 135 AM EDT Tuesday...

After LIFR to IFR river valley fog burns off this morning,
conditions will be VFR for the rest of the day. Some freezing
fog is likely this morning in isolated valleys of Tazewell
County VA and Greenbrier County WV.

Areas of frost are likely in sheltered valleys this morning.
Fog along the Greenbrier River has filled the valley and
impacted the KLWB airport. High confidence that fog will burn
off before 14Z/10AM. Medium confidence that fog will form again
tonight along the river and bring LIFR conditions back to KLWB
after midnight.

Extended Aviation Discussion...

High pressure will remain over the region for the week with VFR
weather through Saturday.


VA...Frost Advisory until 9 AM EDT this morning for VAZ007-009>014-
     Frost Advisory from 2 AM to 9 AM EDT Wednesday for VAZ007-
NC...Frost Advisory from 2 AM to 9 AM EDT Wednesday for NCZ001-002-
WV...Frost Advisory until 9 AM EDT this morning for WVZ042>044-507-
     Frost Advisory from 2 AM to 9 AM EDT Wednesday for WVZ042>044-


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