Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 241111

Area Forecast Discussion
National Weather Service Blacksburg VA
711 AM EDT Mon Oct 24 2016

A dry cold front will slide southeast across the mountains this
morning before passing to the south of the area this afternoon.
High pressure builds in behind the front later today into
Wednesday bringing continued dry and cool weather. Another cold
front looks to cross the region on Thursday with the next chance
of showers.


As of 230 AM EDT Monday...

Deepening upper trough across the northeast U.S. along with northwest
flow aloft will propel a reinforcing cold front through the region
by this afternoon. Main concern continues with stronger westerly
winds just ahead of the boundary this morning, and perhaps with
northwest trajectories for a while behind the front across the
north/west with mixing this afternoon. However given the best jet
aloft early this morning and weakening subsidence this afternoon
as better dynamics pass north, expecting to stay below wind advisory
criteria, but quite breezy/windy espcly northern sections.
Moisture along the front remains quite limited with mostly upslope
aided low clouds that could spill east out to the Blue Ridge this
morning before enhanced post frontal drying occurs. Cant totally
rule out a light shower/sprinkle far northwest mountains as a
shortwave swings by within the upper trough and the better cool
advection develops per latest HRRR but quite iffy. Otherwise
becoming mainly sunny and still rather mild espcly south/east
given lagging cool advection that looks to hang up across the
mountains until later this afternoon. Since this in light of good
downsloping, bumped up highs a good category or more in spots
today with 72-78 east and 61-68 west.

Decent surface ridge builds in behind the front from the northwest
overnight which should allow any lingering upslope clouds to fade and
winds to diminish this evening. However how fast winds decouple and to
what degree remains in question given the parent high still back in the
Ohio Valley around daybreak. Models do attempt to develop a bit of a
bubble high across the mountains where likely to see the deeper valleys
espcly northwest sections lose the gradient for a longer period late.
Also dewpoints look rather low for much frost so given this
combination, cut back frost to more patchy nature in the valleys and
without any advisory headlines at this point. Otherwise mostly clear
with lows ranging from the mid 30s to lower 40s excluding localized
near 30 readings in deepest valleys.


As of 215 AM EDT Monday...

During the first half of this portion of the forecast, surface high
pressure will dominate the weather pattern our our region.
Concurrently, a broad upper level ridge will strengthen across the
central portion of the United States. A persistent upper low/trough
will continue to spin across the Pacific Northwest. By Wednesday
night into Thursday, a piece of energy from the low/trough across
the Pacific Northwest will eject eastward and push through the top
of the upper ridge.

By Thursday morning, the low will progress eastward from the Great
Lakes region into PA/NY/NJ.  Its associated cold front will cross
our area during the day. The latest guidance offers a solution with
a faster arrival and departure times than previously advertised. As
such, have increased the coverage across the western parts of the
area late Wednesday night, and adjusted the peak of coverage across
the area to the forenoon hours Thursday. By late Thursday night,
coverage is expected to be confined to southeast West Virginia
within the upslope flow in the wake of the exiting system.

Average daily temperatures will trend a little cooler through
Wednesday, and then increase slightly Thursday. As a whole, readings
will be near normal for this time of year.


As of 300 PM EDT Sunday...

An area of weak high pressure builds in behind the front from the
northwest on Friday.

Models are not in agreement with next weekends weather. The GFS
quickly brings the next cold front across the region Saturday. The
ECM has high pressure lingering into Friday night, with a warm
frontal passage Saturday followed by a cold front on Monday.

Temperatures will moderate toward normal on Friday. Next
weekends temperatures will depend on timing of each frontal
passage. For now, will carry seasonal temperatures.


As of 645 AM EDT Monday...

Weak cold front pressing in from the north/northwest should push
across the mountains this morning and elsewhere during the
afternoon if not sooner. Given dry air in place, still expecting overall
VFR to prevail today and tonight. Could continue to see periods
of scattered to broken strato-cu near the KLWB-KBLF corridor, along
and espcly behind the front as cool advection/upslope kick in
through early this afternoon. However expecting most of this
canopy to have bases above 3k feet before all moisture mixes out
later this afternoon given mixing of very dry air behind the

Main issue continues with the lingering low level jet early this
morning and subsequent wind shear per near calm surface winds in
spots to start. Guidance suggests enough weakening of the winds
aloft combined with mixing to help alleviate wind shear issues by
mid or late morning. Thus will keep LLWS in until mixing occurs
along and just behind the front by later this morning.

Behind the front winds should gust at times to 20-25kts, then
weaken again by the end of the day as high pressure starts to
build in from the northwest by tonight.

Extended aviation discussion...

Tuesday and Wednesday...Potential for river valley fog in the
mountain valleys with local vsby restrictions between 08-14Z each
morning, otherwise widespread VFR.

Thursday...Low pressure is forecast to move across the upper
midwest and into the Great lakes with a surface front crossing the
Ohio Valley. Threat for showers and sub-VFR will be possible
along this front which would impact the central Appalachians by
Thursday. Attm, this does not appear that it will have a
significant impact to our region. Biggest impact would be from
Ohio Valley north into Great Lakes closer to the surface low.

High pressure builds in from the northwest Friday, with potential
MVFR ceilings at BLF/LWB before the high arrives.


As of 300 AM EDT Monday...

Little or no rain has fallen across the northwest North
Carolina Piedmont in the last 14 days. Conditions are becoming
increasingly dry for western North Carolina, espcly just east of
the Blue Ridge. Drying conditions will continue for this region
again today, and for much of the upcoming work week. Passage of a
dry cold front by this afternoon may pose control problems for
any fires in the lee of the Blue Ridge, and especially for areas
which have not seen rainfall. Greatest concern would be from Mount
Airy, North Carolina, and areas to the southwest, including Pilot
Mountain. Wind gusts of 15 to 25 mph are possible into this
afternoon, coupled with humidity minimums in the 25 to 35 percent
range which will cause added drying of smaller fuels. Therefore
plan to include a headline for now in the fire weather forecast as
a heads up for low humidity and gusty winds today.




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