Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 230754

Area Forecast Discussion
National Weather Service Blacksburg VA
354 AM EDT Fri Sep 23 2016

Low pressure along the coast of the Carolinas will weaken and head
east tonight. A back door cold front enters the area by Saturday
night. As it moves south of us Sunday the flow turns east which
brings in more clouds and a threat of showers into early next


As of 305 AM EDT Friday...

Upper trough situated across the mid-Atlantic and Southeast will
continue to weaken and get kicked eastward ahead of a digging
northern stream shortwave over the northeast through late tonight.
Model do cut off a piece of the upper energy and drift it southwest
to southern Georgia. For our area the upper heights will begin to
build as strong ridge pushes into the Mid Mississippi Valley.

The few showers over southside Virginia into northwest NC will fade
and/or shift southeast of the forecast area by mid morning. Should
see increasing sunshine. There will be a difference in dewpoints
from the mountains to the piedmont, ranging from the mid 50s west to
mid 60s southeast. With drier air and sunshine temperatures are
expected to warm into the 80s, except some upper 70s higher

Tonight, the high pressure at the surface will keep light winds in
place with mainly clear skies. Backdoor front expected to slide into
northern Virginia by 12z Saturday and may push a few clouds toward
the Shenandoah Valley but overall generally clear. Patchy fog in the
river valleys possible in the west. Lows will vary from the mid 50s
deeper valleys in the west to lower to mid 60s elsewhere.


As of 345 AM EDT Friday...

A high amplitude upper level ridge will be building over the eastern
part of the country through the weekend. This will allow surface high
pressure over central Canada to build southward and wedge down the east
side of the Appalachians. After one last very warm day on Saturday, the
wedge will surge into the region behind a backdoor front moving in from
the northeast. Temperatures will be much cooler behind the front and
guidance indicates a good deal of low level moisture and isentropic
lift over the wedge. This looks to bring abundant cloud cover and some
light precipitation to the region for Sunday and into the first part of
next week. By Monday the axis of the upper ridge will move to our east
and allow a large closed low over the Great Lakes region to push a cold
front toward the region from the west. Southwest flow ahead of the
front will continue to generate lift over the wedge, while the western
and southern portions of the region on the fringes of the wedge may get
into enough unstable air to support a slight chance of thunder. Thus,
Monday looks to be another cloudy and cooler day with a chance for

Will continue the trend of lowering max temperatures for Sunday and
Monday as the wedge looks to be solid and wet bulb temperatures are in
the 60s so any precipitation into the wedge will be effective in
holding temperatures down. So after temperatures on Saturday reach well
into the 80s, locations east of the Blue Ridge will be looking at
readings in the lower 70s by Monday with some warmer temps along the
western and southern fringes.


As of 345 AM EDT Friday...

An upper level low over the Great Lakes will slowly push a cold front
into the region Wednesday, then the front stalls just east of the
Blue Ridge. With a blocking pattern in place and the upper low
becomes cutoff from the steering flow per the 12Z GFS, the second
half of the week could be very wet for the region. The Euro also
stalls the next front over the area Wednesday but is booted to the
east by Thursday. Needless to say, there is very little confidence
in next week`s forecast.


As of 125 AM EDT Friday...

Just a few showers near DAN early this morning so kept VCSH in for
another few hours. Looks like DAN will be the only site with MVFR
conditions this morning in terms of ceilings. Given how dry it has
been, fog has not be an issue, however with cooler temperatures,
may see some radiation fog at BCB/LWB but not going any worse than
2sm. Confidence is not high on this, as with these sites it
usually runs either P6sm or < 1sm.

Friday during the day will be seeing clearing with Danville coming
to VFR by 16z. High pressure will keep it VFR til the end of this
taf period with deeper moisture staying southeast of our forecast

Extended aviation discussion...

VFR conditions will prevail through Saturday with high pressure in
place. A back door front passes across late in the weekend into
early next week which may bring sub VFR ceilings as an easterly
flow sets up. These MVFR or lower ceilings may stay in place
through Monday. Rainfall chances will stay low however, though
some upslope component from the southeast could bring showers/rain
to along the Blue Ridge south of Roanoke/Blacksburg Monday.

A strong, but slow moving, cold front will be approaching the
area from the west on Tuesday. Models have significant differences
on the timing and location of this front.




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