Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 260206

Area Forecast Discussion
National Weather Service Blacksburg VA
1006 PM EDT Tue Oct 25 2016

Cool high pressure will build in from the northwest tonight and
remain wedged along the eastern slopes of the Appalachians into
Wednesday. Low pressure crossing the Great Lakes will push a cold
front through our region on Thursday. High pressure follows the
front for the end of the week.


As of 1002 PM EDT Tuesday...

Clouds mainly confined to the Alleghanys but some sneaking past
the Blue Ridge. Temperatures have fallen into the lower to mid 40s
in the piedmont. Still dewpoints around 40-45. At the moment looks
like frost will be patchy enough to have no headlines. Still any
folks worried about any sensitive plants or crops should bring
them in.

Previous early evening discussion...

Clouds of the mid and high variety streaming in from speed max to
our northwest over the Alleghanys and SE WV, with another area
over Eastern TN into Western NC. These clouds plus dewpoints in
the lower to mid 40s out east should preclude any widespread frost
in the foothills and piedmont. Dewpoints are lower to the north
and are expected to advect southward overnight. Will have to watch
how cloud cover morphs over the next few hours and see if we need
a frost advisory out east. At the moment expecting only patchy
frost east of the Blue Ridge.

Previous discussion from the afternoon...

High pressure bubble over eastern Virginia/North Carolina this
afternoon will linger overnight allowing temperatures to radiate
down into the 30s tonight. Temperatures will be cold enough for
frost to form, especially in rural low lying areas. However, upper
level trough over the northeast corner of the US and a warm front
entering the Ohio Valley, may push warm air advection high clouds
into the region overnight limiting frost potential. Since we are
not expecting a hard freeze and high clouds could be a limiting
factor, we will only have patchy frost for tonight east of the
Blue Ridge. Even with cloud cover, many mountain locations will
see more widespread frost, but we will not add to the weather
grids or issue any headlines as the growing season for areas west
of the Blue Ridge has ended (see PNSRNK issued at 922 AM).

A second area of high pressure will wedge south over the forecast
area tomorrow. Some low clouds may accompany this wedge in the
morning, but given the lack of moisture, they will not advance
much southward past the Alleghany Highlands and the Hill City of
Lynchburg. With the lack of clouds and a dry air mass,
temperatures should be able to rebound in the afternoon into the
upper 50s to lower 60s for areas east of the Blue Ridge and in the
wedge. With a warm front tracking north across the Ohio Valley and
the wedge eroding across southwestern Virginia through the day,
the warmest area may be the Richlands-Bluefield tomorrow with
highs in the mid to upper 60s. This area may also have breezy and
gusty conditions with a downsloping southeasterly flow. For the
rest of the mountains north of highway 460 and along the Blue
Ridge may only warm to near 60F tomorrow.


As of 300 PM EDT Tuesday...

The upper ridge axis will move east into Atlantic ocean Wednesday
evening into Wednesday night as a trof approaches our region from
the west. Low pressure over Illinois Wednesday evening will travel
northeast reaching western Pennsylvania Thursday morning and
continue across New England Thursday night into Friday.

The bulk of the shortwave energy in the trof appears to remain
off to our north, along with the best isentropic lift and
strongest winds in the southwesterly low level jet. A cold front
associated with the low will approach Wednesday night and moves
through our area on Thursday.

Clouds increase Wednesday night with isolated to scattered
showers possible in the west. Low temperatures Wednesday night
will range from around 40 degrees in the northern mountains to the
upper 40s in the Piedmont. Scattered convection associated with
cold front will move east across our area Thursday. High
temperatures Thursday will vary from the upper 50s in the
northwest mountains to the upper 60s in the Piedmont.

As the cold front pushes off to our east Thursday night, blustery
west winds combined with lingering moisture will maintain a chance
of showers in the mountains. Low temperatures Thursday night into
Friday morning will drop to around 40 in the northwest mountains
to the lower 50s in the Piedmont.

High pressure will build southeast into our region Friday into
Friday night. It will be breezy Friday with seasonable Highs from
the lower 50s in the mountains to near 70 degrees along the
southern Blue Ridge. Low temperatures friday night into Saturday
will generally be in the Lower and Mid 40s.


As of 250 PM EDT Tuesday...

Low pressure over the Great Lakes Saturday will travel northeast
across New England Sunday and push off into the Atlantic Sunday
night. A nearly dry cold front associated with low center will
move south across our area. The richest moisture along with most
of the convections remains north of our area. The ECMWF remains
stronger further south with shortwave compared to GFS. This
difference effect the timing of frontal passage. High pressure
will settle south for the end of the weekend into early next

Temperatures may cool behind the front Sunday especially in the
northwest, but for most areas will remain above normal into early
next week.


As of 720 PM EDT Tuesday...

Cirrus and altocu is all that is expected through the period
mainly scattered, but at times broken over LWB. VFR continues
through the period. Winds will shift southeast to east by
Wednesday afternoon.

Extended aviation discussion...

Still expecting overall VFR to continue into Wednesday night with
surface high pressure ridging south across the region. However
some potential to see areas of sub-VFR in patchy strato-cu espcly
Blue Ridge and points east although confidence low given such dry
air in place.

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
afternoon. However given best support passing to the north and
limited moisture, expecting best potential for lower cigs/vsbys to
occur across the western mountains and across northern portions of
the area at this point.

High pressure builds in from the northwest Friday, with potential
MVFR ceilings at KBLF/KLWB before the high arrives. Another front
may cross through the region on Saturday with possible showers and
MVFR ceilings in the mountains. However, models were still showing
differences in the timing of the weekend system.


As of 315 PM EDT Tuesday...

Very dry conditions will continue as high pressure builds into
the region from the northwest and wedges down east of the
mountains through Wednesday night. With an easterly wind, humidity
will recover a little on Wednesday and moreso Wednesday night
ahead of an approaching cold front. This front should bring the
next round of scattered showers Thursday although the chances for
widespread wetting rainfall appear low at this point. Dry air
returns again for the end of the week behind the front.




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