Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Remove Highlighting --
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FXUS61 KRNK 011939
Area Forecast Discussion
National Weather Service Blacksburg VA
339 PM EDT Sat Oct 1 2016
Low pressure was over the Ohio Valley and a front was along the
Mid Atlantic and Southeast coast. By Monday high pressure will
build in over much of the eastern United States and remain over
the area through Wednesday. Toward the end of the week a cold
front will approach the region from the west while Hurricane
Matthew tracks off the southeast coast.
.NEAR TERM /THROUGH SUNDAY/...
As of 325 PM EDT Saturday...
Tonight the upper low begins to move northeast then feature will be
over the eastern Great Lakes on Sunday. A low level trof crosses
into the central Appalachians on Sunday turning the surface winds to
the west. Models were showing some moisture below 700 mb over the
mountains on Sunday. Will keep more cloud cover over the mountains
and less east of the Blue Ridge Sunday.
Lows cloud and fog had cleared out as of noon. Good mixing with the
drier air mass above the surface had dew points in the lower 40s to
lower 50s. Enough clearing and winds decouple tonight for a surface
based inversion. Expecting fog in the river valleys. Will stay
cooler than guidance for the overnight lows, especially in the
sheltered valleys. Locations that get more sun on Sunday will have
maximum temperatures about 5 degrees above normal.
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 245 PM EDT Saturday...
During this portion of the forecast, the upper low that has been
parked over the Ohio Valley the past several days, will progress
northeast in advance of a building upper ridge across the
Mississippi Valley. This upper ridge will progress eastward so that
by Tuesday into Tuesday night, it is expected to be overhead. At the
surface, high pressure will build over NY/PA and nose south along
the lee of the Appalachians, forming a wedge that will be in place
across central and eastern parts of the area by late Tuesday night.
Our forecast will reflect a precipitation free forecast through
Tuesday, along with limited cloud cover. Conditions will change as
we progress into Tuesday night. The strengthening wedge and an
increasing onshore flow will yield an increase in cloud cover, along
with the potential for some light rain and patchy drizzle along and
near the crest of the Blue Ridge from roughly Floyd, VA to points
Temperatures during this portion of the forecast will experience
little change from day to day with readings averaging around five
degrees above normal for this time of year.
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 315 PM EDT Saturday...
This portion of the forecast will have a number of challenges to it,
especially in the latter half. The lee side wedge is expected to
hold fast through at least Wednesday, if not Thursday. Small chances
of precipitation will continue through this time period. The
activity may transition to be a bit more showery in nature towards
Thursday, depending on just how much or little we experience in
Friday into Saturday, the forecast will ride on just where Hurricane
Matthew tracks and how quickly. Flow on the northern side of the
system could help greatly enhance the wedge through at least Friday
if it has a track near or across eastern North Carolina. This track
would also allow for associated precipitation and strong winds to
impact the eastern parts of the forecast area on Saturday, via the
left track leaning operational GFS. The 12Z/8AM ECMWF solution is
trending farther west than its 00Z/8PM counterpart, but its solution
is farther east and slower compared to the 12Z/8AM GFS.
The track of the storm also will affect how quickly or involved an
approaching cold front will impact our region at the start of the
weekend. Our forecast will reflect a solution that keeps some
remnant of the wedge across the area still on Friday along with
light precipitation mainly the east, but also allows for
precipitation associated with the approaching cold front to reach
western parts of the area late Saturday.
Temperatures during the period will trend slightly milder through
Friday, with a small decrease on Saturday. Readings will continue to
average around five degrees above average.
.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
As of 135 PM EDT Saturday...
IFR fog and stratus over southwest Virginia and southeast West
Virginia had dissipated as of noon today. Satellite pictures
showed scattered stratocumulus clouds over the region at 1PM.
Winds will decouple tonight and a shallow surface based inversion
will form. High confidence of MVFR to LIFR fog formations in the
river valleys. Lower confidence how much fog will develop east of
the Blue Ridge.
Fog and any low clouds will dissipate quickly after sunrise on
Sunday. High confidence of VFR conditions by 14Z/10AM.
Extended aviation discussion...
The deep upper level low will finally shift farther to the north
and away from the region on Sunday. The weather will trend back
into a dry pattern with mainly VFR conditions next week. However
some sub-VFR low clouds may occur along the eastern slopes of the
Appalachians later Monday night into Tuesday night as the next low
level wedge develops. Also appears some river valley fog could
occur in the mountains, resulting in brief period of late night
early morning LIFR conditions at some of the mountain valley
airports through Wednesday, especially KBCB and KLWB.