Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 191344

Area Forecast Discussion
National Weather Service Blacksburg VA
944 AM EDT Thu Oct 19 2017

A large area of high pressure will remain over the eastern part
of the country this week before slowly sliding off the coast on
Saturday. This will keep skies mostly sunny and allow
temperatures to warm to above normal levels. Early next week, a
strong cold front and deep upper trough will approach from the
Midwest bringing widespread rain showers followed by much cooler


As of 944 AM EDT Thursday...

Valley fog will continue to burn off this morning, leaving us
with another fine fall day for this afternoon. Full sun and dry
conditions will allow for another day with wide diurnal
temperature variation on the order of 40 degrees at some
locations. Highs today a couple degrees warmer than readings

Previous discussion...

Surface high pressure will remain firmly entrenched across the
area today allowing for another bright, blue, sunny day. A weak
and dry upper-level trough was passing over the area this
morning with the only notable associated weather some passing
high clouds. This weak upper trough will continue to move east
of the area today as ridging aloft develops just upstream of the
area. 850mb temperatures will continue to hover in the +10C to
+12C range today, yielding temperatures on par with what we saw
Wednesday. However, with the center of the large surface high
shifting toward the eastern part of the CWA, winds will come
around to the southwest by afternoon for areas west of the Blue
Ridge. This should allow temperatures to creep up a few degrees
in comparison to what we saw yesterday. With the center of the
cool high across eastern areas, they should be the coolest
overall today. Maximum temperatures will be 5-10 degrees above
normal and mostly in the 70s, except 60s higher elevations.

Minimum temperatures Friday morning will continue to warm a few
degrees compared to the previous day and all locations should
remain at or above 37F, mainly in the 40s across the forecast
area. Thus, no frost was included in the grids at this time.
Patchy fog may develop in river and mountain valleys mainly west
of the Blue Ridge.


As of 300 AM EDT Thursday...

An awesome weekend is shaping up weatherwise as a strong ridge of
high pressure is forecast to linger through Sunday. This feature
will maintain the fair dry weather, with temperatures 5 to 10
degrees above normal.

Enjoy the weekend because next week will be unsettled. Clouds will
begin to increase late Sunday, an indication of changes on the


As of 300 AM EDT Thursday...

An active upper air pattern is forecast for next week as full
latitude long wave trough gets carved out over the east central
Continental U.S. (CONUS).  Models indicate an abundance of short
wave energy flowing into the western CONUS this weekend with some of
the energy becoming isolated on the west side of subtropical ridge
of high pressure over the Southeast U.S., and developing into a
cutoff low in the vicinity of the Lower MS valley. This cutoff low
is forecast to eject northeast across the Mid-Atlantic Monday into
Tuesday in an almost winterlike fashion as this energy phases with
an ever increasing energetic northern stream trough along the U.S.
Canadian border. The net result will be a highly amplified full
latitude long wave trough by mid-week which will feature a
significant change in temperature for much of the eastern U.S.

Model consensus is for rain to develop from southwest to northeast
across the region Sunday night into Monday, with the highest
probability for measurable rainfall occurring Monday night into
Tuesday as the southern stream Low ejects northeast across the
region. Stability indices suggest slight potential for thunder Tue.

With the upper trough becoming established over the eastern CONUS
for mid week, temperatures will take a tumble. Arrival of cooler air
Tuesday night into Wednesday may result in some p-type transition
(wet snowflakes?) for the highest elevations of WV/NC and far
western VA, followed by brisk/breezy conditions.


As of 740 AM EDT Thursday...

High pressure will remain firmly entrenched across the region
at the surface through the period. Very patchy morning fog,
resulting in very localized MVFR conditions, will dissipate
quickly within an hour or two of sunrise. Patchy cirrus can be
expected from time-to-time, but most have moved east or south
of the area now. So, much of the TAF valid period will be SKC.
Patchy fog is expected again Friday morning, but again only on
an isolated basis, mainly BCB and LWB. Soon after sunrise,
surface winds should come around to mostly a west or southwest
direction at speeds of 4-6kts. Winds will tend to be more
variable east of the Blue Ridge closer to the center of the
surface high.

High confidence in ceilings and visibilities through the TAF
valid period. except in the 10Z-13Z time frame this morning and
Friday morning because of patchy fog.
Medium confidence in wind direction, high confidence in wind
speed through the TAF valid period.

Extended Aviation Discussion...

High pressure will remain over the region through Sunday with
generally VFR conditions expected, outside the usual late
night/early morning patchy river and mountain valley fog.
A deep upper trough and associated strong cold front will move
into the region from the west by Monday promising a period of
sub-VFR conditions in rain/showers along with increasing wind.
Colder, blustery, unsettled weather with perhaps largely MVFR
conditions across the mountains will linger through the later
half of next week as an upper trough cuts off across the central




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