Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 180839
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
339 AM EST Sat Nov 18 2017

.SYNOPSIS...
A warm front lifts north across the area this morning, followed
by a strong cold front overnight. Colder temperatures follow
this front for Sunday along with windy conditions, starting
tonight. High pressure builds in from the southwest late Sunday
into Monday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 322 AM EST Saturday...

Noticable temperature differences this morning between the mountains
and piedmont where clouds and mixing winds have kept readings in
upper 40s to lower 50s across southwest VA near Richlands/Abingdon
into southern WV, while clearer skies and light winds allow temps to
fall into the mid 30s in the piedmont.

For today, should see increasing clouds as southwest flow increases
ahead of a digging upper trough moving into the mid-MS valley. A
warm front works northward across the Ohio Valley, central
Appalachians with a few showers scattered along it, which may scrape
our Southeast WV counties this morning. Otherwise looking at
prefrontal showers arriving in the mountains by late
afternoon/evening and shifting east to the piedmont by midnight. A
narrow very wind driven line of showers with embedded thunder should
impact WV  by early evening. Some of these showers could mix down
the stronger winds with the showers, especially in higher ridges.
The main line exits to the east by late tonight with dry slot
working toward the NC foothills. Strong post-frontal winds along
with 6 hr pressure rises of 5 to 9 mb will amplify the winds in the
mountains overnight into early Sunday before subsiding. Running
local study on winds with model guidance puts most of the western
CWA in wind advisory level winds, which is gusts 46-57 mph, though
most will be in the 45-50 mph range. After collaboration with
neighboring weather offices, agreed to post wind advisory from late
this afternoon through noon Sunday, first for the potential strong
prefrontal winds and mainly for the post frontal winds. Stronger
winds look to occur midnight to 8am tonight-Sunday.

As the front passes cold air advection will switch rain showers to
snow showers in the mountains of WV down to the high country of NC.
Again deeper moisture appears to push out as cold air rushes in,
then you get upslope snow showers. Through 12z Sunday around an inch
could fall in the western slopes of Greenbrier county with a dusting
elsewhere in the higher ridges of SW VA into NW NC.

Expect mild temps today with upper 50s to mid 60s area wide.
Temperatures tonight will drop to the upper 20s to lower 30s higher
elevations after midnight, to mid to upper 30s rest of the
mountains, while cold air battles downsloping winds with a warming
effect in the east, where lows should be in the mid to upper 40s.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
As of 215 AM EST Saturday...

Gusty northwest winds, with the higher ridge tops in the Advisory
level category, still look promising through mid-day Sunday. By the
afternoon there will be a lull in the stronger winds, only to
reinforce again Sunday night with the passage of yet another jet
max. At this time, there is no plan to have a second Wind Advisory
in place to account for this feature. Would prefer to have the first
come and go prior to any second one. Plus there still is time to
assess the trends future model runs of this feature. However, it is
prudent to have this second surge referenced in the Hazardous
Weather Outlook.

Upslope isolated/scattered rain/snow showers are still expected
across parts of southeast West Virginia, south into the Northern
Mountains of North Carolina during the Sunday and Sunday night time
frame, with decreasing coverage from south to north Sunday night.
Where snow accumulates will be limited to the highest elevations
with totals generally around or less than one inch.

Temperatures on Sunday will struggle to rise much at all in the
west, with only limited increase in the east from the overnight lows
Saturday night. Low temperatures Sunday night will range from the
low to mid 20s across the mountains with upper 20s to near 30 across
the Piedmont.

Monday into Tuesday, look for high pressure to enter the region from
the west and exit to the east. The result will be a gradual trend
towards the prevailing winds becoming southwest, with milder
temperatures. By Tuesday high temperatures will range from the low
to mid 50s across the mountains with mid to upper 50s across the
Piedmont.

A shortwave trough will push through the Great Lakes region Tuesday
night. Moisture and lift will be limited across the area with
precipitation unlikely. More promising will be an increase in cloud
cover, especially across western sections of the area.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
As of 300 PM EST Friday...

A more upper level split flow regime looks to develop for the
rest of the week. High pressure builds in Wednesday afternoon
through Friday. This should result in overall quiet weather with
slightly below normal temperatures through Day7.

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
As of 1230 AM EST Friday...

VFR conditions will continue through 19z Saturday, then MVFR
conditions with convection will enter the forecast area. Look for
ceilings to fall into the MVFR range late Saturday into
Saturday night as a narrow line of showers/convection accompany
the frontal boundary through the region. Until then, ceilings
should mainly be VFR.

Winds will increase from the southwest Saturday as the front
approaches and the large high pressure shifts into the western
Atlantic. By afternoon, low end gusts can be expected at most
TAF sites. Low-level winds will strengthen considerably during
the later portion of the TAF valid period as a strong 850mb LLJ
approaches the region with the front. Areas of low-level wind
shear can be expected.

Visibilities will be VFR for the most part, although a brief
period of MVFR-IFR will be possible in heavier rain showers late
Saturday. Will not include any thunder at the TAF sites given
the lack of indicated instability.

Medium confidence in ceilings through the TAF valid period.
Medium to high confidence in visibilities through the TAF valid
period.
High confidence in wind direction and speed through the TAF
valid period.


Extended Discussion...

A strong cold front moves across the region Saturday night into
Sunday. This will lead to several impacts to aviation,
including a period of rain changing to mountain snow showers
(possible -SHSN at Bluefield) and a frontal wind shift to
northwest with wind gusts further increasing areawide. Best
chance at sub-VFR conditions is Saturday night into Sunday.

For Sunday, may see a continuation of sub-VFR stratus in the
western Appalachians, with breezy/gusty northwesterly wind
conditions areawide also continuing. May see mountain snow
showers coming to an end later Sunday afternoon.

Northwesterly winds finally abate by late Sunday evening.
Conditions then transition to VFR Monday through Thursday.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Wind Advisory from 4 PM this afternoon to noon EST Sunday for
     VAZ007-009>020-022>024-032>035.
NC...Wind Advisory from 4 PM this afternoon to noon EST Sunday for
     NCZ001-002-018.
WV...Wind Advisory from 4 PM this afternoon to noon EST Sunday for
     WVZ044-507-508.

&&

$$
SYNOPSIS...WP
NEAR TERM...WP
SHORT TERM...DS
LONG TERM...JH
AVIATION...AL/KK/RAB


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