Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 181443
AFDRNK

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

.SYNOPSIS...
A warm front will lift north across the area today, followed by
a strong cold front tonight. 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 940 AM EST Saturday...

Made a few changes to the hourly grids to reflect rapidly
increasing temperatures where increased mixing has removed low
level inversion, and also to delay onset of any precipitation
until around or after sunset. After making adjustment for the
next three to four hours to boost rate of thermal climb where
needed, overall thermal trend should merge back into previous
forecast curve by noon.

No ground-based precipitation is evident upstream in central or
southern WV, with only virga noted. Therefore, sprinkles or
light showers no longer expected in Greenbrier County this
morning or in the early-mid afternoon. Further west,
precipitation moving into western KY scant at best, and latest
higher resolution short-range guidance consistent in not
allowing lower troposphere in Blacksburg forecast area to
saturate sufficiently to support ground-based precipitation
until around/after sunset, even across the western portion of
the area - with the better threat of precipitation delayed
until at least mid- late evening.

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 /15Z SATURDAY THROUGH WEDNESDAY/...
As of 630 AM EST Saturday...

Not much change to the previous thinking, as will see southwest
winds increase ahead of a cold front today, with increasing
mid/high clouds. Should be VFR through the day with showers and
MVFR cigs at BLF/LWB arriving after 23z.

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, reaching
BCB/ROA in the 00-02z time frame and LYH/DAN in the 03z-05z time
frame. With strong mixing of winds most of the time will be MVFR
to VFR both cigs/vsbys at all sites. May see IFR cigs at times
late tonight at BLF. Winds shift from the south to southwest by
midday, then west this evening and overnight. Gusts as high as
30 to 50 mph may occur at the mountain taf sites, including
Roanoke, with 20 to 35 mph.


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...

Sunday morning will see some snow showers in BLF possibly LWB
with cigs dropping to IFR at times, while MVFR cigs improve to
VFR with clouds clearing east of the mountains by 15z.

Winds remaining up through the day, with another surge of higher
gusts expected by Sunday evening around dusk. Mountain snow
showers coming to an end by Sunday evening.

Northwesterly winds finally abate by late Sunday night, as high
pressure builds in from the southwest. Conditions then
transition to VFR Monday through Wednesday.

&&

.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...WERT/WP
NEAR TERM...WERT/WP
SHORT TERM...DS
LONG TERM...JH
AVIATION...RAB/WP



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