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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 210131
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
931 PM EDT Tue Apr 20 2021

.SYNOPSIS...
High pressure will give way to the passage of a strong cold
front Wednesday. Expect windy conditions with the passage of
the cold front along with falling temperatures. Well below
normal temperatures can be expected into early Friday. An area
of low pressure will bring rain to the area for the weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 920 PM EDT Tuesday...

   Minor changes to the timing of the cold front Wednesday.

A late season winter interlude is taking place over the nations
mid section with some very cold air over the nations mid section
clashing with warming temperatures in the east. The cold front
which bisects this change in airmass is expected to cross our
forecast area Wednesday morning. It will be a very noticeable
change.

For tonight...ahead of the front...isolated showers over the
mountains will gradually move move northeast and dissipate. Much
of the HiRes guidance had little to no precipitation after
06Z/2AM. Have made minor adjustments to the probability of
precipitation and overnight temperatures based on the latest
radar and observation trends.

For Wednesday...a strong cold front will cross the forecast
area between 8AM and Noon, impacting the mountains between
8-10AM and then east of the mountains between 10AM-Noon. Main
concerns...

Wind...strong gusty winds are expected to accompany the frontal
passage with gusts near 40 mph...rain showers helping with the
momentum mixdown.  Post frontal winds gusting from 25 to 35 mph
will then continue through the afternoon and into Wednesday
night. Attm do not foresee the need for a wind advisory, but
may need to entertain this for the higher elevations if model
trends increase.

Precipitation...expectation is for showers to be associated
with the front with best chance for wetting across the
mountains...amounts generally less than a tenth of an inch.
Model guidance suggest showers will weaken as they cross the
mountains with very little rain anticipated for our foothills
and piedmont. There is some potential for showers
(thunderstorm?) to re-develop as the front crosses the piedmont,
but think this may not take place until afternoon and across an
area that would be east of our forecast area...east of South
Boston where instability will increase from increasing
temperature ahead of the front. On the opposite side of the CWA,
cold air is expected to change any lingering moisture over to
snow showers, with potential for late afternoon showers
supporting snow/graupel, but mainly over the WV/VA highlands.

Temperature...with the frontal passage, expect falling
temperatures. Even with any post frontal clearing, it will be a
struggle for recovery due to strong cold air advection aloft.
Current thinking is that temperatures tomorrow morning may turn
out to be the highs for the day in the mountains with falling
temperatures expected areawide west of the Blue Ridge. East of
the Blue Ridge there will likely be a temperature dip associated
with the frontal passage, followed by some recovery when the sun
pops back out Wednesday afternoon.

In addition to the above concerns, there is also a concern that
conditions may meet red flag criteria for areas farther east,
especially across North Carolina... please see the fire weather
section of this AFD for details. In collaboration with our North
Carolina land managers and weather offices, a Fire Weather Watch
has been issued for areas east of the Blue Ridge...for low RH,
wind, and high fire danger.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 200 PM EDT Tuesday...

Windy with below normal temperatures through the end of the workweek.

Cold and blustery conditions will continue behind the front Wednesday
night into Thursday with enough low level moisture to generate some
upslope snow/rain showers at the higher elevations west of the Blue
Ridge. Winds will be quite gusty especially along the hilltops but it
looks like gusts should generally remain at or below 45MPH so no wind
headlines planned. Temperatures Wednesday night will be well into the
20s in the mountains and will maintain a Freeze Watch here.
Temperatures east of the Ridge will be a bit warmer generally around 30
degrees which lowers confidence on adding these locations to the Freeze
Watch so will leave them out for now.

Thursday will be another windy day as high pressure builds in and
lingering showers subside with temperatures remaining cold as highs
only reach the upper 50s/around 60 east, 40s west. Thursday night may
require another frost/freeze headline with lows below freezing once
again in the mountains and in the low/mid 30s to the east. The center
of the high pushes off to the east on Friday and allows temperatures to
moderate before the next system approaches from the southwest and
pushes precipitation to our doorstep late Friday night.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 200 PM EDT Tuesday...

Widespread precipitation to start the weekend, then improving
conditions with a warming trend into the first part of next week.

A potent low pressure system will move across the Appalachians and
central mid Atlantic region Saturday into Saturday night. The best
dynamics will pass by to our southeast and this should keep any threat
for severe storms out of our region, but will watch closely to see if
trends start pulling energy closer to Southside and the NC piedmont.
As it stands, expect a good dose of rainfall across the region on
Saturday into Saturday night with some lingering upslope showers in the
mountains into early Sunday morning. Ensemble guidance is then in good
agreement in building a large ridge over the eastern US with fair
weather and a trend to above normal temperatures through the first part
of next week, though we may have to contend with some patchy frost in
the mountains again Sunday night.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
As of 920 PM EDT Tuesday...

All TAF locations are expected to remain VFR through 12Z/8AM
Wednesday. Exception will be late toward 12z Wed when MVFR cigs
may be very close to KBLF and KLWB. Gridded LAMP guidance as
well as the NBM have ceilings dropping to MVFR along the front.

A strong cold front is expected to cross the mountains from
west to east Wednesday morning with a significant change in conditions
occurring between 12z/8AM and Noon. MVFR cigs are expected
across the mountains during this period associated with a wind
shift and wholesale increase in wind speed. Expect winds to
become northwester with speeds of 15 to 20 kts sustained and
gusts of 25 to 35 kts. Snow showers are likely in southeast West
Virginia in the afternoon but with VFR visibility.
Thunderstorms will develop along and ahead of the front in the
afternoon, but the boundary will be east of KLYH and KDAN by
that time.

Above average confidence in timing of the front, arrival of
MVFR ceilings, and wind.
Average confidence of areal coverage of precipitation.

Extended Aviation Discussion...

Strong and gusty winds are likely behind a cold front Wednesday
night, with these winds persisting into Thursday before
diminishing. Gusts of 25 to 35 kts are likely, the higher gusts
occurring along the ridges.

Expect VFR Thursday night through Friday under high pressure.

Widespread rain with MVFR or lower conditions are expected Saturday
and Sunday.

&&

.FIRE WEATHER...
Breezy northwesterly winds are expected across much of the
eastern seaboard Wednesday afternoon in the wake of a cold
front which will move through the region. Most model guidance
keeps the frontal passage dry for areas east of the Blue Ridge,
especially across the Carolinas. Similarly dry and breezy
conditions are anticipated in eastern Virginia, but there is a
better chance for precipitation as the front passes through this
region. Sustained winds are expected to be 15 to 20 mph with
gusts of 20 to 30 mph associated with relative humidity of 25 to
35 percent.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Freeze Watch from late Wednesday night through Thursday
     morning for VAZ007-009>020-022>024.
NC...Freeze Watch from late Wednesday night through Thursday
     morning for NCZ001-002-018.
     Fire Weather Watch from Wednesday afternoon through Wednesday
     evening for NCZ003>006-019-020.
WV...Freeze Watch from late Wednesday night through Thursday
     morning for WVZ042>044-507-508.

&&

$$
SYNOPSIS...PM
NEAR TERM...AMS/PM
SHORT TERM...MBS
LONG TERM...MBS
AVIATION...AMS/PM
FIRE WEATHER...PM