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881
FXUS61 KRNK 150908
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
408 AM EST Sun Dec 15 2019

.SYNOPSIS...
High pressure will briefly build into the area today. A low
pressure system will impact the area Monday through Tuesday.
High pressure returns Wednesday and Thursday. The high center
will slide off into the Atlantic ocean Friday, as low pressure
approaches from the Mid- Mississippi Valley.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 619 PM EST Saturday...

Upslope precipitation and clouds will wither away this morning
as moisture moves north of I-64. Winds may also be a bit breezy
this morning before a surface high pressure builds into the
region under zonal flow aloft this afternoon. Temperatures this
afternoon will warm into the 40s across the mountains to the 50s
east of the Blue Ridge. Today`s temperatures will be 3F-6F
warmer than normal.

A warm front will stall across the southern Ohio Valley
tonight. Short waves tracking along this boundary may bring a
brief period of snow to southeastern West Virginia around
midnight, changing to rain through the morning hours Monday.
There is a small chance that surface temperatures will dip below
freezing while warm air enters aloft across Greenbrier county
and the Alleghany Highlands tonight. This may produce a period
of light freezing rain between midnight and sunrise. Snow
(around an inch) and ice (glazing) accumulations will remain
light to not warrant any headlines. For areas south to HWY 460 a
cold rain is likely. South of 460 into northwest North Carolina
should remain dry until Monday.

Low temperatures (in the 30s) across the mountains should occur
by midnight, then remain steady or slowly rise overnight. With
more time under clear skies and light winds tonight east of the
Blue Ridge, lows will occur at their normal time, just before
sunrise.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
As of 315 AM EST Sunday...

Whatever wintry precipitation occurs across the Interstate 64
corridor from early Monday morning should transition over to
rain before noon as temperatures increase above freezing. The
entire region should be under the influence of the warm sector
from the low pressure system by Monday afternoon and Monday
night. The bulk of the moisture should push eastward during
Monday night into Tuesday morning ahead of an approaching cold
front. The increased confidence of rain occurring during this
time period has been denoted in the higher probabilities toward
categorical status.

Although model guidance appears good in agreement with one
another through Monday night, that agreement begins to waver by
Tuesday as the latest GFS pushes the cold front toward the coast
several hours faster than the ECMWF and Canadian models. A
middle of the road approach was utilized for Tuesday by delaying
the departure of the precipitation a little from the previous
forecast. Temperatures will follow a non-diurnal curve as they
fall for most of the day behind the frontal passage west of the
Blue Ridge, while the Piedmont may remain mild until the
afternoon when the cold front arrives. As temperatures fall
below freezing in the mountains courtesy of cold air advection
from increasing northwest winds, expect the rain to transition
to snow showers. Only minor snowfall accumulations are
anticipated for western Greenbrier County for Tuesday afternoon
into Tuesday night. Wind gusts were also bumped upward during
the same timeframe for the entire region, and it may be possible
for the higher ridgetops to approach advisory criteria.

The snow showers, cold air advection, and gusty northwest winds
should begin to subside by early Wednesday morning as high
pressure begins to build eastward from the Plains. 850 mb
temperatures should dip toward -10 C along the Interstate 64
corridor as the upper level trough passes to the north during
Wednesday. The cooler side of guidance was favored for high
temperatures on Wednesday to accommodate for the passing upper
level trough and the lingering cold air advection from northwest
flow. The center of high pressure should reach the Appalachian
Mountains by Wednesday night, which will lend to good
radiational cooling.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
As of 350 PM EST Saturday...

By Wednesday, enough drier air is expected to have arrived to
both end the light snow showers and also clear out the remaining
cloud cover, though winds will remain very gusty into Wednesday
evening. A Wind Advisory for some western counties will likely
need to be considered with later forecast packages for this time
frame.

High pressure will head eastward through the southeast U.S.
into Thursday, with our region experiencing no precipitation and
little to no cloud cover. Temperatures will drop to well below
normal levels with widespread lows in the teens and 20s during
the later half of the week.

Once the center of the high reaches the GA/SC coast on Friday
and low pressure moves east into the mid- Mississippi Valley,
look for a return of southwest winds and both increasing
temperature and moisture advection. At this time, no
precipitation is forecast for Friday. However, cloud cover is
expected to be on the increase. The weekend is very questionable
weatherwise and no specifics can be addressed yet at this point
in time. The GFS advertises potential for a snow storm by the
weekend while the ECMWF insists that such a weather system will
remain far to the south with little to no precipitation this far
north. Have left the weekend with 15% pops for now and just a
rain/snow mix.

Wednesday through Friday, temperatures are expected to average
five degrees below normal.

Confidence in this portion of the forecast is moderate to high.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
As of 1155 PM EST Saturday...

VFR conditions will prevail in the east of the Blue Ridge with
downsloping winds through Sunday. MVFR conditions will continue
overnight and into Sunday morning associated with snow showers.
Isolated sub-VFR vsbys will be possible across the highest
terrain.

Winds will continue to be gusty across the mountains
through Sunday early afternoon before diminishing. Gusts of 30kts
will be possible at the higher elevation with 15 to 25kt gusts
more probably in the mountain valleys. Piedmont regions will
have limited gusts with most under 15 to 20kts

Confidence in the above aviation forecast is moderate.


Extended Aviation Discussion...

VFR conditions and decreasing winds are expected Sunday night.

Monday through Tuesday our next weather system will cross the
area bringing a return to sub-VFR and gusty conditions.

A return to VFR is expected Wednesday and Thursday but with
winds remaining gusty.

Confidence in the above aviation forecast is moderate to high.
The biggest question is the timing, and for some locations
precipitation type, with Monday/Tuesday system.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.

&&

$$
SYNOPSIS...RCS
NEAR TERM...RCS
SHORT TERM...PW
LONG TERM...RAB
AVIATION...PM