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Area Forecast Discussion (AFD)

Issued by Blacksburg, VA (RNK)

                            
000
FXUS61 KRNK 210904
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
404 AM EST Mon Jan 21 2019

.SYNOPSIS...
Gusty winds and dangerously cold wind chills will continue 
into the afternoon as Arctic high pressure approaches from the 
upper Midwest region. This high pressure system will pass 
overhead quickly on Tuesday morning on its way to the Atlantic 
coast by evening time. With the departure of this Arctic air, we
can expect a brief warmup, followed by another cold front 
bringing widespread precipitation to the region Wednesday night 
into Thursday.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 400 AM EST Monday... 

Breezy conditions remain in place this morning as the mid- 
Atlantic remains sandwiched between deep low pressure moving 
away along the coast of Nova Scotia, and a fast-moving Arctic 
high pressure system approaching from the upper Midwest region. 
This is the coldest morning we've had this winter, with observed
temperatures in the single digits across the mountains, below 
zero in spots, while the Piedmont is hovering in the low to mid 
teens. The combination of breezy winds and low temperatures has 
dropped wind chills into dangerous territory across the 
mountains, ranging from 0F to -15F, with a few locations 
reporting -20F or lower. 

Wind chills will be the main concern through the afternoon, 
which are expected to remain well below zero across the 
mountains and the single digits for much of Piedmont. Keeping an
eye on wind gusts from across the region over the past few 
hours, most gusts have held below 40 mph, with only a handful 
reaching above 45 mph. Given that winds are expected to continue
diminishing into the afternoon, will drop our high wind 
warning/wind advisory a few hours early and maintain gusty 
wording in the wind chill advisory. Likewise, any accumulating 
snowfall looks to be confined to western Greenbrier County this 
morning, with only flurries occuring across the remainder of 
southeast West Virginia in to Smyth County VA. Will therefore 
drop with Winter Weather Advisory except for western Greenbrier,
which will remain until noon. 

By mid to late afternoon, wind speeds will diminish 
significantly as the Arctic high draws closer. The frigid air 
will hold afternoon temperatures below freezing areawide, with 
highs not rising out of the teens across southeast West Virginia
into far western Virginia. The Southside of Virginia may touch 
30F for an hour or two, but elsewhere will hold in the 20s. 

Arctic high pressure will pass overhead tonight into early 
Tuesday morning, resulting in light winds and clear skies. As 
such, we can expect Monday night low temperatures to again be on
the frigid side, ranging from around zero in southeast West 
Virginia to the low teens across northern North Carolina. 
However, this high pressure system will be moving very quickly, 
with warmer air aloft already entering our area by dawn Tuesday.
This will set up the mid-Atlantic region for a significant 
rebound in temperatures heading into Tuesday afternoon. 

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 325 AM EST Monday... 

Cold high pressure will begin to drift off the VA/NC coast on 
Tuesday. Even though we are still under some influence of an 
Arctic airmass, temperatures will be warmer Tuesday as compared 
to Monday. However, temperatures will only warm into the 30s 
which is about 10F colder than normal for this time of year. 
Temperatures Tuesday night will vary as warm air aloft may have 
temperatures along the ridges warmer than valleys and foothills.
In any case, Tuesday night's temperatures will drop into the 
20s and will set the stage for the chance for freezing rain 
Wednesday morning.

Also on Tuesday, a cold front will reside over the Mid West. 
This front will move east to the Ohio and Tennessee Valleys 
Tuesday night. According to the 00Z GFS/ECM, this front will 
stall, waiting on a surface wave across the southern states to 
ride northward over the southern Appalachians. This may not 
occur until Wednesday night. While the front is stalled over the
Ohio and Tennessee Valleys, warm moist air will move over low 
level cold air. Weak isentropic lift with a substantial warm 
nose (per forecast soundings) to bring the chance for light rain
to the area late Tuesday night into Wednesday morning. With 2m 
temperatures in the upper 20s and the ground remain frozen, ice 
from freezing rain will create hazardous travel conditions for 
the Wednesday morning commute. By noon, temperatures will warm 
into the mid to upper 30s. As the front approaches the region, 
moderate rain is expected to fall starting across the mountains 
in the late afternoon, then across the entire area Wednesday 
night. First guess rainfall amounts are around an inch. Up to 
one-tenth of an inch of ice is possible Wednesday morning.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 1225 PM EST Sunday...

The system from Wednesday will make a quick exit out of the region 
on Thursday, but not before the westward flank of it allows for some 
morning rain showers across central and eastern parts of the area. 
By the afternoon, increasing northwest flow across western parts of 
the area yield some upslope scattered snow showers. Cold air 
advection will be strong on Thursday such that temperatures will 
trend colder as the day progresses. High temperatures are expected 
in the morning ranging from the mid 30s in the west to around 50 
across the east, with readings some 5 to 10 degrees colder by the 
afternoon across the entire area. These upslope snow showers will 
continue into Thursday evening before ending around midnight.

Another fast moving clipper system is expected to race through the 
Ohio Valley late Thursday night and Friday. This feature is expected 
to bring additional light snow showers to mainly the areas along and 
west of the crest of the Blue Ridge, with the best potential for 
light measurable snow in areas along and north of the Interstate-64 
corridor.

Reinforcing colder air will follow the Friday system such that we 
can expect a return of a mix of single digits and teens for low 
temperatures across the area on Friday night.

After only another brief break from light precipitation, yet another 
clipper system is poised to enter the region either Saturday night 
on Sunday, and again bring scattered snow showers to mainly the 
western sections.

Temperatures during this portion of the forecast will start near 
near normal on Thursday but trend colder through Saturday such that 
readings then will average about twenty degrees below normal. While 
Sunday is expected to be warmer than Saturday, readings still are 
forecast to be below normal by about ten degrees.

Confidence in this portion of the forecast is moderate.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
As of 1134 PM EST Sunday...

Overall expect improving conditions through the morning as low
clouds erode in southeast WV to portions of SW VA. Winds will
also start to ease up, but expect gustiness into early afternoon
Monday. Some MVFR before 12z at LWB/BLF with a few flurries.

VFR from late Monday morning through the end of this taf period.

Confidence is above average for all elements. 

Extended Aviation Discussion... 

Winds will be light Monday night into Tuesday under clear skies.

Surface front enters by Tue night-Wednesday with an increasing 
chance of widespread precip with sub-VFR returning. Front may 
slow down Wednesday night into Thursday with potential to see 
MVFR/IFR linger within precip and low ceilings. Another blast 
of Arctic air comes in for Friday so upslope MVFR clouds and 
snow showers are possible.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Wind Chill Advisory until noon EST today for VAZ007-009>020-
     022>024-032>035-043>047.
NC...Wind Chill Advisory until noon EST today for NCZ001-002-018.
WV...Wind Chill Advisory until noon EST today for WVZ042>044-507.
     Winter Weather Advisory until noon EST today for WVZ508.

&&

$$
SYNOPSIS...NF/WP
NEAR TERM...NF
SHORT TERM...RCS
LONG TERM...DS
AVIATION...AMS/JH/WP