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000
FXUS61 KRNK 172201
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
501 PM EST Sun Feb 17 2019

.SYNOPSIS...
An area of low pressure will progress into and across the area
tonight with its associated frontal boundary crossing the Carolinas.
After a brief break in teh wet weather Monday night into early
Tuesday, the forecast turns very soggy for the remainder of the week.
Tuesday night into Wednesday, enough colder air will be over the
region for the strong potential for a significant winter event.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 245 PM EST SUNDAY...

Low pressure was heading eastward through central Kentucky. In
advance of the low, waves of precipitation have been progressing
across our area. High pressure has been anchored along the U.S. East
Coast, with the precipitation over our area reinforcing the low
level inversion along and just east of the crest of the Blue Ridge.
The highest ridges today have been cold enough for some light icing
to take place. Temperatures have struggled to climb with the region
of stable rain-cooled air. On the western flanks of the forecast
area, outside the influence of the cold air damming, temperatures
have reached the mid-40s, and isolated thunderstorms arrived early
afternoon on the southeast flanks of the approaching low.

North-central sections of the forecast area remain in a Winter
Weather Advisory through 700 pm for the potential for additional
icing, especially along the highest ridges, and then primarily on
elevated surfaces.

Overnight, look for temperatures to rise slowly in advance of the
approaching low and its associated surface front. Another decent
plume of moisture is expected to overspread the region, with the
focus for the best coverage of the heaviest rain over the central
and southern sections of the area. Given this region was impacted
the greatest by today`s rainfall, it will be an area to monitor for
any flooding potential overnight. Have opted not to issue a Flood
Watch at this time because of the localized nature of any flooding.
Also, there will be an even greater potential for flooding headlines
later in the week. Best not to overdo the quantity of watch
headlines at this point and numb down sensitivity potentially of
more substantial events later in the week.

On Monday, we will be on the back side of the departing system, and
winds will shift northwest and become gusty. Gusts of 30 to 40 mph
will be common across the highest terrain along and west of the
crest of the Blue Ridge. Gusts of 15 to 25 mph will be common across
the Piedmont region. These same northwest winds will allow for drier
air to erode cloud cover across the Piedmont. However, clouds will
be slower to erode across the mountains thanks to an upslope
component. Light precipitation in the form of light rain/drizzle or
light freezing rain/drizzle will be possible across western
Greenbrier County heading into the afternoon. A few flakes of snow
are possible as the top of the shallow moisture layer cools to about
-10C late in the day. High temperatures tomorrow will range from the
low to mid 40s across the mountains with low to mid 50s across the
Piedmont.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 400 PM EST Sunday...

Very active and unsettled pattern to continue through the
period with significant potential for a winter storm, with both
significant ice and snow accumulations possible, followed by an
extended period of moderate to heavy rain events. Areal flooding
and river flooding seem almost certain as we move into the mid
part of the week and the weekend. The culprit will be a very
active southwest flow as deep troughing remains anchored across
the southwest U.S. with an endless series of vigorous embedded
short waves tracking from the southwest U.S. into the south
central U.S. then moving east-northeast to northeast toward the
Mid-Atlantic. In essence the main storm track will be right
across our area through the entire time frame. This will supply
persistent cloud cover and numerous rounds of precipitation.
Flooding from excessive rainfall and saturated ground will
clearly be the main concern, especially as the week progresses
continuing into the long term periods.

Unfortunately, with a Canadian air mass lingering just to our
north and meandering/oscillating back/forth across our latitude,
there will be a definite concern for winter weather. That
concern has solidified considerably from yesterday as the depth
of cold air appears more certain and further south than
indicated yesterday, which is consistent with a deeper wedge
developing in response to the slow deepening trough in the south
central U.S. As the warm nose from a strong southwesterly jet
works its way over the shallow cold air mass later in the
night/Wednesday morning, the precipitation will transition to
sleet and then freezing rain. Model signals are strong for
significant snow, sleet, and ice accumulations, and this could
well be the most significant winter storm in terms of total
accumulation since the mid-December event. With good
collaboration via WPC and neighboring offices this afternoon, we
concurred on the potential for winter weather with this event
and have followed their snow and ice accumulations closely,
namely winter storm warning criteria ice of .25 to .50 inch and
snow accumulations of 4-8 inches across the north with 1-3
inches in the south. Given that this is 72+ hours out, no
headlines have been issued yet, but will strongly highlight the
potential in the HWO/eHWO.

Current indications are that the winter weather event will
transition into a flooding event through the day Wednesday and
Wednesday night. Current QPF projections are in the 2-4 inch
range for the Tue-Thu time frame, which is in addition to all
the rain we have received over the weekend and early this week.
WPC has noted that there are numerous models with strong signals
for flooding across a large portion of the southeastern U.S., TN
Valley, and into the southern Appalachians. Again, being that
this is over 72 hours out, no headlines have been issued at this
time, but areal flooding and river flooding appears likely.
Please plan accordingly.

Temperatures will average near normal during this period as we
oscillate between the colder Canadian air mass present just to
our north and the much milder air to our south. Thus, there will
be some fluctuations above and below normal through the time
period. Wednesday will remain below normal, but much above
normal temperatures are expected as the week progresses.

/Confidence in Forecast Parameters/
Temperatures - Moderate to High,
Precipitation Probabilities - High,
Winter Weather Potential - Moderate,
Flooding Potential - Moderate to High,
Winds - Moderate to High.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 430 PM EST Sunday...

Very wet and unsettled weather continues with a positively
tilted mean trough in the western U.S. and a broad subtropical
ridge remaining anchored off the southeast U.S. coast. This will
keep a conveyor belt of deep moisture anchored over the area
along with an active baroclinic zone. Temperatures will start
out below normal on Wednesday, then creep to above normal levels
by the end of the week as the baroclinic zone is nudged a tad
further north thanks to the peristent subtropical ridge off the
southeast U.S. coast. Indications are that the baroclinic zone
will slip south of the area briefly as high pressure builds to
our north on Thursday, to provide a small opportunity for the
heavier rain to shift south of our area. However, another
significant wave emanating from the southwest U.S. trough is
progged to push the baroclinic zone back north into our area
Saturday with more heavy rain and flooding possible at that
time.

At any rate, temperatures will finally warm enough with
southwest flow to erode the returning wedge, that the main
focus through this period will be flooding, not winter weather.

WPC days 1-7 precip outlook currently highlights areas exceeding
4" mainly in western NC, eastern TN, and southwest VA. Areawide,
expect at least 2-3", with local amounts of 4-5 inches likely.
Please remain abreast of the threat of flooding and river
flooding with later forecasts as their is an increasing threat
for areal flooding and river flooding, especially during the
later half of the week.

As noted above, with the region increasingly in the warm sector
during this period, temperatures will average above normal and
remain mostly above freezing.


&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
As of 1245 PM EST Sunday...

Precipitation continues to stream across the area this afternoon
with some breaks developing across western sections.
Temperatures were slowly rising, thus fewer locations are and
will continue to become candidates for freezing rain. Those
ceilings that are still VFR are expected to trend to IFR/MVFR
levels. Those areas already IFR/MVFR will continue that way
through the afternoon, with all locations trending IFR through
the overnight hours. An addition wave of rain is expected to
spread across the area overnight, with the greatest
concentration across the southern half of the area. In the wake
of this system, winds will shift northwest and trend gusty. This
will allow clouds to clear out east of the crest of the Blue
Ridge tomorrow morning, with lingering sub-VFR clouds across
the mountains, along with some patchy rain or freezing rain
across portions of southeast West Virginia.

Forecast confidence in the above scenario is moderate.

Extended Aviation Discussion...

Development of northwest flow behind the departing Low pressure
is expected to bring improving conditions through Monday
afternoon. Lingering mountain cloudiness is expected to
maintain MVFR cigs across the mountains until Monday night.

Brief break in the wet weather is expected Tuesday, conditions
primarily VFR. Tuesday night and Wednesday another low pressure
system will bring sub-VFR conditions as well as providing
another opportunity for winter precipitation.

A frontal boundary will remain close to the region Thursday
into Friday keeping precipitation and the potential for sub-VFR
conditions in the forecast.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Winter Weather Advisory until 7 PM EST this evening for
     VAZ018>020-023-024-034-035.
NC...None.
WV...None.

&&

$$
SYNOPSIS...DS
NEAR TERM...DS
SHORT TERM...RAB
LONG TERM...RAB
AVIATION...DS