Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 171357
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
957 AM EDT Mon Jun 17 2019

.SYNOPSIS...
A stationary front will waver across the Ohio Valley and Mid
Atlantic region this week. Low pressure tracks east along the
front Thursday and Friday. The region will remain in the warm
and humid air on the south side of this boundary through the end
of the week with a daily threat of showers and thunderstorms.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 955 AM EDT Monday...

The 12Z RNK sounding reveals a precipitable water of 1.20 inches
and a considerably high freezing level. Wind shear is rather
light, so the threat for any severe weather today appears
marginal. However, any thunderstorms that develop later this
afternoon will be quite efficient in producing rainfall.

CAPE in the pre-storm airmass will be in the 2000-2500 J/kg
range this afternoon. Both the GFS and NAM have thunderstorms
developing along the Blue Ridge from the southwest to the
northeast. HRRR and HREF support the timing of storms to fire
around 16-18Z/noon-2PM along the Blue Ridge and along the ridge
line from just west of Bluefield into the extreme southwest tip
of Virginia. Storms over the Ohio Valley or their outflow will
reach the mountains in the afternoon and early evening. There
will be lower instability after 03Z/11PM this evening, so
thunder will be kept out of the forecast after midnight.

Cirrus from upstream will limit some heating this morning, but
temperatures are starting rather mild. Little adjustment was
needed to lows tonight.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
As of 300 AM EDT Monday...

Will start Tuesday with a slow-moving frontal boundary drifting
north of the Ohio River. Will also likely have outflow boundaries
(storm-induced cold fronts) lingering across our region that are
left over from Monday night`s thunderstorm activity. These
boundaries, in addition to convergence along the mountain ridges,
will serve as the initiation points for showers and thunderstorms
developing during late morning. Convection will then spread east
during the afternoon and evening as a potent wave of low pressure
passes from the upper Ohio River Valley toward the DelMarVA, riding
the frontal boundary. Given precipitable water values increasing
into the 1.6 to 1.8 range and unidirectional winds through the
atmosphere to support training of storms, would expect a few cells
to produce heavy/prolonged downpours which may result in localized
flooding issues. As such, WPC has included the mountains and
Piedmont along/north of Highway 460 in a marginal risk for excessive
rainfall. Not as much surface heating compared to Monday due to the
increased cloud cover, however 30-35 knots of shear will support a
few strong to severe storms, with localized damaging winds as the
primary threat. As such, will have to keep an eye out for areas
where cloud cover breaks to allow increased surface heating. These
locations may see some of the stronger thunderstorm activity.

Storms may remain across the Piedmont region into the early hours of
Wednesday before exiting to the east. With the passage of the wave,
low level winds will shift more westerly for the afternoon and
evening hours of Wednesday. This downslope wind direction will help
limit the development of afternoon showers and storms, though enough
instability should exist that some disorganized activity will
develop with daytime heating.

More organized shower/thunderstorm activity will return early
Thursday as another strong wave of low pressure pushes east along
the Ohio River Valley. Models are hinting that activity will weaken
and break up in the westerly downslope flow as it passes across the
Appalachian chain, only to refire east of the Blue Ridge during the
afternoon with daytime heating. In any event, passage of this system
will shift winds across our area more northwesterly, making for
drier conditions Thursday night heading into Friday.

Temperatures each day across our area will be near normal for mid-
June.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
As of 330 AM EDT Monday...

Expect a drying trend for Friday and Friday night as winds likely to
remain northwesterly. Plenty of mid level drying progged as well, so
any shower or storm activity may be confined to western slopes.
Still some uncertainty as to timing of this so if it slows down,
that could keep some precip chances a bit higher until later in the
day Friday.

The drying is short-lived however as upper ridge builds in again by
Saturday along with return of deeper moisture for the entire
weekend. Thus chances of showers/storms increase Saturday and more
so into Sunday. Near seasonal temperatures and increasing humidity
as well through next weekend. Generally pretty good agreement in the
guidance for these trends over next weekend.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
As of 735 AM EDT Monday...

A few patches of MVFR in the New River Valley this morning which
will dissipate quickly, otherwise conditions will be VFR
through noon.

Expecting thunderstorms to develop along the Blue Ridge and to
move in from KY/OH by early this afternoon. NAM and GFS as well
as the HRRR all showed thunderstorms forming along the southern
Blue Ridge between 16z/noon and 18Z/2PM. The thunderstorms will
produce localized MVFR ceilings and visibilities. Gusty winds
are possible with any of the stronger storms.

Areal coverage of showers and thunderstorms will diminish by
midnight. Patchy MVFR will form again overnight, especially in
locations that get rain this afternoon and evening.

Confidence in aviation forecast elements is above average.
Confidence in timing and location of thunderstorms today is
average.

Extended Aviation Discussion...

Active pattern Tuesday through Thursday with best chance for
storms each day, especially afternoon/evening as a wavy front
remains in place from the mid-MS Valley to the mid- Atlantic.
Mainly VFR during the day aside from storms, with potential IFR
fog/low clouds late at night due to increased low level
moisture. Appears more in the way of VFR on Friday as somewhat
drier air arrives under weak high pressure.

Confidence is medium this time period.

&&

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

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS/PW
SHORT TERM...NF
LONG TERM...SK
AVIATION...AMS/JH



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