-- Discussion containing changed information from previous version are highlighted. --
861
FXUS61 KRNK 181640
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
1240 PM EDT Sat May 18 2024

.SYNOPSIS...
A nearly stationary front across northern North Carolina will
bring another round of showers and thunderstorms, with locally
heavy rain, across the area today. As this front drifts south
tonight, the chances of precipitation decrease with only
scattered mountain showers and storms expected Sunday. High
pressure will bring dry weather from Monday into most of
Wednesday, before an approaching cold front Thursday brings the
next chance of showers.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1030 AM EDT Saturday...

Morning satellite and surface analysis indicates that a stalled
boundary is situated along the Virginia/North Carolina border.
Some clearing has already occured within this region and dew
points are already into the mid and upper 60s. As such, SBCAPE
has already begun to trend upward to 500 J/kg. Expecting the
trend upward to continue and will likely begin to see convection
develop by early afternoon across the mountains, then spread
east through the afternoon and into the evening. The main threat
today is flooding, with possibly a wind threat in some stronger
storms. A large hail threat will be limited owing to the higher
freezing level. No plans on a Flood Watch since coverage of
storms appear to be scattered.


As of 240 AM EDT Saturday...

Key Message:

1) Around round of locally heavy rain and isolated severe storms
are possible in southern Virginia and northern North Carolina
today.

The 18/00Z RNK sounding showed an anomalously moist air mass in
place with a PWAT value of 1.29 inches which is above the 90th
percentile for this time of year. A weak upper level shortwave
seen on water vapor satellite lifting northeast across southern
WV combined with good isentropic lift north of the weak sfc
boundary to our south has kept widespread showers and isolated
storms over the area early this morning.

As this upper level wave continues to drift northeast away of
our area, widespread showers will gradually shift east and
diminish this morning. However, with the SREF indicating a good
chance (>70%) of SBCAPES exceeding 1000 j/kg in southern VA and
northern NC, combined with continued high PWAT values expected
to be >150% of normal in this same area, as well as increasing
upper level divergence this afternoon as the primary upper level
low across AK pushes east, confidence is high that another
round of showers and storms will develop in the early afternoon
hours.

The primary concern from these developing storms will be
localized flooding and flash flooding as forecast soundings show
a `long and skinny` CAPE which allows more time for the warm
rain processes to occur. In addition, many streams across
northern NC and southern VA are already running above normal as
shown from the National Stream Analysis Anomaly map. For now,
will let the current flood watch continue until 10 AM to account
for the current area of rain, but a new flood watch may need to
be issued shortly after this expires in our southern forecast
area.

The showers and storms, along with the threat for heavy rains
ends tonight as the low level boundary shifts south. Did not
deviate from the NBM for temperatures today and tonight.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
As of 1215 PM EDT Saturday...

Key Messages:

1). Mainly Dry through the period for a change.

2). Temperatures near seasonal normal.

The weak and broad upper trough across the eastern U.S. will
lift out of the region Sunday allowing an upper ridge to build
eastward and northeastward into the region from the south
central U.S. Dynamics/forcing will be limited under the upper
ridge with warming temperatures aloft. At the surface, a
lingering wedge will remain across the area into Monday, but
gradually dissipate through the period. Increased sunshine, less
precipitation, and the dissipating wedge will allow
temperatures to warm back to seasonal levels compared to the
last few rather cool days. Other than a scattering of diurnally
driven showers across the western mountains, and principally the
southwest VA/northwest NC mountains, little if any
precipitation is expected through this time frame.

Temperatures will range mostly from the 50s at night to the 70s
mountains into the lower 80s elsewhere through the period.

/Confidence Levels in Forecast Parameters/
- Moderate to High Confidence in Temperatures,
- Moderate Confidence in Precipitation Probabilities,
- Moderate Confidence in Wind Direction and Speed.
-- End Changed Discussion --


&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
-- Changed Discussion --
As of 1215 PM EDT Saturday...

Key Messages:

1). Increasingly unsettled weather pattern evolves during the
later half of the week.

2). Temperatures remain near seasonal normals.

Upper ridging across the eastern U.S. will gradually break down
through the later half of the week as a strong short wave tracks
from the Midwest toward the Great Lakes. An associated cold
front will move slowly into the region Thu-Fri. Shower and
thunderstorm chances will increase as the front approaches from
the west, especially along and west of the Blue Ridge. Timing is
a bit uncertain as the ECMWF is quite a bit slower than the GFS.
The ECMWF would delay the bulk of the precipitation until Friday
going into the weekend. Activity looks to be somewhat scattered
and mostly diurnal at this point with a low severe threat. Heavy
rain may eventually be a greater concern, but too far out to
hone in on any specific threats.

Temperatures are expected to remain relatively near seasonal
normals with a slight cooling trend from midweek to the weekend
as clouds and precipitation coverage increase. Look for lows
mostly in the 50s to lower 60s urban areas with high
temperatures primarily in the 70s mountains with lower 80s
Piedmont.

/Confidence Levels in Forecast Parameters/
- Moderate Confidence in Temperatures,
- Moderate Confidence in Precipitation Probabilities,
- Moderate Confidence in Wind Direction and Speed.
-- End Changed Discussion --

&&

.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
As of 650 AM EDT Saturday...

LIFR to MVFR conditions were observed at all TAF sties early
this morning. While some improvement to MVFR is expected for
most areas, and confidence is low, KLYH has the highest chance
of remaining at LIFR to IFR through the day Saturday.

Another round of rain and thunderstorms will be possible
Saturday afternoon, with highest confidence of storms being from
BCB to ROA and points south. If cigs improve to MVFR Saturday,
they quickly will drop to IFR at all sites by Saturday night.
While winds will generally be less than 10 knots, localized
strong wind gusts will be possible under and near storms
Saturday early afternoon into evening.

EXTENDED AVIATION OUTLOOK...

Showers and thunderstorms will slowly wane Saturday night, but
scattered storms re-develop, especially in the mountains on
Sunday. MVFR/IFR clouds and showers remain in the area for
Sunday and Sunday night.

Some improvements by Monday as the slow moving storm system
begins to depart east. Tuesday is the most likely day to be VFR.

&&

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

&&

$$

SYNOPSIS...PH
NEAR TERM...BMG/PH
SHORT TERM...RAB
LONG TERM...RAB
AVIATION...BMG/PH