-- Discussion containing changed information from previous version are highlighted. --
878
FXUS61 KRNK 052312
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
712 PM EDT Sun May 5 2024

.SYNOPSIS...
An upper level trough of low pressure is slowly moving across
the Mid-Atlantic region, resulting in mostly cloudy skies,
areas of rain and rain showers, and a few thunderstorms.
Rainfall amounts will be highly variable, with the heaviest
occuring along and east of the Blue Ridge. Daily afternoon
showers and thunderstorms are possible through much of the
upcoming week.

&&

.NEAR TERM /THROUGH MONDAY/...
-- Changed Discussion --
As of 700 PM EDT Sunday...

Scattering cloud cover across the mountains this afternoon
allowed temperatures to spike some 5 to 8 degrees over the span
of a couple hours, and triggered spotty showers with an isolated
rumble of thunder or two. These lingering showers will persist
through around 10 pm and will gradually fade heading into late
evening with the loss of heating. Still looking for clouds to
redevelop overnight, with patchy fog forming more so after
midnight.


As of 145 PM EDT Sunday...

Key Messages:

1. Scattered showers and thunderstorms this afternoon and again
Monday afternoon.
2. Warmer temperatures Monday.

The wedge of high pressure will finally erode by later today, and
the warm front lifts northward, putting the area in the broad warm
sector behind the front. So, through this afternoon and evening,
scattered showers and isolated thunderstorms can be expected, with
the highest probabilities along and west of the Blue Ridge.
Thunderstorm coverage will depend on how much the atmosphere can
destabilize through diurnal heating from any breaks in the
clouds. Right now, some pockets of sunshine and thinner cloud
cover is observed west of the Blue Ridge, in far southwest VA
and northwest NC mainly. Most of the showers and storms will
diminish by tonight, but plenty of residual moisture will lead
to overcast skies and patchy fog, especially over the higher
terrain, through the overnight and into tomorrow morning.

A cold front is currently situated from the upper Ohio Valley into
the Tennessee Valley, with the surface low in the ArkLaTex region.
By tomorrow, this low will track northeastward along the front and
closer to the Mid Atlantic, moving just west of the forecast area by
Monday afternoon. Monday will start off dry as mid level ridging
builds in overhead, and generally low level southwesterly flow
brings warmer and more moist air into the area. However, heating
throughout the day will help to increase instability, with
SBCAPE forecast to reach around 1000 J/kg by the afternoon,
highest along and east of the Blue Ridge. However, the better
upper level dynamics will be closer to the surface low, mainly
over the western mountains, and closer to the frontal boundary,
which will be draped across the upper Mid Atlantic region. That
all being said, thinking for Monday afternoon is showers
beginning first in the west and expanding eastward into the
Foothills and Piedmont, but with a higher potential for some
thunderstorms in the east where the greater instability will be.

Temperatures overnight will be mild, with overcast skies preventing
much radiational cooling. Highs Monday will be warmer than
today, as south and southwesterly flow ahead of the cold front
increases and mid level ridging builds overhead.

Forecast confidence is moderate, but lower on specific locations
of thunderstorms this afternoon and tomorrow.
-- End Changed Discussion --

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 200 PM EDT Sunday...

Key Messages:

1. Showers and thunderstorm possible each day, especially in the
afternoons and evenings.

2. Moderate rainfall possible as well as damaging winds and
marginally severe hail.

3. Warm temperatures continue.

Monday night into Tuesday, a short wave will cross the forecast
area, helping to steer an elongated baroclinic zone towards us from
the north. This will keep scattered to numerous showers and
thunderstorms in the area. Another short wave moves through Tuesday
afternoon and evening, and this will trigger some stronger
thunderstorms, mainly over the western mountains. However,
antecedent cloud cover and rain as well as weak ridging aloft and
westerly winds should keep a lid on the severe potential, but an
isolated damaging wind gust or marginally severe hail will be
possible, along with moderate rainfall.

On Wednesday, we remain in the warm sector, and a surface trough
crossing the area should help organize convection. Expect showers
and storms to develop during the afternoon and evening, with MLCAPE
increasing to between 500 and 1000 J/kg over the southern Shenandoah
Valley and the Piedmont based on GEFS probabilities. Dew points will
be in the 50s to low 60s for the mountains, so prolonged
thunderstorm activity there looks less likely. Forecast soundings
indicate tall, skinny CAPE each day, along with unidirectional
westerly flow, which would indicate more linear bowing structures
could develop with damaging winds. Very slow storm motion as well as
PWATs approaching our recorded maximum for these dates indicate
urban, small stream, and flash flooding may be a concern.

Temperatures during this time will be on the warm side, with 70s and
80s each day, reaching the mid to upper 80s for areas east of the
Blue Ridge Wednesday.

Confidence in the short term is moderate.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 200 PM EDT Sunday...

Key Messages:

1. Warming trend to start the work week, cooler and dry next
weekend.

2. Showers and thunderstorm chances each day.

Thursday into Thursday night we will see more chances for showers
and thunderstorms. A slowly filling surface low will move west to
east across the OH Valley, putting us just south of the triple point
and well under dense cloud cover for most of the area. Instability
looks best for our northern NC counties, which may see some strong
thunderstorms. The initial short wave trough associated with the
upper level system will be positively tilted and crosses the
Appalachians Friday and Saturday, pushing a cold front ahead of it.
This will mean more widespread rain and thunderstorms. While there
are mixed signals as far as severe thunderstorm chances, the chances
for moderate to heavy widespread rainfall leading to flooding
increases each day during this wet period, and at the moment looks
like the bigger threat.

High temperatures gradually decrease each day Thursday through
Saturday with overcast skies and the passage of the front. We may
finally see the sun either late Friday or Saturday. The weekend
looks cooler and drier with dew points dropping into the 30s and
40s, and this is supported by NAEFS situational awareness
projections.

Confidence in the long term is moderate for most parameters, but
lower for timing of showers and storms.

&&

.AVIATION /23Z SUNDAY THROUGH FRIDAY/...
As of 200 PM EDT Sunday...

Mostly MVFR to IFR ceilings are observed at this time, although
some pockets of VFR can be found in far southwest VA and
northwest NC. In these same areas, starting to see development
of scattered showers. Coverage of said scattered showers will
increase through this afternoon and evening, with the potential
for some thunderstorms, greatest probabilities being in the
west. Confidence is not high enough in thunderstorm impacting
specific terminals, so have opted to leave out of the TAFs for
now.

Showers and any thunderstorms will diminish overnight, but
plenty of residual moisture will lead to lowering ceilings and
reduced visibilities from patchy fog. Thinking the lowest
ceilings and visibilities will be along and west of the Blue
Ridge, especially along the higher elevations. Ceilings will
lift and visibilities will improve by mid to late morning
Monday, around 14Z or so. Chances for showers and thunderstorms
increase again Monday afternoon, first in the west, by the end
of the current TAF period, before expanding eastward in
coverage, so have only included VCSH Monday afternoon for KLWB,
KBLF, and KBCB at this time.

Winds will generally south and southwesterly up to 5 to 10
knots through the period, but could have stronger winds and
gusts in the vicinity of any showers/storms Sunday afternoon and
evening.

Forecast confidence is average, but lower on specific locations
of showers and storms Sunday and Monday afternoons.


Extended Aviation Outlook...

Unsettled weather is expected for much of the upcoming week.
Daily threat of SHRA/TSRA Tuesday through Friday. This will
bring periods of MVFR/IFR ceilings and visibilities at times.
Winds through Wednesday will favor a SW direction and may be
gusty at times.

&&

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

&&

$$

SYNOPSIS...PM
NEAR TERM...AS/NF
SHORT TERM...RAB
LONG TERM...RAB
AVIATION...AS/PM