554
FXUS61 KRNK 211753
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
153 PM EDT Sat Sep 21 2024

.SYNOPSIS...
A frontal system will move through the region through tonight.
Showers and storms will be possible but should diminish after
dark. Sunday looks pleasant with some clouds lingering over the
east and high pressure building in. A cold front will gradually
approach during the next work week, resulting in a higher
chance of showers and thunderstorms that will persist into next
weekend.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 140 PM EDT Saturday...

Key Messages:

1) A few strong to severe storms possible over S. Shenandoah Valley,
parts of the central/northern Blue Ridge, and the VA/NC piedmont
this afternoon and evening. Main concerns are localized damaging
winds and urban flooding.

2) Other areas may see showers/storms but likely not anything
strong. Heavy rain/isolated flooding still possible.

3) Fog and stratus possible overnight; stratus may linger over
the east through noon tomorrow under high pressure wedge.

The region remains in between broad upper level troughing over
the NE states and ridging centered over TX. At the surface, a
frontal system was approaching from the west. Farther north over
the eastern Great Lakes, the system was in the process of
occluding. IR imagery shows plenty of dry air aloft, with weak
mid level capping in place. This capping will continue to erode,
especially over the southern Shenandoah Valley and piedmont
areas by this afternoon.

PW values were around 1.2" this morning at KRNK, and will
increase  to about 1.4" or so through this afternoon in the
Shenandoah Valley, parts of the central/northern Blue Ridge, and
the piedmont ahead of the frontal system. Southerly winds will
increase convergence along the terrain, so convection will also
form along the Blue Ridge before drifting south. An upper level
left front jet streak and passing short wave energy will also
help support convection areawide. Instability and shear amounts
will be low to moderate over our area, but better to the NE and
E. We should still have enough ingredients to support a few
strong to isolated severe storms, again mainly over the S.
Shenandoah Valley, parts of the central/northern Blue Ridge and
the piedmont. Most of the activity will be multicell
clusters/lines and should be sub-severe, but may still contain
heavy rain. These main ideas are supported by SPC`s Day 1
Outlook, SREF ensembles, machine learning and CAMs.

The main concerns for the above mentioned areas will be isolated
damaging downdraft winds, as well as moderate to heavy rain
leading to isolated urban, small stream, and possibly flash
flooding.

Overnight we will be in the warm sector briefly before a
backdoor front moves through, allowing PW values to drop to
0.7 inches or less over the mountains by morning. This will
support moderate radiational cooling where skies clear, leading
to temperatures in the 50s to low 60s. Stratus will develop/move
over the foothills and also the eastern piedmont in association
with the passage of the backdoor front. Models are indicating
this stratus will hang around our eastern counties for much of
the day. Where skies clear overnight, and especially where it
rains, expect localized dense fog.

For Sunday, the upper level energy will be lacking for much of
the area, but there will be a stripe of PVA crossing over the
piedmont. At the surface, much drier air and high pressure
wedging in from the NE will likely smother most convection that
tries to form, but a stray shower will be possible later in the
day. Otherwise, expect mostly to partly sunny skies (outside of
where the stratus lingers) with highs in the upper 70s to mid
80s.

Confidence in the near term is moderate.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 130 AM EDT Saturday...

Key Messages:

1) Mostly dry on Sunday, but some clouds will remain in place.

2) Wetter pattern returns for Monday and Tuesday.

A brief dose of drier weather for Sunday behind a frontal
boundary and a weak backdoor front drops into Virginia through
the day. Will see winds shift back to the northeast for much of
the day, along with partly cloudy skies. Could perhaps see a few
late day showers as easterly flow increases Sunday evening, but
overall most areas will remain dry.

Southwest flow increases again Monday and a weak warm front
will be in the vicinity. Should see better coverage of rain and
maybe a few thunderstorms by later Monday afternoon as moisture
begins to increase in response to the retreating warm front.
Much of the same for Tuesday as well, but slightly better
coverage of rain and storms as low pressure begins to develop
and organize over the Ohio Valley.

Warmest day will be Sunday with highs in the low/mid 80s, but
cooling off again Monday and Tuesday with highs in the mid/upper
70s. Lows through the period mild in the 50s and 60s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 145 AM EDT Saturday...

Key Messages:

1) High uncertainty remains in the long term period.

2) Chance of rain lingers through much of the week.

Quite a bit of variance among guidance this morning for the
period beyond Wednesday. This does not lead to much confidence
in the long term forecast, however ensemble guidance continues
to paint a rather stagnant pattern featuring daily chance of
rain and perhaps thunderstorms through mid to late week.

With rain potential and cloud cover, temperatures remain
slightly on the cooler side, generally in the 70s during the day
and 50s/60s overnight.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
As of 150 PM EDT Saturday...

Showers and thunderstorms will affect the Southern Shenandoah
Valley and parts of the Blue Ridge during early to mid
afternoon, and much of the piedmont during the evening. Storms
will be capable of damaging winds, large hail and heavy
downpours limiting visibility locally to less than 1SM. Outside
of convection, VFR conditions are expected into late Saturday
night, when patchy fog will redevelop. For LYH and DAN, low
stratus looks more likely and will linger into Sunday.

EXTENDED AVIATION OUTLOOK...

Isolated to widely scattered showers and thunderstorms are
expected again Sunday afternoon/evening. Otherwise, VFR during
the day then areas of MVFR/IFR fog and stratus at night.

Daily chance of showers, thunderstorms, and lingering sub-VFR
conditions continue Monday through at least midweek as a slow-
moving cold front approaches from the west.

&&

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

&&

$$

SYNOPSIS...SH/NF
NEAR TERM...SH
SHORT TERM...BMG
LONG TERM...BMG
AVIATION...SH/NF