Severe Thunderstorm Warning 117, NWS Blacksburg, VA

Area Forecast Discussion
National Weather Service Blacksburg VA
933 PM EDT Thu Jul 13 2023

.SYNOPSIS...
The region has evolved into an active weather pattern, which
will remain in place for much of the next 7 days. A frontal
boundary will sag through the area over the next couple of days.
However, more importantly is a deepening upper trough anchored
over the Great Lakes that will send a series of disturbances
through the area over the next several days. Temperatures will
be held down by cloud cover remaining near to slightly below
seasonal normals for mid-July.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 930 PM EDT Thursday...

Severe weather threat slowly diminishing. Severe Thunderstorm
Watch has expired as of 900 PM EDT. No additional watches
expected per SPC. Showers and thunderstorms will continue
overnight along the slowly southward moving front. Main concern
going forward will be heavy rain and flooding. Flash flooding
ongoing in the Lynchburg area at this time.

As of 800 PM EDT Thursday...

     Severe Thunderstorm Threat Continues Through the Evening...

Very active severe weather afternoon/evening across the forecast
area with over a dozen SVRs and one FFW issued. While the severe
threat will diminish with the loss of daytime heating and as the
upper short wave responsible for the widespread convection moves
on, a lingering frontal system, abundant moisture, and a
deepening trough over the Great Lakes will continue the threat
for scattered showers and isolated thunderstorms through the
night. Activity will increase in coverage and intensity once
again Friday afternoon, especially across the southeast half of
the CWA. A few of those thunderstorms could also be strong to
severe, but upper-level dynamics and instability will be less
than that observed today. Rainfall will become an increasing
problem as the days pass with repeated rainfall.

Pops and temperatures have been adjusted accordingly to reflect
current trends. Max temperatures for Friday will be lower across
the board because of clouds and showers/thunderstorms.

As of 100 PM EDT Thursday...

     Isolated severe storms possible later this afternoon into
tonight...

Main focus continues to be the threat of strong to isolated severe
convective development later this afternoon into tonight as an upper
disturbance pushes eastward across the TN and Ohio valleys ahead of
a frontal boundary. CAMs lack some consensus on coverage though
mostly agree on some initial triggering along the Blue Ridge earlier
this afternoon, which are starting to see signs of in recent radar
analysis, then a bit more organized cluster of storms by this
evening into the overnight. RAP progged SBCAPE looks to be in the
2500-3000 J/kg range for much of the area and with marginal deep
layer bulk shear of about 30-35 kts some isolated severe development
is possible with the main threat of strong to damaging wind.
Downdrafts could be aided by hydrometeor loading with increasing
PWATs of 1.75-2 inches as moisture advection kicks in from the SW.
Heavy rainfall from efficient precip producers and an isolated
flooding threat will also be possible especially if there are some
training storms which may occur given not much directional shear.

Some patchy or areas of fog may develop late tonight into Friday
morning especially where any low level moisture is increased from
what convection occurs late today/tonight and if winds lax.

Friday afternoon could have a bit more instability present, though
the bulk shear looks a bit less or more confined to the eastern CWA.
Will advertise some decent chance to likely pops for scattered
shower and storm potential with a few strong to severe possible but
not as great of a threat as today.

Forecast confidence is medium to high.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 100 PM EDT Thursday...

     Scattered showers and storms possible for the weekend
with the greater chance Saturday...

We should see a diminishing trend to convection Friday night as the
front and moisture axis pushes southward, though this axis looks to
have a northward surge ahead of the next amplifying shortwave set to
influence the area Saturday afternoon into night. Have increasing
pops accordingly. As the moisture and instability could be more
limited for Sunday with the progression of the cold front, the upper
trough axis remains west of the area so we could still have weak
upper forcing to aid any diurnally driven convection and am
advertising mainly general chance pops.

Max temps for the weekend look to be generally near climo norms,
then a bit cooler in the mountains for Sunday as the aforementioned
front pushes eastward.

Forecast confidence is high.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
The weather pattern favors mainly afternoon and evening
scattered showers and thunderstorms through the weekend. Fog
development is also possible each morning through the weekend
and into early next week.
As of 1130 AM EDT Thursday...

Confidence is moderate for increasing chances of showers and
thunderstorms towards the middle of the week.

The overall synoptic pattern throughout this week will feature a
large upper level ridge in the southwestern United States and
ongoing troughs moving across southeastern Canada and the Great
Lakes. The Mid Atlantic will thus reside in a persistent west to
northwest flow aloft. With a cold front departing offshore on
Monday, that day appears to be the driest of this week as weak high
pressure crosses the Appalachian Mountains. However, another cold
front should approach by Tuesday to bring increasing chances of
showers and thunderstorms. The frontal boundary could stall across
southwest Virginia on Wednesday and linger into Thursday, which
would keep conditions unsettled with daily chances of
convection.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
As of 800 PM EDT Thursday...

Synopsis: Weak frontal boundary will sag southward through the
area and linger for the next several days. Deepening upper
trough over the Great Lakes will dominate the area for the next
several days. Expect scattered to numerous showers and
thunderstorms, peaking in intensity and coverage during the
afternoon/evening hours. Activity will favor the north/west
tonight and more of the south/east Friday.

Ceilings...Mostly MVFR ceilings through the period with periods
of IFR-LIFR during the late night/early morning hours in dense
fog. Brief IFR conditions also possible in heavier
thunderstorms, mainly until 04Z tonight and after 17Z Friday.

Visibility...Mostly VFR except in late night dense fog,
especially in areas of wet ground/substantial rainfall Thursday
resulting in LIFR FG in the 08Z-14Z time frame Friday morning.
Brief MVFR-IFR conditions possible in heavier
showers/thunderstorms and higher elevations above 3000 ft.
tonight/Friday morning.

Winds...Highly variable through the period, favoring WSW 5-7kts
in areas outside thunderstorms and especially across the
Piedmont.

/Confidence Levels in Forecast Parameters/
- Moderate Confidence in Ceilings,
- Moderate Confidence in Visibilities,
- Low Confidence in Wind Direction and Speed.

EXTENDED AVIATION OUTLOOK...
Unsettled and active weather pattern will remain in place
through the period. Scattered to numerous showers/thunderstorms
expected each afternoon/evening with scattered showers overnight
hours. Late night and early morning fog likely in many areas
with high humidity and wet ground conditions.

&&

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

&&

SYNOPSIS...BMG/AB
NEAR TERM...RAB/AB
SHORT TERM...AB
LONG TERM...PW
AVIATION...RAB

Hazardous Weather Outlook
National Weather Service Blacksburg VA
219 PM EDT Thu Jul 13 2023

WVZ042>044-507-508-141830-
Mercer-Summers-Monroe-Eastern Greenbrier-Western Greenbrier-
219 PM EDT Thu Jul 13 2023

...SEVERE THUNDERSTORM WATCH 482 IN EFFECT UNTIL 9 PM EDT THIS
EVENING...

This Hazardous Weather Outlook is for southeast West Virginia.

.DAY ONE...This afternoon and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Severe Thunderstorm Watch.

Severe storms are possible this afternoon and evening, with the main
threat being damaging winds. Heavy rainfall could lead to localized
flooding.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Heavy rain from thunderstorms may result in localized flooding.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed. Reports should be submitted by
phone by calling 1-866-215-4324, social media, by email at
rnk.skywarn@noaa.gov or online at www.weather.gov/rnk.

NCZ001>006-018>020-VAZ007-009>020-022>024-032>035-043>047-058-059-
141830-
Ashe-Alleghany NC-Surry-Stokes-Rockingham-Caswell-Watauga-Wilkes-
Yadkin-Tazewell-Smyth-Bland-Giles-Wythe-Pulaski-Montgomery-Grayson-
Carroll-Floyd-Craig-Alleghany VA-Bath-Roanoke-Botetourt-Rockbridge-
Patrick-Franklin-Bedford-Amherst-Henry-Pittsylvania-Campbell-
Appomattox-Buckingham-Halifax-Charlotte-
219 PM EDT Thu Jul 13 2023

This Hazardous Weather Outlook is for north central North Carolina,
northwest North Carolina, central Virginia, south central Virginia,
southwest Virginia and west central Virginia.

.DAY ONE...This afternoon and tonight.

Severe storms are possible this afternoon and evening, with the main
threat being damaging winds. Heavy rainfall could lead to localized
flooding.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Heavy rain from thunderstorms may result in localized flooding.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed. Reports should be submitted by
phone by calling 1-866-215-4324, social media, by email at
rnk.skywarn@noaa.gov or online at www.weather.gov/rnk.

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