Severe Thunderstorm Warning 185, NWS Blacksburg, VA

Area Forecast Discussion
National Weather Service Blacksburg VA
300 PM EDT Mon Aug 7 2023

.SYNOPSIS...
Low pressure will move from Midwest to the eastern Great Lakes
today. Thunderstorms, some severe, are expected to develop in a
warm, moist, and unstable airmass across the region this
afternoon. The risk of seeing thunderstorms will continue until
the passage of a cold front by Tuesday morning. High pressure is
then expected to work across the Tennessee Valley Tuesday, with
drier weather through Wednesday. An area of low pressure,
moving along a front from the lower Mississippi Valley to the
Carolinas, will bring our next chance for storms Thursday.

&&

.NEAR TERM /NOW THROUGH TUESDAY/...
Issued at 300 PM EDT MON AUG 07 2023

Key Messages:
- Severe thunderstorms possible through this evening. Moderate risk
  (Level 4 out of 5) remains in place for much of the area.

- Please have multiple ways of receiving weather information this
  afternoon and evening.

The shortwave trough, associated with an upper low over the Great
Lakes, has started to eject across our area at mid-afternoon. In
response to this, as well as the approach of a speed max associated
with the 250 mb jet stream, convection has started to fire across
the region.

Data from the 1800 UTC (2 PM EDT) sounding indicates MLCAPE values
around 1500 J/kg, with a SBCAPE just over 4000 J/kg. The storms
might have a little bit of a subsidence inversion to overcome
initially, but I suspect this will be weakened a little bit with the
approach of the shortwave trough. This will allow the convective
coverage to increase and storms form into (probably) a broken line
of storms as it moves across our area. Admittedly, it's still a
little unclear how the line will ultimately evolve. Regardless,
though, environmental parameters (including DCAPE values in excess
of 1200 J/kg) ahead of the projected line suggest a continued risk
of damaging winds (possibly in excess of 70 MPH) and tornadoes.

Like I said this morning, there's been no significant change in the
expected development/progression of the convection through this
evening. Thunderstorms, and the risk of severe weather will move
west to east across the forecast area through 0000 UTC (8 PM). After
the line moves through, we'll likely continue to see at least some
scattered showers/thunderstorms continue through the night as the
upper low pushes the surface front east into our area.

The front should move east of our region tomorrow morning. Drier air
is expected to move into the region in wake of the front, and allow
quiet weather conditions to be seen heading toward the middle of the
week.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 1235 PM EDT Monday...

Key Messages:

- Potential for Storms on Thursday.
- Wednesday will be dry for most locations.

Discussion:

Surface high pressure will become established over the area
following the passage of a cold front, leading to quiet, dry weather
for most locations through Wednesday night. A warm front draped
across the southeastern US will slowly lift northward, as a cold
front approaches from the Great Lakes through Thursday, which will
provide the next opportunity for strong storms over the area through
Thursday. Increased mid level winds associated with the more
northern system will advect greater moisture into the area, as
indicated by forecast PWATs over 1.5 inches by Thursday morning.
This set up may contribute to heavy rainfall within any of the
storms that develop. Models are suggesting that the strongest storms
will be along the southern Blue Ridge and the Piedmont, given the
eastward movement of a strong low level jet across Tennessee and the
Carolinas. With the upslope flow from strong westerly winds,
mountain showers and storms could continue into Friday.

Temperatures will be near normal through this forecast period, with
highs in the upper 70s in the west and mid to upper 80s in the east.

Forecast confidence is average to high.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 1255 PM EDT Monday...

Key Messages:

- Storms possible on Saturday, Sunday and Monday look dry for most.
- Near normal temperatures are expected.

Discussion:

A surface frontal system develops over the Great Lakes, and while
the center low looks to track northeastward through eastern Canada,
the cold front will drop through the Mid Atlantic over the weekend.
This system will provide the next chance for the area to see showers
and thunderstorms. Showers and storms will likely develop by
Saturday afternoon over the mountains, then push eastward and
eventually diminishing by the overnight hours in the east. Some
showers and storms may linger over the mountains through early
Sunday morning. Some models are also hinting at the front slowing
down to the east over the area, over far eastern Virginia and North
Carolina, which may lead to continued chances for showers and storms
over the Piedmont through Sunday. However, given how far out this is
in the forecast period, confidence is not very high.

Temperatures will be near normal through this forecast period.

Forecast confidence is average through Friday, but low over the
weekend.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
Issued at 215 PM EDT MON AUG 07 2023

SHRA/TSRA, with some +TSRA possible, will impact many terminals
across the forecast area during the 07/1800 UTC TAF period. The
convection will result in CIG/VSBY reductions to MVFR or IFR in
vicinity of any convection. Timing to narrow down SHRA/TSRA
impact timing for specific terminals is still rather difficult,
but expect impact timing for terminals to be roughly as follows:

Western Terminals: 07/1800-2000 UTC
Blue Ridge Terminals: 07/1900-2100 UTC
Eastern Terminals: 07/2000-2400 UTC

Gusty, mostly SW, winds and VFR flight categories will likely be
seen prior to the arrival of storms. Aviation interests should be
aware of the possibility of +TSRA, which could result in wind
gusts in excess of 50kts and GR, mainly through 08/0000 UTC or
so.

After the line of SHRA/TSRA moves E, lingering convection will
likely be seen until a cold front moves E of the region between
08/0600-1200 UTC. After FROPA, expect improving flight categories
with winds veering to a W-NW direction around 10 kts.

OUTLOOK TUESDAY NIGHT THROUGH FRIDAY...

Tuesday night: Flight category reductions possible in river valleys
due to BR/FG. Otherwise, mostly VFR flight categories expected.

Wednesday: Mainly VFR flight categories expected.

Thursday and Friday: Restrictions possible due to SHRA/TSRA.

&&

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

&&

SYNOPSIS...DB
NEAR TERM...DB
SHORT TERM...AS
LONG TERM...AS
AVIATION...DB

Hazardous Weather Outlook
National Weather Service Blacksburg VA
153 PM EDT Mon Aug 7 2023

NCZ001>006-018>020-VAZ007-009>020-022>024-032>035-043>047-058-059-
WVZ042>044-507-508-081800-
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-Mercer-Summers-Monroe-
Eastern Greenbrier-Western Greenbrier-
153 PM EDT Mon Aug 7 2023

...TORNADO WATCH 603 IN EFFECT UNTIL 9 PM EDT THIS EVENING...

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

   Tornado Watch.

There is a moderate, or Level 4 out of 5, risk of severe
thunderstorms this afternoon and evening. This area is generally
west of a Boone North Carolina, to Martinsville and Buckingham
Virginia Line. Across the remainder of Southside Virginia and the
North Carolina Piedmont, there is an enhanced, or Level 3 out of 5,
risk of severe thunderstorms this afternoon and evening.

Thunderstorms will bring the potential for damaging winds, possibly
in excess of 70 miles an hour, and hail. Tornadoes will be possible,
especially west of the Interstate 81 corridor. Localized flooding
is also a possibility.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

There is a low probability for widespread hazardous weather.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather by
calling 1-866-215-4324, social media, email at rnk.skywarn@noaa.gov
or online at www.weather.gov/rnk.

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