2023 Mid-Atlantic Severe Wx Thread (General Discussion)

[wxdude64]

22 minutes ago, yoda said:

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Baltimore MD/Washington DC
245 PM EDT Mon Aug 7 2023

The National Weather Service in Sterling Virginia has issued a

* Tornado Warning for...
  Northwestern Augusta County in western Virginia...
  Central Highland County in western Virginia...
  South central Pendleton County in eastern West Virginia...

* Until 315 PM EDT.

* At 244 PM EDT, a severe thunderstorm capable of producing a tornado
  was located 7 miles south of Monterey, moving east at 45 mph.

  HAZARD...Tornado and golf ball size hail.

  SOURCE...Radar indicated rotation.

  IMPACT...For those in the direct path of a tornado touchdown,
           flying debris will be dangerous to those caught without
           shelter. Damage to roofs, siding, and windows may occur.
           Mobile homes may be damaged or destroyed. Tree damage is
           likely.

* This tornadic thunderstorm will remain over mainly rural areas of
  northwestern Augusta, central Highland and south central Pendleton
  Counties, including the following locations... West Augusta, Palo
  Alto, Clover Creek, Mustoe, Mcdowell, Doe Hill, Head Waters,
  Vanderpool, Sirons Mill and Liberty.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW! Move to a basement or an interior room on the lowest
floor of a sturdy building. Avoid windows. If you are outdoors, in a
mobile home, or in a vehicle, move to the closest substantial shelter
and protect yourself from flying debris.

&&

LAT...LON 3825 7969 3839 7971 3847 7924 3825 7922
TIME...MOT...LOC 1844Z 264DEG 38KT 3830 7962

TORNADO...RADAR INDICATED
MAX HAIL SIZE...1.75 IN

$$

 

18 minutes ago, Chinook said:

Currently there is one new tornado warning in the mountain corridor of the WV/VA state line. One note on an amazing event in years past, in the 1974 super outbreak I believe there was an F-3 tornado climbed up and down one or more mountain ridges in West Virginia. So there's that.

Yes to the 1974 outbreak, I was only 10 but remember the storms. The IMPRESSIVE thing about that Highland County storm is the 60-70 DBz's on radar. That area basically is a radar 'hole', I can't remember ever seeing that high of a value up there. 

[weatherwiz]

One over Saint James is a monster for sure 

[Terpeast]

Radar already showing storms congealing into a line even before crossing the blue ridge

[09-10 analogy]

59 minutes ago, mappy said:

It absolutely is. I was anxious about just having to travel later in it, having a safe place at the studio should we need to shelter, and all that. Just too many moving parts when people are coming from multiple areas to the studio for classes. Not worth all that risk. 

Believe me, when I saw that tree that had pancaked a (fortunately, parked) car from last week's downburst in DC ... well, I've seen tons of pictures of that kind of thing, but to see it first-hand, it brings home how dangerous 70-80+ straight-line winds can be in areas with lots of big old elm and oak trees. Bit of a quandary, because I want to park under a big-canopy tree to protect my car somewhat from hail, but that same tree might demolish my car. (No garage at my house, most people on my street have one at the back of their property, but I'm right next to a corner lot and the way our neighborhood is laid out, corner lots and those adjacent don't have garages that back onto alleys.) 

[09-10 analogy]

1 hour ago, Eskimo Joe said:

The downside to this event is that we need the higher end potential to be realized. It's been hyped so much now that for this to bust would erode public trust. 

How much of that hype do you think can be attributed to last week's storms?

[MN Transplant]

18z HRRR with less wind coverage, but one intense area (67kt).  However, per usual, it is running dew points 5 degrees below actual.

 

[Hank Scorpio]

2 minutes ago, weatherwiz said:

One over Saint James is a monster for sure 

Looks like it's still growing, too

[pazzo83]

That tornado-warned storm coming out of Highland into Augusta - lol, I wonder how many times Highland County has had a tornado warning.

[AmericanWxFreak]

1 minute ago, MN Transplant said:

18z HRRR with less wind coverage, but one intense area (67kt).  However, per usual, it is running dew points 5 degrees below actual.

 

Yeah that run had a weird evolution of things 

[TSSN+]

Those front end storms are crawling 

[SomeguyfromTakomaPark]

Hagerstown storm getting a bit of a hook. 

[yoda]

SPC in their updated MCD says tor threat should increase as the afternoon/evening goes on across the region

Mesoscale Discussion 1888
   NWS Storm Prediction Center Norman OK
   0217 PM CDT Mon Aug 07 2023

   Areas affected...central into northern Virginia...eastern
   Maryland...southern into central Pennsylvania

   Concerning...Tornado Watch 602...

   Valid 071917Z - 072045Z

   The severe weather threat for Tornado Watch 602 continues.

   SUMMARY...The severe threat continues across Tornado Watch 602.
   Large hail and damaging gusts are the main threat in the short-term,
   but the tornado risk should continue to steadily increase through
   the afternoon.

   DISCUSSION...Multiple mature supercells and quasi-linear structures
   are progressing eastward across the central Appalachians into the
   Mid Atlantic this afternoon, some with a history of severe hail and
   damaging gusts. Given the favorable ambient buoyancy/deep-layer
   shear preceding the ongoing storms, the supercells and quasi-linear
   structures should maintain intensity, with the large hail/damaging
   gust threat continuing. At the moment, regional VADs and forecast
   soundings show hodographs with relatively straight curvature, which
   may be limiting the current tornado threat to a degree. However, as
   the mid-level trough continues to approach and shunts the 850 mb
   southwesterly jet axis eastward, an increase in low-level hodograph
   length and perhaps curvature should ensue, which would support an
   increased tornado threat later this afternoon.

   ..Squitieri.. 08/07/2023

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...PHI...BGM...AKQ...CTP...LWX...

[pazzo83]

DCA 89 or 90 with a dewpoint of 76.

[wxdude64]

2 minutes ago, pazzo83 said:

That tornado-warned storm coming out of Highland into Augusta - lol, I wonder how many times Highland County has had a tornado warning.

I think I can remember one in the eastern part of that county about 15 years ago.

[09-10 analogy]

23 minutes ago, Always in Zugzwang said:

Wow...looks almost similar to this (IAD sounding just before the derecho hit in 2012)...

Is that hodo the "wavy" kind that was mentioned in an SPC/LWX AFD (I forget which office) a day or so ago? 

[nj2va]

Nearby DPs on PWS in my area are between 77-82.  

[EastCoast NPZ]

Can already see the split forming to the SW.  Exact same storm motion as all summer long.  And the current DP is 77F.  As high as I can remember seeing.  Will make this failure all the more painful.

[dailylurker]

Headed towards Thurmont. She's a beautiful cell. 

[H2O]

2 minutes ago, nj2va said:

Nearby DPs on PWS in my area are between 77-82.  

Mine has bounced between 78-80 all afternoon

[yoda]

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
321 PM EDT Mon Aug 7 2023

.SYNOPSIS...
Scattered to numerous strong to severe thunderstorms are expected
today as a strong cold front pushes through the region. High
pressure returns behind the front Tuesday into Wednesday with breezy
conditions. A warm frontal boundary approaches from the south
Thursday into Friday bring additional showers and
thunderstorms. Unsettled conditions linger into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Based on the thermodynamic and kinematic environments in place,
the setup is rather extreme for early August standards. While
instability is typically in place for many summer days, the
vertical shear is off the charts. The 18Z KIAD sounding being
launched is currently showing 40-50 knots of westerly flow in
the 700-500 mb layer. This is only continuing to increase the
deep layer shear across the area. While cells remain in discrete
in nature, all severe hazards are possible through the afternoon
hours. Most mid-afternoon convection has been exhibiting
supercellular characteristics with bounded weak echo regions
(BWER) and developing hook echoes. At this juncture, only a
couple rotating wall clouds have been observed. However, given
the environment is ripe for rotating thunderstorms, a Tornado
Watch is in effect until 9 PM this evening across the entire
area.

The regional radar imagery shows an expansive cluster of
multicells and line segments pushing through West Virginia.
Based on the latest radar, satellite, and high-resolution model
trends, this upstream activity should evolve into a quasi-linear
convective system (QLCS). The downdraft CAPE is very impressive
from the Shenandoah Valley eastward with values of around 1,000
to 1,200 J/kg per the 18Z RAP objective analysis. This
congealing of the convective complex is where the damaging to
locally destructive wind threat emerges late this afternoon into
the evening hours. Given an increasing low-level jet around
dark, the increasing 0-1 km shear will enhance the threat for
spin ups along the QLCS. A bulk of the Mid-Atlantic region
continues to be in a Moderate risk for severe thunderstorms.
Locally, this is something which is only seen a couple times a
decade.

Given the degree of hazardous weather affecting the region,
ensure you have multiple ways to obtain NWS warnings. In case
severe weather impacts you, find shelter and utilize the most
interior space inside the structure. As always lightning is
always a hazard in any thunderstorm. Wait at least 30 minutes
until the last sound of thunder before returning outside.

The convective threat will push through the DC and Baltimore
metros during the evening rush hour before exiting into the
Chesapeake Bay by the late evening. Besides the threat for
hazardous weather, conditions are hot and humid with high
temperatures topping out in the upper 80s to low 90s. Combine
these temperatures with dew points in the low/mid 70s yields
heat index values of 97 to 101 degrees.

[pazzo83]

5 minutes ago, wxdude64 said:

I think I can remember one in the eastern part of that county about 15 years ago.

Definitely you see them every so often in Western Augusta, but usually after they cross the Alleghenies.  Yeah - I'd think it's pretty rare actually in Highland.

[Wxtrix]

4 minutes ago, EastCoast NPZ said:

Can already see the split forming to the SW.  Exact same storm motion as all summer long.  And the current DP is 77F.  As high as I can remember seeing.  Will make this failure all the more painful.

i hope it splits—i don’t want any part of it.

[Wxtrix]

the Hagerstown storm from my back deck:

 

[pazzo83]

6 minutes ago, nj2va said:

Nearby DPs on PWS in my area are between 77-82.  

88/78 in NW.

[pazzo83]

6 minutes ago, EastCoast NPZ said:

Can already see the split forming to the SW.  Exact same storm motion as all summer long.  And the current DP is 77F.  As high as I can remember seeing.  Will make this failure all the more painful.

75+ dews in the Valley are pretty rare.  Damn.

[Eskimo Joe]

Kind of surprised that Thurmont storm doesn't have a tornado warning.

[Darkstorm]

Live in St James area. Can confirm nice little round of hail came down. Wife was frantically running around worried her car was dented. Can report we got lucky there.

[Eskimo Joe]

2 minutes ago, yoda said:

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
321 PM EDT Mon Aug 7 2023

.SYNOPSIS...
Scattered to numerous strong to severe thunderstorms are expected
today as a strong cold front pushes through the region. High
pressure returns behind the front Tuesday into Wednesday with breezy
conditions. A warm frontal boundary approaches from the south
Thursday into Friday bring additional showers and
thunderstorms. Unsettled conditions linger into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Based on the thermodynamic and kinematic environments in place,
the setup is rather extreme for early August standards. While
instability is typically in place for many summer days, the
vertical shear is off the charts. The 18Z KIAD sounding being
launched is currently showing 40-50 knots of westerly flow in
the 700-500 mb layer. This is only continuing to increase the
deep layer shear across the area. While cells remain in discrete
in nature, all severe hazards are possible through the afternoon
hours. Most mid-afternoon convection has been exhibiting
supercellular characteristics with bounded weak echo regions
(BWER) and developing hook echoes. At this juncture, only a
couple rotating wall clouds have been observed. However, given
the environment is ripe for rotating thunderstorms, a Tornado
Watch is in effect until 9 PM this evening across the entire
area.

The regional radar imagery shows an expansive cluster of
multicells and line segments pushing through West Virginia.
Based on the latest radar, satellite, and high-resolution model
trends, this upstream activity should evolve into a quasi-linear
convective system (QLCS). The downdraft CAPE is very impressive
from the Shenandoah Valley eastward with values of around 1,000
to 1,200 J/kg per the 18Z RAP objective analysis. This
congealing of the convective complex is where the damaging to
locally destructive wind threat emerges late this afternoon into
the evening hours. Given an increasing low-level jet around
dark, the increasing 0-1 km shear will enhance the threat for
spin ups along the QLCS. A bulk of the Mid-Atlantic region
continues to be in a Moderate risk for severe thunderstorms.
Locally, this is something which is only seen a couple times a
decade.

Given the degree of hazardous weather affecting the region,
ensure you have multiple ways to obtain NWS warnings. In case
severe weather impacts you, find shelter and utilize the most
interior space inside the structure. As always lightning is
always a hazard in any thunderstorm. Wait at least 30 minutes
until the last sound of thunder before returning outside.

The convective threat will push through the DC and Baltimore
metros during the evening rush hour before exiting into the
Chesapeake Bay by the late evening. Besides the threat for
hazardous weather, conditions are hot and humid with high
temperatures topping out in the upper 80s to low 90s. Combine
these temperatures with dew points in the low/mid 70s yields
heat index values of 97 to 101 degrees.

Oh shit

[Mrs.J]

 

Just now, Eskimo Joe said:

Kind of surprised that Thurmont storm doesn't have a tornado warning.

Yeah my daughter and I were looking at that. 

[09-10 analogy]

1 minute ago, yoda said:

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
321 PM EDT Mon Aug 7 2023

.SYNOPSIS...
Scattered to numerous strong to severe thunderstorms are expected
today as a strong cold front pushes through the region. High
pressure returns behind the front Tuesday into Wednesday with breezy
conditions. A warm frontal boundary approaches from the south
Thursday into Friday bring additional showers and
thunderstorms. Unsettled conditions linger into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Based on the thermodynamic and kinematic environments in place,
the setup is rather extreme for early August standards. While
instability is typically in place for many summer days, the
vertical shear is off the charts. The 18Z KIAD sounding being
launched is currently showing 40-50 knots of westerly flow in
the 700-500 mb layer. This is only continuing to increase the
deep layer shear across the area. While cells remain in discrete
in nature, all severe hazards are possible through the afternoon
hours. Most mid-afternoon convection has been exhibiting
supercellular characteristics with bounded weak echo regions
(BWER) and developing hook echoes. At this juncture, only a
couple rotating wall clouds have been observed. However, given
the environment is ripe for rotating thunderstorms, a Tornado
Watch is in effect until 9 PM this evening across the entire
area.

The regional radar imagery shows an expansive cluster of
multicells and line segments pushing through West Virginia.
Based on the latest radar, satellite, and high-resolution model
trends, this upstream activity should evolve into a quasi-linear
convective system (QLCS). The downdraft CAPE is very impressive
from the Shenandoah Valley eastward with values of around 1,000
to 1,200 J/kg per the 18Z RAP objective analysis. This
congealing of the convective complex is where the damaging to
locally destructive wind threat emerges late this afternoon into
the evening hours. Given an increasing low-level jet around
dark, the increasing 0-1 km shear will enhance the threat for
spin ups along the QLCS. A bulk of the Mid-Atlantic region
continues to be in a Moderate risk for severe thunderstorms.
Locally, this is something which is only seen a couple times a
decade.

Given the degree of hazardous weather affecting the region,
ensure you have multiple ways to obtain NWS warnings. In case
severe weather impacts you, find shelter and utilize the most
interior space inside the structure. As always lightning is
always a hazard in any thunderstorm. Wait at least 30 minutes
until the last sound of thunder before returning outside.

The convective threat will push through the DC and Baltimore
metros during the evening rush hour before exiting into the
Chesapeake Bay by the late evening. Besides the threat for
hazardous weather, conditions are hot and humid with high
temperatures topping out in the upper 80s to low 90s. Combine
these temperatures with dew points in the low/mid 70s yields
heat index values of 97 to 101 degrees.

"the vertical shear is off the charts." That's the summertime equivalent of "robust frontogenesis will lead to rates of 2-3"/hour."