2023 Mid-Atlantic Severe Wx Thread (General Discussion)

[wxdude64]

105 mph!?! wow.

Public Information Statement
National Weather Service Blacksburg VA
638 PM EDT Tue Aug 8 2023

...NWS Damage Survey completed for the August 7th, 2023 
Thunderstorm Wind Event...

.Meteorologists from the National Weather Service in Blacksburg,
VA have completed a survey of storm-related damage in northwest 
Summers County, WV that occurred on the evening of August 7th, 
and have concluded that the damage was caused by intense straight-
line winds.

Estimated Peak Wind:          105 mph
Wind Swath Length /statute/:  8.1 miles
Wind Swath Width /maximum/:   roughly 2,000 yards
Fatalities:                   0
Injuries:                     0

Start Date:                   08/07/2023
Start Time:                   5:54 PM EDT
Start Location:               1 SW Hinton / Summers County / WV
Start Lat/Lon:                37.66/-80.91

End Date:                     08/07/2023
End Time:                     6:06 PM EDT
End Location:                 1 NW Talcott / Summers County / WV
End Lat/Lon:                  37.66/-80.76

Summary: An already strong thunderstorm over Raleigh County, WV 
continued to strengthen to severe intensity as it neared Summers 
County, prompting the issuance of a Severe Thunderstorm Warning at
5:37 PM EDT. Once in Summer County, Doppler radar briefly detected
strong rotation in the thunderstorm near the community of Jumping
Branch, prompting the issuance of a Tornado Warning at 5:58 PM 
EDT. 

First noted signs of wind damage occurred along Highway 3 just
southwest of Hinton, where numerous hardwood trees were snapped
or uprooted by the force of the winds, estimated to be up to 100
mph. One home sustained damage to both the roof and the siding in
this area. Additional damage was observed along Highway 20 just to
the north, where dozens of trees were blown down by estimated 105
mph wind gusts. The storm continued east, snapping or uprooting 
numerous trees from the community of Bellepoint eastbound along
Highway 3 following the Greenbrier River with 100 to 105 mph wind
gusts. Shortly afterward, the storm began to weaken, though still
produced significant damage to dozens of trees along Judson Road
near the community of Talcott with estimated 70-75 mph wind 
gusts. While additional reports of damage were received further 
east with this storm, this was the eastern-most extent of the 
storm survey.

[Eskimo Joe]

As expected, SPC and NWS are out doing real yeoman's work again. AWell done.

 

[TSSN+]

Thursday could have a few boomers 

[Eskimo Joe]

^yes. Thursday has sneaky severe potential.

[mappy]

37 minutes ago, Eskimo Joe said:

As expected, SPC and NWS are out doing real yeoman's work again. AWell done.

 

I read CPT's PWS from yesterday -- lot of straight line wind damage, but they did find some clusters of intense damage in southern York they were going to investigate further today. Didn't say where, I wonder if it's the Glen Rock area. 

[Eskimo Joe]

5 minutes ago, mappy said:

I read CPT's PWS from yesterday -- lot of straight line wind damage, but they did find some clusters of intense damage in southern York they were going to investigate further today. Didn't say where, I wonder if it's the Glen Rock area. 

To be honest, we're fortunate the low level winds weren't more conducive for sustained rotating updrafts. Monday had the potential to be a late breaking High Risk day. Once the 18z special RAOBs went up, it was clear this was going to be a straight line wind kind of day, with embedded spin ups. This reinforces my belief that real mesoscale forecasting hinges on things like soundings, mesonets, and a well rained cadre of field spotters (SKYWARN, fire, EM, DT etc.). It's hilarious and frustrating to see DC bros cackling about how this was a complete bust because the national mall wasn't wiped off the face of the earth, while the suburbs where everyone lives were hit much harder. 

[mappy]

3 minutes ago, Eskimo Joe said:

To be honest, we're fortunate the low level winds weren't more conducive for sustained rotating updrafts. Monday had the potential to be a late breaking High Risk day. Once the 18z special RAOBs went up, it was clear this was going to be a straight line wind kind of day, with embedded spin ups. This reinforces my belief that real mesoscale forecasting hinges on things like soundings, mesonets, and a well rained cadre of field spotters (SKYWARN, fire, EM, DT etc.). It's hilarious and frustrating to see DC bros cackling about how this was a complete bust because the national mall wasn't wiped off the face of the earth, while the suburbs where everyone lives were hit much harder. 

For sure. Could have been much worse than it was. My people at the dance studio were asking me all sorts of questions, what to look for on radar for tornado threats, how to read velocity. Was pretty funny to me that they actually wanted to know all the nerdy details. 

I am incredibly glad we closed Monday night, could not have imagined having a dance studio full of kids, parents traveling and such. Two other studios in the area stayed opened and we heard they had families trapped for hours because they just couldn't travel home. 

[Eskimo Joe]

9 minutes ago, mappy said:

For sure. Could have been much worse than it was. My people at the dance studio were asking me all sorts of questions, what to look for on radar for tornado threats, how to read velocity. Was pretty funny to me that they actually wanted to know all the nerdy details. 

I am incredibly glad we closed Monday night, could not have imagined having a dance studio full of kids, parents traveling and such. Two other studios in the area stayed opened and we heard they had families trapped for hours because they just couldn't travel home. 

Agreed. The CWG articles about how this was a bust because no tornadoes were recorded is short sighted. They should know better that damage assessments day up to 10 days and these watch boxes will more than verify.

[mappy]

13 minutes ago, Eskimo Joe said:

Agreed. The CWG articles about how this was a bust because no tornadoes were recorded is short sighted. They should know better that damage assessments day up to 10 days and these watch boxes will more than verify.

They really said that? That's a shame. Just because there were no confirmed tornadoes as of yet, doesn't mean the severe threat was a bust. 

[Terpeast]

36 minutes ago, Eskimo Joe said:

Agreed. The CWG articles about how this was a bust because no tornadoes were recorded is short sighted. They should know better that damage assessments day up to 10 days and these watch boxes will more than verify.

Luckily my area wasn’t as bad as northern MD, l’ve seen a few trees and a street lamp down in my neighborhood. That’s enough to justify the watch, had the wind been a few mph stronger that might have had been enough to cause a lot more damage

[frd]

Early next week has decent potential, as discuseed by Mount Holly this morning. 

 

Model guidance next week suggest that a strong shortwave will round the base of thee upper-low
persisting over eastern Canada, possibly phasing with it and
resulting in a more dynamic cold front passing through early
next week. That will certainly deserve monitoring for
thunderstorms, followed by high pressure bringing a cooler and
drier airmass around the middle of the week.

 

 

[Eskimo Joe]

CC: @mappy

 

 

[TSSN+]

Drove up Hanover pike between Manchester and the PA line for work today and there was a good bit of damage I seen there. Trees down on houses and power lines down. Had to turn around from my original route cause the road was closed. 

[Eskimo Joe]

10 minutes ago, TSSN+ said:

Drove up Hanover pike between Manchester and the PA line for work today and there was a good bit of damage I seen there. Trees down on houses and power lines down. Had to turn around from my original route cause the road was closed. 

Saw Mill Rd was wrecked. The storm that went through there ultimately became the tornado warned event in York County.

[TSSN+]

12 minutes ago, Eskimo Joe said:

Saw Mill Rd was wrecked. The storm that went through there ultimately became the tornado warned event in York County.

It looked pretty bad. I seen someone’s trampoline laying in a corn field about 1000 feet from the house it used to be at. Was a wild ride for sure. When I was watching it come in it sounded like a train coming in. 

[yoda]

Morning AFD from LWX about Monday's severe weather threat mentions August 7th as reference 

 

LONG TERM /SUNDAY THROUGH WEDNESDAY/...
A rather potent mid-upper level trough/closed low will pivot through
the eastern Great Lakes early next week pushing a strong cold
front through the region Monday night. Timing differences among
global models have diminished considerably since yesterday
indicating a sharp frontal passage across the area around 06Z
Tue per ECMWF, slower timing on the GFS. Strong height falls
(110 meter/24 hr) are fcst across the region during the day
Monday, which are similar in magnitude to what we saw this past
Mon Aug 07. Strong mid-level wind speeds will enhance the
potential for severe wx. Latest timing from Euro and GFS show
the best potential for thunderstorms later at night in the
00Z-06Z Tue time frame which may temper the severe wx risk
somewhat. Additional showers will remain possible during the
middle of next week as individual shortwaves rotate around the
mean trof, but it looks as moisture and instability will be
fairly limited. Flooding risk will remain very minimal due to
expected very fast storm motions.

 

[09-10 analogy]

So to recap (for LWX region):

July 28: Corridor of significant wind damage from Frederick to Baltimore County, with a secondary cluster around the northern and eastern suburbs of DC; scattered hail and wind damage reports in NVA. (82 reports total)

https://www.spc.noaa.gov/exper/reports/?date=20230728&hoursBefore&all

July 29: Corridor of significant/major wind damage from NVA and southern MOCO through DC; scattered reports elsewhere (141 reports total; 749 nationwide)

https://www.spc.noaa.gov/exper/reports/?&all&date=20230729

August 7: Corridor of major/extreme wind damage and hail reports along and south of Mason/Dixon line (tornado reports pending?); numerous wind (and some hail) reports in eastern WVA, northern VA, and central MD; scattered reports in DC (203 reports total; 1389 nationwide)

https://www.spc.noaa.gov/exper/reports/?&all&date=20230807

(Links go to CONUS map; I drilled down to just Sterling CWA; I don't know how to make the link focus on just our area)

That about right?

[yoda]

00z NAM throwing up some alarming soundings for Monday night -- yes, caveats apply and the such but still... yikes

[yoda]

That is a sounding for KDCA

 

Sounding location in PG County/Charles County area of MD

[yoda]

Morning AFD from LWX on the Monday evening into Monday night severe threat

 

Monday presents yet another chance for some severe
thunderstorms, particularly late Monday into Monday night. A
potent low pressure system will scoot by well to our north
across the Great Lakes region. This will be accompanied by
positively tilted and relatively deep upper trough (for August).
As this approaches from the west, expect shower and
thunderstorms to develop late Monday into Monday night. Could
see some development ahead of the primary system as well along
the lee trough due to diurnal heating as well. As usual, these
could bring some isolated damaging wind gusts. But the main
threat comes with the Monday night round. Damaging wind gusts
and large hail are the primary concerns with these storms.
Additionally, flooding can`t be ruled out, especially if the
front manages to stall near the area. Do think the deep
southerlies should push the warm front north of the area rather
quickly, but still, given 2+ inch PWATs and a lingering
boundary, there exists at least an isolated flooding threat
Monday night.

[FXW176]

22 minutes ago, yoda said:

Morning AFD from LWX on the Monday evening into Monday night severe threat

*Snip*

Last few Afds and guidance were kinda meh re Mon. Seems to be kinda an overnight event with a few localized boomers. Like this season imby.

(Yuck, just made a wx post…)

[yoda]

Sounds like an interesting evening into overnight coming?

NEAR TERM /THROUGH TONIGHT/...
Latest satellite imagery shows a CU field developing beneath a
mid-level stratus deck. Most of the cu south of Mason-Dixon has
been more shallow compared to the cu north into central PA.
Overall thinking through this afternoon is any storms that do
develop should be pretty isolated in nature and not last long
for any given location.

Focus then turns to this evening. There are a few main periods
of interest:

1) The northern periphery of the decaying MCS over West Virginia is
progged to move over the forecast area early this evening
(20-23Z). This will need to be monitored as it could lead to the
development of a rogue thunderstorm, which could be
supercellular given soundings somewhere across central or
northern VA.

2) The approaching frontal boundary from the northwest. While
the better forcing is indeed to the north, guidance continues to
bring convection into western Maryland and the eastern WV
Panhandle between 22-06Z. This area has the greatest potential
to see SVR wx as indicated by the slight risk from SPC. Greatest
threat appears to be wind, especially if an MCS forms upstream.

3) A small jetlet (25-35 kts) is forecast to develop near the
US-29/I-95 corridor this evening (00-06Z). There is also some
backed flow near a pressure trough at the sfc. Some guidance has
redevelopment off the aforementioned threat from above near the
nose of the jet. This makes sense if the abundant CAPE over the
Bay is advected onshore.

Otherwise, summer heat will continue today with high
temperatures in the low 90s, accompanied by a notable increase
in humidity. The addition of humidity will fuel heat indices
into the mid 90s, particularly east of the Blue Ridge and
Catoctins.

[87storms]

2nd time I've seen machine learning mentioned in the LWX disco (didn't realize AI tech was already used in forecasting):

Monday continues to look like the next widespread potential for
rain and some severe thunderstorms. The one aspect of this
system different from the past few SVR events, is the better
forcing is slightly delayed from peak heading. A potent low
pressure system will scoot by well to our north across the Great
Lakes region. Guidance recently has trended slightly south with
the low. This inherently impacts the warm frontal position. The
low will be accompanied by a positively tilted and relatively
deep upper trough (for August). As this approaches from the
west, expect shower and thunderstorms to develop late Monday
into Monday night. Could see some development ahead of the
primary system as well along the lee trough due to diurnal
heating as well. As usual, these could bring some isolated
damaging wind gusts. But the main threat comes with the Monday
night round. Damaging wind gusts and large hail are the primary
concerns with these storms. CSU machine learning continues to
highlight the FA with modest SVR probs as well as SPC with a
Slight Risk for SVR wx generally west of the Blue Ridge. The
warm frontal positioning will influence the tornado threat.
Additionally, flooding can`t be ruled out, especially if the
front manages to stall near the area. Do think the deep
southerlies should push the warm front north of the area rather
quickly, but still, given 2+ inch PWATs and a lingering
boundary, there exists at least an isolated flooding threat
Monday night.

[yoda]

18z NAM back with some really impressive soundings for the region late Monday evening into the overnight....don't remember seeing STP of 7 to 8 with large curved hodographs and MLCAPE over 2K

[North Balti Zen]

Looks like that storm cluster currently near Pittsburgh really might hold together and get to at least the baltimore area around midnight. Not great news for meteor hunting tho. 

[yoda]

For those out in W MD and the NW portion of the LWX CWA 

https://www.spc.noaa.gov/products/md/md1975.html

 

 

   Mesoscale Discussion 1975
   NWS Storm Prediction Center Norman OK
   0631 PM CDT Sat Aug 12 2023

   Areas affected...portions of southeastern OH...northern
   WV...southwestern PA and western MD.

   Concerning...Tornado Watch 634...

   Valid 122331Z - 130100Z

   The severe weather threat for Tornado Watch 634 continues.

   SUMMARY...Ongoing severe storms in the southern half of WW634 will
   likely persist beyond the 01z expiration. A new watch will likely be
   needed.

   DISCUSSION...As of 2330 UTC, several supercells were ongoing across
   parts of far eastern OH, and western PA. These storms have
   maintained intensity and should continue to do so after the 01z
   expiration of WW634. 40-50 kt of effective shear and 1500 J/kg of
   MLCAPE will favor organized storms including supercells and short
   line segments. Damaging wind gusts and hail appear likely with the
   strongest storms into this evening. Veered low-level flow in the
   wake of the earlier rounds of storms suggests the tornado threat is
   not overly high. However, a brief tornado will remain possible given
   the supercell mode and 15-20 kt of 0-1km shear. The severe threat
   will likely extend beyond the 01z expiration of WW634. A new watch
   will likely replace southern parts of the watch to cover the severe
   risk into early tonight.

   ..Lyons/Thompson.. 08/12/2023

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

   ATTN...WFO...CTP...LWX...PBZ...RLX...

 

[yoda]

Severe Thunderstorm Watch until 2am coming for NW portion of the LWX CWA 

[yoda]

10 minutes ago, yoda said:

Severe Thunderstorm Watch until 2am coming for NW portion of the LWX CWA 

 

---

000
WWUS61 KLWX 130009
WCNLWX

WATCH COUNTY NOTIFICATION FOR WATCH 639
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
809 PM EDT SAT AUG 12 2023

MDC001-023-043-WVC003-023-027-031-057-065-130600-
/O.NEW.KLWX.SV.A.0639.230813T0009Z-230813T0600Z/

THE NATIONAL WEATHER SERVICE HAS ISSUED SEVERE THUNDERSTORM WATCH
639 IN EFFECT UNTIL 2 AM EDT SUNDAY FOR THE FOLLOWING AREAS

IN MARYLAND THIS WATCH INCLUDES 3 COUNTIES

IN NORTH CENTRAL MARYLAND

WASHINGTON

IN WESTERN MARYLAND

ALLEGANY                       GARRETT

IN WEST VIRGINIA THIS WATCH INCLUDES 6 COUNTIES

IN EASTERN WEST VIRGINIA

GRANT                       HAMPSHIRE
HARDY                       MINERAL

IN THE EASTERN PANHANDLE OF WEST VIRGINIA

BERKELEY                       MORGAN

THIS INCLUDES THE CITIES OF CUMBERLAND, FORT ASHBY, FROSTBURG,
GRANTSVILLE, HAGERSTOWN, KEYSER, MARTINSBURG, MOOREFIELD,
MOUNTAIN LAKE PARK, OAKLAND, PAW PAW, PETERSBURG, AND ROMNEY.

[yoda]

That's a good amount of TWs showing up right now entering SW PA and W WV

[TSSN+]

3 minutes ago, yoda said:

That's a good amount of TWs showing up right now entering SW PA and W WV

Confirmed one in PA 

To repeat, a tornado is on the ground. 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.