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2023 Mid-Atlantic Severe Wx Thread (General Discussion)


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1 minute ago, yoda said:

Hmmm

 

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
246 PM EDT Thu Jul 27 2023

.SYNOPSIS...
A Bermuda high will remain in place offshore through Saturday.
A surface trough will remain overhead through Saturday before a
cold front passes through the area Saturday night into Sunday.
High pressure will likely return early next week while an
upper-level trough builds overhead.

&&

.NEAR TERM /THROUGH TONIGHT/...
The mid-level clouds have dissipated for the most part, and this
has allowed for hot and humid conditions. The Heat Advisory for
near/east of Interstate 81 to the Bay remains in effect for heat
indices around 100 to 105 degrees.

The heat and humidity has led to plenty of instability. Latest
mesoanalysis shows around 1 to 3 KJ/KG of MLCAPE, but there is
inhibition as of early this afternoon. Current feeling is that a
surface trough axis over southwest PA will merge into a weak
trough over north-central MD into northern VA as the upper-level
trough axis to our north moves eastward. This added lift should
be enough for some storms to develop late this afternoon. If
storms do develop, then more storms will likely develop due to
the boundaries produced by the convection. Shear is marginal,
but higher CAPE and DCAPE suggest that damaging winds are a
threat, along with the possibility of large hail. There is the
possibility that coverage of severe storms can be numerous
around northern VA into the DC and Baltimore Metro areas for
reasons mentioned above.

Do mesos not handle the boundary triggered storms well? I still see some very boring looks to those models...

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Just now, Eskimo Joe said:

Cell approaching Harper's Ferry, WV just got warned. Solid hail core developing and tops shooting up. Might have broken through the cap.

Severe Thunderstorm Warning
MDC021-043-VAC107-WVC037-272015-
/O.NEW.KLWX.SV.W.0169.230727T1936Z-230727T2015Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
336 PM EDT Thu Jul 27 2023

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Southeastern Washington County in north central Maryland...
  Southwestern Frederick County in north central Maryland...
  North central Loudoun County in northern Virginia...
  Central Jefferson County in the Panhandle of West Virginia...

* Until 415 PM EDT.

* At 336 PM EDT, a severe thunderstorm was located over Ranson, or
  near Shepherdstown, moving east at 25 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Damaging winds will cause some trees and large branches
           to fall. This could injure those outdoors, as well as
           damage homes and vehicles. Roadways may become blocked by
           downed trees. Localized power outages are possible.
           Unsecured light objects may become projectiles.

* Locations impacted include...
  Frederick, Charles Town, Ballenger Creek, Brunswick, Ranson,
  Braddock Heights, Harpers Ferry, Kearneysville, Point Of Rocks,
  Corporation Of Ranson, Adamstown, Jefferson, Lovettsville, Bolivar,
  Buckeystown, Shenandoah Junction, Rosemont, Rohrersville,
  Burkittsville and Gapland.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

To report severe weather, contact your nearest law enforcement
agency. They will send your report to the National Weather Service
office in Sterling Virginia.

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 3927 7796 3936 7794 3941 7789 3946 7744
      3924 7745
TIME...MOT...LOC 1936Z 266DEG 22KT 3935 7783

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH
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21 minutes ago, Eskimo Joe said:

Looks like that lead warned cell is generating a bit of a cold pool? More stuff firing along and behind it. HRRR alluded to this earlier today.

I guess we are also watching the stuff back in Garrett County?  Warning says its moving SE

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Probably some flood warnings will be coming soon as well

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
422 PM EDT Thu Jul 27 2023

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Northwestern Montgomery County in central Maryland...
  Southwestern Frederick County in north central Maryland...
  Northeastern Loudoun County in northern Virginia...
  Southeastern Jefferson County in the Panhandle of West Virginia...

* Until 515 PM EDT.

* At 422 PM EDT, severe thunderstorms were located along a line
  extending from 6 miles southwest of Brunswick to near Charles Town,
  moving east at 5 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Damaging winds will cause some trees and large branches
           to fall. This could injure those outdoors, as well as
           damage homes and vehicles. Roadways may become blocked by
           downed trees. Localized power outages are possible.
           Unsecured light objects may become projectiles.

* Locations impacted include...
  Charles Town, Poolesville, Brunswick, Ranson, Point Of Rocks,
  Corporation Of Ranson, Adamstown, Lovettsville, Barnesville,
  Hillsboro, Waterford, Neersville, Doubs, Park Mills, Lucketts,
  Dickerson, Beallsville, Tuscarora, Millville and Taylorstown.
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14 minutes ago, Terpeast said:

big anvil cloud passing just to my north. Still sunny here. Probably another miss

EDIT: just stepped outside and looked directly upwind. All clear skies. 

These storms are definitely struggling to maintain themselves once they roll off the terrain. That cap must not be fully eroded.

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Mesoscale Discussion 1741
   NWS Storm Prediction Center Norman OK
   0346 PM CDT Thu Jul 27 2023

   Areas affected...Parts of PA into northern MD/VA...eastern
   WV...DC...Northern DE...NJ

   Concerning...Severe Thunderstorm Watch 555...

   Valid 272046Z - 272215Z

   The severe weather threat for Severe Thunderstorm Watch 555
   continues.

   SUMMARY...The damaging-wind threat may gradually increase into early
   evening.

   DISCUSSION...Late this afternoon, convection is gradually deepening
   along two corridors across parts of the Northeast/Mid Atlantic. The
   southernmost corridor is a broadly confluent zone from southwest PA
   into northern MD, within a region of somewhat greater low/midlevel
   moisture. Storms have been gradually intensifying along this
   corridor, where deep-layer shear is rather weak, but sufficient for
   a modestly organized cells/clusters capable of damaging wind in the
   presence of moderate buoyancy and steep low-level lapse rates. An
   uptick in the damaging-wind threat is possible along this corridor
   as storm coverage gradually increases into early evening. 

   Farther north, increasing cumulus is noted along a diffuse surface
   boundary from western into northeast PA, with storms gradually
   developing from northeast to southwest. Deep-layer shear is
   generally rather weak in this area as well, though low/midlevel flow
   gradually increases with eastward extent, in closer proximity to a
   departing mid/upper-level shortwave trough across New England.
   Isolated storms may develop as far west as west-central PA, but
   somewhat greater coverage is expected across eastern PA into this
   evening. Steepened low-level lapse rates will support at least a
   localized damaging-wind threat with any stronger storms across this
   area.

   ..Dean.. 07/27/2023

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

   ATTN...WFO...PHI...BGM...CTP...LWX...PBZ...
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2 minutes ago, yoda said:
Mesoscale Discussion 1741
   NWS Storm Prediction Center Norman OK
   0346 PM CDT Thu Jul 27 2023

   Areas affected...Parts of PA into northern MD/VA...eastern
   WV...DC...Northern DE...NJ

   Concerning...Severe Thunderstorm Watch 555...

   Valid 272046Z - 272215Z

   The severe weather threat for Severe Thunderstorm Watch 555
   continues.

   SUMMARY...The damaging-wind threat may gradually increase into early
   evening.

   DISCUSSION...Late this afternoon, convection is gradually deepening
   along two corridors across parts of the Northeast/Mid Atlantic. The
   southernmost corridor is a broadly confluent zone from southwest PA
   into northern MD, within a region of somewhat greater low/midlevel
   moisture. Storms have been gradually intensifying along this
   corridor, where deep-layer shear is rather weak, but sufficient for
   a modestly organized cells/clusters capable of damaging wind in the
   presence of moderate buoyancy and steep low-level lapse rates. An
   uptick in the damaging-wind threat is possible along this corridor
   as storm coverage gradually increases into early evening. 

   Farther north, increasing cumulus is noted along a diffuse surface
   boundary from western into northeast PA, with storms gradually
   developing from northeast to southwest. Deep-layer shear is
   generally rather weak in this area as well, though low/midlevel flow
   gradually increases with eastward extent, in closer proximity to a
   departing mid/upper-level shortwave trough across New England.
   Isolated storms may develop as far west as west-central PA, but
   somewhat greater coverage is expected across eastern PA into this
   evening. Steepened low-level lapse rates will support at least a
   localized damaging-wind threat with any stronger storms across this
   area.

   ..Dean.. 07/27/2023

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

   ATTN...WFO...PHI...BGM...CTP...LWX...PBZ...

mcd1741.png

 

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BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
457 PM EDT Thu Jul 27 2023

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Central Grant County in eastern West Virginia...
  Western Hardy County in eastern West Virginia...

* Until 530 PM EDT.

* At 457 PM EDT, a severe thunderstorm was located 7 miles east of
  Davis, moving east at 20 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Damaging winds will cause some trees and large branches
           to fall. This could injure those outdoors, as well as
           damage homes and vehicles. Roadways may become blocked by
           downed trees. Localized power outages are possible.
           Unsecured light objects may become projectiles.

* Locations impacted include...
  Petersburg, Streby, Maysville, Welton, Cabins, Arthur, Kline Gap,
  Seymourville and Lahmansville.
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Will it be a miss for @EastCoast NPZ?

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
502 PM EDT Thu Jul 27 2023

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Southeastern Frederick County in northwestern Virginia...
  West central Clarke County in northwestern Virginia...
  The City of Winchester in northwestern Virginia...

* Until 545 PM EDT.

* At 502 PM EDT, a severe thunderstorm was located near Winchester,
  moving east at 20 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Damaging winds will cause some trees and large branches
           to fall. This could injure those outdoors, as well as
           damage homes and vehicles. Roadways may become blocked by
           downed trees. Localized power outages are possible.
           Unsecured light objects may become projectiles.

* Locations impacted include...
  Winchester, Millwood Pike, Berryville, Stephens City, Boyce,
  Millwood, Greenwood, Briggs and Stringtown
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BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
512 PM EDT Thu Jul 27 2023

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Central Montgomery County in central Maryland...

* Until 600 PM EDT.

* At 512 PM EDT, a severe thunderstorm was located near Boyds, or
  near Poolesville, moving east at 15 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Damaging winds will cause some trees and large branches
           to fall. This could injure those outdoors, as well as
           damage homes and vehicles. Roadways may become blocked by
           downed trees. Localized power outages are possible.
           Unsecured light objects may become projectiles.

* Locations impacted include...
  Germantown, Rockville, Gaithersburg, Olney, Poolesville, Aspen
  Hill, Potomac, North Bethesda, Montgomery Village, North Potomac,
  Redland, Boyds, Clarksburg, Darnestown, Derwood, Washington Grove,
  Laytonsville, Barnesville, Dickerson and Beallsville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

To report severe weather, contact your nearest law enforcement
agency. They will send your report to the National Weather Service
office in Sterling Virginia.

Large hail and damaging winds and continuous cloud to ground
lightning is occurring with this storm. Move indoors immediately.
Lightning is one of nature`s leading killers. Remember, if you can
hear thunder, you are close enough to be struck by lightning.
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12 minutes ago, yoda said:

Will it be a miss for @EastCoast NPZ?

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
502 PM EDT Thu Jul 27 2023

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Southeastern Frederick County in northwestern Virginia...
  West central Clarke County in northwestern Virginia...
  The City of Winchester in northwestern Virginia...

* Until 545 PM EDT.

* At 502 PM EDT, a severe thunderstorm was located near Winchester,
  moving east at 20 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Damaging winds will cause some trees and large branches
           to fall. This could injure those outdoors, as well as
           damage homes and vehicles. Roadways may become blocked by
           downed trees. Localized power outages are possible.
           Unsecured light objects may become projectiles.

* Locations impacted include...
  Winchester, Millwood Pike, Berryville, Stephens City, Boyce,
  Millwood, Greenwood, Briggs and Stringtown

Went 1/2 mile to my north.

  • Haha 2
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2 minutes ago, Eskimo Joe said:

Winchester ASOS just gusted to M69 mph.

Preliminary Local Storm Report
National Weather Service Baltimore MD/Washington DC
522 PM EDT Thu Jul 27 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0517 PM     Tstm Wnd Gst     Winchester Rgnl Arpt    39.14N  78.14W
07/27/2023  M69 mph          Frederick          VA   AWOS

            A wind gust of 60 knots (69 MPH) was measured by the
            AWOS at Winchester Regional Airport (KOKV).


&&

Event Number LWX2301510
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BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
526 PM EDT Thu Jul 27 2023

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Central Loudoun County in northern Virginia...

* Until 600 PM EDT.

* At 526 PM EDT, a severe thunderstorm was located over Purcellville,
  or 8 miles west of Leesburg, moving east at 15 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Damaging winds will cause some trees and large branches
           to fall. This could injure those outdoors, as well as
           damage homes and vehicles. Roadways may become blocked by
           downed trees. Localized power outages are possible.
           Unsecured light objects may become projectiles.

* Locations impacted include...
  Leesburg, Purcellville, Round Hill, Bluemont, Oatlands, Hamilton,
  Paeonian Springs, Gleedsville, Philomont, Lincoln and Hughesville.
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15 minutes ago, Eskimo Joe said:

Time sensitive! Pull up TIAD radar and look at lowest base velocity scan. Sick downburst over western Montgomery/Southern Frederick Counties!

Preliminary Local Storm Report
National Weather Service Baltimore MD/Washington DC
519 PM EDT Thu Jul 27 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0511 PM     Tstm Wnd Dmg     1 SSW Dickerson         39.21N  77.44W
07/27/2023                   Montgomery         MD   County Emergy Mg

            Several trees and wires blew down near Dickerson,
            including near the intersection of MD-28 Dickerson Road
            and Martinsburg Road.


&&

Event Number LWX2301509
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Preliminary Local Storm Report
National Weather Service Baltimore MD/Washington DC
539 PM EDT Thu Jul 27 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0514 PM     Tstm Wnd Dmg     1 NE Winchester         39.18N  78.16W
07/27/2023                   Frederick          VA   911 Call Center

            Several trees blew down in the City of Winchester.


&&

Event Number LWX2301511
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5 minutes ago, 09-10 analogy said:

It'll be interesting to see if the powerful storms moving thru MOCO/NVA can lay down any boundaries that may goose (or perpetuate) the storms lining up on I-66 in the Front Royals area, so that (yes, MBY) NW DC can get in on some good stuff a bit later. 

https://weather.cod.edu/satrad/nexrad/index.php?type=LWX-N0Q-1-24

can see some semblance of outflow in this loop (at least as of right now, 5:43PM) moving S or SSE from the storms up in Loudoun/Montgomery

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