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2023 Mid-Atlantic Severe Wx Thread (General Discussion)


Kmlwx
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21 minutes ago, Kmlwx said:

The HRRR is quite stormy for the overnight period. The overnight nature probably means limited severe threat, however. These nocturnal storms tend to be prolific lightning producers when the atmosphere is humid, though. 

Night thunderstorms with lots of lightning are my favorite.  We used to go to near Atlantic Beach, southern outer banks and that place was ideal for night storms.  One time we had one that went on for an hour and there was so much lightning it was like a strobe light.

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42 minutes ago, Kmlwx said:

The HRRR is quite stormy for the overnight period. The overnight nature probably means limited severe threat, however. These nocturnal storms tend to be prolific lightning producers when the atmosphere is humid, though. 

Things seem most active after 10pm it seems? Trying to see a concert in Columbia tonight. 

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mcd1565_full.png

Mesoscale Discussion 1565
   NWS Storm Prediction Center Norman OK
   0250 PM CDT Sat Jul 15 2023

   Areas affected...Portions of far northwestern NC...southwestern into
   central/northern VA...the eastern WV Panhandle...MD...DC...south-
   central into southeastern PA...northern DE...and NJ

   Concerning...Severe potential...Watch unlikely 

   Valid 151950Z - 152215Z

   Probability of Watch Issuance...20 percent

   SUMMARY...An isolated threat for hail and damaging winds should
   gradually increase this afternoon. While watch issuance is unlikely
   in the short term (next 1-2 hours), trends will be closely
   monitored.

   DISCUSSION...Isolated to widely scattered thunderstorms have
   developed this afternoon along and just east of the Blue Ridge
   Mountains extending from far northwestern NC into southwestern and
   central VA. A separate area of convection is ongoing across parts of
   southeastern PA into northern DE and NJ. This activity is likely
   being aided by modest large-scale ascent preceding a shortwave
   trough moving eastward over the OH/TN Valleys. A very moist
   low-level airmass, with surface dewpoints generally in the low to
   mid 70s, is present along and east of the ongoing convection. Ample
   daytime heating has eroded remaining MLCIN, and moderate to locally
   strong instability has developed in response.

   Although low-level winds remain weak per recent VWPs from KFCX/KLWX,
   modest strengthening of mid-level southwesterlies to around 30-35 kt
   has been noted with the approach of the shortwave trough. Similar
   values of deep-layer shear should foster modest updraft
   organization. Multicells should be the primary convective mode. But,
   marginal supercell structures may also occur, posing an isolated
   hail and damaging wind threat. At this point, overall convective
   coverage should tend to remain fairly isolated. Poor mid-level lapse
   rates should also temper updraft intensity/acceleration to some
   extent. A loosely organized cluster of thunderstorms over WV may
   also move into parts of western MD/VA over the next couple of hours
   with an isolated strong to damaging wind threat. While watch
   issuance appears unlikely in the short term, trends will be closely
   monitored.

   ..Gleason/Bunting.. 07/15/2023

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

   ATTN...WFO...PHI...AKQ...CTP...LWX...RNK..

https://www.spc.noaa.gov/products/md/md1565.html

 

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3 hours ago, BlizzardNole said:

Night thunderstorms with lots of lightning are my favorite.  We used to go to near Atlantic Beach, southern outer banks and that place was ideal for night storms.  One time we had one that went on for an hour and there was so much lightning it was like a strobe light.

Sleeping weather.

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36 minutes ago, yoda said:

Probably going to be sub-severe, but decent storms in WV headed eastward 

Sort of rooting for this to hold together. As I believe @BlizzardNole mentioned a bit further up, there's nothing better than strobe light-ish lightning in a particularly humid atmo at nighttime this time of year. I remember that happening often when I was growing up in northcentral PA...haven't seen it as much living in NoVA.

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BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
756 PM EDT Sat Jul 15 2023

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Western Washington County in north central Maryland...
  Allegany County in western Maryland...
  Northeastern Garrett County in western Maryland...
  Northwestern Morgan County in the Panhandle of West Virginia...
  Northeastern Mineral County in eastern West Virginia...
  North central Hampshire County in eastern West Virginia...

* Until 900 PM EDT.

* At 756 PM EDT, severe thunderstorms were located along a line
  extending from near Frostburg to near Romney, moving northeast 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...
  Cumberland, Frostburg, Bel Air, Paw Paw, La Vale, Fort Ashby,
  Ridgeley, Cresaptown, Potomac Park, Wiley Ford, Eckhart Mines,
  Mount Savage, Rawlings, Ellerslie, Springfield, Corriganville,
  Midland, Midlothian, Green Spring and Flintstone.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Large hail and damaging winds and continuous cloud to ground
lightning is occurring with these storms. 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:

Storms starting to fire in S MD now as well, especially near La Plata

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
807 PM EDT Sat Jul 15 2023

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Southeastern Prince Georges County in central Maryland...
  Northeastern Charles County in southern Maryland...

* Until 845 PM EDT.

* At 806 PM EDT, a severe thunderstorm was located near La Plata,
  moving north 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...
  Waldorf, La Plata, Saint Charles, Accokeek, Brandywine, Baden,
  Bryantown, Port Tobacco Village, Northwood, Dentsville, White
  Plains and Bel Alton.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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.

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.
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BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
815 PM EDT Sat Jul 15 2023

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Southwestern Prince Georges County in central Maryland...
  Central Charles County in southern Maryland...

* Until 900 PM EDT.

* At 815 PM EDT, a severe thunderstorm was located over Port Tobacco
  River, moving north 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...
  Port Tobacco River, Accokeek, Bryans Road, Pomfret, Port Tobacco
  Village, Port Tobacco, Faulkner and Ripley.
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Preliminary Local Storm Report
National Weather Service Baltimore MD/Washington DC
825 PM EDT Sat Jul 15 2023

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

0822 PM     Hail             La Plata                38.53N  76.97W
07/15/2023  M1.00 inch       Charles            MD   Law Enforcement


&&

Event Number LWX2301401
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BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
831 PM EDT Sat Jul 15 2023

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Northwestern Washington County in north central Maryland...
  Eastern Allegany County in western Maryland...
  Northern Morgan County in the Panhandle of West Virginia...
  Northwestern Berkeley County in the Panhandle of West Virginia...

* Until 915 PM EDT.

* At 831 PM EDT, severe thunderstorms were located along a line
  extending from near Paw Paw to near Martinsburg, moving northeast
  at 45 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...
  Hancock, Berkeley Springs, Great Cacapon, Clear Spring,
  Pecktonville, Big Pool, Johnsons Mill, Cherry Run, Tomahawk,
  Johnsontown, Lineburg, Valley View, Spohrs Crossroads, Spruce Pine
  Hollow, Highland Ridge, Smith Crossroads, Berryville, New Hope,
  Sleepy Creek and Shady Grove.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Large hail and damaging winds and continuous cloud to ground
lightning is occurring with these storms. 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.

Torrential rainfall is occurring with these storms, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.
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10 hours ago, Kmlwx said:

The HRRR is quite stormy for the overnight period. The overnight nature probably means limited severe threat, however. These nocturnal storms tend to be prolific lightning producers when the atmosphere is humid, though. 

It's 84 degrees at nearly 11pm. Something is going to give here. 

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SPC mentioned us Thursday into Friday on the Day 4-8 OTLK... LWX AFD also mentions it

LONG TERM /THURSDAY THROUGH SUNDAY/...
Shower and thunderstorm chances round out the workweek with drier
and slightly cooler conditions expected for the weekend.

Synoptically, not much change in the overall pattern. The upper
level ridge remains in the west while the mean upper level trough
builds east from the Great Lakes. With west to northwest flow aloft,
multiple shortwave disturbances and a front will be able to track
across the region. Timing and placement of these systems still
remains uncertain with a focus on western portions of the forecast
area. Even with that said, 12z guidance shows some alignment for
the highest probability of convection Thursday into Friday as
shortwave energy dives south and the resultant cold front crosses
the region. 12z deterministic/ensemble guidance shows increasing
instability and shear during this time leading to the potential for
strong to severe storms. Currently SPC makes a mention of this
potential threat in there Day 5/6 discussion, but no areas have been
highlighted at this time. Primary threats with these storms would be
damaging winds, large hail, and isolated instances of flooding. WPC
currently has the area highlighted in a marginal risk for excessive
rainfall during the Day4/5 (Thursday-Friday) timeframe.
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8 minutes ago, Eskimo Joe said:

Some of the CAMs blow through a dying MCS after midnight tonight. We have a decent pool of mid level lapse rates ahead of this line per SPC mesoanalysis (maybe a bit of an EML?) and a lot of DCAPE. Might be an interesting night. At least we stand to get some rain.

Especially the MPAS runs on the NSSL site. 

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24 minutes ago, Eskimo Joe said:

Some of the CAMs blow through a dying MCS after midnight tonight. We have a decent pool of mid level lapse rates ahead of this line per SPC mesoanalysis (maybe a bit of an EML?) and a lot of DCAPE. Might be an interesting night. At least we stand to get some rain.

That bow near Toronto looks interesting. SPC has >40% between 4z and 12z. It seems like there is a Slight risk every day though, with not much clouds in the sky. 

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Good afternoon discussion from LWX on tonight's threat 

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
A broken cumulus deck has started to pan out across the area
early this afternoon, with high level cirrus clouds overhead.
Moisture out ahead of an approaching front coupled with
increasing instability further east has generated a few strong
to even severe thunderstorms early this afternoon across
portions of PA/MD, mainly across PHI`s area. Lingering slight
chance PoPs exist further east throughout the afternoon but
widespread scattered showers/thunderstorms are not expected
through the remainder of the afternoon and evening.

By tonight, a cold front will continue to traverse closer to the
region from the Ohio Valley. Climatologically speaking, this event
does not fit quite into the usual category, especially for the
middle of July. Nonetheless, CAMs and other guidance has continued
to suggest a strong line of showers and thunderstorms overnight and
into Friday morning across a good portion of the forecast area. A
general timeline for the feature path would be 6-8z across the far
western areas and not leaving the eastern segments of the CWA until
after 12-14z Friday morning. Latest guidance suite has slowed the
progression down an hour or so for the life cycle but overall
intensity has generally stayed the same. There still remains
uncertainties with this event with respect to intensity especially.
Convection ahead of the frontal passage may inhibit further
development across certain areas which would limit overall impacts.
Should the CI remain light/brief then hazards will be more
widespread across portions of the area.

There continues to be a multi-hazard possibility for the overnight
hours. Strong to severe thunderstorms will be possible, especially
along and east of the Blue Ridge Mountains and along and north of I-
66. One caveat to mention would be across NE MD early Friday
morning, where the shear profiles and instability look to be
greatest. Damaging winds and an isolated/tornado or waterspout are
possible across those areas especially. Lapse rates do not look as
favorable during this time across those area, thus hail threat looks
to be limited but certainly non-zero. Also, isolated instances of
flooding due to training storms is possible across areas east of US-
15, where especially the urban corridors have lower FFG values. We
will continue to monitor the trends of this system as it continues
to dive into the Mid-Atlantic and Northeast states later today and
into early Friday morning. Highs will top out in the upper 80s to
low 90s across the lower elevations, with mid to upper 70s for the
mountains.
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mcd1649.png

Mesoscale Discussion 1649
   NWS Storm Prediction Center Norman OK
   0356 PM CDT Thu Jul 20 2023

   Areas affected...Parts of western NY...western PA...and far eastern
   OH

   Concerning...Severe potential...Severe Thunderstorm Watch likely 

   Valid 202056Z - 202230Z

   Probability of Watch Issuance...95 percent

   SUMMARY...The risk of severe winds will increase in the next few
   hours as an organized MCS overspreads the area from the west. A
   watch issuance is likely for parts of the area in the next hour or
   so.

   DISCUSSION...Recent radar data from KDTX depicts a well-organized
   bowing MCS tracking eastward at around 40 kt in Ontario -- where a
   recent 63-kt gust was measured. Ahead of the MCS, antecedent diurnal
   heating of a relatively moist air mass (generally lower/middle 60s
   dewpoints) has contributed to weak/moderate surface-based
   instability -- with the greater instability confined to western PA
   and eastern OH (see 20Z observed PIT and 19Z BUF soundings). 40-50
   kt midlevel winds should support continued convective organization
   as it crosses Lake Erie and approaches western NY, eastern OH, and
   western PA -- with a risk of severe winds during the next few hours.
   While there is some uncertainty on how intense the northern portion
   of the line will be given less instability farther north, the
   well-established cold pool and favorable deep-layer shear will still
   pose a risk of severe outflow winds. A watch will likely be issued
   in the next hour or so.

   ..Weinman/Hart.. 07/20/2023

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

   ATTN...WFO...BGM...BUF...CTP...PBZ...CLE...

https://www.spc.noaa.gov/products/md/md1649.html

 

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