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2023 Mid-Atlantic Severe Wx Thread (General Discussion)


Kmlwx
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   SPC AC 071640

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1140 AM CDT Mon Aug 07 2023

   Valid 071630Z - 081200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS FAR
   EASTERN KY/NORTHEAST TN/NORTHWEST NC...WESTERN AND NORTHERN
   VA...SOUTHERN AND EASTERN WV...CENTRAL MD...AND SOUTH-CENTRAL PA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL
   AND SOUTHERN HIGH PLAINS...

   ...SUMMARY...
   A severe weather outbreak is expected across parts of the eastern
   U.S. today with widespread and locally destructive damaging winds
   and tornadoes as the greatest threats, especially across the
   southern/central Appalachians and Mid-Atlantic States.

   ...Southeast to the Upper Ohio Valley to the Mid-Atlantic States...
   Owing to a very moist/unstable air mass and very strong winds aloft
   for August, a widespread severe-weather risk is already unfolding at
   late morning/midday across a broad region, initially west of the
   Appalachians spine. Refer to ongoing Watches and Mesoscale
   Discussions for the latest regional details.

   A shortwave trough over the Lower Ohio Valley will continue to
   advance toward the northern Appalachians by evening. A pair of
   500-mb speed maxima from 55-65 kts are expected to be centered by
   late afternoon across eastern KY/TN and southern WV into western
   VA/NC, and separately over the Mid-South. Peak flow within an
   expansive 700-mb jet should be centered between the 500-mb maxima
   across the TN Valley. A plume of large potential buoyancy supported
   by high PW and steep mid-level lapse rates, and centered over the
   Mid-South/TN Valley will expand east-northeast towards the
   central/southern Appalachians with an expansive swath of MLCAPE from
   2000-3500 J/kg expected by peak heating.

   Ongoing storms across eastern portions of TN/KY and WV/southern OH
   will progress into an increasingly favorable thermodynamic and
   kinematic environment downstream, yielding many supercells capable
   of producing large hail, damaging winds, and tornadoes. Upscale
   growth into several linear clusters with embedded supercells is
   anticipated this afternoon as convective coverage becomes widespread
   from PA/MD south-southwest across the southern Appalachian states.
   Forecast soundings suggest the greatest tornado threat will probably
   exist across eastern KY/TN northeast across southern/eastern WV,
   western VA, central MD and into southeast PA. Given the supercell
   wind profiles, significant severe wind gusts will also be possible
   on a localized basis.

   Across the Southeast, aided by a separate mid-level speed max,
   linear clusters of storms will continue to develop and spread
   generally eastward across parts of the TN Valley toward the southern
   Appalachians and Carolinas, with damaging winds as the most common
   hazard.
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Just now, weatherwiz said:

If anything I'd think there is more of a chance of an upgrade to high risk/60% wind then there is upping the TOR probs given the predominate linear mode. 

Spc has informally said they won’t go high for wind and now reserve that for big tornado outbreaks. Even though that policy contradicts their stated guidelines. 

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1 minute ago, weatherwiz said:

If anything I'd think there is more of a chance of an upgrade to high risk/60% wind then there is upping the TOR probs given the predominate linear mode. 

EDIT: But I think the overall look may be just short of that kind of upgrade. 

Agreed, it would have to be a real time upgrade based on widespread reports/damage and sig severe reports. 
 

as a side note, you must be pretty impressed with the set up if the look is “just below” that ;) 

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Just now, Tezeta said:

Spc has informally said they won’t go high for wind and now reserve that for big tornado outbreaks. Even though that policy contradicts their stated guidelines. 

Makes sense that they’re keeping their word, no bigger event than the iowa Illinois 2020 derecho. If that’s not getting a high for wind, nothing is…

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CZC SPCPWOSPC ALL
   WOUS40 KWNS 071649
   DCZ000-DEZ000-GAZ000-KYZ000-MDZ000-NCZ000-PAZ000-SCZ000-TNZ000-VAZ000-WVZ000-080200-

   PUBLIC SEVERE WEATHER OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1149 AM CDT MON AUG 07 2023

   ...Severe thunderstorms expected over parts of the Eastern U.S. this
   afternoon and evening...

   * LOCATIONS...
     Virginia
     West Virginia
     Maryland
     Eastern Tennessee
     Eastern Kentucky
     Southern Pennsylvania
     Western and Central North Carolina
     District of Columbia
     Western South Carolina
     Northern Georgia
     Delaware

   * HAZARDS...
     Widespread damaging winds, some hurricane force
     A few tornadoes
     Isolated large hail up to baseball size

   * SUMMARY...
     A severe weather outbreak is expected across parts of the
     eastern U.S. today with widespread and locally destructive
     damaging winds and tornadoes as the greatest threats, especially
     across the southern/central Appalachians and Mid-Atlantic
     States.

   Preparedness actions...

   Review your severe weather safety procedures for the possibility
   of dangerous weather today. Stay tuned to NOAA Weather Radio,
   weather.gov, or other media for watches and warnings. A watch
   means that conditions are favorable for severe thunderstorms
   over the next several hours. If a severe thunderstorm warning is
   issued for your area, move to a place of safety, ideally in an 
   interior room on the lowest floor of a sturdy building.

   &&

   ..Guyer.. 08/07/2023
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3 minutes ago, Tezeta said:

Spc has informally said they won’t go high for wind and now reserve that for big tornado outbreaks. Even though that policy contradicts their stated guidelines. 

Interesting since straight line winds in a bow are more destructive over a larger area than a tornado, generally. 

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1 minute ago, DDweatherman said:

Agreed, it would have to be a real time upgrade based on widespread reports/damage and sig severe reports. 
 

as a side note, you must be pretty impressed with the set up if the look is “just below” that ;) 

Yeah I am rather impressed. Pretty steep mid-level lapse rates, rich llvl theta-e air, and a pretty potent H3 and H5 jet max punching into the region. I was a little unsure yesterday/early morning exactly how big this could be, but those 2-6km lapse rates are pretty steep and if often times a big discriminator in big wind vs. non big wind events. There could be a very narrow swath of some pretty significant wind damage should a bow develop. 

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Just now, canderson said:

Interesting since straight line winds in a bow are more destructive over a larger area than a tornado, generally. 

My guess is that it’s done for social scientific reasons related to human deaths. They want highs to coincide with  PDS tornado days since that’s statistically where the death comes, even if spatially and from a property damage standpoint big bow echoes deserve attention. 

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So it begins

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
1254 PM EDT Mon Aug 7 2023

The National Weather Service in Sterling Virginia has issued a

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

* Until 145 PM EDT.

* At 1253 PM EDT, a severe thunderstorm was located 8 miles southeast
  of Fort Ashby, or 9 miles northeast of Romney, moving northeast at
  55 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...
  Romney, Paw Paw, Greenwood, Berkeley Springs, Springfield, Great
  Cacapon, Green Spring, Oldtown, Little Orleans, Johnsons Mill,
  Valley View, Fishers Bridge, Spohrs Crossroads, Oakland, Rock Gap,
  Bloomery, Points, Smith Crossroads, Unger and Wapocomo.

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.

&&

LAT...LON 3972 7834 3964 7809 3959 7812 3959 7814
      3941 7822 3931 7873 3940 7880 3944 7877
      3946 7874 3972 7837
TIME...MOT...LOC 1653Z 240DEG 49KT 3943 7862

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH
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Going to need to see improvements in the wind profiles over the Mid Atlantic coinciding with convection to get a higher tornado/sig wind threat here. Current VADs from the area are pretty paltry on low level shear (and the RAP doesn't offer substantial improvements). They are better back in E TN/E KY though.

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Just now, andyhb said:

Going to need to see improvements in the wind profiles over the Mid Atlantic coinciding with convection to get a higher tornado/sig wind threat here. Current VADs from the area are pretty paltry on low level shear (and the RAP doesn't offer substantial improvements). They are better back in E TN/E KY though.

Yea kind of wonder why so many people are worried about the tornado risk up towards DC.

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1 minute ago, andyhb said:

Going to need to see improvements in the wind profiles over the Mid Atlantic coinciding with convection to get a higher tornado/sig wind threat here. Current VADs from the area are pretty paltry on low level shear (and the RAP doesn't offer substantial improvements). They are better back in E TN/E KY though.

not much low level turning

hrrr_2023080716_005_38.89--77.03.png

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