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2024 Severe Weather General Discussion


Kmlwx
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Maybe some intrigue tomorrow?  From morning AFD from LWX 

Friday`s high temperatures look similar to Thursday, with a bit of
uncertainty should any cloud debris from upstream be a little
thicker than currently anticipated. Humidity/Tds look higher,
though, which should more than offset any slight temperature
deviations. Heat index values of 105-110 are likely for most east of
the Blue Ridge/Catoctin Mountains, with 100-105 for the lower
elevations to the west during the afternoon. There should be some
more clouds Saturday which may lower temps/heat indices a bit, but
very hot and humid conditions will continue regardless.

The combination of the hot, humid, and unstable airmass as well as
modestly increasing flow and height falls associated with the
approaching trough/surface cold front lend to the potential of
somewhat more widespread and organized severe weather. Some guidance
(00Z CMC, NAM12, NAMNest, ECMWF) have mid-level lapse rates
approaching 6.5 C/km Friday afternoon which would further bolster
this potential. The main threat with the increased flow and steep
low-level lapse rates looks to be damaging wind, but if the mid-
level lapse rates can steepen to around or steeper than 6.5 C/km
there could be a more notable (albeit marginal) hail threat, too.
Upper flow of 50+ kts and low/mid-level flow of 25-35 kts is
expected Saturday which could further organize storms into lines or
bands and result in a conditional hail threat in addition to wind.
Low-level flow looks weaker but more backed on Friday, so a
conditional/marginal tornado threat could evolve depending on subtle
mesoscale variations which have inherently low predictability a
couple days in advance.

Increasing PWs to 2+ inches along with the potential for multiple
rounds of training storms along and ahead of the slow-moving front
may introduce an increasing flood/flash flood threat as well,
despite the recent drought conditions. This type of environment
could favor rainfall rates of a couple inches in an hour, so any
persistent or repeat convection could result in isolated excessive
totals and subsequent flooding during this time.

The potential for showers and thunderstorms currently looks highest
during the typical afternoon/evening time, unless any more organized
wave or complex develops and approaches from upstream. This latter
scenario is of low certainty, and is the less favored outcome at
this time.

 

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On 8/1/2024 at 10:44 AM, yoda said:

Maybe some intrigue tomorrow?  From morning AFD from LWX 

Friday`s high temperatures look similar to Thursday, with a bit of
uncertainty should any cloud debris from upstream be a little
thicker than currently anticipated. Humidity/Tds look higher,
though, which should more than offset any slight temperature
deviations. Heat index values of 105-110 are likely for most east of
the Blue Ridge/Catoctin Mountains, with 100-105 for the lower
elevations to the west during the afternoon. There should be some
more clouds Saturday which may lower temps/heat indices a bit, but
very hot and humid conditions will continue regardless.

The combination of the hot, humid, and unstable airmass as well as
modestly increasing flow and height falls associated with the
approaching trough/surface cold front lend to the potential of
somewhat more widespread and organized severe weather. Some guidance
(00Z CMC, NAM12, NAMNest, ECMWF) have mid-level lapse rates
approaching 6.5 C/km Friday afternoon which would further bolster
this potential. The main threat with the increased flow and steep
low-level lapse rates looks to be damaging wind, but if the mid-
level lapse rates can steepen to around or steeper than 6.5 C/km
there could be a more notable (albeit marginal) hail threat, too.
Upper flow of 50+ kts and low/mid-level flow of 25-35 kts is
expected Saturday which could further organize storms into lines or
bands and result in a conditional hail threat in addition to wind.
Low-level flow looks weaker but more backed on Friday, so a
conditional/marginal tornado threat could evolve depending on subtle
mesoscale variations which have inherently low predictability a
couple days in advance.

Increasing PWs to 2+ inches along with the potential for multiple
rounds of training storms along and ahead of the slow-moving front
may introduce an increasing flood/flash flood threat as well,
despite the recent drought conditions. This type of environment
could favor rainfall rates of a couple inches in an hour, so any
persistent or repeat convection could result in isolated excessive
totals and subsequent flooding during this time.

The potential for showers and thunderstorms currently looks highest
during the typical afternoon/evening time, unless any more organized
wave or complex develops and approaches from upstream. This latter
scenario is of low certainty, and is the less favored outcome at
this time.

 

Today's latest day 1 outlook mentions possibility of an upgrade to SLGT from MRGL in some areas of the east:

...Eastern States...
   A broad upper trough is present over the eastern 1/3 of the CONUS
   today, with slightly cooler mid-level temperatures and cyclonic flow
   aloft throughout the region.  Morning visible satellite imagery
   shows strong heating across much of the Mid-Atlantic, Southeast, and
   TN Valley regions.  This combined with a very moist surface air mass
   will yield steep low-level lapse rates and moderate CAPE later
   today, with several clusters of thunderstorms expected.  Winds aloft
   are relatively weak, and mid-level lapse rates are not particularly
   steep.  This suggests the bulk of this activity will be relatively
   disorganized.  Nevertheless, given the coverage of afternoon
   thunderstorms and the pervasive hot/humid conditions, there is a
   widespread risk of gusty or occasionally damaging wind gusts this
   afternoon and early evening.  Two areas of somewhat greater wind
   damage potential are from New York City region into northern VA, and
   from northern MS/AL into east TN.  Both areas will be monitored and
   re-considered for upgrade to SLGT risk at 20z.
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URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 591
   NWS Storm Prediction Center Norman OK
   120 PM EDT Sat Aug 3 2024

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     Southwest Connecticut
     District Of Columbia
     Delaware
     Northeast Maryland
     New Jersey
     Southeast New York
     Southeast Pennsylvania
     Northern Virginia
     Coastal Waters

   * Effective this Saturday afternoon and evening from 120 PM until
     900 PM EDT.

   * Primary threats include...
     Scattered damaging wind gusts to 70 mph likely
     Isolated large hail events to 1 inch in diameter possible

   SUMMARY...Thunderstorms will continue to increase in coverage and
   intensity through the afternoon and early evening, posing a risk of
   locally damaging wind gusts.
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Severe Weather Statement
National Weather Service Baltimore MD/Washington DC
258 PM EDT Sat Aug 3 2024

VAC043-107-WVC037-031930-
/O.CON.KLWX.SV.W.0214.000000T0000Z-240803T1930Z/
Loudoun VA-Clarke VA-Jefferson WV-
258 PM EDT Sat Aug 3 2024

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 330 PM EDT
FOR NORTHWESTERN LOUDOUN...EASTERN CLARKE AND SOUTHEASTERN JEFFERSON
COUNTIES...

At 258 PM EDT, a severe thunderstorm was located near Purcellville,
or 9 miles southeast of Charles Town, moving east at 20 mph.

HAZARD...70 mph wind gusts and quarter size hail.

SOURCE...Emergency Manager Reported.

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, Lovettsville, Hamilton,
Hillsboro, Paeonian Springs, Waterford, Neersville, Lucketts,
Millville, Lincoln, Hughesville, and Taylorstown.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm is producing wind damage across northwestern Loudoun
County. SEEK SHELTER NOW inside a sturdy structure and stay away
from windows.

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 3908 7784 3931 7781 3932 7767 3930 7762
      3930 7757 3918 7750 3917 7752 3915 7753
      3913 7753 3904 7762
TIME...MOT...LOC 1858Z 270DEG 18KT 3919 7773

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...OBSERVED
MAX WIND GUST...70 MPH
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10 minutes ago, AmericanWxFreak said:

Wow, Middleburg cell warned for 80mph winds….

BULLETIN - EAS ACTIVATION REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
502 PM EDT Sat Aug 3 2024

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Southwestern Loudoun County in northern Virginia...
  North central Fauquier County in northern Virginia...
  Northwestern Prince William County in northern Virginia...

* Until 530 PM EDT.

* At 500 PM EDT, a severe thunderstorm was located near Delaplane, or
  15 miles north of Warrenton, moving east at 40 mph.

  THIS IS A DESTRUCTIVE STORM FOR DELAPLANE, MIDDLEBURG, AND ALDIE.

  HAZARD...80 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Expect considerable damage to trees and power lines. Your
           life is at significant risk if outdoors. In addition to
           some trees falling into homes, wind damage is possible to
           roofs, sheds, open garages, and mobile homes.

* Locations impacted include...
  Middleburg, Marshall, Saint Louis, Aldie, Halfway, and Rectortown.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This is an EXTREMELY DANGEROUS SITUATION. This storm is producing
widespread wind damage across Delaplane, Middleburg, and Aldie. SEEK
SHELTER NOW inside a sturdy structure and stay away from windows!

Large hail, damaging wind, and continuous cloud to ground lightning
are 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 3887 7790 3896 7793 3907 7765 3890 7759
TIME...MOT...LOC 2100Z 251DEG 34KT 3893 7786

THUNDERSTORM DAMAGE THREAT...DESTRUCTIVE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...80 MPH
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BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
520 PM EDT Sat Aug 3 2024

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  West central Montgomery County in central Maryland...
  Loudoun County in northern Virginia...
  Northwestern Fairfax County in northern Virginia...
  East central Clarke County in northwestern Virginia...
  North central Fauquier County in northern Virginia...
  Northwestern Prince William County in northern Virginia...
  South central Jefferson County in the Panhandle of West Virginia...

* Until 545 PM EDT.

* At 520 PM EDT, severe thunderstorms were located along a line
  extending from Round Hill to near Brambleton to near Warrenton,
  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...
  Centreville, Leesburg, South Riding, Herndon, Broadlands,
  Lansdowne, Lowes Island, Brambleton, Poolesville, Dulles
  International Airport, Ashburn, Linton Hall, Sterling, Chantilly,
  Great Falls, Bull Run, Countryside, Purcellville, Haymarket, and
  Middleburg.
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BULLETIN - EAS ACTIVATION REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
519 PM EDT Sat Aug 3 2024

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Southeastern Loudoun County in northern Virginia...
  Northwestern Prince William County in northern Virginia...

* Until 545 PM EDT.

* At 518 PM EDT, a severe thunderstorm was located near Oatlands, or
  near Brambleton, moving east at 35 mph.

  THIS IS A DESTRUCTIVE STORM FOR EASTERN LOUDOUN COUNTY.

  HAZARD...80 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Expect considerable damage to trees and power lines. Your
           life is at significant risk if outdoors. In addition to
           some trees falling into homes, wind damage is possible to
           roofs, sheds, open garages, and mobile homes.

* Locations impacted include...
  Broadlands, Lansdowne, Brambleton, Ashburn, Sterling, Countryside,
  Arcola, Oatlands, Belmont, and Sterling Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This is a DANGEROUS SITUATION. This storm is producing widespread
wind damage across eastern Loudoun County. SEEK SHELTER NOW inside a
sturdy structure and stay away from windows!

Large hail, damaging wind, and continuous cloud to ground lightning
are 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 3907 7746 3907 7740 3905 7737 3901 7737
      3895 7744 3893 7762 3902 7765 3910 7748
TIME...MOT...LOC 2118Z 254DEG 31KT 3897 7765

THUNDERSTORM DAMAGE THREAT...DESTRUCTIVE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...80 MPH
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13 minutes ago, yoda said:
BULLETIN - EAS ACTIVATION REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
502 PM EDT Sat Aug 3 2024

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Southwestern Loudoun County in northern Virginia...
  North central Fauquier County in northern Virginia...
  Northwestern Prince William County in northern Virginia...

* Until 530 PM EDT.

* At 500 PM EDT, a severe thunderstorm was located near Delaplane, or
  15 miles north of Warrenton, moving east at 40 mph.

  THIS IS A DESTRUCTIVE STORM FOR DELAPLANE, MIDDLEBURG, AND ALDIE.

  HAZARD...80 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Expect considerable damage to trees and power lines. Your
           life is at significant risk if outdoors. In addition to
           some trees falling into homes, wind damage is possible to
           roofs, sheds, open garages, and mobile homes.

* Locations impacted include...
  Middleburg, Marshall, Saint Louis, Aldie, Halfway, and Rectortown.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This is an EXTREMELY DANGEROUS SITUATION. This storm is producing
widespread wind damage across Delaplane, Middleburg, and Aldie. SEEK
SHELTER NOW inside a sturdy structure and stay away from windows!

Large hail, damaging wind, and continuous cloud to ground lightning
are 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 3887 7790 3896 7793 3907 7765 3890 7759
TIME...MOT...LOC 2100Z 251DEG 34KT 3893 7786

THUNDERSTORM DAMAGE THREAT...DESTRUCTIVE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...80 MPH

Paging @aldie 22 -- IS it that destructive??

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Just now, yoda said:

Sounds like Hume in Fauquier county got smoked

Preliminary Local Storm Report
National Weather Service Baltimore MD/Washington DC
538 PM EDT Sat Aug 03 2024

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

0445 PM     Tstm Wnd Dmg     Hume                    38.83N  78.00W
08/03/2024                   Fauquier           VA   Emergency Mngr

            County emergency manager reported numerous trees down,
            a roof blown off a house and a shed collapsed in the
            area of Hume Rd and Leeds Manor Rd, and northeast
            towards I-66.


&&

Event Number LWX2403697
 
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