2024 Severe Weather General Discussion

[MN Transplant]

7 minutes ago, yoda said:

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

 

Side note, Leeds Manor is one of the best drives in the state.

[Lucketts]

Getting hit with a 3rd t-storm now. Power still out here. 

[MN Transplant]

Very impressed with the outflow.  The winds are loud in the trees.  Radar is optimistic with the storms firing from Fairfax to Manassas.

[frd]

Cell between Elk Neck to its East,  and Hance Points Estates to its NE,  is getting stronger .  

[Kmlwx]

If only we were in S PA. CSU MLP and SPC seem decently enthusiastic about their odds for severe t'storms today.

[batmanbrad]

so far SPC isn't too bullish on the potential tornado (or even overall severe) potential for Friday, though still time for that to change with the ever-evolving track forecast updates on Debby.  Much of the subforum is in MRGL risk zone for now.  From the early morning D3 outlook:

...Northern Mid Atlantic...
   Despite the weakening trends to Debby, models suggest that the
   evolution of sizable clockwise-curved low-level hodographs and
   appreciable boundary-layer buoyancy may be maintained into at least
   Friday afternoon, focused in a sector to the northeast of the
   accelerating surface low.  It appears that this may be in the
   process of overspreading the Chesapeake/Delmarva vicinity as daytime
   heating contributes to boundary-layer destabilization, before
   spreading northward through the northern Mid Atlantic in advance of
   the more inhibiting mid-level warm core.  Within this environment,
   the evolution of a few supercell structures posing a risk for
   tornadoes appears possible, before this threat wanes with the loss
   of daytime heating Friday evening.

[yoda]

Don't know if this got mentioned earlier but Day 3 will now have a morning and afternoon update

 

 

[George BM]

The 12z hrrr was fairly aggressive with CAPE for tomorrow afternoon (locally 2000+ J/kg MLCAPE) with good looking sim-radar across a good portion of the area. 

SPC has upgraded the immediate DC suburbs eastwards to a SLGT for tomorrow as well.

[CAPE]

From Mount Holly AFD-

A brief lull is possible late morning/early afternoon, though isolated to scattered showers and storms will remain possible during this time. Our second round of heavy rain and storms for the day looks to begin forming across eastern PA during the early/mid afternoon as the cold front associated with this system begins its eastward trek across the region. At this time, the upper level trough will begin to dig and support increased baroclinic forcing along the front. Dew points will rise into the low to mid 70s with PWATs over 2.0 inches ahead of this line of storms. As a result, rainfall forecasts of widespread 1-3 inches total are expected with local amounts of 4 inches or more possible. With this in mind, a Flood Watch was issued for the I-95 corridor and areas north & west into the Lehigh Valley and Berks County. Additionally, though daytime heating will be limited, there is a bit of uncertainty if there will be any breaks in the clouds. If any amount of daytime heating does occur, instability and lapse rates could jump and increase the severe potential for the afternoon and evening. Still a lot of uncertainty with this potential to form, but with deep layer shear around 30kts, parameters could become sufficient to support severe thunderstorms with the best conditions across southern NJ and the Delmarva. SPC has placed this region into a Slight Risk (2 of 5) for severe weather. High temperatures in the afternoon look to be in the low-80s.

[Kmlwx]

DC jackpot on the CSU MLP for today   

[Eskimo Joe]

Last two runs of the HRRR try to run an UHI track from Olney up through Pikesville. . .

[nw baltimore wx]

14 minutes ago, Eskimo Joe said:

Last two runs of the HRRR try to run an UHI track from Olney up through Pikesville. . .

You know that’s wrong. 

[Eskimo Joe]

5 minutes ago, nw baltimore wx said:

You know that’s wrong. 

Yup. Kind of surprised there's a flood watch honestly. The storm mode seems rather progressive today.

[high risk]

1 hour ago, Eskimo Joe said:

Yup. Kind of surprised there's a flood watch honestly. The storm mode seems rather progressive today.

 

 Would only take about 1" in an hour to cause problems in parts of the area, per flash flood guidance.     That seems achievable, even if storms are progressive.

 

[RDM]

19 minutes ago, high risk said:

 

 Would only take about 1" in an hour to cause problems in parts of the area, per flash flood guidance.     That seems achievable, even if storms are progressive.

 

Interesting chart - thanks for sharing High Risk.  Assume because there is a valid date for the map, it takes into account recent precip, soil type, terrain etc - yes?  Just curious.  Don't recall seeing that map before. 

[high risk]

30 minutes ago, RDM said:

Interesting chart - thanks for sharing High Risk.  Assume because there is a valid date for the map, it takes into account recent precip, soil type, terrain etc - yes?  Just curious.  Don't recall seeing that map before. 

        Yes, the labeling shows that the product covers today, and it absolutely does include recent precip and accounts for the fact that some areas can achieve flash flood risk more than others (independent of recent precip).

[yoda]

Severe Thunderstorm Watch coming soon 

https://www.spc.noaa.gov/products/md/md1943.html

Mesoscale Discussion 1943
   NWS Storm Prediction Center Norman OK
   1209 PM CDT Sun Aug 18 2024

   Areas affected...southeast New York...New Jersey...eastern
   Pennsylvania...Maryland...and northern Virginia.

   Concerning...Severe potential...Watch likely 

   Valid 181709Z - 181845Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Strong to severe thunderstorms are likely this afternoon
   and evening. A severe thunderstorm watch will be issued by
   mid-afternoon.

   DISCUSSION...Thunderstorms have started to develop across the
   Appalachians from central Pennsylvania into southern New York as
   cold-air advection aloft overspread the region. Farther east, some
   inhibition remains across eastern Pennsylvania amid broken
   cloudcover. However, this stratus deck has started to erode and
   should allow for significant surface heating over the next 1 to 2
   hours. Under the influence of weak height falls and cyclonic flow
   aloft, expect scattered thunderstorm development within the uncapped
   environment from eastern Pennsylvania to eastern Virginia. 20 to 25
   knots of effective shear (per RAP forecast soundings) will support
   some multicell organization with a primary threat from downbursts.
   An additional round of storms is possible this afternoon/evening as
   storms which develop over the mountains move into the lower
   elevations with some congealing into one or more linear segments
   possible.

   ..Bentley/Hart.. 08/18/2024

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

   ATTN...WFO...OKX...ALY...PHI...BGM...AKQ...CTP...LWX...

[nj2va]

Also have a Precipitation Meso discussion:

https://www.wpc.ncep.noaa.gov/metwatch/metwatch_mpd_multi.php?md=0898&yr=2024

[yoda]

Severe Thunderstorm Watch until 10pm 

https://www.spc.noaa.gov/products/watch/ww0634.html

 

   URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 634
   NWS Storm Prediction Center Norman OK
   200 PM EDT Sun Aug 18 2024

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     District Of Columbia
     Delaware
     Central and Eastern Maryland
     New Jersey
     Southeast New York
     Eastern Pennsylvania
     Northern Virginia
     Eastern Panhandle of West Virginia
     Coastal Waters

   * Effective this Sunday afternoon and evening from 200 PM until
     1000 PM EDT.

   * Primary threats include...
     Scattered damaging wind gusts to 70 mph likely
     Isolated large hail events to 1.5 inches in diameter possible

   SUMMARY...Scattered thunderstorms will increase in coverage through
   the afternoon across the watch area.  The more intense storms will
   pose a risk of locally damaging wind gusts and hail.

   The severe thunderstorm watch area is approximately along and 85
   statute miles east and west of a line from 55 miles east of
   Charlottesville VA to 40 miles east northeast of Wilkesbarre PA. For
   a complete depiction of the watch see the associated watch outline
   update (WOUS64 KWNS WOU4).

[CAPE]

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
319 PM EDT Sun Aug 18 2024

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  Central Sussex County in southern Delaware...

* Until 400 PM EDT.

* At 319 PM EDT, a severe thunderstorm was located near Millsboro, or
  near Georgetown, moving northeast at 20 mph.

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

  SOURCE...Radar indicated.

  IMPACT...Minor damage to vehicles is possible. Wind damage to 
           roofs, siding, trees, and power lines is possible.

* Locations impacted include...
  Georgetown, Millsboro, Milton, and Henlopen Acres.

[ge0]

Nice storm in Berryville. pea sized hail, strong winds. Some flooding

[AlexD1990]

Barely even got sprinkles from the earlier storms. Yawn.

Sent from my SM-F711U using Tapatalk

[vastateofmind]

15 minutes ago, AlexD1990 said:

Barely even got sprinkles from the earlier storms. Yawn.

Yeah...the Stanardsville to Culpeper line completely fizzled out here in NoVA over the past 1-2 hours. Second line back in the valley...looks pretty on radar right NOW, but I'm not gonna count on that NOT holding together until it gets here. Honestly...that "watch" light on my wx radio really needs to outen itself right now.

[nw baltimore wx]

9 hours ago, Eskimo Joe said:

Last two runs of the HRRR try to run an UHI track from Olney up through Pikesville. . .

8 hours ago, nw baltimore wx said:

You know that’s wrong. 

[Eskimo Joe]

 

 

[ge0]

Was driving down Trappe Rd. the other day and stumbled on what appears to be some tornado damage from the Middleburg-Bluemont tornado during Debby

 

[yoda]

Hmmm... from this mornings 0600Z SPC OTLK disco.  Granted it's 0/0/5... but...

..Portions of New England into the Mid Atlantic...
   A 500 mb impulse/speed max will pivot around the backside of the
   mid-level trough and overspread portions of the Hudson Valley today,
   encouraging convective initiation in two zones. First, scattered
   multicells and perhaps transient supercells should initiate over New
   England and track southeast toward Cape Cod and Long Island through
   the afternoon. The stronger mid-level flow will contribute to
   straight/elongated hodographs and accompanying 30-40 kts of
   effective bulk (speed) shear. Strong gusts and large hail will
   accompany the stronger storms. The best chance for any severe
   wind/hail will be over southern New England, where over 1000 J/kg
   MLCAPE may overlap the stronger vertical shear to support stronger,
   longer-lived updrafts. Secondly, a cluster of
   multicellular/supercellular storms may develop ahead of the 500 mb
   speed max over the central Appalachians and track southeast toward
   the Atlantic Coast. Given modest low-level lapse rates and hodograph
   elongation, strong wind gusts may accompany these storms as well.

 

[midatlanticweather]

I take it tomorrow is a stretch. Not looking very probable - 

 

  ...Mid-MS/OH Valleys to the Mid-Atlantic...

   Uncertainty remains this forecast cycle, particularly from around
   central PA eastward to the northern Mid-Atlantic Coast/Chesapeake
   Bay vicinity. Severe thunderstorm probabilities have been focused
   along and just ahead of a southward sagging cold front and
   instability gradient from central OH to the NJ coast. Rich
   boundary-layer moisture (dewpoints in the upper 60s to mid 70s F)
   will contribute to a corridor of MLCAPE around 2000-4000 J/kg from
   the Mid-MS Valley eastward to the NJ coast. Warm midlevel
   temperatures may lead to lingering inhibition, particularly across
   eastern portions of the Slight and Marginal risk areas. Height falls
   associated with troughing over eastern Canada will remain well north
   of the region, and resulting in somewhat nebulous large-scale ascent
   amid very modest vertical shear (effective shear magnitudes
   generally less than 25 kt).

   Convection from the Day 1/Tue period may be ongoing Wednesday
   morning across parts of the Great Lakes vicinity and shift east
   along the instability gradient/southward-sagging surface front
   through the afternoon. Vertical shear may be locally enhanced with
   any MCV that may be present with this activity, and damaging winds
   are possible as the downstream boundary layer destabilizes.
   Additional isolated thunderstorm development is possible from
   central PA/northern VA eastward to the coast. This activity could
   produce locally damaging gusts and perhaps small hail if capping can
   be overcome and longer-lived updrafts develop.

   Weak shear further west toward the Mid-MS Valley vicinity will
   likely preclude a more organized severe risk. However, strong
   heating amid the very moist/unstable airmass will support isolated
   strong/locally damaging gusts during the afternoon. 

[yoda]

1 hour ago, George BM said:

This mornings convection appears to be developing off of an EML between ~850-750mb. 750mb fits pretty closely with where the cloud bases have been. (8,000+ft)

 

35 minutes ago, Eskimo Joe said:

SPC mesoanalysis definitely has a bit of a remnant EML overhead.

1630z OTLK from SPC just added SLGT risk for most of us

[midatlanticweather]

40% chance of a watch

 

Mesoscale Discussion 2028
   NWS Storm Prediction Center Norman OK
   1220 PM CDT Thu Aug 29 2024

   Areas affected...central Pennsylvania into western and central
   Virginia

   Concerning...Severe potential...Watch possible 

   Valid 291720Z - 291915Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Scattered storms will develop from central Pennsylvania
   southwestward along the Blue Ridge, with locally strong to damaging
   gusts possible into surrounding areas to the east later today.

   DISCUSSION...A moist and unstable air mass is in place today south
   and west of the New England surface ridge, and despite slow drying
   from the east. Visible imagery clearly indicates a very moist air
   mass with expansive cumulus fields over much of PA and southwestward
   along the Blue Ridge. GPS PWAT sensors show values of 1.75-2.00"
   from eastern VA/DelMarVa northwestward into central PA.

   Continued heating will lead to accelerated development over the
   higher terrain of eastern WV and western VA over the next few hours,
   with additional activity expected over much of central PA where weak
   convergence exists. Shear will remain weak over most of the area,
   with propagating clusters of storms expected to move east/southeast
   into the remainder of central and northern VA and parts of MD.
   Locally damaging gusts will be possible given the favorable timing
   of the development with peak heating, and as outflow pushes into
   regions with steep low-level lapse rates later this afternoon.