2024 Severe Weather General Discussion

[southmdwatcher]

New tornado watch issued until 1am up through central VA to near Fredericksburg and Richmond. 

[high risk]

Hard not to be interested with a red box now up for areas just to the southwest, and the latest guidance showing a surge of instability ahead of the line segment.    Overall, the CAMs show a weakening trend, and the hodographs aren't all that impressive, but I'll definitely be watching for a while longer.

[Eskimo Joe]

42 minutes ago, high risk said:

Hard not to be interested with a red box now up for areas just to the southwest, and the latest guidance showing a surge of instability ahead of the line segment.    Overall, the CAMs show a weakening trend, and the hodographs aren't all that impressive, but I'll definitely be watching for a while longer.

Same. CIMMS I'm over in the obs thread for this event. 

[NorthArlington101]

Down in Cville today in the TOR watch box. Definitely not chasing - but my first tornado watch of the season!

[AlexD1990]

Tornado warning near Martinsburg

Sent from my SM-F711U using Tapatalk

[yoda]

Could be interesting if any storm can get into our area tomorrow evening 

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Flow aloft will become more zonal in nature tomorrow, with a
broad belt of west-southwesterly flow extending from the Upper
Midwest toward the East Coast. A shortwave disturbance will
descend down in the west-northwesterly flow from the Great Lakes
toward Upstate NY. A weak area of low pressure will accompany
the shortwave, along with an attendant cold front which will
drop southward out of NY into northern PA Sunday afternoon.
Locally, it will be a warm day to the south of the boundary,
with temperatures climbing into the upper 70s to near 80 beneath
partly cloudy skies. Thunderstorms are expected to form near the
aforementioned frontal boundary up in PA Sunday afternoon. Much
of this activity is expected to remain to our north during the
daylight hours.

As we move into the evening and the first half of the
overnight, these storms are expected to drift southward along
with the frontal boundary, eventually reaching northern portions
of the forecast area. With loss of daytime heating, the trend
should be for these storms to gradually weaken as they move in
from the north, but a few stronger storms can`t be ruled out.
The environment will be an uncommon one for this part of the
country, with steep lapse rates of 7-8.5 C/km in place as an
elevated mixed layer moves in aloft. If storms do persist as
they track into the area, some instances of large hail may be
possible. SPC currently has portions of northern Maryland and
the West Virginia Panhandle outlooked in a Marginal Risk for
severe thunderstorms.

[Eskimo Joe]

As we move into a more favorable time for severe weather, I'd like to pass along some personal and professional resources for severe weather that I have found useful over the years.

First, the professional resources:

• The Storm Prediction Center's (SPC) Rich Thompson gave a nine part series on tornado forecasting some years ago at the University of Oklahoma. It was recorded and uploaded on YouTube and has significantly expanded my knowledge of tornado forecasting and severe weather in general. Each video is about one hour long. Link: https://youtube.com/playlist?list=PLxeAIQgAiFqvsaAx79xN3gBjc8baIiWMn&si=O2fmocu33d95yGPd
• You will hear a lot about Elevated Mixing Layer (EML) over the coming months. There is a great research paper regarding the role of EMLs and northeast severe weather. While we are technically in the Mid Atlantic, the underlying fundamentals discussed in the paper are great for improving your knowledge. Link: https://journals.ametsoc.org/view/journals/wefo/25/4/2010waf2222363_1.xml
• Each year, there are questions about the SPC probabilistic outlooks. This link does a great job cross explaining the outlook and cross walking the percentages and the corresponding categories. Link: https://www.spc.noaa.gov/misc/SPC_probotlk_info.html
• Here is a great research paper focused on the SPCs probabilistic verification of their outlooks: https://journals.ametsoc.org/view/journals/wefo/33/1/waf-d-17-0104_1.xml
• Some helpful links for real time observations:
  • Delaware mesonet: https://www.deos.udel.edu/
  • Maryland mesonet: https://mesonet.umd.edu/
  • Keystone (Pennsylvania) mesonet: https://keystone-mesonet.org/ 

Second, some personal observations:

• There are numerous mesoscale boundaries across the area. They play a unique role in forming and disrupting convection and wreck havoc on forecasting. 
• The wedge always wins, until it doesn't.
  • If we have a steady south-southwest wind, that seems to be better are eroding the wedge quicker.
• Getting a Day 2 Moderate Risk is a jinx.
• Events seem to set up further south at the last minute. See June 13, 2013. Day 1 Moderate Risk for DC that ended up in North Carolina. 
• I have found that it is better to be level headed and expect a bust. There are so many small scale features that aren't resolved until 4 to 8 hours prior to the event.
• Downsloping kills events, but if you have either really cold temps aloft or better yet, a stout EML, then we can all win. Learn to look for these features.
• During large outbreaks, look to western North Carolina for what's coming our way. That's usually 4 to 6 hours from DC metro.

I hope this helps and good luck to everyone this year.

[Rhino16]

33 minutes ago, Eskimo Joe said:

As we move into a more favorable time for severe weather, I'd like to pass along some personal and professional resources for severe weather that I have found useful over the years.

First, the professional resources:

• The Storm Prediction Center's (SPC) Rich Thompson gave a nine part series on tornado forecasting some years ago at the University of Oklahoma. It was recorded and uploaded on YouTube and has significantly expanded my knowledge of tornado forecasting and severe weather in general. Each video is about one hour long. Link: 
• You will hear a lot about Elevated Mixing Layer (EML) over the coming months. There is a great research paper regarding the role of EMLs and northeast severe weather. While we are technically in the Mid Atlantic, the underlying fundamentals discussed in the paper are great for improving your knowledge. Link: https://journals.ametsoc.org/view/journals/wefo/25/4/2010waf2222363_1.xml
• Each year, there are questions about the SPC probabilistic outlooks. This link does a great job cross explaining the outlook and cross walking the percentages and the corresponding categories. Link: https://www.spc.noaa.gov/misc/SPC_probotlk_info.html
• Here is a great research paper focused on the SPCs probabilistic verification of their outlooks: https://journals.ametsoc.org/view/journals/wefo/33/1/waf-d-17-0104_1.xml
• Some helpful links for real time observations:
  • Delaware mesonet: https://www.deos.udel.edu/
  • Maryland mesonet: https://mesonet.umd.edu/
  • Keystone (Pennsylvania) mesonet: https://keystone-mesonet.org/ 

Second, some personal observations:

• There are numerous mesoscale boundaries across the area. They play a unique role in forming and disrupting convection and wreck havoc on forecasting. 
• The wedge always wins, until it doesn't.
  • If we have a steady south-southwest wind, that seems to be better are eroding the wedge quicker.
• Getting a Day 2 Moderate Risk is a jinx.
• Events seem to set up further south at the last minute. See June 13, 2013. Day 1 Moderate Risk for DC that ended up in North Carolina. 
• I have found that it is better to be level headed and expect a bust. There are so many small scale features that aren't resolved until 4 to 8 hours prior to the event.
• Downsloping kills events, but if you have either really cold temps aloft or better yet, a stout EML, then we can all win. Learn to look for these features.
• During large outbreaks, look to western North Carolina for what's coming our way. That's usually 4 to 6 hours from DC metro.

I hope this helps and good luck to everyone this year.

Any observations about warm fronts in combination with a wedge, and how they can play into severe? I vaguely recall something of the sorts, but I’d have to research again. Perhaps it’s a more early season issue.

[high risk]

9 hours ago, yoda said:

Could be interesting if any storm can get into our area tomorrow evening 

      No doubt, but the problem is that the CAMs seem in pretty good agreement that the timing is just really bad for us.    Those storms won't approach the PA/MD border until just after dark at the earliest, and temps will be cooling fast.     For the record, it's complete bullsh*t that central PA gets a legit early season threat before we do.

[Kmlwx]

The few chances we've had already this year have been failing on timing. We need something to come through during peak hearing or just after and also not while we are wedged north of a warm front. 

[yoda]

New Day 1 has SLGT risk in W MD eastward till around HGR, also includes parts of the Panhandle of WV that borders Maryland 

[George BM]

12 hours ago, high risk said:

      No doubt, but the problem is that the CAMs seem in pretty good agreement that the timing is just really bad for us.    Those storms won't approach the PA/MD border until just after dark at the earliest, and temps will be cooling fast.     For the record, it's complete bullsh*t that central PA gets a legit early season threat before we do.

Lol. A little part of me dies every time this occurs.

[Kmlwx]

Meh

[yoda]

Hmmm... later today surprise?

NEAR TERM /THROUGH TONIGHT/...
Showers and a few thunderstorms continue to slowly drift
southeastward across the northern half of the forecast area
early this morning. This remnant activity should continue to
weaken over the coming hours, and eventually dissipate prior to
daybreak. Clouds associated with this activity may linger for
the first half of the morning, but clearing and ample sunshine
is expected during the second half of the morning into the early
afternoon.

A diffuse cold front will continue to slowly drift southward
across the forecast area today. Daytime heating will allow
instability to build, with around 1000 J/kg of CAPE present by
peak heating this afternoon. Additional thunderstorms are
expected to develop within the zone of low-level convergence
near the surface front later this afternoon. There`s some
uncertainty as to where exactly this will occur. Any location in
the forecast area has at least a slight chance for a
thunderstorm, but the greatest chance should generally be south
of I-66/US-50 and east of US-15. Further west, westerly flow
and downsloping will act to further dry out an already dry
boundary layer, which should limit storm coverage as a result.
Further north, they`ll likely end up to the north of the best-
low-level convergence, which should also limit the coverage of
storms. Where storms do form, they`ll likely be strong to
severe. Model soundings show an environment that is more typical
of the High Plains than the Mid-Atlantic. Boundary layer
moisture will be rather limited, with dewpoints only in the 50s,
but lapse rates will be very steep (dry adiabatic in the lowest
three kilometers, with mid- level lapse rates around 7.5-8
C/km). Flow will be relatively weak in the boundary layer, but
pick up rapidly in the mid- levels, with continued shear through
the upper levels. Hodographs are relatively straight, so storm
splits may be possible, with both multicells and right/left
moving supercells. Model soundings check a lot of boxes in
recent research for hail producing storms. That may be the
primary threat this afternoon, although the steep lapse rates
and DCAPE values around 1000 J/kg should make damaging winds a
threat as well. Tornadoes aren`t expected with a dry boundary
layer and little to no low- level shear in place. The I-95
corridor south of DC to southern Maryland should stand the
greatest chance of seeing a severe stoms. These storms will
progress off to the south and east this evening, leading to dry
conditions overnight.

[yoda]

SLGT risk pushed north to DC metro... MRGL to near Mason-Dixon line on 1300z SPC OTLK 

[yoda]

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
910 AM EDT Mon Apr 15 2024

.SYNOPSIS...
A cold front will drop southward through the area tonight,
before returning northward as a warm front on Wednesday. A
strong cold front will move through this weekend, with high
pressure building in early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...

Model trends past 24 hrs have shown storms this afternoon
developing further north than anticipated yesterday roughly now
from along and south of the US-50 corridor or south of I-70
along a lee-side trof. New 13Z SPC DY1 Otlk has shifted the
Slight risk further north into areas south of the Capital
Beltway. Hail is expected to be the primary threat given 7.3
C/km mid-level lapse rates and decent CAPE above -20C seen on
the 12Z IAD sounding. Storms would also be relatively fast
movers with 0-6 km mean winds of 28kt posing a marginal damaging
wind threat.

[midatlanticweather]

[SnowenOutThere]

Severe warned T-Storm crossing into Virginia north of Winchester, wonder if it could act as a forcing mechanism and lay down some boundaries for those further north. 

[yoda]

4 minutes ago, midatlanticweather said:

Mesoscale Discussion 0438
   NWS Storm Prediction Center Norman OK
   1001 AM CDT Mon Apr 15 2024

   Areas affected...portions of eastern West Virginia...northern
   Virginia and western Maryland

   Concerning...Severe potential...Watch unlikely 

   Valid 151501Z - 151630Z

   Probability of Watch Issuance...5 percent

   SUMMARY...Isolated showers and thunderstorms may produce gusty winds
   or small hail the next couple of hours across parts of the West
   Virginia, Maryland and Virginia border vicinity.

   DISCUSSION...A couple of thunderstorms have developed late this
   morning ahead of a stationary boundary near the WV/MD/VA border.
   This activity is likely somewhat elevated. Nevertheless, weak
   instability (generally less than 500 J/kg MUCAPE) amid steep
   midlevel lapse rates and modest effective shear could support
   sporadic small hail. A dry, mixed boundary-layer and light low-level
   flow also may foster gusty winds around 40-50 mph. This initial
   thunderstorm activity is expected to remain isolated and the overall
   severe threat limited over the next couple of hours, and a watch is
   not expected. The severe threat will increase across portions of
   Mid-Atlantic later this afternoon, and this later threat will be
   addressed with additional MCDs in the coming hours.

   ..Leitman/Smith.. 04/15/2024

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

   ATTN...WFO...LWX...PBZ...RLX...

[Wxtrix]

we had a shower earlier and now it's thundering, but that's it so far.

[Eskimo Joe]

The terrain out west and the front in Pennsylvania are probably providing enough lift to get storms started. But it's clear they can't sustain themselves closer into the metro.

[yoda]

Wonder if the 1630z OTLK will pull the SLGT risk a bit further north and west 

[yoda]

24 minutes ago, yoda said:

Wonder if the 1630z OTLK will pull the SLGT risk a bit further north and west 

Yup

And added ENH to our south including EZF into S MD

[yoda]

1630z disco

.Lower OH Valley into the Mid-Atlantic states...
   Morning surface mesoanalysis places a residual frontal zone draped
   over central IN/OH with a low-level moisture reservoir (low 60s deg
   F surface dewpoints) extending from the confluence of the MS/OH
   rivers northeastward into the lower Wabash Valley.  Atop this
   moisture, a plume of steep 700-500 mb lapse rates (8.0 to 8.3 deg
   C/km) sampled at the Lincoln, IL and Wilmington, OH raob sites, will
   overspread the OH Valley eastward into VA today.  The richer
   low-level moisture will likely remain west of the Appalachians
   across the lower OH Valley where 1500-2500 J/kg MLCAPE is forecast. 
   Widely scattered thunderstorms are forecast to develop by mid
   afternoon within the moist axis along/south of a stalled front over
   the OH Valley.  Effective shear 25-35 kt will support a mix of
   supercells and organized line segments capable of hail and wind.  

   Farther east, steep lapse rates from the surface to 500 mb are
   depicted in forecast soundings by early to mid afternoon (8 deg
   C/km).  Although PW will be lower across the Mid-Atlantic region, a
   more deeply mixed boundary layer is forecast with strong westerly
   mid-level flow (40 kt).  Initial cellular storms will likely develop
   over the higher terrain with subsequent development across northern
   VA.  A band of storms posing a risk for severe gusts (60-70 mph) and
   resultant wind damage is forecast.  Given the lapse rate profile
   coupled with ample mid- to high-level flow and a linear mode, have
   increased wind probabilities and an upgrade to level 3 categorical
   outlook this update.  The overall severe threat should gradually
   diminish through late evening with the loss of diurnal heating.

 

[yoda]

Storms entering NW VA increasing in intensity and some hail cores slowly starting to appear 

[yoda]

Severe Thunderstorm Watch coming soon per SPC MCD 

[yoda]

 

 

   Mesoscale Discussion 0439
   NWS Storm Prediction Center Norman OK
   1203 PM CDT Mon Apr 15 2024

   Areas affected...portions of West
   Virginia...Virginia...Maryland...and Delaware

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

   Valid 151703Z - 151900Z

   Probability of Watch Issuance...95 percent

   SUMMARY...Thunderstorm activity is expected to increase by 3-4pm
   EDT. Damaging gusts to 60-70 mph and large hail to 1.5 inches in
   diameter will be possible through early evening.

   DISCUSSION...Gradual destabilization is occurring from west to east
   early this afternoon across the MCD region. Increasing cumulus
   development is noted over the past hour across the higher terrain of
   West Virginia into northern Virginia as temperatures have warmed
   into the 70s to low 80s. The 12z MPAS-HT high-res guidance appears
   to have the best handle on morning convection across the region, and
   in the expected convective evolution through early evening. Based on
   this guidance, and current observed trends, thunderstorm activity is
   expected to increase by 19-20z/3-4pm EDT near/south of a residual
   frontal boundary draped west to east across the region. This
   development will be aided by continued heating/destabilization,
   increasing midlevel moisture and a very steep low and midlevel lapse
   rate environment (midlevel lapse rates around 8 C/km with southward
   extent across VA).

   While low-level winds will remain light, a belt of 30-40 kt midlevel
   flow will foster effective shear magnitudes suitable for organized
   convection. Initial cellular activity will pose a risk for large
   hail and strong gusts. Meanwhile, a deeply mixed boundary-layer with
   inverted-v sub-cloud thermodynamic profiles suggest strong outflow
   winds will occur with this activity and clustering is likely to
   occur via outflow interactions. A damaging wind threat will increase
   with southeastward extent across Virginia toward the Chesapeake Bay
   vicinity where steep low-level lapse rates and DCAPE over 1000 J/kg
   will be focused.

   A severe thunderstorm watch will likely be needed for portions of
   the MCD vicinity by 18-19z.

   ..Leitman/Smith.. 04/15/2024

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

   ATTN...WFO...PHI...AKQ...LWX...RNK...PBZ...RLX...

[yoda]

7 minutes ago, yoda said:

Storms entering NW VA increasing in intensity and some hail cores slowly starting to appear 

Warnings issued for both cells

[yoda]

Severe warned storm by Berryville should be near DC metro by 3

Is that a hook up by Waterford?

[NorthArlington101]

Severe warned storm by Berryville should be near DC metro by 3

Severe Thunderstorm Watch just issued as well.