2026 Mid-Atlantic Severe Storm General Discussion

[TSSN+]

23 minutes ago, high risk said:

There seems to be growing consensus that an intense MCS will form over northeast OH and western PA late this afternoon and move southeast.   While it (shocker) appears that the best threat will be over southeast PA, at least some of the complex should make it into northern MD and potentially into the Baltimore-Washington corridor later this evening or overnight.     

Best threat over SE Pa or NW? That area is under the enhanced risk. 

[yoda]

Radarscope claims rotation with the storm out in W VA (near Broadway)

[yoda]

23 minutes ago, yoda said:

Radarscope claims rotation with the storm out in W VA (near Broadway)

SVR warned for hail to ping pong ball size and winds to 60mph

[high risk]

34 minutes ago, TSSN+ said:

Best threat over SE Pa or NW? That area is under the enhanced risk. 

Sorry.  Bad wording on my part.  The southeast PA reference was regarding where the complex heads as it moves out of western PA. 

[TSSN+]

Well if get anything later tonight it’s that complex developing over Michigan. 

[high risk]

The front is slower than had been shown, so the updated Day2 has expanded the SLGT back to the north.  Still tons of CAM disagreement (of course).  

[Eskimo Joe]

1 hour ago, yoda said:

Radarscope claims rotation with the storm out in W VA (near Broadway)

It's likely the hail core interfering with the radar beam. Note how the broad rotation is behind the best VIL. 

[yoda]

Excellent afternoon AFD from LWX for tonight into tomorrow 

.DISCUSSION...
KEY MESSAGE 1...Slight Risk of severe thunderstorms today and
Friday.

Clouds have readily thinned in the wake of morning shower and
thunderstorm activity. This is allowing for temperatures to rise
quickly through the 80s to near 90. This heating will play an
important role in the potential for severe weather through the
evening hours.

As of 2:30 PM, a few discrete (transient supercell)
thunderstorms had developed over the Shenandoah Valley, and had
a history of producing large hail and wind damage. These storms
are developing in an area that has been clear since daybreak,
and in an area of enhanced low-level convergence due to residual
outflow from morning convection to the north, a washed out
front, and terrain circulations. Anticipate this activity to
continue into the late afternoon hours with a risk of localized
damaging wind gusts and large hail.

Meanwhile, upstream over the lower Great Lakes and Ohio Valley,
a large reservoir of MLCAPE 3000-4000+ J/kg exists. The north
end of this CAPE pool lies along the southern edge of the
westerlies, with a 100+ kt 300 hPa jet streak and mid-level
shortwave impulse located just to the north. This setup is
favorable for the development of a Mesoscale Convective Complex
(MCS), which is an organized line of thunderstorms that persists
for several hours.

Locally, mid-level lapse rates of 6.5-7 C/km (per latest
mesoanalysis and the KIAD 12Z RAOB) atop a very moist boundary
layer with surface dew points well into the 70s F will lead to
increasing CAPE despite the late start at surface heating. The
question then becomes just how organized upstream storms become,
and how stable the boundary layer is heading further into the
evening. A more organized and potent line of storms a bit
earlier in the evening would result in a notably higher risk for
more numerous damaging wind gusts, especially focused along the
residual baroclinic zone/theta-e gradient which should lie near
the Potomac River/US-50/I-66 this evening. A somewhat slower
and/or more disorganized line would result in a lower risk for
severe surface gusts, though some isolated damaging winds would
still be possible given high CAPE/DCAPE and the shallow nature
of the stable layer near the surface. Areas of western Maryland
and perhaps into the eastern West Virginia panhandle are most
likely to see the storms prior to the onset of appreciable
nocturnal boundary layer stability.

The area remains in a Slight Risk (level 2 out of 5) for severe
weather from SPC as of the midday outlook update, driven mostly
by the threat of damaging wind gusts. There is a threat for
large hail in stronger cores, though mid-level lapse rates will
gradually become less steep tonight. A linear storm mode would
tend to be less favorable for large hail production (as opposed
to discrete/individual cells), as well. A few discrete cells
are possible this evening in weak low-level WAA, however,
independent of any linear system that may affect the region.
These storms would be most likely to develop over northern and
central Virginia into central Maryland along a weak surface
trough and the aforementioned moisture/instability gradient.

Additional showers and thunderstorms, possibly strong to severe,
are anticipated again on Friday. Timing is a bit uncertain given
the subtle waves aloft, but increasing low-level convergence
paired with another upper impulse may very well result in
another round or two of storms with a damaging wind risk. The
latest guidance has nudged the threat a bit further north,
encompassing areas as far north as I-70 or the Mason-Dixon line
(as opposed to I-66/US-50). This will depend on any residual
early day clouds or convection, of course.

 

[yoda]

Fwiw, both 16z and 17z HRRR have an MCS/line/complex come rolling through the region between midnight and 3am.  

17z HRRR encompasses more of the region than the 16z run did.  Not saying its severe, just something to think about overnight as we watch it develop out to our NW

ETA - 18z HRRR same idea... but an hour or so faster

[high risk]

1 hour ago, TSSN+ said:

Well if get anything later tonight it’s that complex developing over Michigan. 

It’s actually more likely the storms firing out ahead over northeast Ohio.  That would be better, because we want these storms to arrive as early as possible. 

[yoda]

Granted its 1km AGL reflectivity and composite reflectivity, but I don't hate what the 18z RRFS is showing between 02z and 06z for the region

[yoda]

6 minutes ago, yoda said:

Granted its 1km AGL reflectivity and composite reflectivity, but I don't hate what the 18z RRFS is showing between 02z and 06z for the region

@high risk when looking at future radar, should i be looking more at composite or 1km AGL?  Or neither lol

[mappy]

Local news did a good job mentioning the risk for later tonight in the brief weather hit. Hopefully people pay attention. 

[mappy]

33 minutes ago, high risk said:

It’s actually more likely the storms firing out ahead over northeast Ohio.  That would be better, because we want these storms to arrive as early as possible. 

Thanks for this. I sent radar image of that line and sent to friends saying this was the storms to watch for later 

[yoda]

Watch needed soon for PA into parts of W and N MD per MCD

 

[yoda]

https://www.spc.noaa.gov/products/md/md2218.html

 

Mesoscale Discussion 2218
   NWS Storm Prediction Center Norman OK
   0316 PM CDT Thu Sep 03 2026

   Areas affected...Eastern Ohio into central Pennsylvania...western
   Maryland...and far northern West Virginia

   Concerning...Severe Thunderstorm Watch 649...

   Valid 032016Z - 032215Z

   The severe weather threat for Severe Thunderstorm Watch 649
   continues.

   SUMMARY...Supercells across eastern Ohio and northwestern
   Pennsylvania will likely grow upscale and pose a more substantial
   wind threat downstream into central Pennsylvania through the
   evening. Downstream watch issuance is expected soon.

   DISCUSSION...Discrete to semi-discrete supercells are evident in
   regional radar imagery across northeast OH and northwest PA with a
   few instances of severe hail noted over the past hour. Regional VWPs
   continue to sample elongated hodographs favorable for splitting
   supercells with an attendant threat for large hail for the next hour
   or so. Given the propensity for splitting cells and tight clustering
   of convection, upscale growth into one or more organized lines
   appears probable over the coming hours. As this occurs, the
   potential for severe wind should increase as convection moves into
   central PA where air mass recovery has been ongoing through the
   afternoon (MLCAPE has increased to 1000-1500 J/kg per recent
   mesoanalysis estimates).

   ..Moore.. 09/03/2026

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

   ATTN...WFO...CTP...LWX...PBZ...CLE...

   LAT...LON   41068148 41388079 41698017 41397732 41157698 40807689
               39967720 39607747 39487796 39527869 40278123 40498158
               40728172 40888169 41068148 

   MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
   MOST PROBABLE PEAK WIND GUST...65-80 MPH
   MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN