2026 Mid-Atlantic Severe Storm General Discussion

[87storms]

I missed out on the Friday storms in Frederick (was in DC/Harbor), so I'm all in.

[high risk]

2 hours ago, Nomz said:

RRFS simref eye candy. Outlier run, but it's fun to look at.

      In the 00Z suite, although they differ greatly on timing and coverage every CAM other than the NAM Nest has convection in our area at some point during Wednesday afternoon in a modestly favorable environment for severe.    I'd say that the initial Day 2 outlook will at a minimum keep us in a MRGL, and a SLGT isn't out of the question.    The only shot at severe is with the open warm sector storms, as whatever is on the front early Thursday will be weak.

[Nomz]

43 minutes ago, high risk said:

      In the 00Z suite, although they differ greatly on timing and coverage every CAM other than the NAM Nest has convection in our area at some point during Wednesday afternoon in a modestly favorable environment for severe.    I'd say that the initial Day 2 outlook will at a minimum keep us in a MRGL, and a SLGT isn't out of the question.    The only shot at severe is with the open warm sector storms, as whatever is on the front early Thursday will be weak.

I definitely think we go slight at some point. It's a bit of a balancing act with the NAM depiction vs some of the other models (thread the needle...). The NAM has a faster 700mb jet, which leads to a better EML over our area, but leaves subsidence in the exit region of the jet. The other models are much slower with the 700mb flow, so the EML is much weaker (<750 CAPE), but we are in the favorable area of the jet, so we get decent forcing for ascent and actual convection. 

[yoda]

4 hours ago, high risk said:

      In the 00Z suite, although they differ greatly on timing and coverage every CAM other than the NAM Nest has convection in our area at some point during Wednesday afternoon in a modestly favorable environment for severe.    I'd say that the initial Day 2 outlook will at a minimum keep us in a MRGL, and a SLGT isn't out of the question.    The only shot at severe is with the open warm sector storms, as whatever is on the front early Thursday will be weak.

Day 2 SLGT for all

 

[yoda]

Oh ok (morning AFD from LWX)

KEY MESSAGE 2...Severe thunderstorms are possible Wednesday
afternoon and evening as a strong cold front pushes through; a
significant drop in temperatures and gusty winds will accompany
the front Thursday.

A deep, digging, positively northern stream trough and its
associated strong cold front dive out of the Great Lakes
Wednesday. The cold front crosses the area late Wednesday
night into Thursday morning. Meanwhile, southern stream energy
will be lifting northward ahead of the boundary Wednesday
afternoon and evening. All of this creates a very complex severe
weather setup across the region. The latest update from the
Storm Prediction Center expanded the Slight Risk (level 2 out of
5) to include most of the area. However, it does come with some
caveats, which I`ll reiterate here. Primary among them is the
question of ongoing morning showers/convection, and the
potential impact that could have no destabilization during the
afternoon. As is typical, model guidance is very split on how
much instability is able to recover ahead of the pre-frontal
trough that will be the primary severe threat on the day. I do
think that seeing the latest CAM guidance in favor of 750-1250
J/kg of CAPE being able to develop has me a bit more concerned.
Assuming that we do get adequate CAPE, storms will fire along a
pre-frontal trough during the early afternoon hours across
eastern WV before moving east towards the metros during the
evening. The environment where storms may develop will be
impressive from a shear standpoint, with 40-50 kts of deep-layer
shear, and substantial amounts of Storm Relative Helicity (150+
m2/s2 0-1km, and 400+ m2/s2 in the 0-3 km layer). This is more
than favorable for supercell structures to develop, with
damaging winds, large hail, and even a tornado or two not out of
the question. Looking at the combination of shear and instability,
the STP is actually pretty impressive in model guidance. For
this reason, there is actually a CIG1 hatched area in our 2-5%
tornado probabilities across western MD and into the Potomac
Highlands. I wouldn`t even argue having with having that threat
even extended a bit further east along the MD/PA border in a
future update, but will let the 12z CAMs and machine learning
guidance come in for evaluation. Additionally, damaging winds,
large hail, and heavy rainfall will all be threats with any
storms that develop on Wednesday afternoon.

At any rate, Wednesday afternoon/evening is a day to watch
closely. Have your severe weather plans ready, in case you find
yourself needing to act on them. Continue to monitor the latest
forecasts from our office, as well as the Storm Prediction
Center, for the latest updates.

Confidence drops off significantly with the severe threat along
the immediate cold front given the projected timing late
evening into the overnight period. Even with that said, a gusty
line of showers could exist Wednesday night into Thursday as the
front pushes through. Would expect this to be more along the
lines of a gusty surge along the front (30-40 mph), followed by
increased synoptic winds shortly thereafter.

[TSSN+]

5 hours ago, yoda said:

Oh ok (morning AFD from LWX)

KEY MESSAGE 2...Severe thunderstorms are possible Wednesday
afternoon and evening as a strong cold front pushes through; a
significant drop in temperatures and gusty winds will accompany
the front Thursday.

A deep, digging, positively northern stream trough and its
associated strong cold front dive out of the Great Lakes
Wednesday. The cold front crosses the area late Wednesday
night into Thursday morning. Meanwhile, southern stream energy
will be lifting northward ahead of the boundary Wednesday
afternoon and evening. All of this creates a very complex severe
weather setup across the region. The latest update from the
Storm Prediction Center expanded the Slight Risk (level 2 out of
5) to include most of the area. However, it does come with some
caveats, which I`ll reiterate here. Primary among them is the
question of ongoing morning showers/convection, and the
potential impact that could have no destabilization during the
afternoon. As is typical, model guidance is very split on how
much instability is able to recover ahead of the pre-frontal
trough that will be the primary severe threat on the day. I do
think that seeing the latest CAM guidance in favor of 750-1250
J/kg of CAPE being able to develop has me a bit more concerned.
Assuming that we do get adequate CAPE, storms will fire along a
pre-frontal trough during the early afternoon hours across
eastern WV before moving east towards the metros during the
evening. The environment where storms may develop will be
impressive from a shear standpoint, with 40-50 kts of deep-layer
shear, and substantial amounts of Storm Relative Helicity (150+
m2/s2 0-1km, and 400+ m2/s2 in the 0-3 km layer). This is more
than favorable for supercell structures to develop, with
damaging winds, large hail, and even a tornado or two not out of
the question. Looking at the combination of shear and instability,
the STP is actually pretty impressive in model guidance. For
this reason, there is actually a CIG1 hatched area in our 2-5%
tornado probabilities across western MD and into the Potomac
Highlands. I wouldn`t even argue having with having that threat
even extended a bit further east along the MD/PA border in a
future update, but will let the 12z CAMs and machine learning
guidance come in for evaluation. Additionally, damaging winds,
large hail, and heavy rainfall will all be threats with any
storms that develop on Wednesday afternoon.

At any rate, Wednesday afternoon/evening is a day to watch
closely. Have your severe weather plans ready, in case you find
yourself needing to act on them. Continue to monitor the latest
forecasts from our office, as well as the Storm Prediction
Center, for the latest updates.

Confidence drops off significantly with the severe threat along
the immediate cold front given the projected timing late
evening into the overnight period. Even with that said, a gusty
line of showers could exist Wednesday night into Thursday as the
front pushes through. Would expect this to be more along the
lines of a gusty surge along the front (30-40 mph), followed by
increased synoptic winds shortly thereafter.

Confusing cause the point and click forecast says rain likely and doesn’t even mention thunderstorms. Haha 

[batmanbrad]

the next D2 outlook from SPC will be out in about 45 minutes.  Since the previous discussion had mentioned upgrade possibilities existed (but not at the time for our zones), wondering if they will get any more aggressive with their probabilities.

[MillvilleWx]

18 minutes ago, TSSN+ said:

Confusing cause the point and click forecast says rain likely and doesn’t even mention thunderstorms. Haha 

The overnight Met at Sterling mucked up the Wx grids as they did not include the mention of thunder anywhere in the CWA despite the AFD. That's very confusing and I'm not sure what happened there. An oversight. There is a chance of thunderstorms tomorrow, no question and should be updated with the afternoon package, if I had to guess. 

[TSSN+]

14 minutes ago, MillvilleWx said:

The overnight Met at Sterling mucked up the Wx grids as they did not include the mention of thunder anywhere in the CWA despite the AFD. That's very confusing and I'm not sure what happened there. An oversight. There is a chance of thunderstorms tomorrow, no question and should be updated with the afternoon package, if I had to guess. 

Ya for sure I’d hope it gets updated. I read the disco then seen the grids and was like huh? lol 

[yoda]

29 minutes ago, batmanbrad said:

the next D2 outlook from SPC will be out in about 45 minutes.  Since the previous discussion had mentioned upgrade possibilities existed (but not at the time for our zones), wondering if they will get any more aggressive with their probabilities.

Tor driven moderate on the day 1 1630z OTLK 

[yoda]

SLGT risk pushed further south and eastward all the way to the coast on the 1730z 

[yoda]

 

[yoda]

Oh @high risk @Kmlwx @Eskimo Joe

 

[yoda]

Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1228 PM CDT Tue Mar 10 2026

   Valid 111200Z - 121200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE LOWER
   MISSISSIPPI VALLEY INTO THE UPPER OHIO VALLEY AND MID-ATLANTIC...

   ...SUMMARY...
   Isolated to scattered severe thunderstorms are expected on Wednesday
   from the ArkLaTex and Lower Mississippi Valley northeastward through
   the Ohio Valley and Mid-Atlantic.

   ...Synopsis...
   Another day of scattered severe weather is anticipated for
   Wednesday. Two upper waves - evident in early-afternoon water-vapor
   imagery over the northern Rockies and northern Mexico - will
   traverse eastward over the next 24 hours. Substantial amplification
   of the northern wave is expected as it migrates into the upper OH
   Valley through the day. Strong broad-scale ascent ahead of the wave
   and within the left-exit region of a strengthening upper jet will
   promote steady intensification of a surface cyclone as it progresses
   from the Great Lakes into southeastern Quebec by Thursday morning. 

   A broad fetch of southerly flow will support poleward moisture
   return as far north as the upper OH Valley by Wednesday afternoon. A
   trailing cold front attendant to the surface low will push
   east/southeast through the day, reaching the Mid-Atlantic and
   northern Gulf Coast by 12 UTC Thursday. Strong to severe
   thunderstorm chances will be focused along and ahead of this front
   through the day as it pushes east/southeast. 

   ...Upper OH Valley...
   A corridor of higher severe wind, and perhaps tornado, potential may
   emerge across OH into parts of WV and western PA Wednesday morning
   into the afternoon hours. Latest guidance shows reasonably good
   agreement in a swath of pre-frontal 40-50 knot flow within the
   lowest kilometer overspreading the upper OH Valley. Within this
   strong flow field, guidance also depicts a pronounced plume of
   higher theta-e values advecting northward along the western
   Appalachians. The intersection of the strong flow with subtle
   low-level warm advection will likely support a corridor of
   regionally higher buoyancy and enhanced effective SRH (on the order
   of 200-300 m2/s2) favorable for well-organized convection, including
   supercells. 

   The primary uncertainty pertains to antecedent storm coverage across
   the region during the morning hours. Residual convection from late
   Tuesday night will likely linger over the mid/upper OH Valley,
   though guidance shows some uncertainty regarding coverage and
   intensity of this activity. Sparse storm coverage should help
   maximize diurnal destabilization and will support a more robust
   severe threat. Greater coverage of morning convection will act to
   modulate the thermodynamic environment by muting the influence of
   daytime heating and the northward extent of richer moisture.
   Regardless, updraft/UH signals in CAM ensembles and recent
   calibrated guidance depict a corridor of stronger convection across
   far eastern IN into OH, WV, and southwest PA. Increased wind
   probabilities (30%) have been introduced across this corridor where
   one or more rounds of storms within a strong flow field will pose a
   threat for damaging/severe winds. Higher risk categories may be
   needed if morning storm coverage is minimal and a more potent
   thermodynamic environment emerges.

[yoda]

https://www.spc.noaa.gov/exper/conditional-intensity-information/

For those that missed it re the CIG

[Kmlwx]

9 minutes ago, yoda said:

Oh @high risk @Kmlwx @Eskimo Joe

*image snipped*

I know there's a lot of mixed thoughts about the CIG hatching - but this is probably where it is going to have a good amount of utility regardless of how confused people are. 

Bear in mind that prior to the new outlooks - this map would just be a straight 2% tornado prob for us. 

[yoda]

Just now, Kmlwx said:

I know there's a lot of mixed thoughts about the CIG hatching - but this is probably where it is going to have a good amount of utility regardless of how confused people are. 

Bear in mind that prior to the new outlooks - this map would just be a straight 2% tornado prob for us. 

True.  Interesting to note LWX in the morning AFD noted that they thought the CIG 1 would come further east due to the potential 

[yoda]

Wow... LWX went all out with a long, detailed, and excellent afternoon discussion for tomorrow 

KEY MESSAGES...
- 1) Severe Thunderstorms are possible Wednesday afternoon and
  evening.

- 2) Well above normal temperatures through Wednesday
  afternoon.

- 3) A series of cold fronts crossing the area into early next
  week will lead to multiple temperature swings.

&&

.DISCUSSION...
KEY MESSAGE 1...Severe Thunderstorms are possible Wednesday
afternoon and evening.

Tomorrow`s forecast is an extremely challenging one. At this point,
there`s a wide range of potential solutions on the table, with very
low confidence in which solution will ultimately verify. Forecast
details follow below...

A potent northern stream trough will continue to amplify as it
tracks eastward from the Northern Plains toward the Great Lakes
during the day tomorrow. A corresponding surface low will deepen as
it tracks northeastward from Lower Michigan across the Lower Great
Lakes and into the St. Lawrence Valley. The low-level mass response
to the deepening cyclone will lead to strengthening low-mid level
winds, as a 700 mb jet of 50-70 knots develops over the Ohio Valley
tomorrow morning, and then spreads northeastward over our forecast
area by peak heating tomorrow afternoon. Southerly flow at low-
levels will draw deeper moisture (low 60s dewpoints) northward into
the area, which when combined with daytime heating (surface temps
climbing into the upper 70s and lower 80s) will lead to surface-
based destabilization (MLCAPE values around 500-1500 J/kg). Assuming
that storms occur, the environment in place with MLCAPE values of
500-1500 J/kg and effective bulk shear values of around 50 knots
(with nearly all of it below 700 mb) will be very favorable for the
development of severe thunderstorms. However, many questions remain
with respect to the coverage of storms, the storm mode, hodograph
shape, and resultant storm impacts locally.

00z/12z CAM guidance is in good agreement that there will be plenty
of ongoing convection tonight upstream in the Ohio Valley. Some of
this activity will likely impact the West Virginia Panhandle,
western Maryland, and potentially north-central Maryland tomorrow
morning. Much of this activity will likely be elevated in nature,
but some heavier downpours, lightning, and maybe even a little small
hail may be possible during the morning hours as this activity moves
through. Further south and east, conditions will likely remain dry
through the morning, with daytime heating occurring through a broken
cloud deck.

Forecast uncertainty increases moving into the afternoon hours, with
various sources of model guidance advertising a wide array of
potential solutions. On one extreme lies the 3km NAM, which fails to
produce any additional storms after the elevated activity moves
through during the morning. Inspection of 3km NAM forecast soundings
shows strong capping, which in turn inhibits the development of new
storms. A tendency toward under-mixing and overcapping is a well
known forecast bias of the 3km NAM. In this type of scenario, there
would be no severe weather threat across the bulk of the forecast
area tomorrow. A potential exception would be with any remnant
squall line moving into the Alleghenies from the Ohio Valley
tomorrow evening. On the other end of the spectrum lies the HRRR,
which produces numerous additional storms during the afternoon and
evening hours. Most of these storms actually form upstream in the
Ohio Valley during the morning and persist into the forecast area
during the mid afternoon to evening hours. Inspection of HRRR
forecast soundings shows much deeper mixing, which is unsurprising,
since overmixing/undercapping is a known bias of the HRRR. In terms
of storm mode, the HRRR solution shows both supercells and smaller
bowing segments.

Other sources of guidance lie somewhere between these scenarios. The
Hi-Res Canadian falls into the 3km NAM camp, keeping things capped
and producing no additional storms locally. The FV3 is the next
lowest in terms of storm coverage, only producing a few isolated
cells, primarily across northern Maryland and northern portions of
the West Virginia Panhandle. The RRFS also keeps activity
predominantly confined to northern WV/MD, but more in the form of an
organized squall line. The WRF-ARW develops a much larger
QLCS/squall line with embedded bowing segments out of pre-exisiting
convection that emanates out of southern WV. In that scenario, the
QLCS could would impact most of the forecast area. The WRF-NSSL is
much different that any of the above solutions, tracking a strong,
elevated QLCS across northern MD during the morning hours, which
lays out an east-west oriented outflow boundary. Then in the
afternoon, it has a string of intense, isolated supercells
developing along the differential heating boundary produced by the
outflow, which then track eastward across northern Maryland.

Beyond the differences in convective evolution/mode, there are also
significant hodograph shape differences between the models. More
overmixed models like the HRRR show close to straight hodographs,
while undermixed models like the 3km NAM show much more hodograph
curvature. The WRF-NSSL shows the greatest hodograph curvature of
all, as a result of the remnant outflow boundary.

The uncertainty with respect to convective mode and hodograph
curvature cascades into uncertainty with regard to the potential
hazards as well. The environment in place will make damaging winds
possible with any storms that form. However, that threat would
likely be maximized in scenarios that produce a more linear
convective mode, with a QLCS or smaller bowing segments. A more
cellular mode would likely lead to supercells, a greater threat for
both severe hail and tornadoes, and lesser areal coverage of
damaging winds compared to a linear mode. At the moment SPC has most
of the area outlooked in a Slight Risk, driven by damaging wind
potential. They also have a 5 percent hail contour, and 2/5 percent
tornado contours, along with a CIG 1 hatching (suggesting that a
reasonable max tornado intensity of EF-2, if a tornado were to
occur). The CIG1 hatching hints at the higher end potential of the
severe threat tomorrow. There is no CIG 1 hatching for wind
tomorrow, but hurricane force gusts (74+ mph) are needed to justify
wind hatching. It wouldn`t be a shock to see some 60-70 mph gusts in
any bowing segments, if storms do occur.

With the high level of forecast uncertainty, following observations
will be critical over the next 24 hours. The level of mid-level
capping, along with how upstream convection over the Ohio Valley
evolves will be critical factors in determining what ultimately
occurs here tomorrow.

A brief summary of the main takeaways follows below:

-Forecast uncertainty is very high tomorrow. Plausible scenarios
range from no severe thunderstorms at all, to a very impactful
severe thunderstorm event.

-Confidence in elevated storms impacting the WV Panhandle/western MD
tomorrow morning is high, but those storms likely won`t pose much of
a severe threat.

-Any storms that do form tomorrow afternoon will likely turn severe,
posing at least a threat for damaging winds, and potentially large
hail and tornadoes too (if the storm mode is supercellular).

-The timing of the most intense storms is expected to be in the
afternoon and evening hours, with the strongest storms (if they
occur at all) expected to move through the I-95 corridor between
roughly 3 and 8 PM.

-A squall line will likely approach from the Ohio Valley and
 track toward the Alleghenies tomorrow evening, but will likely
 be weakening as it does so. Any severe threat with this line
 will likely stay confined to along/west of the Allegheny Front.