Mesoscale Discussion 2451
NWS Storm Prediction Center Norman OK
1017 AM CST Thu Nov 12 2026

Areas affected...southeast Pennsylvania into central New
Jersey...far northern Delaware and northeastern Maryland

Concerning...Severe potential...Watch possible 

Valid 121617Z - 121845Z

Probability of Watch Issuance...60 percent

SUMMARY...Storms are expected to develop after 17Z from far
southeast Pennsylvania into extreme northeast Maryland and northern
Delaware, moving into central New Jersey during the afternoon. A few
severe storms producing brief tornadoes and hail are anticipated.

DISCUSSION...Surface analysis shows a surface low over northern VA,
and a warm front extending northeastward into central NJ. On the
warm side, mid 50s F dewpoints are present, with temperatures rising
into the lower 60s F. 

Visible satellite shows areas of heating upstream into parts of MD
and DE, with mid 60s F temperatures possible. Meanwhile, area VWPs
indicate moderate southeast to south winds just above the surface.
These factors should aid a degree of northward movement/mixing of
this boundary.

Several models indicate cells will develop around 17Z, increasing
into the early afternoon as they travel northeastward toward the
warm front. Forecast soundings support the notion of supercells,
with very cold temperatures aloft and veering winds with height. 

Given such cool temperatures aloft, little if any heating will be
necessary to support a severe risk, assuming dewpoints can rise into
the 54-56 F range.

..Jewell.. 11/12/2026

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

ATTN...WFO...PHI...CTP...LWX...

LAT...LON   39597412 39377519 39277596 39557626 39857626 40187608
            40437544 40487394 40317389 39777401 39597412 

MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0648 AM CST Thu Nov 12 2026

Valid 121300Z - 131200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE COASTAL MID-ATLANTIC...

...SUMMARY...
Strong to severe thunderstorms capable of producing isolated severe
hail, damaging winds, and perhaps a tornado may impact parts of the
coastal Mid-Atlantic this afternoon.

...Coastal Mid-Atlantic...
Within large-scale upper troughing encompassing much of the
central/eastern CONUS, an embedded mid-level shortwave trough over
the OH Valley will move eastward across the Mid-Atlantic today. A
related weak surface low is also expected to develop eastward across
MD/DE/southern NJ this afternoon. While low-level moisture ahead of
these features should remain modest over land (generally low to mid
50s surface dewpoints), an effective warm front is forecast to
extend from the surface low across eastern PA into NJ. Thunderstorms
may initiate along/near this boundary by 16-18Z, with weak
instability expected to develop as filtered daytime heating occurs.
Stronger flow associated with a mid-level jet will tend to remain
displaced to the south of the coastal Mid-Atlantic through the day,
but veering winds with height through mid-levels will still support
around 25-40 kt of deep-layer shear.

Given cold mid-level temperatures (around -20 to -22 C at 500 mb)
and modestly steepened lapse rates aloft, any of the stronger cells
that develop could produce severe hail. Isolated damaging winds also
appear possible as this convection spreads from eastern PA into NJ
and vicinity before moving offshore. Low-level winds and related
shear should remain fairly modest, but a somewhat more favorable
zone for a tornado may exist if a persistent supercell can interact
with/cross the surface warm front this afternoon across eastern PA
into NJ. The northern extent of the severe risk will likely remain
constrained by the warm front, and it still appears likely that
appreciable severe risk will tend to remain offshore/south of Long
Island and southern New England.

..Gleason/Wendt.. 11/12/2026

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1019 AM CST Thu Nov 12 2026

Valid 121630Z - 131200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
OVER A SMALL PART OF EASTERN PENNSYLVANIA AND CENTRAL NEW JERSEY....

...SUMMARY...
Strong to severe thunderstorms capable of producing isolated severe
hail, a tornado or two, and perhaps damaging winds may impact parts
of the coastal Mid-Atlantic this afternoon.

...Eastern PA/NJ/Northern DE...
Latest surface analysis shows a developing surface low over northern
VA.  This low is expected to deepen somewhat through the day and
track eastward across NJ as a potent shortwave trough moves into the
region.  The zone near the surface low and extending eastward along
the surface warm front will be a focused region of ascent and
destabilization this afternoon, with forecast soundings showing
MLCAPE of 500-900 J/kg, steep lapse rates, and considerable
low-level shear/helicity profiles.  A consensus of morning
HRRR/RRFS/REFS solutions show the development of isolated supercell
storms in this focused area.  The risk area is quite small, but
given the consistent guidance have opted for a small SLGT risk to
cover the potential threats.  Hail is probably the main concern with
any persistent supercell structure, but a tornado or two is also
possible.  Refer to MCD #2451 for further details.

..Hart/Dean.. 11/12/2026

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1107 AM CST Thu Nov 12 2026

Valid 131200Z - 141200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast across the U.S. Friday and
Friday night.

...Synopsis...
An upper-level wave currently off the CA coast will progress inland
and into the Southwest through the day Friday. A combination of
cooling mid-level temperatures and broad ascent ahead of the wave
will promote widespread showers and thunderstorms across southern
AZ, NM, and into western TX through the day. Latest CAM ensemble and
calibrated guidance suggests some wind threat could materialize
across southern AZ/NM through the afternoon, and possibly into far
West TX during the evening hours. However, these solutions may be
overly influenced by recent RRFS solutions, which show more
substantial moistening and ascent (and consequently better buoyancy)
ahead of the upper wave compared to other guidance. Omitting these
solutions, the general consensus is that buoyancy and shear through
the CAPE-bearing layer will remain too limited for robust/organized
convection. 

Elsewhere, occasional lightning flashes appear possible along the
northern CA and OR coasts as a secondary upper wave and attendant
cool mid-level temperatures overspread the Pacific Northwest. This
wave will spread east overnight and may support sporadic lightning
flashes across the Great Basin, though lightning coverage will
likely remain below 10%.

..Moore.. 11/12/2026