827
ACUS01 KWNS 011249
SWODY1
SPC AC 011247

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0747 AM CDT Tue Jul 01 2025

Valid 011300Z - 021200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
MID-ATLANTIC REGION AND ACROSS WESTERN PORTIONS OF NEBRASKA AND
SOUTH DAKOTA...

...SUMMARY...
Scattered strong to severe storms are possible across parts of the
Mid-Atlantic into the Northeast this afternoon/evening.  A few
severe thunderstorms are possible over western parts of Nebraska and
South Dakota.

...Mid-Atlantic states into the Northeast and Southeast...
Water-vapor imagery this morning indicates an upper trough is moving
east across the Great Lakes/lower OH Valley and other minor
perturbations are located over the Mid South.  The primary
disturbance will overspread the Appalachians by mid-late evening.
In the low levels, a cold front analyzed over the southern Great
Lakes into the lower OH Valley/Mid South will gradually progress
east/southeast during the period.

12 UTC raob data from the OH Valley and Mid South eastward to the
Mid-Atlantic region shows a very moist troposphere with limited
700-500 mb lapse rates (less than 5.5 deg C/km).  Nonetheless,
diurnal heating of the moist boundary layer will result in moderate
buoyancy from portions of the Northeast southwestward through the
Mid-Atlantic states and into the Southeast.  Models continue to
indicate modest southwesterly mid-level flow across the Mid-Atlantic
states will contribute to adequate shear, supporting some
organization of storms into line segments/clusters.  Scattered
thunderstorms will increase in coverage with time and numerous
thunderstorms are expected by mid-late afternoon while moving east
across PA/WV/VA/MD.  Strong to severe gusts (50-65 mph) are possible
with the stronger downdrafts.  Less organized but scattered to
numerous storms are forecast farther southwest into portions of the
southern Appalachians with a risk for damaging gusts with the
stronger storms.  Strong-severe convection should spread off the
Middle Atlantic Coast during the evening.

...Black Hills into the central High Plains...
A weak mid-level disturbance is moving east across northern
WY/southern MT towards the SD/NE vicinity later today.  A weak lee
trough will likely serve as a focus for thunderstorm development
this afternoon from near the Black Hills southward into northeast
CO.  Forecast soundings show around 30-kt effective shear in the
presence of steep lapse rates and moderate MLCAPE (1000-2500 J/kg).
Some of the recent MPAS guidance indicates a few stronger
thunderstorms will develop across western NE and perhaps into
western SD.  A couple of supercells with an attendant large-hail
risk are possible, thereby prompting an increase in hail
probabilities this outlook update.  Some severe risk may linger into
the mid-late evening coincident with a strengthening of a southerly
LLJ centered over west-central NE before this activity dissipates.

..Smith/Broyles.. 07/01/2025

$$