LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0746 AM CDT Sat Jul 01 2023
Valid 011300Z - 021200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE MID
MS AND LOWER OH VALLEYS...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE TN
VALLEY/APPALACHIANS AND WEST CENTRAL TX...
...SUMMARY...
Severe thunderstorms with swaths of damaging winds and large hail
are expected later today into early tonight across the mid
Mississippi and lower Ohio Valleys. More isolated severe storms
will be possible farther east into the Appalachians and across west
Texas.
...Mid MS and OH Valleys through tonight...
A midlevel shortwave trough over the central Plains will progress
eastward to the mid MS Valley by tonight, as embedded,
convectively-enhanced perturbations rotate around its southern and
eastern periphery. At the surface, the primary undisturbed warm
sector resides from the Mid-South into southeast MO/southern
IL/western KY this morning, with ongoing convection reinforcing
rain-cooled air just south of I-70 across MO/IL into southwest IN.
In the wake of the morning convection, the unstable warm sector will
spread northeastward some across IL/IN/KY, where MLCAPE will
increase to 2500-3500 J/kg during the day.
Additional thunderstorm development is expected by mid-late
afternoon across eastern MO near a weak surface cyclone and cold
front, and storms will then spread eastward across IL and the OH
Valley through tonight. Midlevel flow will increase to near 40 kt
atop the warm sector, which will favor a mix of supercells and
multicell clusters capable of producing damaging winds and large
hail. There will be the potential for upscale growth into a larger
cluster or line, with a corresponding threat for swaths of wind
damage late this afternoon through late evening. The severe threat
could persist into tonight across eastern KY/southern OH, assuming
sufficient destabilization in the wake of today's convection over
the OH Valley.
...Appalachians area through this evening...
There is some potential for intensification of storms along residual
outflows and/or a weak surface trough just east of the Blue Ridge,
as the low levels warm/moisten through the afternoon. The stronger
flow aloft will remain farther west, but moderate buoyancy could
support clusters/line segments capable of producing occasional
damaging gusts and marginally severe hail later today into this
evening.
...West/southwest TX area this afternoon/evening...
Weak convergence/ascent along a convectively-enhanced cold front, in
combination with daytime heating/mixing, will likely support
thunderstorm development near and east of the Davis Mountains and
higher terrain in southeast NM. This area will remain south of the
stronger midlevel westerly/northwesterly flow, but modest deep-layer
shear and MLCAPE near 2000 J/kg will support storm clusters capable
of producing a few severe outflow gusts and isolated large hail.
...PA/NY this afternoon/evening...
Subtle/embedded perturbations will move over the lower Great Lakes
region today, around the southern periphery of the midlevel low over
the ON/QC border. Surface heating in cloud breaks and
boundary-layer dewpoints well into the 60s will support MLCAPE of
1000-1500 J/kg from PA northward into NY (east of the influence of
Lake Erie/Ontario). Lapse rates will not be steep, but some modest
enhancement to mid-upper flow could be sufficient for a few
semi-organized clusters capable of producing isolated wind damage
for a few hours this afternoon/evening.
...Southern MT to northwestern ND this afternoon/evening...
Though forcing for ascent will be weak, at least isolated
thunderstorm development will be possible this afternoon/evening
from edge of the higher terrain in southern MT northeastward along a
weak pre-frontal trough. Surface heating/deep mixing will drive
inverted-V profiles with MLCAPE at or above 1000 K/kg, and DCAPE
near 1200 J/kg. Weak flow supports relatively slow-moving
cells/clusters capable of producing isolated strong-severe outflow
gusts.
..Thompson/Gleason.. 07/01/2023
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