RSS Mesoscale Discussions from Storm Prediction Center
SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0750 AM CDT Sat Jul 04 2026
Valid 041300Z - 051200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE MID-ATLANTIC AS WELL AS ACROSS PORTIONS OF SOUTHERN KANSAS
AND NORTHERN OKLAHOMA...
...SUMMARY...
Clusters of storms will move across parts of the Allegheny Plateau
into the Mid-Atlantic, with potential for widespread damaging wind
gusts. Additional severe thunderstorms are expected across the Great
Plains this afternoon and evening, posing a risk for severe wind
gusts and large hail.
...Upper OH Valley into the Mid-Atlantic/southern New England...
A belt of moderate mid-level westerly flow aloft currently extends
across the OH Valley and Mid-Atlantic States, situated between the
upper troughing over eastern Canada and higher heights over the
southeast CONUS. A modest vorticity maximum appears to be moving
within these westerlies across Lower MI, downstream of two more
prominent, convectively augmented vorticity maxima across IA and KS.
There also appears to be a very modest shortwave trough moving over
the KY vicinity, evidenced by a subtle shift in the mid-level winds
across the region. Both of these features are expected to continue
eastward today, progressing into a very warm, moist, and unstable
airmass across the Upper OH Valley and Mid-Atlantic by the early
afternoon.
Interaction between the modest ascent associated with these features
and the unstable airmass forecast to be in place will support
thunderstorm development. This development is expected first over
the Blue Ridge Mountains/Shenandoah Valley vicinity during the early
afternoon (likely supported by the modest KY shortwave trough)
before then progressing northeastward through northern VA, DC,
central MD, DE, and southern NJ. Weak deep-layer shear amid a deeply
mixed airmass (with afternoon temperatures in the upper 90s/low
100s) will support outflow-dominant storm structures, and strong
cold pools capable of widespread damaging wind gusts. An isolated
gust or two around 70-75 mph is possible. A similar convective
evolution is anticipated farther north (from the Allegheny Plateau
through the northern Mid-Atlantic and southern New England) later in
the afternoon as the Lower MI vorticity maximum moves through the
region. Damaging gusts will be the primary risk here as well, with
slightly less coverage and magnitude than farther south.
...Central/Southern Plains...
Outflow associated with a decaying convective cluster over
western/central KS currently arcs from southeast CO across far
southwest KS into central KS. This cluster is forecast to continue
weakening as it gradually moves east-southeastward, with its
associated outflow likely extending from east-central KS back
southwestward across south-central KS by this afternoon. Airmass
destabilization is expected by the mid to late afternoon amid strong
heating, steep mid-level lapse rates, and ample low-level moisture.
Moisture convergence along this boundary within this convectively
uninhibited airmass will result in additional thunderstorms. Given
the strong buoyancy and moderate deep-layer vertical shear in place,
a few supercells are possible early in the convective cycle. Large
to isolated very large hail as well as strong downbursts are
possible with any supercells. A tornado or two could also occur,
particularly with sufficient residence time along the boundary.
Outflow-dominant storm structures will likely result in one or more
forward-propagating convective clusters throughout the evening.
Widely scattered thunderstorm development is anticipated within the
moist upslope flow over the central High Plains, with at least some
potential for the development of a convective line that then
progresses into western NE, northeastern CO, and northwestern KS.
Widely scattered thunderstorm development is also expected along the
dryline extending from the central/western OK Panhandle
southwestward across the TX Panhandle and into far east-central NM.
Weak vertical shear will likely prevent sustained updraft
organization, but a few storms could briefly be robust enough to
produce strong updrafts/downdrafts and resulting damaging gusts.
...Lower MO Valley into the Lower/Central OH Valley...
Scattered to numerous thunderstorms are expected this afternoon as a
pair of vorticity maxima, one associated with the convection over KS
and the other from overnight storms across IA, progress eastward
into the moist and diurnally destabilized airmass over the region.
Vertical shear across the region will be modest, limiting updraft
organization and promoting an outflow-dominant storm mode. Even so,
some cold pool amalgamation is possible, with the resultant
forward-propagating clusters capable of damaging gusts.
..Mosier/Dean.. 07/04/2026
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