173
ACUS48 KWNS 160904
SWOD48
SPC AC 160902

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0402 AM CDT Thu Jul 16 2026

Valid 191200Z - 241200Z

...DISCUSSION...
The mid-level pattern across the US will continue to be
characterized by a West Coast trough, Intermountain West ridge, and
Great Lakes/East Coast trough through the extended period. The main
belt of westerlies will be found along the northern periphery of the
Intermountain West ridge.

A couple of short-wave troughs will feature prominently during the
forecast period. The first of these will be moving off the East
Coast on Sunday (Day 4). The second will be the closed low located
across the Pacific Northwest on Sunday. This low will open into a
mid-level short-wave trough as it crests the Intermountain West
ridge, before diving southeast across the Great Lakes early next
week.

Sunday`s East Coast departing mid-level wave will leave behind a
surface boundary arced from Virginia west-northwest into the Upper
Midwest. To the south of this boundary, a warm, moist airmass will
support afternoon MUCAPE values in the 1500-2500 J/kg range, locally
higher. This boundary will slowly push southward into the Carolinas
during the afternoon.

Modest height falls will overspread this boundary across the
Carolinas during the afternoon as a the region remains on the
southern fringes of the departing wave`s basal region. Additionally,
a weak mid-/upper-level level low across Florida/the eastern Gulf
will lift northward as it rejoins the westerlies. The combination of
modest height falls, strong instability, and the presence of a
surface boundary will result in scattered thunderstorm development
capable of producing strong thunderstorm outflows and wind damage. A
15% area has been introduced across the Carolinas for Sunday/Day-4
to account for this potential.

The next time/area of potential concern will be across portions of
the Upper Midwest/western Great Lakes on Monday/Day-5. Here, both
the physics-based GEFS and EC ensemble guidance and the GFS and
EC-based AI emulators are in good agreement that height falls will
overspread the region ahead of the next short-wave trough. However,
the GFS-based ensemble means are considerably weaker with the
strength of the trough, partially owing to differences in timing of
the main wave. The background environment will likely be favorable
for severe thunderstorms, with MUCAPE values in the 2000-3000 J/kg
range and strong vertical shear, the magnitude of which will be
largely influenced by the strength of the mid-level wave. That said,
west/southwesterly flow in the 925-700 millibar layer should support
a strong EML given the antecedent hot and dry airmass upstream of
this flow. This leads to concerns regarding convective initiation
within the favorable severe background environment. These concerns
are supported by the ensemble guidance with varying degrees of QPF
shown within the ensemble members. Given this is still 5 days away,
will hold off on introducing unconditional severe probabilities with
this forecast.

..Marsh.. 07/16/2026