505
ACUS48 KWNS 150901
SWOD48
SPC AC 150859

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CDT Wed Jul 15 2026

Valid 181200Z - 231200Z

...DISCUSSION...
The mid-level pattern will continue to transition toward a western
US ridge and eastern Canada trough during this forecast period. The
strongest mid-level flow across the US will be in the region between
the ridge and trough, namely the Upper Midwest into the Northeast
and Mid-Atlantic.

Ensemble guidance suites continue to indicate several stronger
mid-level short-wave troughs moving through the longwave trough
across eastern North America. In particular, one such trough will
move across the Great Lakes and Northeast on Saturday into Sunday,
with a secondary wave moving across the same general area late
Monday into early Wednesday. In between these main waves,
smaller-scale vorticity/speed maxima are likely to traverse the
region.

Prior cyclones moving across the region will have left behind a
surface boundary arcing from the Great Lakes into the Mid-Atlantic.
As each of the previously mentioned waves approaches this boundary,
the surface boundary will lift northward before being pushed farther
southward in the wake of the departing wave. By the end of the
forecast period, this boundary may push as far south as the
Southeast US.

Widespread showers and thunderstorms will be possible with each
passing wave, with more isolated potential in between the main waves
in association with any of the small/subtle vorticity/speed maxima
moving through the flow. The best areas for thunderstorms look to be
south of the better mid-level flow, which would tend to favor any
severe potential being driven by the degree of low-level
warming/steepening of the low-level lapse rates. At this time it
appears that the timing of the midlevel waves may favor early day
convection, especially across the Lower Great Lakes into the
northern Mid-Atlantic area. This early day convection may temper
afternoon heating and the overall organization/areal extent of any
severe potential. Thus, confidence remains too low to introduce
unconditional 15% severe weather probabilities at this time, despite
the acknowledgment that some severe potential is likely during this
time period.

..Marsh.. 07/15/2026