955
ACUS48 KWNS 250847
SWOD48
SPC AC 250845

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0345 AM CDT Sat Jul 25 2026

Valid 281200Z - 021200Z

...DISCUSSION...
...Day 4/Tuesday...
An upper low is forecast to develop from southwest ON into the
northern Mid-Atlantic with an attending belt of 35-45 kt mid-level
flow extending from the OH Valley into the southern Mid-Atlantic.
At the surface, a cyclone will remain vertically aligned with the
upper low, while a trailing cold front advances through the upper OH
and TN Valleys into the Mid-Atlantic, Carolinas, and Gulf Coast
states. A lee trough is expected to develop ahead of the cold front
along the Piedmont Tuesday afternoon.

Showers and thunderstorms (some potentially strong) are expected to
be ongoing Tuesday morning from the upper OH Valley into the
Mid-Atlantic, aided by forcing for ascent ahead of the upper low and
low-level warm air and moisture advection along a 30-40 kt low-level
jet. That activity is expected to linger into the afternoon from NY
and PA into western New England, which will limit the potential for
air mass destabilization in those areas. Stronger daytime heating
appears possible south of the Mason-Dixon Line, where moderate
instability is forecast across the pre-frontal warm sector.

Thunderstorms are expected to increase in coverage and intensity
during the afternoon along the cold front and lee trough from the
Delmarva into central Appalachians and VA/NC Piedmont. The moderate
instability combined with 35-40 kt of deep-layer shear will support
organized storm modes with the primary hazard being damaging wind
gusts.

Other more isolated severe storms appear possible over the central
High Plains within a low-level upslope regime.


...Day 5/Wednesday...
The Day 4/Tuesday upper low is forecast to slowly drift northeast
with a belt of stronger mid-level winds overspreading New England. A
surface low will remain vertically aligned with the mid-level system
with convergence in the vicinity of that feature and a trailing
front serving as the focus for afternoon thunderstorm development.
The models suggest that southern to central parts of New England may
become moderately unstable, which, combined with the slight shear
enhancement, may support a few strong to severe storms.

Additional strong to severe storms appear possible along a frontal
zone in the Southeast, where a very moist air mass will contribute
to moderate to strong instability.

Uncertainty in the extent of the severe weather threat in both areas
precludes the delineation of a 15% probability contour.


...Days 6-8/Thursday through Saturday...

The 00Z ensemble means are in reasonably good agreement in depicting
the retrogression of the upper high from the Southern Rockies into
the lower CO Valley. A concurrent weakening and broadening of the
eastern CONUS trough is also forecast. There is a model signal for a
stronger mid-level system to move into BC and the Pacific Northwest
by Day 8/Saturday. Deterministic guidance indicates a series of weak
disturbances tracking from the northern Plains to along and east of
the MS Valley during this time period with sporadic occurrences of
severe weather possible. However, the large-scale pattern currently
appears unsupportive of an organized severe weather episode.

..Mead.. 07/25/2026