ACUS02 KWNS 170534
SWODY2
SPC AC 170532

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1232 AM CDT Fri Jul 17 2026

Valid 181200Z - 191200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE OHIO
VALLEY INTO THE MID-ATLANTIC AND SOUTHERN NEW ENGLAND...

...SUMMARY...
Severe thunderstorms are expected across portions of the Ohio Valley
and Lower Great Lakes into the Mid-Atlantic, mainly Saturday
afternoon into the evening. Some threat may linger into late
Saturday night.

...Ohio Valley/Great Lakes to Mid-Atlantic...

An upper shortwave trough over the Great Lakes is expected to
amplify as it pivots east across the Ohio Valley and into the
Mid-Atlantic/Northeast region on Saturday. As this occurs,
deep-layer flow will increase, with guidance suggesting 850-500 mb
flow in the 40-50 kt range will be common. At the surface, low
pressure will deepen as it shifts east across Ontario and Quebec. A
trailing cold front will develop south/southeast across the region
during the late afternoon into nighttime hours. Ahead of the front,
a quasi-warm front is expect to be oriented across the Mid-Atlantic
and will lift northward through the day within a strong warm
advection regime. Initially modest boundary layer moisture across
PA, northward through the Hudson Valley will rapidly moisten ahead
of the approaching cold front. A corridor of moderate to strong
destabilization is expected from the Mid-MS and OH Valleys into the
Mid-Atlantic. 

Convection may be ongoing across parts of PA/NY into the
Mid-Atlantic Saturday morning within the strong warm advection
regime. Some potential for an initial round of severe storms could
accompany this activity, especially near the surface warm front.
Additional thunderstorms will develop during the afternoon near a
prefrontal trough and along higher terrain in VA/NC. Vertical shear
will be somewhat less with southward extent, but scattered cells and
clusters will develop east through early evening posing a risk for
damaging wind gusts. Supercell wind profiles are apparent in
forecast soundings and a tornado risk is also possible, especially
near the surface warm front and prefrontal trough where 0-1 km SRH
will be maximized. 

Substantial thunderstorm development is also expected within a
second corridor near the surface cold front from southern Quebec
into MI/IN/IL by midday. Surface dewpoints in the mid 60s to low 70s
F will provide ample support for 2000+ J/kg MLCAPE from the Mid MS
Valley toward western PA. Organized cells and line segments will
pose a risk for damaging wind swaths across the region.

Some uncertainty still exists due to effects from morning convection
and possible impacts from persistent smoke across parts of the
Mid-Atlantic. However, the overall pattern supports a broad area of
severe potential, with several swaths of damaging winds and a few
tornadoes expected. 

...MT/ID...

A plume of steep midlevel lapse rates will overspread the area on
the southern periphery of stronger southwesterly flow aloft as an
shortwave upper trough shifts east across the Canadian Rockies.
Ample midlevel moisture amid steep lapse rates will foster MLCAPE
near 1000 J/kg. Forecast soundings also indicate elongated/straight
hodographs amid 35 kt effective shear magnitudes. Isolated organized
cells will pose a risk for hail and strong wind gusts through early evening.

..Leitman.. 07/17/2026

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