Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0759 PM CDT Thu Jul 16 2026
Valid 170100Z - 171200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
WESTERN MONTANA AND EASTERN NORTH DAKOTA INTO WESTERN MINNESOTA...
...SUMMARY...
Severe thunderstorms capable of producing large hail and gusty winds
remain possible across parts of the northern Rockies this evening.
Severe storms with hail and a tornado or two are also expcted over
parts of the Upper Midwest into tonight.
...Northern Rockies...
Evening water vapor imagery showed a very large upper ridge centered
over the CONUS, with a broad plume of monsoon moisture east of an
upper low off the coast of the Olympic Peninsula. Numerous
thunderstorms are ongoing over the Intermountain West and northern
Rockies this evening and should persist for several more hours
tonight.
The strongest of these storms, including some supercells, should
persist over parts of the eastern ID panhandle and western MT this
evening. Here, moderate buoyancy and 40+ kt of effective shear will
continue to favor storm organization. Hail is likely, along with
some potential for severe gusts given steep lapse rates in the lower
and middle troposphere.
...Eastern into western MN...
At the crest of the expansive upper ride, several weak vorticity
maxima and jet streak were migrating along the Canadian/ND border.
An effective warm front/modified outflow boundary was observed from
near the international border into western MN. South of the front,
surface temperatures in the 90s and dewpoints in the lower to middle
70s F are supporting a very unstable air mass with MLCAPE of
4000-5000 J/kg. Veering wind profiles along and south of the warm
front will favor supercells or organized clusters this evening into
tonight as developing convection spreads southeastward toward the
Red River Valley. Despite only modest mid-level lapse rates, strong
to extreme buoyancy and 35-40 kt of deep-layer vertical shear will
support a risk for large hail (some 2+ in) with dominant supercells.
Backed low-level flow and enhanced ESRH along the cool side of the
boundary could support a tornado or two as well.
The primary focus for the severe storms will be along the warm front
where convergence is maximized, though isolated storms ongoing
farther southwest are possible with a localized threat for hail and
damaging winds in the more strongly mixed air mass. A Level 2 Slight
Risk has been introduced to cover the increase in severe risk
through this evening from eastern ND into western MN.
...Elsewhere...
Strong to severe storms have largely exited the eastern seaboard
this evening. Additional disorganized storms over the southeastern
US and southern Plains should linger into the overnight hours while
steadily weakening. Waning buoyancy and meager deep-layer vertical
shear should limit severe potential.
..Lyons.. 07/17/2026
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