557
ACUS01 KWNS 180102
SWODY1
SPC AC 180100

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0800 PM CDT Fri Jul 17 2026

Valid 180100Z - 181200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
IDAHO AND MONTANA...HE UPPER MIDWEST...AND PORTIONS OF THE
SOUTHEAST...

...SUMMARY...
Strong to potentially severe storms remain possible this evening and
tonight across parts of the Upper Midwest and northern Great Lakes
and western Montana/northern Idaho. Sporadic strong to severe storms
with damaging wind gusts cannot be ruled out over parts of the
Southeast.

...Upper Midwest and Great Lakes...
Early evening water vapor imagery showed an upper trough and belt of
enhanced mid-level flow moving from southern Canada into the
northern Great Lakes. Ahead of the trough, a prominent warm front is
in place along the southern edge of Lake Superior, into the UP of
MI. Along the front, an associated surface cyclone was observed over
Lake Superior with a cold front trailing southwestward into eastern
MN and northwest WI.

Several strong to severe storms have developed and intensified
across far eastern MN, northern WI and the shelf waters of Lake
Superior this evening ahead of the cold front. High-res model
guidance and convective trends suggest these storms should generally
spread southeastward across northern WI this evening. Here in the
warm sector, mid to upper 80s F surface temperatures and seasonably
high dewpoints in the 60s and 70-s F are supporting a moderate to
strongly unstable air mass, more than sufficient for maintenance of
the ongoing severe storms. 40-50 kt of deep-layer shear are also
supporting organized clusters and some supercell structures. This
suggests hail and damaging winds are possible into early tonight.

Across the UP, convection has been slower to evolve owing to
lingering inhibition and weaker buoyancy. However, model guidance
and recent radar trends show a gradual increase in storm coverage
this evening. If some clustering can occur, a brief tornado risk may
also develop given enhanced low-level shear along the warm front and
near the lakes. An isolated risk for damaging winds could also
continue overnight across the UP and far northern Lower MI with any
longer-lived clusters along the front.

...ID and MT...
On the northern fringes of an expansive upper ridge, an upper low
over the Pacific Northwest was supporting a broad fetch of
seasonably high monsoon moisture and moderate destabilization.
Scattered thunderstorms are ongoing over parts of ID and MT this
evening and should continue into the early overnight period. While
displaced from stronger westerly flow aloft, effective shear near
25-30 kt could support a few organized storms with a risk for hail
and damaging winds over parts of ID and MT. Especially if any
clustering can occur.

...OH valley to the Southern Appalachians and Southeast...
Numerous storms ongoing this evening should slowly diminish in
coverage and intensity over the next couple of hours as the
boundary-layer stabilizes. The highest concentration of stronger
storms should remain across parts of the Southeast in FL and GA
where a larger reservoir of moderate to large buoyancy remains. An
isolated damaging gust will remain possible with the more persistent
thunderstorm clusters this evening. However, the weakening buoyancy
and increasing stabilization should gradually limit the damaging
wind risk into tonight.

..Lyons.. 07/18/2026

$$