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

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