ACUS11 KWNS 172012
SWOMCD
SPC MCD 172012
MTZ000-IDZ000-172215-

Mesoscale Discussion 1642
NWS Storm Prediction Center Norman OK
0312 PM CDT Fri Jul 17 2026

Areas affected...West and southwest Montana and extreme northeast
Idaho

Concerning...Severe potential...Watch unlikely

Valid 172012Z - 172215Z

Probability of Watch Issuance...20 percent

SUMMARY...Scattered thunderstorms are expected to form through
mid-late afternoon with a gradual increase in the threat for
isolated severe outflow gusts and large hail.

DISCUSSION...Visible satellite imagery reveals deepening convection
over the high terrain across southwest and western MT where surface temperatures have warmed well into the 80s with dewpoints in the
mid-upper 50s. The 18z soundings from TFX and BOI suggest that
surface temperatures need to warm to 90+ F to eliminate convective
inhibition for the lower elevations, though inhibition has
diminished over the higher terrain. Though forcing for ascent will
remain subtle, there are embedded perturbations rotating northward
over ID/western MT around the northwest periphery of the midlevel
ridge. These perturbations, in combination with additional surface
heating, will support scattered thunderstorm development the next
few hours. Steepening low-level lapse rates will favor
strong-severe outflow gusts as the main threat in an environment
with moderate buoyancy. Isolated large hail may also occur with any
more organized/supercell storms, given effective bulk shear of 30-35
kt.

..Thompson/Guyer.. 07/17/2026

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fjg!48iXkpFWfyxwYBZ6a7IJ-z9VnX8fmNJkxX9-zhpSsdknQYYvoqybarwV1WXNsFIo9-PTUUoUlHPYTSBgbFjjQSbeNmQ$ for graphic product...

ATTN...WFO...BYZ...TFX...MSO...OTX...

LAT...LON 46011013 45580943 45210931 45080955 45271109 45631269
45671368 46071469 47121509 48091510 48921488 48951402
48931310 47981257 47041194 46431126 46011013

MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN


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