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Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1253 AM CDT Tue Aug 20 2024

Valid 211200Z - 221200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
EASTERN MONTANA AND WESTERN NORTH DAKOTA...

...SUMMARY...
Scattered thunderstorms, some with severe hail and damaging gusts 
are expected to develop on Wednesday over parts of far eastern
Montana and western North Dakota.

...Central and Northern Plains...
An upper-level ridge is forecast to move eastward across the
northern Plains on Wednesday, as a subtle shortwave trough moves
into the northern High Plains in southwesterly mid-level flow. At
the surface, a lee low in southeastern Montana is forecast to deepen
ahead of an approaching front. Warming surface temperatures ahead of
the front co*bined with surface dewpoints in the lower to mid 60s F,
will likely result in a southeast-to-northwest corridor of moderate
instability by afternoon. Thunderstorms appear likely to develop in
the mid to late afternoon near the front and in the higher terrain
of central and southern Montana. The models are now in better
agreement concerning the magnitude of instability, with MLCAPE
expected to reach the 3500 to 5000 J/kg range along the instability
axis. Thunderstorms that move toward the instability axis will have
a chance to be severe. Most NAM forecast soundings near the
instability axis by 00Z/Thursday have 0-6 km shear in the 40 to 50
knot range with 700 to 500 mb lapse rates of 8 to 9 C/km. This would
be favorable for supercells with large hail. Storm bases should be
high due to large temperature-dewpoint spreads, which will
contribute to the wind-damage potential. Far eastern Montana and
western North Dakotas should be impacted during the evening, as
low-level flow gradually ramps up.

Further to the south into the central High Plains, an axis of
moderate instability is forecast to develop by afternoon from
west-central Nebraska south-southwestward into northeastern
Colorado. By mid afternoon, thunderstorms are expected to form in
the higher terrain of southern Wyoming and central Colorado, with
this convection moving eastward into the lower elevations.
Thunderstorms that move into the most and unstable airmass over the
central High Plains will have a chance to beco*e severe. 0-6 km
shear around 30 knots co*bined with steep mid-level lapse rates will
support an isolated threat for large hail and severe gusts, with the
threat concentrated in the late afternoon and early evening.

..Broyles.. 08/20/2024