SPC Jun 25, 2019 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook

Day 3 Outlook Image

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0234 AM CDT Tue Jun 25 2019

Valid 271200Z - 281200Z


Scattered severe thunderstorms capable of large hail and strong wind
gusts are possible across parts of northern Montana into western
North Dakota on Thursday.

...Montana into the Upper Midwest...

The upper low over the Pacific Northwest will continue to slowly
pivot eastward on Thursday. Strong southwesterly flow aloft will
overspread the northern Rockies while the Plains ridge drifts
eastward. Low-level easterly flow across the northern Plains into MT
will maintain 50s to low 60s surface dewpoints across eastern into
north-central MT. High-based supercells will be possible in this
moist, upslope regime. Similar to Day 2/Wednesday, vertical shear
and elongated hodographs amidst very steep midlevel lapse rates will
support very large hail in addition to damaging gusts. As a
low-level jet increases overnight, some upscale growth and a
continuation of severe potential could shift eastward into western
North Dakota.

The severe threat further east/southeast across the Dakotas into the
Upper Midwest is a bit more uncertain/conditional. A very moist and
unstable airmass will reside across the Mid-MO Valley into portions
of southern MN/western WI. Some guidance suggests a potential MCV
related to prior convection or weak shortwave impulse will top the
ridge and shift southeast across this region. If this occurs,
potential exists for the development of a severe MCS during the
evening/overnight hours somewhere in the vicinity of MN/WI or
perhaps eastern SD/NE into IA. Given uncertainty and conditional
nature of the threat, have included Marginal risk probabilities,
which may need to be adjusted depending on the evolution of
convective systems over the next two days.

..Leitman.. 06/25/2019

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