SPC Jun 19, 2025 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1227 PM CDT Thu Jun 19 2025

Valid 201200Z - 211200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM FAR
EASTERN MONTANA ACROSS PARTS OF THE DAKOTAS AND MINNESOTA...

...SUMMARY...
Severe thunderstorms are likely Friday into Friday night across
parts of the northern Plains and upper Midwest. Areas of significant
severe wind and hail are expected.

...Synopsis...
Upper ridging will occur over the northern Plains during the day, as
a shortwave trough and strong midlevel jet nose into the northern
Rockies. Low pressure will deepen from eastern MT into SD, with a
warm front extending east across northern SD, southern MN and
western WI. Near the warm front, backed winds and a capping
inversion will help maintain a zone of 70s F dewpoints from the
upper MS Valley westward along the SD/ND border. Westerly 850 mb
winds early Friday will back to southerly and increase during the
afternoon and evening, with a broad zone of 40-50 kt developing and
aiding northward heat and moisture transport. Very hot conditions
are expected near the surface low in SD with gusty southwest winds
and drying. Overnight, a cold front associated with the slow-moving
upper trough should push into western Dakotas.

...From eastern MT across the northern Plains and into upper MI...
Areas of thunderstorms may be ongoing Friday morning across IA,
southern MN and southwest WI. Lift will exist along and east of a
deep-layer instability gradient, with theta-e advection out of the
southwest with a 50 kt low-level jet. This activity may produce hail
and locally strong gusts Friday morning, with a weakening trend
during the day.

Strong instability will then develop throughout the day as
temperatures warm and moistening occurs along the warm front and in
a plume north of the MT/SD low. Storms are first expected to form
over western/central MT beneath the cooler temperatures aloft, with
a few cells producing strong gusts or marginal hail. However, by 21Z
or so, supercells are expected over eastern MT. Deep-layer shear
will be strong by virtue of easterly low-level winds beneath
increasingly westerlies aloft. Very large hail should be expected as
these cells move into ND, with MUCAPE increasing to 3000-4000 J/kg.
Potential may also exist for a severe bow moving across ND and
northwest MN, with significant damaging gusts.

Farther east along the warm front, much of the area will remain
capped during the day. However, the nose of the low-level lapse rate
plume should result in at least a small area of uncapped and very
unstable air mass, perhaps over northeast SD and southeast ND. Here,
a conditional supercell and tornado risk will exist. Should storms
form in this area around or after 00Z, very large hail and tornadoes
appear likely as low-level shear will be maximized here.

Otherwise, additional elevated storms should develop within the warm
advection wing across northern MN, WI, and upper MI. Hail appears
likely as instability will be large, though damaging wind potential
is less certain and will depend on boundary layer temperatures.

..Jewell.. 06/19/2025

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