ACUS02 KWNS 261728

SWODY2

SPC AC 261726



Day 2 Convective Outlook  

NWS Storm Prediction Center Norman OK

1226 PM CDT Thu Jun 26 2025



Valid 271200Z - 281200Z



...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE FRIDAY INTO

FRIDAY NIGHT ACROSS MUCH OF NORTH AND SOUTH DAKOTA INTO PARTS OF

WESTERN MINNESOTA AND NORTH CENTRAL NEBRASKA...



...SUMMARY...

Scattered strong thunderstorms, and perhaps one or two small

organizing clusters, may impact parts of the northern Great Plains

late Friday afternoon into Friday night, accompanied by a risk for

severe hail and wind.



...Discussion...

Although a mid to upper low is likely to linger across parts of the

Southeast, perhaps migrating slowly northward across the northern

Florida into Georgia vicinity, modest subtropical ridging at

mid-levels will generally prevail across much of the central and

southern tier of the U.S. through this period.  Models indicate that

modest mid-level westerlies will remain confined to the northern

tier, with one embedded short wave trough forecast to slowly

progress across the Great Lakes region.  A couple of, perhaps, more

subtle perturbations within a broader cyclonic regime are forecast

to progress east-northeastward near and north of the Montana/North

Dakota international border vicinity.



In lower levels, a surface cold front, in the wake of a digging

short wave trough well offshore of the northern Atlantic coast, may

make further southward progress through portions of the northern Mid

Atlantic states, before retreating northeastward late Friday through

Friday night.  Upstream, another cold front, likely into the upper

Great Lakes vicinity and through much of the northern Great Plains

by 12Z Friday, is forecast to continue to advance eastward across

the Great Lakes through the remainder of the period, while the cool

air gradually modifies from west to east across the Dakotas.  In

between and south of these boundaries, seasonably moist conditions,

including upper 60s to 70+ F dew points, appear likely to persist

across most areas east of the high plains.



...Northern Great Plains...

Models indicate that low-level warming and moistening across the

western into central Dakotas may contribute to strong potential

instability by Friday afternoon, beneath warm elevated mixed-layer

air advecting east of the northern Rockies, ahead of the broad

approaching upstream mid-level troughing.  This destabilization will

become focused east of the modestly deep lee surface trough axis,

along a developing warm frontal zone aided by strengthening

differential surface heating.  



The northern periphery of the warmer and more strongly capping

elevated mixed-layer air is forecast to nose across western through

central South Dakota by early Friday evening. 

Lower/mid-tropospheric warm advection on the edge of this air mass

may provide the focus for an upscale growing cluster of storms

across north central South Dakota, or perhaps south central North

Dakota, aided by a modestly strengthening low-level jet Friday

evening.  This would likely tend to propagate east-southeastward

overnight, beneath  strengthening westerly mid/upper flow (including

30-40+ kt at 500 mb). 



Otherwise, widely scattered strong to severe thunderstorms,

including a couple of supercells, may initiate near/east of the lee

trough during the late afternoon into evening across the western

Dakotas, and perhaps parts of north central Nebraska into

northeastern Colorado, though this is a bit more uncertain due to

potentially stronger mid-level inhibition.



...Lower Great Lakes Vicinity...

Latest model output indicates that strengthening thunderstorm

development is possible in a narrow pre-frontal corridor across

parts of southwestern Ontario and southeastern Lower Michigan into

northwestern Indiana and northwestern Ohio, near or after 28/00Z. 

Although this is after peak diurnal heating, moderately large

residual CAPE, in the presence of southwesterly deep-layer mean flow

strengthening to 20-30 kt, might become supportive of convection

capable of producing a few locally strong to severe wind gusts,

before storms weaken late Friday evening.



...Appalachians into Southeast...

In the presence of relatively weak mid-level inhibition, forcing for

ascent aided by orography and inland advancing sea breezes may

support considerable diurnal thunderstorm development, as insolation

within a seasonably moist boundary-layer contributes to moderate

potential instability.  Stronger convection will probably pose a

risk for locally damaging downbursts, before activity weakens early

Friday evening.



..Kerr.. 06/26/2025



$$

