ACUS03 KWNS 261930

SWODY3

SPC AC 261929



Day 3 Convective Outlook  

NWS Storm Prediction Center Norman OK

0229 PM CDT Thu Jun 26 2025



Valid 281200Z - 291200Z



...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SATURDAY AFTERNOON

INTO SATURDAY NIGHT ACROSS PARTS OF CENTRAL AND EASTERN SOUTH

DAKOTA...NORTHEASTERN NEBRASKA...MUCH OF SOUTHERN AND CENTRAL

MINNESOTA...ADJACENT NORTHWESTERN WISCONSIN...



...SUMMARY...

Scattered strong thunderstorms, posing a risk for severe hail and

wind, are possible across parts of the middle Missouri Valley into

Upper Midwest Saturday afternoon into Saturday night.



...Discussion...

Little change in the large-scale mid/upper flow is forecast from

Friday into Saturday, with modest westerlies remaining generally

zonal and confined to the northern tier of the U.S. and adjacent

portions of southern Canada.  Within this regime, one notable short

wave trough is forecast to progress east of the Great Lakes into New

England Saturday through Saturday night, as broad upstream 

troughing (with at least a couple of embedded smaller-scale

perturbations) progresses eastward along the north central

Canadian/U.S. border vicinity.  



In lower-levels, cooler and drier boundary-layer air is likely to be

maintained across parts of northern New England, with another influx

of cooler air spreading southeast of the Great Lakes through the

upper Ohio Valley, northern Mid Atlantic coast and southern New

England by late Saturday night.  A trailing cold front is likely to

continue slowly advancing east/southeast of the northern Rockies,

through the northern Great Plains.  Elsewhere, east of the high

plains, seasonably moist boundary air may become characterized by

moderate to strong potential instability with daytime heating.



...Northern Great Plains...

The extent of convective development and its evolution remain

unclear for this period due to a number of lingering uncertainties. 

Focus for renewed thunderstorm development could be impacted by

outflow from convection developing Friday night into early Saturday.

Additionally, strongest potential instability by Saturday afternoon

is likely to become focused beneath the nose of the warmer and more

strongly capping elevated mixed-layer air, roughly across the

northern/eastern South Dakota vicinity, before slowly becoming

suppressed southeastward.  However, this might tend to become

displaced to the south of the stronger and more favorably sheared

westerlies.



Even so, given thermodynamic profiles becoming characterized by

steep lower/mid-tropospheric lapse rates and large CAPE, scattered

strong to severe thunderstorm development appears possible ahead of

the southeastward advancing cold front by late afternoon.  Aided by

forcing for ascent supported by low-level warm advection beneath

broadly difluent upper flow, activity may consolidate into one or

two eastward/southeastward propagating clusters by Saturday evening.



...Northern Mid Atlantic into Champlain Valley...

A corridor of moderate to large developing mixed-layer CAPE, ahead

of the southeastward advancing cold front, and within preceding

deepening surface troughing, seems likely to provide the focus for

vigorous thunderstorm development by late Saturday afternoon. 

Although lapse rates may be modest, and stronger potential

instability across the northern Mid Atlantic may be displaced to the

south of the better flow/shear across Upstate New York into New

England, the environment may still become conducive to scattered

strong thunderstorms accompanied by a risk for potentially damaging

wind gusts.  If/when lingering uncertainties become more clear, it

is possible that severe probabilities could still be increased a bit

further in later outlooks for this period.



..Kerr.. 06/26/2025



$$

