Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Sun Jun 22 2025
Valid 221200Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE GREAT PLAINS...UPPER MISSISSIPPI VALLEY AND NORTHEAST...
...SUMMARY...
Isolated to scattered thunderstorms are expected to develop today
across the northern Plains and Upper Mississippi Valley, some of
which could have large hail, damaging wind gusts and an isolated
tornado threat. Storms associated with severe gusts and hail may
also develop across parts of the Northeast, and in the southern and
central Plains.
...Great Plains/Upper Mississippi Valley...
At mid-levels, southwest flow will be in place today across the
Great Plains, as a trough moves into the northern Rockies. At the
surface, a cold front will advance southeastward across the northern
Plains, as a low moves from the eastern Dakotas into northwest
Minnesota. The boundary will be the focus for convective
development. To the east of the front, a very moist airmass will be
in place with surface dewpoints in the upper 60s to mid 70s F from
the central Plains northeastward into upper Mississippi Valley.
Moderate to strong instability is forecast to develop across much of
the region this afternoon. This, coupled with moderate deep-layer
shear, will be favorable for severe thunderstorm development.
Thunderstorms are expected to first develop across parts of North
Dakota and northwest Minnesota this morning. This activity could be
associated with large hail and isolated severe gusts. As surface
temperatures warm and low-level convergence increases near the
boundary early this afternoon, scattered storms are expected to
develop across parts of the central and northern Plains. These
storms will gradually grow upscale into a organized convective
cluster, moving through eastern South Dakota and western Minnesota.
RAP forecast soundings near Sioux Falls, SD at 21Z have MLCAPE in
the 3000 to 3500 J/kg range with 25 to 30 knots of 0-6 km shear. In
addition, 700-500 mb lapse rates are forecast to be near 9 C/km.
This should be favorable for supercells and/or intense multicells
capable of producing large hail and wind damage. Supercells that
track through the more unstable air to the east of the front could
produce hailstones greater than 2 inches in diameter, and have an
isolated tornado threat. If an intense line segment can organize,
then severe gusts above 70 mph will be possible as well.
Further south-southwest into parts of the southern and central High
Plains, scattered thunderstorms are expected to develop this
afternoon and evening. Surface dewpoints in the 60s F will
contribute to moderate instability. This, combined with very steep
lapse rates from the surface to 700 mb, will likely support a
marginal severe threat. Hail and a few severe gusts will be the
primary threats.
...Northeast...
A line or cluster of thunderstorms will likely be ongoing across the
Northeast at the start of the period. The outflow boundary
associated with this convection is expected to move south and
southwestward into the central Appalachians of Pennsylvania and New
York this morning. Moisture advection will result in a steady
increase in surface dewpoints across much of the region today, with
surface dewpoints increasing into the lower 70s F. As surface
temperatures warm, an axis of strong destabilization is expected to
take shape around midday. Thunderstorms that can develop near the
boundary will move southeastward along the axis of strong
instability. RAP forecast soundings from 18Z to 21Z near the
boundary have MLCAPE around 3000 J/kg range, with 700-500 mb lapse
rates of 7 C/km and moderate deep-layer shear. This should support a
threat for large hail and damaging wind gusts during the afternoon.
..Broyles/Moore.. 06/22/2025
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/TLVCsn
