Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0700 AM CDT Sat Jun 27 2026
Valid 271300Z - 281200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON INTO EARLY TONIGHT ACROSS EASTERN MT AND WESTERN ND...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS INTO WESTERN SOUTH
DAKOTA AND NEBRASKA...AND ACROSS NORTH CAROLINA...
...SUMMARY...
A mix of initial supercells and later storm clusters will produce
swaths of severe outflow winds and very large hail across the
northern High Plains late this afternoon into early tonight.
...Northern High Plains this afternoon into tonight...
Water-vapor imagery this morning shows a mid- to upper-level low
over the Vancouver/Washington coast with a large-scale trough
enveloping much of the West. Strong cyclonic 500-mb flow will
extend through the base of the trough and into parts of the northern
High Plains later today coincident with the ejection of a lead
disturbance into the western Dakotas. Boundary-layer dewpoints in
the 60s will continue to spread northward from KS/NE to the Dakotas,
east of a deep lee trough/cyclone across the central/northern High
Plains. The moistening will occur beneath a plume of steep midlevel
lapse rates emanating from the Great Basin and north-central
Rockies.
Morning showers and thunderstorms over parts of this region will
move downstream and away from where strong to severe thunderstorm
development is expected later this afternoon, along both the
surface trough/lee cyclone near the MT/ND border and near the Big
Horn Mountains. Some of the stronger initial storms will likely be
supercellular owing to moderate to large CAPE. The risk for large
to very large hail (2-3 inches in diameter) is greatest near the
ND/MT border where supercells are forecast early in the convective
life cycle. A couple of tornadoes are also possible but relatively
large temperature-dewpoint spreads and a transition to upscale
growth may temper the tornado threat. As more storms develop
leading to storm mergers and coalescing outflow, a linear cluster
may potentially develop into a bow echo across western ND this
evening. The NSSL-WRF and some recent HRRR time-lagged solutions
imply this scenario but uncertainty remains due to appreciable model
spread. Nonetheless, the very unstable airmass over western ND
combined with a supercell to linear cluster transition in the
presence of steep low to mid-level lapse rates, lends confidence in
highlighting a corridor over western ND in a level 2 intensity
(locally 80-100 mph gusts). More isolated supercells will also be
possible farther south into western SD/NE where isolated very large
hail and significant severe outflow gusts will be possible.
...TN/southern KY to NC this afternoon...
A series of MCVs in a corridor from south-central KS into MO and
east near the WV/VA border will provide a focus for additional
thunderstorm activity through the day. In areas void of morning
showers/thunderstorms, a very moist boundary layer featuring lower
to mid 70s F surface dewpoints will gradually heat and destabilize
through the mid afternoon. Some enhancement of midlevel flow in
proximity to the MCVs may aid in storm organization primarily in the
form of multicellular clusters. Isolated to widely scattered wind
damage will be the primary risk with this activity, but an isolated
tornado may also occur in the warm advection zone with enhanced
low-level hodograph curvature across TN on the southwest flank of
the western MCV, though confidence in this scenario remains low.
...TX Panhandle into west TX late this afternoon/evening...
Though forcing for ascent will be weak at best this far south,
strong surface heating/mixing along the lee trough/dryline could
support high-based thunderstorm development late this afternoon.
Inverted-V profiles will favor the potential for isolated severe
outflow gusts of 60-75 mph.
..Smith/Jewell.. 06/27/2026
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