Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0740 PM CDT Sun Sep 06 2026
Valid 070100Z - 071200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
WESTERN AND CENTRAL MONTANA AND OVER A SMALL PART OF THE LOWER
MISSOURI VALLEY...
...SUMMARY...
Widely scattered large hail occurrences with hailstones up to two
inches are expected over portions of western and central Montana
this evening into tonight. More sporadic occurrences of large hail
and severe wind gusts appear possible over the northern and central
High Plains, and across parts of the lower Missouri Valley.
...Northern Rockies into the northern Plains...
Separate vorticity lobes and associated wind maxima will progress
into the northern Rockies and northern High Plains tonight with a
resultant zone of height falls/forcing for ascent overspreading the
region. In the lower levels, a surface cyclone will be maintained
over southeast MT while a nocturnal jet develops over the northern
and central High Plains.
Thunderstorms currently intensifying over western MT are expected to
increase in coverage and intensity while spreading into
north-central MT ahead of the western vorticity lobe rounding the
base of the Pacific Northwest upper low. While the boundary layer is
somewhat cool/stable, the presence of steep mid-level lapse rates,
MUCAPE up to 1000-1500 J/kg, and 40-45 kt of effective bulk shear
will be supportive of supercells with the primary hazard being large
hail up to two inches.
Farther east, isolated to widely scattered storms have developed
along and ahead of a lee trough and the MT surface low from western
ND into northeast CO within a steep lapse rate and moderately
unstable environment (see the 00Z UNR and LBF soundings). Veering
winds with height with up to 35-40 kt of deep-layer shear are
sufficient to support an observed supercell storm mode with the
primary hazards being large hail potentially in excess of two inches
and locally severe wind gusts. A tornado was recently reported with
a slow-moving supercell over McKenzie County, ND. However, sizable
temperature-dewpoint spreads within the inflow air mass, and the
tendency for increasing convective inhibition in the coming hours
are likely to limit a continuing tornado threat despite increasing
low-level shear.
Storm coverage is expected to remain limited through the remainder
of the evening with a potential increase later tonight with the
arrival of the eastern vorticity lobe and strengthening low-level
jet. As such, the threat for sporadic large hail and severe wind
gust occurrences may linger into the overnight hours from eastern MT
into the western parts of the Dakotas and NE.
For additional information, see recently issued mesoscale discussion
#2259.
...Lower Missouri Valley...
Widely scattered strong to severe storms are ongoing this evening
over parts of southeast NE, northeast KS, and northwest MO with
activity focused along outflow boundaries and a synoptic front in
the area. The inflow air mass remains hot and relatively moist as of
00Z with observed soundings indicating steep low-level lapse rates
with MLCAPE up to 1500-3000 J/kg. The 00Z TOP sounding sampled
around 30 kt of deep-layer shear, which will remain supportive of
episodic supercell structures for the next couple of hours with an
associated risk for large hail and locally damaging wind gusts.
For additional information, see recently issued mesoscale discussion
#2258.
..Mead.. 09/07/2026
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