755
ACUS02 KWNS 261732
SWODY2
SPC AC 261730

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Wed Jun 26 2024

Valid 271200Z - 281200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN
MONTANA...THE WESTERN DAKOTAS...FAR NORTHEAST WYOMING...WESTERN
NEBRASKA...AND EXTREME NORTHEAST COLORADO...

...SUMMARY...
Severe thunderstorms producing gusts to 80 mph, large hail greater
than 2.5 inches, and a couple of tornadoes are possible across parts
of eastern Montana into western portions of the northern and central
Plains Thursday afternoon and evening.

...MT/ND/SD/NE vicinity...

An upper ridge will initially be positioned over the northern High
Plains vicinity on Thursday. The ridge will flatten and shift east
through the period as an upper shortwave trough over the Pacific
Northwest develops east across the northern Rockies. Strong height
falls will result in a deepening surface low over eastern MT during
the day. The low will develop east/southeast into the western
Dakotas during the evening while an associated surface cold front
shifts east across the region into the overnight hours. A surface
trough/dryline will extend southward from the low across the
northern/central High Plains.

South/southeasterly low-level flow will transport 60s F dewpoints
northward across KS/NE and into the Dakotas/eastern MT. Cooling
aloft/steepening midlevel lapse rates atop this moist boundary-layer
will result in a corridor of moderate to strong instability.
Vertically veering wind profiles indicate supercells storm mode will
be possible with initial convection developing during the afternoon.
Initial storms are likely to first develop over higher terrain and
near the surface low in MT, and southward along the dryline in an
area of strong low-level convergence and increasing large-scale
ascent. With time, a southerly low-level jet is forecast to increase
during the evening. Thunderstorm clusters may grow upscale into a
coupe of smaller bowing MCSs from far eastern MT/western Dakotas,
and possibly across western NE. Large instability, a deeply mixed
boundary layer with steep low-level lapse rates, and some dry air
above 700 mb will support strong downdrafts capable of severe to
significant wind gusts. Isolated to widely scattered large to very
large hail (2.5+ inch diameter) also will be possible, especially
with any discrete supercells. As the low-level jet increases toward
evening, low-level SRH will increase and hodographs will become
enlarged, especially near the surface low. A few tornadoes will be
possibly, mainly in the 23-03z time frame.

Severe potential will gradually wane with eastward extent overnight
as capping increases across central/eastern ND/SD/NE.

...Eastern CO/KS into the southern High Plains/northwest OK...

Vertical shear will be more marginal (20-30 kt effective shear
magnitudes) with stronger deep-layer flow remaining displaced
northward. Nevertheless, a narrow corridor for rich boundary-layer
moisture and strong instability will exist along/just east of the
surface dryline. Isolated/widely scattered thunderstorm activity is
expected by late afternoon into the evening. Transient supercells
capable of mainly strong/severe gusts and hail will be possible
during the afternoon/evening. Clustering may occur during the
evening over KS as the low-level jet increases, but strong capping
with eastward extent will likely limit severe potential overnight.

...UT/AZ/NM/western CO/WY...

A relatively moist airmass will be in place, with surface dewpoints
in the upper 40s to upper 50s F common across the region. This will
aid in afternoon destabilization, with MLCAPE up to 750 J/kg
forecast. Vertical shear will support at least transient organized
cells as the area remains on the southern fringe of stronger
mid/upper westerly flow. Isolated strong to severe gusts and
marginal hail will be possible with storms during the afternoon into
mid-evening.

...Eastern Carolinas/Southeast vicinity...

Modest upper troughing will be oriented over the Southeast on
Thursday. A weak surface boundary may sag southward across the
Carolinas/GA while some forecast guidance indicates an MCV may be
located over AL. A very moist airmass will be in place, and strong
heating will aid in a corridor of moderate to strong instability.
The most likely area for a few strong to severe storms will exist
over the eastern Carolinas where strongest instability will align
with modest vertical shear (around 25 kt effective shear
magnitudes). Damaging gusts and isolated hail to near 1 inch
diameter will be possible. Further west across parts of GA and AL,
vertical shear will be very weak (less than 15 kt). This should
preclude organized severe potential further west, but PW values
greater than 2 inches and sufficient instability could result in a
couple of strong gusts.

..Leitman.. 06/26/2024

$$