181
ACUS01 KWNS 170100
SWODY1
SPC AC 170059

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0759 PM CDT Mon Sep 16 2024

Valid 170100Z - 171200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN PLAINS...

...SUMMARY...
Thunderstorms capable of severe wind gusts and isolated large hail
will be possible this evening across parts of the northern Plains.
An isolated tornado threat will continue across parts of eastern
North Carolina. A marginal severe threat may continue in parts of
the Four Corners region.

...Northern Plains...
Southwest mid-level flow is evident on water vapor imagery over the
north-central U.S. A shortwave trough appears to be in northern
North Dakota, where the RAP is analyzing a distinct vorticity max.
At the surface, a low is in southeast Montana with a warm front
extending east-northeastward across central and northeast North
Dakota. Scattered thunderstorms are ongoing to the north of the
front from northern North Dakota into northwest Minnesota. This
activity is located along and to the north of an axis of moderate
instability, where the RAP has MLCAPE in the 2000 to 3000 J/kg
range. Near this convection, regional WSR-88D VWPs have 0-6 km shear
around 35 knots, with a substantial amount of directional shear in
the low to mid-levels. RAP forecast soundings in the same area have
steep 700-500 mb lapse rates. This environment will support a
potential for supercells with isolated large hail and severe wind
gusts. Organized bowing line segments with a wind-damage threat will
also be possible, especially in areas where low-level lapse rates
are steep due to warmer surface temperatures. The severe threat will
likely continue through much of the evening, as a strong to severe
line segment moves east-northeastward across north-central and
northeastern North Dakota.

...Eastern North Carolina...
A tropical cyclone will  move northwestward across northern South
Carolina this evening. Rainbands extend from north of the center
east-southeastward across central and eastern North Carolina. The
latest RAP has moderate instability in place along much of the North
Carolina coast, with MLCAPE in the 1000 to 2000 J/kg range. The
Moorehead City WSR-88D VWP has a gradually veering wind profile from
the surface to about 4 km, with 0-3 km storm-relative helicity
around 320 m2/s2. This suggesting the environment will be favorable
for rotating storms and possibly tornadoes. The tornado threat will
be maximized with cells that remain semi-discrete and are close to
the coast where surface dewpoints are higher. The threat is expected
to gradually shift northward into the Cape Hatteras area by late
evening.

...Four Corners Region...
According to water vapor imagery, a mid-level low is located over
northern California, with southwest flow from much of the Desert
Southwest into the central Rockies. The RAP has a pocket of
instability near the Four Corners with another in eastern Arizona.
Isolated to scattered thunderstorms are ongoing in these areas.
Moderate deep-layer shear and steep lapse rates should be enough for
a marginal severe this evening, with isolated severe winds and hail
as the primary threats.

..Broyles.. 09/17/2024

$$