132
ACUS01 KWNS 180600
SWODY1
SPC AC 180558

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1258 AM CDT Wed Sep 18 2024

Valid 181200Z - 191200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MID MISSOURI VALLEY NORTHWARD INTO EASTERN SOUTH DAKOTA AND
WESTERN MINNESOTA...

...SUMMARY...
Thunderstorms capable of severe wind gusts and isolated large hail
are possible today across parts of the eastern Dakotas and Minnesota
southward in the mid Missouri Valley. A marginal severe threat will
also be possible in parts of the central and southern Plains.

...Northern Plains/Upper Mississippi Valley/Mid Missouri Valley...
An upper-level low will move northeastward through the northern High
Plains today, as an associated mid-level speed max translates
northeastward through the northern Plains. At the surface, a low
will move through northeastern Montana, with a trough extending
southward across the High Plains. To the east of the trough in the
mid Missouri Valley and northern Plains, surface dewpoints will
generally be in the lower to mid 60s F. As surface temperatures warm
today, moderate instability will develop within a narrow corridor
from eastern Nebraska northward into the eastern Dakotas. Isolated
to scattered thunderstorms are expected to form to the east of the
surface trough near the instability axis during the afternoon. These
storms will move northeastward across the eastern portion of the
central and northern Plains during the late afternoon and evening.
RAP forecast soundings at 00Z/Thu near the instability axis at Sioux
Falls, South Dakota have 0-6 km shear in the 30 to 35 knot range.
Some speed shear is evident in lowest 3 km, and low-level lapse
rates are forecast to be steep, peaking in the 7.5 to 8 C/km range.
This environment should support supercell development during the
late afternoon and early evening. Supercells will likely be capable
of producing severe wind gusts and isolated large hail.

Further south into the southern and central Plains, low-levels are
forecast to be drier near the surface trough, with dewpoints
expected to be mostly in the upper 50s and lower 60s F. For this
reason, instability is expected to remain relative weak today. This,
combined with limited large-scale ascent will likely keep any severe
threat isolated and marginal.

..Broyles/Weinman.. 09/18/2024

$$