614
ACUS01 KWNS 181235
SWODY1
SPC AC 181233

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0733 AM CDT Wed Sep 18 2024

Valid 181300Z - 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...
Water-vapor imagery depicts a mid-level low over southeast MT this
morning and this feature will continue northeastward during the
period and reach southeastern SK by early Thursday morning.  A
mid-level ridge extending northward from the northwest Gulf Coast
into the upper MS Valley will slowly shift eastward into the Upper
Great Lakes.  A ribbon of stronger southwesterly mid-level flow will
extend from southern CA through the central High Plains and wrapping
cyclonically through the eastern Dakotas and into southern Canada.

In the low levels, a surface trough will be the primary feature of
interest with a plume of 60s deg F dewpoints extending northward to
the east of the boundary from the southern Great Plains into the
Upper Midwest.  In wake of early day dissipating shower/thunderstorm
activity (e.g., eastern Dakotas, southern KS), heating of an
adequately moist boundary layer will result in moderate
destabilization by mid afternoon (1500-2500 J/kg SBCAPE).  Isolated
to scattered thunderstorms are forecast within a zone of 25-40 kt
0-6 km shear.  Some model guidance varies on storm coverage across
the Slight Risk (isolated vs. scattered) but forecast sounding
profiles indicate a risk for organized storms mainly in the form of
organized multicells and supercells.  Hail/wind may accompany the
stronger storms during the late afternoon through the early evening
before this activity begins to weaken.

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.  Warmer
mid-level temperatures and limited large-scale ascent than farther
north will likely contribute to tempering the overall intensity of
the updrafts and resultant severe intensity/coverage.  Models
suggest perhaps locally higher storm coverage and resulting
severe-wind threat from the TX Panhandle north-northeast into far
southern KS during the late afternoon/early evening.

..Smith/Mosier.. 09/18/2024

$$