Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
15 %
16,446
187,161
No Major Population Center in Risk Area
5 %
53,698
5,317,755
Columbia, SC...Duluth, MN...North Charleston, SC...Rock Hill, SC...Sumter, SC...
Probabilistic Large Hail Graphic
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
SPC AC 251239
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0739 AM CDT Fri Sep 25 2020
Valid 251300Z - 261200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING
ACROSS EXTREME NORTHERN WI AND WESTERN UPPER MI...
...SUMMARY...
A couple of tornadoes, damaging winds, and large hail will be
possible this evening across extreme northern Wisconsin and western
Upper Michigan.
...Lake Superior vicinity this evening...
A series of low-amplitude shortwave troughs will progress eastward
from the northern Rockies/northern Plains to the upper Great Lakes
by tonight. At the surface, a remnant lee cyclone in SD will move
east-northeastward in advance of the shortwave troughs/height falls,
and will reach western Lake Superior this evening. To the east of
the cyclone, a warm front will develop northward to near the
southern shore of Lake Superior by late afternoon. Surface
temperatures in the 70s and boundary-layer dewpoints increasing into
in the low 60s along and south of the warm front will contribute to
MLCAPE near 1500 J/kg.
The stronger forcing for ascent will likely be confined to the warm
front (near the path of the surface cyclone), with areas farther
south in the warm sector potentially remaining capped given the
modest moisture return. Thus, the more probable corridor for
near-surface-based storms will be across extreme northern WI into
western Upper MI late this afternoon into this evening (22-00z).
The storm environment will conditionally favor supercells given the
moderate buoyancy and large, curved hodographs with effective bulk
shear of 50-60 kt and effective SRH in excess of 300 m2/s2. There
will be a few hour window of opportunity for a couple of tornadoes,
damaging winds, and large hail, with the threat expected to diminish
after about 03z.
...SC and vicinity today...
The remnants of tropical cyclone Beta have phased with a midlevel
shortwave trough over the southern Appalachians. The surface
reflection has weakened during the past 24 hours, but there will
still be a baroclinic zone to focus thunderstorm development today
across the Carolinas. Midlevel lapse rates will remain poor, but
low-level and deep-layer vertical shear will be sufficient for a
low-end supercell threat with isolated damaging gusts and a brief
tornado.
..Thompson.. 09/25/2020
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
| 
)
