Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
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 %
29,374
1,429,074
Cedar Rapids, IA...Rochester, MN...Waterloo, IA...Cedar Falls, IA...Mankato, MN...
SPC AC 050550
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1250 AM CDT Sat Sep 05 2020
Valid 051200Z - 061200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE UPPER MIDWEST...
...SUMMARY...
Scattered thunderstorms with isolated large hail and wind damage may
develop tonight across parts of the Upper Midwest.
...Upper Midwest...
West-northwest mid-level flow will be in place across the
north-central U.S. today into tonight. A subtle shortwave trough is
forecast to move southeastward from southern Canada into the
northern Plains this afternoon and evening. Ahead of the shortwave
trough, moisture advection will occur across the central and
northern Plains resulting in a corridor of instability from northern
Missouri into southeast South Dakota by this evening. Thunderstorm
development will likely take place along the nose of the low-level
jet from northeastern South Dakota into southwest Minnesota during
the mid evening. From late evening into the overnight period,
convective coverage is forecast to expand eastward the upper
Mississippi Valley.
Thunderstorms that develop on the nose of the low-level jet during
the mid to late evening will do so over the top of a sharp capping
inversion. NAM forecast soundings at 06Z in western Minnesota show
moderately instability starting at 700 mb with MUCAPE near 2500
J/kg. Effective shear is forecast to be near 70 kt with mid-level
lapse rates of 7.0 to 7.5 C/km. This environment should support the
development of supercells with large hail. The large hail threat is
expected to be maintained across southern Minnesota during the early
overnight period. Further to the southeast across northeast Iowa,
the surface inversion is not forecast to be as sharp. This may allow
for strong wind gusts to reach the surface associated with
supercells or multicell line segments. The severe threat should
become marginal during the overnight period as the convection moves
eastward into the upper Mississippi Valley.
..Broyles/Cook.. 09/05/2020
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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