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.
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.
Day 1 Hail Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
15 %
34,593
176,518
Rapid City, SD...Rapid Valley, SD...Sturgis, SD...
5 %
127,330
2,633,503
Omaha, NE...Lincoln, NE...Council Bluffs, IA...Ames, IA...West Des Moines, IA...
SPC AC 261629
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1129 AM CDT Sat Aug 26 2017
Valid 261630Z - 271200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS UPPER TX GULF
COAST...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS WESTERN SD AND
NORTHERN NE...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS UPPER TX GULF
COAST AND FAR SOUTHWEST LA...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS NORTHERN/CENTRAL
GREAT PLAINS TO IA...
...SUMMARY...
A few tornadoes are possible over the Upper Texas Coastal Plain
through early Sunday. Widely scattered large hail and severe wind
storms are possible across western South Dakota into northern
Nebraska late afternoon and evening.
...Western Gulf Coastal Plain...
At least a low-end tornado threat should continue through the period
within persistent outer bands of TC Harvey, on the periphery of
sufficient low-level shear for transient mesocyclones. This risk may
increase late afternoon into evening if weak diabatic heating can
persist amid thinner cloud coverage between the ongoing outer band
over the Upper TX Coastal Plain and the inner stratiform core over
the Middle TX Coastal Plain. Should this occur within more favorably
enlarged low-level hodographs, a secondary wave of transient
supercell structures may develop within a relatively confined
corridor of the Upper TX Coastal Plain. Refer to MCD 1573 for
additional short-term information.
...Western SD to northern NE...
Downstream of a subtle mid-level impulse across eastern MT/far
western ND, robust diabatic heating is underway which should yield
MLCAPE of 1000-2000 J/kg amid surface dew points mixing into the 50s
by late afternoon. Widely scattered storm development should occur
in this time frame. Veering of the wind profile with height
augmented by moderately fast mid/upper-level west-northwesterlies
will foster a few supercells with large hail as the initial primary
hazard. These may congeal into a southeast-moving cluster into parts
of northern NE with a mixed risk of severe wind/hail before
gradually waning tonight.
...IA to central High Plains...
More isolated coverage of severe wind and hail is anticipated along
a weak cold front that should become quasi-stationary. The greatest
low-level convergence should occur across the Mid-MO Valley portion
of the boundary aided by a shortwave impulse drifting across the
Upper MS Valley. This should be sufficient to overcome MLCIN and
yield widely scattered storms late afternoon to mid-evening. Modest
veering of the wind profile with height could support a short-lived
cluster with isolated severe hail/wind.
..Grams/Cohen.. 08/26/2017
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z
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