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.)
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.
SPC AC 110557
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1257 AM CDT Fri May 11 2018
Valid 111200Z - 121200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
SOUTHEAST WYOMING AND ADJACENT NORTHEAST COLORADO AND SOUTHWEST
PARTS OF THE NEBRASKA PANHANDLE...
Isolated thunderstorms with accompanying large hail and wind
potential will be possible across parts of the central High Plains
this afternoon and evening. A stronger/marginally severe storm or
two may also occur over a portion of the southern High Plains
vicinity, and across the upper Ohio Valley area.
Fast west-northwesterly flow aloft will prevail across the Midwest
and Northeast, north of a southeast U.S. ridge and east of a large
upper trough evolving over the western states. Within the broader
cyclonic flow, a closed low is forecast to dig southward into the
Great Basin through the period.
At the surface, a wavy frontal zone should extend from the central
High Plains across Kansas and northern Missouri into/across the
Midwest, while a cold front crosses the Great Basin and vicinity.
Elsewhere, high pressure will prevail over the Southeast.
...Southeast Wyoming into parts of northeast Colorado and adjacent
parts of the Nebraska Panhandle...
Easterly upslope flow to the cool side of the surface boundary in
conjunction with modest destabilization should support development
of isolated thunderstorms -- perhaps as far west as south-central
Wyoming nearer the eastern fringe of the upper low. Flow veering
with height to southwesterly at mid levels will yield shear
sufficient for organized storms, and thus a few of the
stronger/rotating cells will likely pose a risk for locally damaging
winds and/or hail. Risk should remain confined to the High Plains,
as an increasingly capped airmass with eastward extent should prove
hostile for migration of convection off the higher terrain.
...Eastern portions of the Texas and Oklahoma Panhandles into parts
of southwest Kansas and western Oklahoma...
Deep diurnal mixing near the dryline, and a moderately unstable
airmass farther east, may support development of a couple of
thunderstorms over eastern portions of the Texas and Oklahoma
Panhandles/southwest Kansas vicinity by late afternoon. Capping
should prohibit more widespread convective development, but
potential for wind damage associated with evaporatively aided gusts
appears sufficient to maintain a small MRGL risk area. Convection
should rapidly diminish after sunset, as the boundary layer
stabilizes and the capping inversion becomes re-established.
...The upper Ohio Valley vicinity...
As a weak/fast-moving short-wave trough crosses the Midwest, diurnal
heating will contribute to moderate destabilization along the
surface frontal zone progged to lie across the upper Ohio Valley
area. Weak ascent associated with the short-wave feature -- focused
in the vicinity of the front -- may support development of isolated
storms during the late afternoon and early evening hours. With
strengthening/weakly veering flow with height providing ample shear,
one or two of these storms may reach severe levels, with attendant
risk for a locally damaging gust or two, and possibly marginal hail.
Storms should diminish gradually through the evening as they shift
across western Pennsylvania and into the mountains.
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z