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.)
Some Larger Population Centers in Risk Area
Sioux Falls, SD...Fargo, ND...Sioux City, IA...St. Cloud, MN...Grand Island, NE...
Wichita, KS...Newark, NJ...Jersey City, NJ...Fort Wayne, IN...Akron, OH...
SPC AC 131957
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0257 PM CDT Tue Jun 13 2017
Valid 132000Z - 141200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
EASTERN SD/ND...EASTERN NE...WESTERN MN...AND NORTHWEST IA...
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PORTIONS
OF THE EASTERN TX PANHANDLE AND WESTERN OK...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER SOUTHERN NEW
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
SOUTHERN GREAT LAKES TO SOUTHERN NEW ENGLAND...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE
Severe thunderstorms, capable of large hail, damaging winds, and a
few tornadoes, will be possible across the northern Plains and upper
Mississippi Valley this afternoon and evening. Farther south across
the central/southern Plains, scattered severe storms, primarily
capable of large hail and damaging winds, are expected through the
evening hours. Isolated severe storms will also be possible across
southern New England.
Minor changes have been made to the severe risk areas in the central
US, mainly to adjust the higher threat area slightly westward into
central parts of South Dakota and Nebraska where visible imagery
indicates cumulus clouds deepening along the surface convergence
boundary. Otherwise the current outlook addresses the threat areas
well and no other changes have been made. See Mesoscale Discussion
1013 for more details regarding near-term severe storm threat in the
northern plains, and Mesoscale Discussion 1011 for details over the
southern high plains.
...Southern New England...
The Slight Risk area has been adjusted westward toward the Hudson
River where strong/severe storms have recently developed. There
remains a possibility of isolated severe storms developing over the
next few hours before activity diminishes this evening.
...Southern Great Lakes eastward toward southern New England....
The Marginal Risk area has been extended westward and refined based
on visible satellite imagery showing locations of primary outflow
boundaries, lake breeze convergence zones, and boundary
intersections that are providing foci for additional strong
thunderstorm development. The winds aloft and associated vertical
shear above this corridor is modest at best resulting in loosely
organized small thunderstorm clusters with updrafts tending to
exhibit pulse characteristics. Brief hail and locally strong wind
gusts may accompany the stronger storms into the evening hours.
.PREV DISCUSSION... /ISSUED 1122 AM CDT Tue Jun 13 2017/
An upper cyclone continues to affect the central/northern Rockies
today, while a series of shortwave troughs rotate through the base
of the cyclone and into the central/northern Plains. Strong daytime
heating and rich low-level moisture will result in high CAPE values
this afternoon along and east of a surface front/dryline extending
from the central Dakotas into KS. Models are consistent in the
development of thunderstorms along the boundary by late afternoon,
tracking eastward across the ENH/SLGT risk areas. Supercells
capable of large hail and a tornado or two are initial threats, but
most 12z model solutions suggest a fairly rapid transition to bowing
structures, with damaging winds becoming the dominant concern as
storms move into MN.
Have maintained a small 10% tornado risk area over parts of
MN/SD/ND. Rapid recovery behind the morning MCS should result in a
corridor of favorable environment later today. Forecast soundings
in this region show backed low-level winds and strong CAPE.
However, confidence in discrete storm initiation along the warm
front has decreased from previous outlooks, and will be re-addressed
Full sunshine along the surface dryline/front over west TX/OK and
parts of KS will result in strong CAPE and scattered thunderstorm
development by late afternoon. Deep-layer vertical shear will
promote rotating storms, with large hail /possibly very large/ and
damaging wind gusts possible. Given the consistency in 12z model
guidance regarding the timing/placement of convective development,
have added a narrow ENH risk zone to parts of western OK and the TX
Visible satellite imagery shows strong heating occurring over
southern New England today, where surface dewpoints are in the mid
60s. Scattered thunderstorms are likely to develop this afternoon
as a mid-level trough approaches from the northwest. Forecast
soundings are not particularly impressive, with only moderate lapse
rates and rather weak low-level winds. However, sufficient CAPE and
deep layer vertical shear suggest the risk of a few intense cells
capable of hail and damaging wind gusts.
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