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
Providence, RI...Toms River, NJ...New Bedford, MA...Fall River, MA...Plymouth, MA...
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 220100
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0800 PM CDT Sat Jul 21 2018
Valid 220100Z - 221200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHEAST AND NORTHERN HIGH PLAINS...
A few severe storms remain possible across parts of the Southeast
and northern High Plains this evening. A strong storm or two will
also be possible late tonight across the Mid-Atlantic and southern
Scattered strong to severe thunderstorms are persisting within
northwesterly flow along the southern fringe of a deep mid-level
trough. Where prior convection has not overturned the low/mid-level
air mass, clusters of multi/supercells will remain possible for a
few more hours this evening into early tonight. The highest severe
potential may be focused near the Georgia/Alabama border, where
westerly deep-layer flow, sufficient effective shear, and
moderate/strong buoyancy should maintain a southward-moving cluster
of strong/severe cells. Large hail and damaging winds will continue
to be the primary threat. Over time, this cluster should encounter
an increasingly hostile thermodynamic environment, though, resulting
in a gradual downturn in intensity.
The primary severe threat will exist ahead of a severe cluster of HP
supercells progressing south/southeast over western North Dakota
this evening. Although convective inhibition will increase with both
time and southeastward extent, a rather mature cold pool should
encourage new, robust updrafts into early tonight, considering the
steep mid-level lapse rates noted in the 12Z UNR sounding. Farther
south, isolated/widely scattered severe storms, capable of large
hail and damaging winds as well, may also continue into at least
A strengthening low-level jet and surface destabilization associated
with an approaching warm front are forecast to yield a conditional
threat of a brief tornado across coastal areas late tonight. Enough
low-level instability will be present to foster this threat (via
stretching of near-surface vorticity), although warming/drying near
700mb may limit deep updraft acceleration and dampen the threat
some. Any potential tornado threat should maximize around 06-12Z.
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z