SPC AC 161723
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1223 PM CDT Sun Jul 16 2017
Valid 171200Z - 181200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL SOUTH
DAKOTA INTO NORTHERN MINNESOTA...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
PENNSYLVANIA ACROSS MUCH OF NEW YORK AND VERMONT...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
THE NORTHERN PLAINS AND VICINITY...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS NEW YORK
AND WESTERN NEW ENGLAND SOUTHWARD ACROSS THE APPALACHIANS...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN
A few severe thunderstorms are expected Monday afternoon and evening
from South Dakota into northern Minnesota, and during the day from
Pennsylvania into New York and Vermont. Isolated severe storms are
expected from Wyoming into Nebraska, across the Appalachians, and
across southern Arizona.
A broad upper trough will move eastward across south central Canada,
with strong westerly flow aloft affecting the northern Plains. To
the east, a weak upper trough will stretch from New England
southward across the Appalachians, with cool temperatures aloft and
weak flow. At the surface, a moist air mass will exist from the
Plains eastward to the Atlantic coast, the exception being over the
upper Great Lakes where high pressure will exist. A deepening
surface trough over the northern Plains will provide the main focus
for severe storms producing large hail or locally damaging wind
gusts. Elsewhere, isolated gusty winds are possible over AZ late in
...Northern Plains and vicinity...
A deepening surface trough and strong heating will provide a focus
for severe storm development, most probable from the Dakotas into MN
during the late afternoon and evening. Hot temperatures across SD
suggest gusty winds likely. The strongest winds aloft will be over
ND and MN, where large, perhaps very large hail is possible along
with damaging winds. Other localized clusters of severe storms are
possible into central NE, and extending westward across the Black
Hills and into WY.
Cool air aloft with the upper trough will result in steep lapse
rates for this time of year, and this will in turn maximize updraft
potential. Daytime heating and sufficient convergence within a
surface trough will result in scattered storms. Although wind
profiles will be weak, they will veer with height, supporting
perhaps a few supercells. Substantial instability will further
support a severe risk, most likely in the form of large hail. Storms
should form relatively early given lack of any capping.
Farther south across the Appalachians, heating combined with cool
temperatures aloft will result in scattered afternoon storms capable
of marginal hail.
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