spc ac 150523
day 1 convective outlook
nws storm prediction center norman ok
1223 am cdt sat aug 15 2020
valid 151200z - 161200z
...there is a slight risk of severe thunderstorms over the central
high plains and northern minnesota...
isolated severe storms capable of large hail and damaging winds will
be possible over the central high plains as well as northern
minnesota. a more marginal risk for a few severe storms will exist
from the great lakes into the midwest region.
...central high plains...
a modest west to northwest upper flow regime will reside across the
central high plains saturday. in the low levels an east-southeast
post-frontal flow regime will become established. this will result
in advection of higher theta-e air beneath steep mid-level lapse
rates, contributing to a corridor of moderate to strong instability
with 2000-3000 j/kg mlcape. weak forcing aloft and a modest capping
inversion may limit thunderstorm coverage. however, at least
isolated storms are expected to develop in this regime and activity
will subsequently spread southeast. effective bulk shear from 30-40
kt will support potential for some supercell structures with
isolated large hail and locally strong to damaging gusts the main
threats. a few storms might evolve into clusters as they develop
southeast into the evening before weakening.
post frontal low-level moisture with dewpoints only in the 50s f
will reside across this region. however, cool temperatures aloft
with -14 c at 500 mb along with diabatic warming of the boundary
layer will contribute to 500-1000 j/kg mlcape. a shortwave trough
embedded in the northern stream will approach this area during the
afternoon, and at least isolated storms will develop. effective bulk
shear from 40-50 kt will support potential for some supercell
structures with large hail and a few strong to damaging gusts the
main threat through early evening.
...great lakes through the midwest...
widely scattered to scattered thunderstorms will likely once again
develop along an eastward-advancing cold front from the great lakes
into the ohio valley and midwest regions saturday afternoon. the
environment will be characterized by moderate instability, but the
stronger winds aloft will remain north and west of the warm sector
with weak vertical shear supportive of multicells. a few storms may
produce locally strong wind gusts and hail through early evening.
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note: the next day 1 outlook is scheduled by 1300z