- Day Three
acus02 kwns 210417
Storm Prediction Center ac 210416
Day 2 convective outlook
National Weather Service Storm Prediction Center Norman OK
1116 PM CDT sun may 20 2018
Valid 221200z - 231200z
..there is a marginal risk of severe thunderstorms across parts of
the High Plains and Ohio Valley...
Isolated strong thunderstorms are expected across portions of the
High Plains from West Texas into southeast Montana. A few strong
storms may also develop across the Ohio Valley.
Strong mid-level jet will round the base of Southern California trough
during the day1 period before ejecting into The Four Corners region
and weakening Tuesday. As stronger flow aloft translates into Colorado/nm
downstream upper ridge should be nudged east and the Prospect for
scattered deep convection will increase in the Lee of The Rockies
from West Texas into southeast Montana. Even so, deep-layer shear will be
seasonally weak but likely adequate for the maintenance of a few
robust updrafts, especially given the expected steep lapse rates.
Latest guidance continues to suggest an early-day disturbance
(possibly related to late day1 convection) will eject into West Texas
and convection may be ongoing at the beginning of the period.
Renewed development may take place if sufficient heating can
materialize in the wake of this activity.
Farther north, weak large-scale forcing for ascent should spread
into southwest Wyoming during the afternoon which should contribute to an
easterly boundary-layer component across the plains. This should aid
scattered thunderstorm development that could grow upscale into the
Black Hills region after dark, especially as low level jet increases across
Mid-level heights are expected to fall across the lower Great Lakes
region during the day2 period along the southwestern flank of a
trough that will dig toward New England. Associated surface front
should progress into western Ohio/southern in by 18z and a corridor of
pre-frontal boundary-layer heating is expected to contribute to
instability that will support a few robust thunderstorms. This
activity will be strongly diurnal in nature and gusty winds and
perhaps marginally severe hail are the primary threats.
..maximum risk by hazard...
Tornado: 2% - marginal
wind: 5% - marginal
hail: 5% - marginal