- Day Three
acus03 kwns 240730
Storm Prediction Center ac 240729
Day 3 convective outlook
National Weather Service Storm Prediction Center Norman OK
0229 am CDT Thursday Jul 24 2014
Valid 261200z - 271200z
..there is a slight risk of severe thunderstorms from the Central Plains to the Ohio
Valley/lower Great Lakes...
Clusters of severe storms will be possible from the central Great
Plains to the Great Lakes and central Appalachians.
A vigorous middle-level cyclone over the southern prairie provinces will
accelerate southeast into the upper Midwest by early sun. A broad belt of
strong middle-level westerlies should be prevalent from the northern plains to the
lower Great Lakes. At the surface...a quasi-stationary front should
be draped across parts of the Central Plains to lower Great Lakes. An
occluded front will extend S of the primary Canadian cyclone across
the upper Midwest.
..cntrl plains to Ohio Valley/lower Great Lakes...
S of the quasi-stationary front...a strong to extremely unstable air
mass should be present from parts of the Central Plains to Midwest as
the plains eml plume is advected east towards the northern Appalachians.
Warm air advection-driven elevated thunderstorm clusters should be ongoing at 12z/Sat over
parts of the Midwest. In the wake of this activity...capping should
largely inhibit surface-based thunderstorm development until late day. The
degree of inhibition should generally be less compared to d2...owing
to minor height falls and cooler 700 mb temperatures /especially east
of the MS river/.
Scattered clusters of storms should form by evening within the
frontal zone. Given the degree of instability...along with
strengthening deep-layer shear...an organized mesoscale convective system or two may
develop. Large hail will be most probable during the late afternoon
and evening...with potential for one or more swaths of damaging
winds during the evening into Sat night. If shorter-term mesoscale
predictability increases...corridors of higher severe probabilities
may become evident in later outlooks.
..upper MS valley...
Deep-layer shear will be favorable for organized convection along
the occluded front Sat afternoon/evening. The primary uncertainties
are -- 1) Richer low-level moisture remaining S of the Central Plains
to Midwest front...2) potential elevated storms over South Dakota late d2
hindering diurnal destabilization and 3) strength of convergence
along the occluded front. Still...an isolated severe hail and
locally damaging wind threat appears possible.