U.S. Severe Weather Forecast (Convective Outlook)

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. 

.Grams.. 07/24/2014