The NOAA Storm Prediction Center issues convective outlooks for Days 1 through 8, ranking severe thunderstorm potential in five categories: Marginal, Slight, Enhanced, Moderate and High. A Slight risk is not “slight danger” — it means organized severe storms are expected, just fewer of them. Moderate and High days are the ones that make history; take them seriously.
When conditions sharpen inside the outlook window, SPC issues mesoscale discussions — short-fuse technical notes that often precede a tornado or severe thunderstorm watch by 30 to 90 minutes. If a mesoscale discussion box appears over your county, that is your cue to pay attention before any warning exists.
The fuel gauge behind it all is CAPE — convective available potential energy. Values above 1,000 J/kg support strong storms; above 3,000 J/kg with wind shear, the atmosphere is loaded. Watch the interactive CAPE map above, then check what the day looks like from a chaser’s seat on the storm chasing page, or get your own county’s outlook on My Weather.
ECMWF vs GFS, side by side and interactive.
SPC short-fuse guidance and active watches, decoded.
The 3-day national picture without jargon.
