High-Resolution Rapid Refresh model — 3 km resolution, updated hourly

Mesoanalysis parameters help forecasters and storm chasers assess the atmospheric environment for severe weather. Each product is updated hourly from the HRRR model or the SPC. Tap any card to view the live map.

Convective Available Potential Energy calculated using a surface air parcel. The primary measure of atmospheric instability — higher values fuel stronger updrafts.

• 1,000–2,500 J/kg: Moderate instability
• 2,500+ J/kg: Significant severe threat
• Updated hourly via HRRR model

CAPE calculated from the most unstable parcel in the lowest 300mb of the atmosphere. Better captures elevated instability and is the preferred parameter for severe weather.

• More sensitive than SB-CAPE alone
• Key for elevated convection events
• Elevated parcels can produce strong storms even with capped surface

Convective Inhibition — the energy that must be overcome before convection can initiate. High CIN suppresses storm development even when CAPE is large.

• 0 to -25 J/kg: Weak cap, storms fire easily
• -50 to -200 J/kg: Moderate cap, storms need a trigger
• Below -200 J/kg: Strong cap, convection unlikely

The rate of temperature decrease with height in the mid-levels. Steep lapse rates indicate a conditionally unstable atmosphere capable of supporting large hail and strong updrafts.

• 7+ °C/km: Steep, supports large hail
• 8+ °C/km: Very steep, extreme hail threat
• Key ingredient for the Significant Hail Parameter

Temperature decrease in the lowest 3 km of the atmosphere. Steep low-level lapse rates enhance boundary layer instability and increase tornado potential near the surface.

• 7.5+ °C/km: Favorable for tornado development
• Steep near-surface lapse rates = better surface inflow
• Part of several tornado composite parameters

Change in wind speed and direction across the lowest 6 km (deep-layer shear). Determines storm mode — whether thunderstorms become organized supercells or disorganized clusters.

• 25–35 kt: Organized multi-cell storms possible
• 35–50 kt: Supercell and bow echo potential
• 50+ kt: Classic supercell environment

Wind shear in the lowest 1 km. Critical for tornado potential — larger low-level shear tilts updrafts, helps separate inflow from outflow, and promotes stretching of vorticity near the ground.

• 20+ kt: Favorable for tornadoes with supercells
• 30+ kt: Significant tornado environment
• Combine with SRH for full picture

Measures the potential for storm rotation in the lowest 1 km. One of the most important tornado parameters — higher values indicate stronger rotational potential near the surface.

• 150–299 m²/s²: Significant tornado threat
• 300–499 m²/s²: Extreme tornado threat
• 500+ m²/s²: Violent tornado potential

A multi-ingredient index combining MUCAPE, 0–6km shear, and 0–3km SRH. Identifies areas favorable for supercell thunderstorms — the parent storm of most significant tornadoes and large hail events.

• 1–4: Supercell possible
• 4–8: Significant supercell environment
• 8+: Exceptional supercell potential

Combines SB-CAPE, 0–6km shear, 0–1km SRH, and low-level lapse rates into a single index for violent tornado (EF2+) potential. Developed and used operationally by the SPC.

• 1–2: Significant tornado possible
• 2–4: High-end tornado threat
• 4+: Extreme, potentially violent tornadoes

SPC Mesoscale Discussions are issued by the Storm Prediction Center to highlight areas of significant weather potential in the near term — typically 1–3 hours before a watch is expected. They are one of the most actionable products for storm spotters and chasers.