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Storm Prediction Center (SPC) Convective Outlooks

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SPC Watches

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Severe Weather Reports

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Click on a map to read the reports of severe weather received by the SPC.

Maps

SPC Mesoanalysis Maps

SBCAPE MLCAPE MUCAPE LCL Height
LFC Height 0-6 km shear 0-1 km shear 0-1 km storm-relative helicity
  • Convective Available Potential Energy (CAPE): CAPE is the amount of positively buoyant area on an upper-air sounding that can be converted into updraft velocities. On a sounding, this is found by looking at the area enclosed by the parcel temperature on the right (warmer) and the environmental temperature on the left (colder). If the parcel temperature is cooler than the environmental temperature, this is called negative buoyancy or convective inhibition (CIN or CINH). Generally, the larger the CAPE, the more intense thunderstorms can become, with values of over 1,000 J kg-1 considered sufficiently large for thunderstorms, and values of over 2,000 J kg-1 for severe thunderstorms. The units of CAPE are Joules of energy per kilogram of air (J kg-1).
  • Surface-Based CAPE (SBCAPE): CAPE computed using a parcel of air originating from the surface. This value is best once thunderstorms are underway and surface-based.
  • Mixed Layer CAPE (MLCAPE): CAPE computed using a parcel originating from a well-mixed boundary layer. This value is best in the afternoon before thunderstorm initiation.
  • Most Unstable Layer CAPE (MUCAPE): CAPE computed using a parcel originating from the most unstable layer in the atmosphere. This value is best used when elevated thunderstorms (storms based above the boundary layer) are expected.
  • Lifted condensation level (LCL): the altitude at which a lifted parcel becomes saturated and water vapor begins to condense. Practically speaking, this is where cloud bases are usually found (relative humidity = 100%). Values of less than 1,500 meters are generally preferred.
  • Level of free convection (LFC): the altitude at which a lifted parcel becomes positively buoyant (i.e. its temperature is warmer than the environmental temperature). Once a parcel reaches this level, it can freely rise from buoyany alone. Values of less than 2,000 meters are usually preferred.
  • Wind shear: change in wind speed and direction with altitude. High wind shear environments tend to be supportive of severe thunderstorms since the wind shear acts to tilt the updraft, preventing the cold, descending outflow from interfering with the warm, ascending inflow, allowing the storm to grow more intense. 0-6 km shear tends to be most important for severe and supercell thunderstorm development, with values of over 35 knots (about 40 MPH) being ideal. 0-1 km shear tends to be most important for tornadic development, with values of over 15 knots (about 18 MPH) being ideal.
  • Storm-relative helicity: the amount of horizontal "spin" in the atmosphere (due to wind shear) that can be ingested and tilted into a thunderstorm updraft, leading to tornadic development. Values of over 100 m2 s-2 are generally considered ideal.

Surface Conditions

Temperature Dewpoint Temperature 10 meter winds Sea-level pressure
More maps are available in the map room

Mesoanalysis Maps

Temperature Dewpoint Surface winds Sea-level pressure
Convective Available Potential Energy (CAPE) Convective Inhibition (CINH) Surface Convergence Surface Equivalent Potential Temperature (Theta-E)

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