* Exception to wind speed less than 10 mph is the "low level" (surface to 2000 ft agl) jet around 15 to 25 mph with winds generally decreasing to an average of less than 15 mph through 2000 to 6000 ft agl. PLUME DOMINATED FIRES REQUIRE DENSE, HEAVY, DRY FUELS TO PRODUCE THE ENERGY RELEASE TO ALLOW THE PLUME TO BUILD.

In the absence of the DENSE, HEAVY, DRY fuels (e.g., only grasses present), the Risk Category is 1 for humidity from 15 to 45 percent with winds below 10 mph. It is a Risk Category 2 if the humidity is below 15 percent and winds below 10 mph in the absence of DENSE, HEAVY, DRY FUELS.

DRY THUNDERSTORMS ARE HIGH BASED THUNDERSTORMS WITH LESS THAN 0.1 INCH PRECIPITATION. LOW LEVEL HUMIDITY AT OR BELOW 45 PERCENT.

Dry thunderstorms ( 5 to 10% probability)- Risk Category 1

Dry thunderstorms (10 to 20 % probability)- Risk Category 2

Dry thunderstorms (20 to 30% probability)- Risk Category 3

Dry thunderstorms (30 to 50% probability)- Risk Category 4

Dry thunderstorms (> 50% probability)- Risk Category 5