12-HR UNCONDITIONAL PROBABILITY OF SEVERE WEATHER: The probability that a severe thunderstorm will occur in the 12 hours ending at the
specified time. A severe thunderstorm is one with wind gusts
of 50 kts or greater and/or hail 3/4 inch or more in diameter and/or tornadoes.
This probability is created by multiplying the probability of thunderstorms
by the conditional probability of severe weather