What is POP?

POP stands for Probability of Precipitation. Probability of precipitation refers to the percent chance that a specific location (i.e., the local airport) will receive measurable precipitation (.01 inch of rain or melted snow) in these type of weather conditions. For example, on ten days when the weather is similar to today's, the airport will receive at least .01 inches of rain on four of those days if the chance of rain is 40%.

Expressions of Uncertainty:
No mention of Precipitation < 20%
SLIGHT CHANCE 20%
CHANCE 30%,40%
GOOD CHANCE 50%
LIKELY 60%,70%
Unqualified > 70%

Expressions of areal coverage:
ISOLATED or FEW < 15%
WIDELY SCATTERED 15% to 24%
SCATTERED 25% to 54%
NUMEROUS, WIDESPREAD > 54%

Expressions of Intensity: Rainfall Rate:
VERY LIGHT, SPRINKLES, NA
DRIZZLE, FLURRIES NA
LIGHT < .10 inch per hr
MODERATE (or no qualifier) 10 to .30 inch per hr
HEAVY > .30 inch per hr

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