Hazard

Criteria

Heavy Rain

WPC Medium Range Marginal/Slight Risk Excessive Rainfalll Outlook (ERO Days 4-5, hazards days 3-4).

Internal experimental Marginal/Slight Risk Excessive Rainfall Outlook first guess (EXP Days 6-8, hazards days 5-7).

Alaska: Variable thresholds based on season, geographic region, and duration

Heavy Snow

40% probability of Moderate snow-related Impacts based on WPC’s Experimental Probabilistic Winter Storm Severity Index

Alaska: Variable thresholds based on season, geographic region, and duration

Heavy Precipitation

Used when both heavy rain and snow criteria are met, or when there is precipitation type uncertainty but either type would meet the criteria if it were to occur. Often used for West Coast Atmospheric River events.

Freezing Rain

40% probability of moderate ice-related impacts based on WPC’s Experimental Probabilistic Winter Storm Severity Index

Hazardous Heat

40% probability of exceeding widespread NWS Heat Advisory criteria

Alaska: High temperature thresholds ranging between 70-90 degrees during the Summer months

Frost/Freeze

40% probability of low temperatures < 36 (frost) or < 32 (freeze) during transition seasons

High Winds

40% probability of gusts greater than 55 mph (48 knots)

Alaska: Variable thresholds between 40 - 55 knots based on geographic region

Significant Waves

Greater than 20 foot waves along coast or nearby waters

Severe Thunderstorms

Based on Storm Prediction Center medium range severe weather outlooks of 15% or greater

Drought

Areas at or above D2 on the U.S. Drought Monitor

Flooding likely, possible, or occurring

WPC Flood Outlook

Critical Wildfire Risk

SPC medium range fire weather outlooks