Convective SIGMETs (WST) are issued in the conterminous U.S. for any of the following:

Severe thunderstorm due to:

surface winds greater than or equal to 50 knots

hail at the surface greater than or equal to 3/4 inches in diameter

tornadoes

Embedded thunderstorms

Line of thunderstorms

Thunderstorms greater than or equal to VIP level 4 affecting 40% or more of an area at least 3000 square miles

Any Convective SIGMET implies severe or greater turbulence, severe icing, and low level wind shear. A Convective SIGMET may be issued for any convective situation which the forecaster feels is hazardous to all categories of aircraft. WST warning areas or lines appear in red, outlooks appear as light green polygons.

Back to SIGMETs