Perhaps one of the most underutilized weather products shown on the ForeFlight Map view arethe yellow-shaded polygonscalled convective outlooks. On any given eight-hour shift, theyare issuedhourlyby a highly trained meteorologist at the Aviation Weather Center (AWC) in Kansas City. In fact, convective SIGMETs shown by a red-shaded polygon are also issued by this same forecaster.
Let’s start with convective SIGMETs
Convective SIGMETs(WSTs)define regions of airspace with active areas of thunderstorms that meet specific criteria. The important wordhere is active. In other words, convective SIGMETs represent more of a NOWcast for thunderstorms than a forecast. Here’s the way it works. Each and every hour the convective SIGMET forecaster at the AWC looks for thunderstorms throughout the lower 48 United States and coastal waters that meet specific criteria.A single cell pulse thunderstorm isn’t necessarily hazardousas long as you don’t fly through the same airspace that it occupies. However, when thunderstorms form long lines, are clustered close together in widespreadareas, are embedded or severe, they become more of a threat to aviation and the forecasterwill issue a convective SIGMET for those areas of thunderstormsat 55 minutes past eachhour.
Despite the fact that convective SIGMETs are valid for two hours when issued, the following hour the forecaster will once again evaluate the convective threat and issue a new round of convective SIGMETs. Eachnew issuance at 55 minutes past the hour will supersede the previous set of convective SIGMETs. Effectively, no convective SIGMET will ever exist for two hours.
This is not to say that you must fly around convective SIGMET areas. For a convective SIGMET to be issued, the area of convectionmust contain significant radar echoes that fill aminimum of 40% of the area at least 3,000 square miles or 40% of a line of at least 60 miles in length. This leaves a fair amount of airspaceto navigate through someconvective SIGMET areas.
What about convective outlooks?
First, they are not “outlook SIGMETs” as I’ve seen them called. In fact, they are not SIGMETs at all. Unlike convective SIGMETs, convective outlooks are trulyforecasts; there isn’t arequirement that active thunderstorms existwhen they are issued. Instead, they define larger regions of airspace that are expected to containthunderstorms that meet convective SIGMET criteria in the next two to six hours after the outlook was issued. These may includeongoing areas or lines of convection covered by a convective SIGMET or they may includenew areas or lines of thunderstorms that are expected to develop and reach convective SIGMET criteria in thetwo to six hours valid period.
That two to six hour window is a perfect “sweet spot” for many of us making flights. There may not be any thunderstorms when you go to depart, but if your proposed route takes you through one of these convective outlook areas in the valid time specified you may see one or more convective SIGMETs issued within this outlook area during your flight.
What about ADS-B or SiriusXM?
At the moment, convective outlooks are not broadcast over the ADS-B ground stations and are not part of the SiriusXM satellite weather broadcast. In ForeFlight, we attempt to preserve the latest convective outlooks until they expire six hours later. So be sure to use the Pack feature of ForeFlightprior to departure.
