The coming winter storm: There’s an app for that. But how reliable is it and what’s inside?

Smartphone weather apps that summarize their forecasts with eye-popping numbers and bright icons may be handy during mild weather, but meteorologists say it’s better to listen to human expertise during multi-faceted, dangerous winter storms like the one blowing through the U.S.

The multistate storm’s combination of heavy snow, treacherous ice and subzero temperatures shows why it’s best to seek out forecasters who can explain its nuances via local TV or radio newscasts, online livestreams or detailed websites...