A winter storm that brings an Arctic blast, snow and ice to Oklahoma hits on Friday, and the wintry conditions will continue into the weekend.

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.

Ever wonder how sleet is formed? This National Weather Service social media post explains it.

According to a Jan. 21 forecast from the National Weather Service in Memphis, this weekend will see bitterly cold temperatures and several chances for sleet, snow and freezing rain. Temperatures are expected to drop and remain low throughout the weekend, while the chance for precipitation nears 100% multiple days.

Here are resources you may need during and after a winter storm.

Snow, sleet and rain are in the Chattanooga forecast with little accumulation expected.

Chances of snow and freezing rain begin on Friday night and last throughout the week in Greenville and Greenwood. The low temperature in Greenville on Sunday morning is expected to be 19 and 20 in Greenwood.