NOAA's National Weather Service - Birmingham, Alabama

· Red Flag Warning (RFW)
A "Red Flag Warning" is issued when the heat index will reach 110 degrees or higher for 2 consecutive days, with temperatures not getting cooler than 75 degrees at night. An "Excessive Heat Warning" is issued when the heat index will reach 115 degrees or higher for 2 consecutive days, with temperatures not below 75 degrees at night.
· Heat Advisory (NPW)
A "Heat Advisory" is issued when the heat index will reach 110 degrees or higher for 2 consecutive days, with temperatures not getting cooler than 75 degrees at night. An "Excessive Heat Warning" is issued when the heat index will reach 115 degrees or higher for 2 consecutive days, with temperatures not below 75 degrees at night.
· Freeze Warning (NPW)
A"Freeze Warning" will typically be issued in the spring or fall growing season if temperatures are expected to be at or below 32 degrees Fahrenheit for at least 3 consecutive hours. In the fall, this advisory will be issued until a killing freeze occurs. Other freeze warnings may be issued for pipe-bursting freezes, and freezes after spring vegetation is already in bloom.
· Wind Chill Advisory (NPW)
A "Wind Chill Advisory" is issued when cold temperatures and breezy winds combine to create a wind chill below zero for an hour or more. If wind chills drop below -10, a "Wind Chill Warning" will be issued.
· Wind Advisory (NPW)
A "Wind Advisory" is generally issued for sustained winds of 24 to 39 mph that will persist for an hour or more. If caution is not exercised, the wind could be hazardous to high profile vehicles.
· High Wind Watch (NPW)
A "High Wind Watch" is an alert to the potential for sustained winds of 40 mph or higher, and gusts equal to or greater than 58 mph. A watch may be issued from 12 to 48 hours in advance of the occurrence of the event.
· High Wind Warning (NPW)
A "High Wind Warning" is issued for sustained winds of 40 mph or higher, for 1 hour or longer, and gusts equal to or greater than 58 mph.
· Dense Fog Advisory (NPW)
A "Dense Fog Advisory" is issued when widespread visibilities are expected to be 1/4 mile or less for any extended period of time. If temperatures are below freezing, ice could form on bridges and overpasses.