Rare Southern U.S. Winter Storm; Dangerous Cold Weather For Much of the Eastern U.S.; Critical Fire Weather for Southern California

A rare winter storm impacting the Southern U.S. will move offshore Wednesday morning. Behind the storm, arctic air will continue encompassing the eastern two-thirds of the Nation with only a slow return to normal temperatures expected by the end of the week. Moderate to strong Santa Ana winds and low humidity will maintain Critical fire weather conditions in southern California into Thursday. Read More >

Dispersion Index Table

DISPERSION INDEX TABLE

Dispersion Index	Interpretation
>100	Very Good (but may indirectly indicate hazardous conditions.)
60-100	Good (typical burning values)
41-60	Fair to Good (climatological afternoon values for most inland forests.)
21-40	Fair (stagnation if accompanied by persistent low wind speeds.)
13-20	Poor to Fair (stagnation, if persistent; better than average for nighttime.)
7-12	Poor (stagnant, but near average at nighttime.)
1-6	Very Poor (climatological nighttime value for most locations.)