A FREEZING RAIN ADVISORY remains in effect tonight and Thursday morning (purple color). The tan color is a WINTER WEATHER ADVISORY. Those counties will have some sleet mixed in making the roads slick there as well.
UPDATED at 9:55 PM: the winter weather advisory has been cancelled for Bremer, Butler and Franklin.
The atmosphere near Decorah is setting up for when precipitation falls to be rain changing to freezing rain or freezing drizzle later tonight. There needs to be a cold layer of air above and below the warm layer. See image blow.
At 9 PM the surface temperatures are still slightly above freezing 34F or 1.1C. The temperatures higher up in the atmosphere are above freezing until about 500 mb.
This means as the ice crystal at 500 mb falls through part of the atmosphere above freezing it will melt…until it reaches the ground. The temperatures are forecast to reach the freezing point around 2-5 AM Thursday. At that time any precipitation that falls would be freezing rain or freezing drizzle. Surface temperatures are forecast to get above freezing around 9 or 10 AM Thursday.
Posted under Update
This post was written by Schnack on April 10, 2013