Thursday, October 20, 2016
Frosty Nights; Why No Freeze Warnings?
The NWS won't issue Freeze Warnings unless a widespread freeze event is expected across a particular county. In other words, unless the NWS is confident that a majority of any given county will experience temperatures below 32°, they won't issue a Freeze Warning. For tonight, some parts of Jo Daviess, Carroll, Stephenson, Green, and Rock Counties will likely dip to 32°, if not lower. However, each of those counties will likely have many locations that stay at 33° or above tonight. Thus, a Frost Advisory in effect despite some locations likely seeing a freeze event tonight.
If a widespread freeze event is anticipated, a Freeze Warning will be issued. Thus far this fall, temperatures have not met the guidelines for a Freeze Watch/Warning. It doesn't look likely that we will meet Freeze Warning credentials for the next week or so, per the latest forecast models. Once temperatures are forecast to drop to 32° or lower for most of any given county, a Freeze Warning will be issued. And, once the first "widespread" freeze event occurs in a given area, the growing season officially comes to an end. As a result, Frost Advisories and Freeze Watches/Warnings will no longer be issued. Frost Advisories and Freeze Watches/Warnings are only used in the fall until a killing freeze event occurs. They are used in the spring when it is late enough to cause damage to new crops and plants.