First Freeze of 2011

What a difference a few months makes!  After the sweltering summer heat, many residents of West Central Texas have been begging for the cooler autumn weather to arrive.  These requests were met this weekend in the wake of the strongest cold front of the season.  The cold front blasted through the San Angelo County Warning Area (CWA) late Wednesday, ushering in much cooler conditions for the remainder of the work week.  Temperatures remained in the 40s on Thursday as the cold air filtered into the area and patchy light rain fell across the region.  The abundance of low clouds, in conjunction with the north winds around 10 mph, kept temps from cooling too much Thursday night.  The clouds broke on Friday and winds became light and variable as the surface anticyclone settled over the region.  This set the stage for strong radiational cooling conditions for Friday night and early Saturday morning. 
Map of first freeze in 2011
Image 1.  Click on image for larger version.

To the right is a map (Image 1) depicting low temperatures observed on the morning of Saturday, October 29, 2011.  As can be seen, all locations in the San Angelo CWA fell below 40 degrees with subfreezing temperatures observed across more than half of the area.  The coldest temperatures were typically found along the river valleys of the Northwest Hill Country, namely along the Pecan Bayou and San Saba, Llano, and Colorado Rivers. 

Many locations in the Big Country remained above freezing and a number of other sites only experienced a light freeze.  However, this event may very well served as a killing freeze, representing the end of the growing season, for some of the colder locations. 

A freeze during the last week of October is only a week or two ahead of the climatological average.  The normal first freeze typically arrives during the first two weeks of November in many locations, as early as October 31 and as late as November 13.

This freeze does not even approach the earliest freeze on record which occurred before October 20 at all sampled sites. Image 2 shows the freeze data for various sites across the San Angelo CWA, including the dates for the average, first and last freeze for each site.  Below is the aforementioned freeze data.

Freeze Data for San Angelo forecast area
Image 2.  Click on image for larger version. is the U.S. government's official web portal to all federal, state and local government web resources and services.