National Weather Service United States Department of Commerce

The Freeze Watch has been upgraded to a Freeze Warning for the San Joaquin Valley from 2 AM to 8 AM Saturday. Temperatures are expected to drop into the upper 20s to lower 30s over much of the area, briefly reaching the mid 20s in a few of the typically coldest locations. Temperatures this cold can negatively impact people, animals, plants and pipes. Take precautions to protect plants and pipes, and please be sure to check on the elderly and make sure your pets and livestock have warm shelter during the overnight hours during this event.


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Upper Air Observations

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Alternate Sources for Upper Air Soundings
University of Wyoming
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California Wind Profiler Data Can be Found Here

Information About the Upper Air Program Can be Found Here

Why Do Forecasters Still Rely on Weather Balloons?

Twice every day, from nearly 100 locations in the United States, the National Weather Service launches weather balloons, carrying instrument packages called radiosondes. Radiosonde sensors measure upper-air conditions such as atmospheric pressure, temperature and humidity, wind speed and direction. The data is important for aviation safety, and meteorologists use radiosonde information to prepare weather forecasts. Details...