Extreme heat will smother portions of the western U.S. later this week, with forecast high temperatures expected to be more than 10 degrees hotter than previous records. According to the National Weather Service, this week’s heat from the West Coast to the Plains will set hundreds of daily records—many by several degrees. Some areas may even set March records, with temperatures more typical of June.
A highly amplified pattern featuring an expanding extremely anomalous upper-high over the western U.S. will bring an increasingly summer-like period of heat this week and into the weekend. Well above average temperatures by as much as 20-30 degrees initially across California and into the Great Basin/Desert Southwest early this week will expand eastward into the Rockies and then Plains by Thursday. According to the National Weather Service, numerous, widespread daily and monthly record highs for March are expected as temperatures soar into the 80s, 90s, and even the 100s in the Desert Southwest and many locations within the Desert Southwest are likely to see their earliest 100 degree temperature on record.
Heat-related Advisories and Warnings are in place across the Desert Southwest and the central/southern California coasts where this heat may pose more notable health risks considering both how hot the temperatures are and how relatively early they are occurring.
The heat wave looks to continue into the weekend before conditions begin to return closer to average early next week. Another concern will be rapid snowmelt in the mountains leading to rising water levels and swift currents for regional rivers. That snow melt entering rivers may be hazardous; the National Weather Service says, “Although air temperatures are warm, anyone entering the water is at risk of cold water shock and hypothermia.”
Extreme Heat Watches around the Phoenix area were upgraded to an Extreme Heat Warning today. This is the earliest heat warning to go into effect, with the current earliest instance occurring between April 26th and 30th of 2020.
