CW3E AR Update: 23 March Post Event Summary

March 23, 2018

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A strong AR made landfall over southern California this week

• The atmospheric river made initial landfall over Big Sur around 1800 UTC Wednesday, 20 March 2018
• AR conditions were present over southern California about ~1200 UTC Friday, 23 March 2018
• This was an R-Cat 1 event as over 200 mm of precipitation was observed just south of Big Sur and over the northern Sierra Nevada over 72 hours
• This event produced nearly 7 percent of normal annual precipitation over all of California and the Northern Sierra 8 Station Index

Images from CIMSS/Univ. of Wisconsin

Click IVT or IWV image to see loop of 0-48 hour GFS forecast Valid 1200 UTC 22 March – 1200 UTC 24 March 2018

NEXRAD Radar Reflectivity Valid 00 UTC 20 March – 12 UTC 23 March 2018

Precipitation began over central CA early morning on 20 March 2018 Moderate to heavy precipitation occurred over central and Southern CA for nearly 72 hours during 20–23 March The highest precipitation amounts occurred over the Coastal Mts. between Santa Barbara and Big Sur and over the southern Sierra Nevada Several thunderstorms also occurred during this event on 22 and 23 March as evident by the highest reflectivity values observed by radar

Summary provided by C. Hecht, B. Kawzenuk, and F.M. Ralph; 3 PM PT Friday 23 March 2018

*Outlook products are considered experimental