AQPI: Precipitation Forecasts over the San Francisco Bay Area from the High-Resolution Rapid Refresh Model during an Atmospheric River Event on 21-23 Mar 2018

An atmospheric river event impacted California during 21-23 March 2018, producing heavy rain in the northern San Francisco Bay area. Here we describe quantitative precipitation forecast (QPF) performance from the NOAA hourly-updating operational 3-km High-Resolution Rapid Refresh (HRRR) numerical weather prediction system. We compare forecasts from two versions of the HRRR model: Version 2, which was running operationally at the National Centers for Environmental Prediction (NCEP) from August 2016 to July 2018; and version 3, which began running operationally at NCEP in July 2018. The HRRRv3 includes changes to the data assimilation, vertical coordinate system, and planetary boundary layer parameterization, amongst other changes. Model forecasts are compared to widely-used quantitative precipitation estimation (QPE) products such as the Stage IV analysis, as well as against trusted rain gauges in the Bay Area.