During the summer of 2018, NCEP’s operational version of the High Resolution Rapid Refresh (HRRR) began producing forecasts out to 36 hours for four of its daily cycles (0000, 0600, 1200, and 1800 UTC). This presents an opportunity to add HRRR members to the HREF, which currently also generates forecasts out to 36 hours. The increased ensemble spread obtained by adding one or more HRRR members could also potentially justify removing some or all of the time-lagged members from the current HREFv2 configuration. These 36-hour HRRR forecasts were run experimentally in conjunction with the 2018 Hazardous Weather Testbed (HWT) Spring Forecasting Experiment (SFE), allowing for testing of several new candidate HREF configurations during the peak of the spring convection season. Objective verification metrics and subjective evaluations from the 2018 HWT SFE for model fields relevant to forecasting severe convective storms are presented for these candidate HREF configurations, illuminating the practical and statistical significance of configuration differences.