Solar flare activity on UT day 21-May is expected to be at the R0 level, with a chance of R1. S0 solar radiation conditions are expected. The solar wind speed is expected to be moderate to light. G0 geomagnetic conditions are expected. HF radio propagation conditions are expected to be mostly normal. Maximum Usable Frequencies (MUFs) in the Australian region are expected to be near predicted monthly values, with the chance of mild depressions, particularly in the southern Australian region.