Space Weather Forecasting with Particles in the Heliosphere: SEP Advance Warnings for Human Space Exploration Posner, A NASA/HQ, Science Mission Directorate, 300 E St. SW, Washington DC 20543 Since 2008, the REleASE method of short-term forecasting of the intensity of prompt solar energetic protons of hazardous energies (~40 MeV) with relativistic electrons has been implemented online. REleASE translates near-real-time electron data of the SOHO/COSTEP instrument from L1 into near-future proton fluxes. Electrons (and other particles) provide reliable early signs of solar energetic particle events in progress. The forecasting of the sudden increase in intensity of protons from solar energetic particle events is relevant for radiation protection of humans on exploration missions and extravehicular activities. Electrons probe the ever-changing heliospheric transport conditions that act on the slower moving protons. We show an analysis of the REleASE output and discuss it in the context of related methods. Relevant results from STEREO observations will be discussed. Moreover, we show how REleASE forecasts from a nearEarth vantage point can be used to provide essential warnings also for human space exploration of Mars via the Hohmann-Parker effect.