We can not precisely quantify the risk without further detail information from the EPA, our assumption is that it is not immediately life threatening. Nonetheless given that our indoor readings appear normal, staying indoors is likely a wise risk mitigation action.
(edited to add) Based on the Outdoor - Indoor readings, this spike is likely driven ALPHA and/or BETA emitting radionuclides.
Notes:(1) The lone drop out on the outdoor radiation chart occurred as we were checking that Geiger Counters com port identification to verify that it was the outdoor unit.
(2) Normally we are several miles up wind of the West Lake Landfill's underground nuclear fire, only on the rare occasions that surface winds blow from East to West are we noticeably exposed to airborne emanations from that Superfund site.