Forecaster summary - Issued 2025-09-20T00:13:43

High energy (greater than 2MeV) electron flux as observed by GOES-19 was at high levels with a peak of 5020 pfu at 19/1205 UTC. Similar high levels are expected to continue through Day 1 (20 Sep) and likely Day 2 (21 Sep), before a probable reduction as the HSS from CH80/- arrives by Day 3 (22 Sep). However, the extent of a decline in electron levels is dependant on a suitably robust connection with CH80/-, which is somewhat uncertain and therefore low confidence. 

The associated 24 hour fluence is currently above the Active threshold and on a relatively flat trend. Fluence is expected to continue at Active levels through Day 1 (20 Sep) and into Day 2 (21 Sep), perhaps with a slight downward drift. A sharper declining trend is then likely into Days 3 and 4 due to the anticipated connection with CH80/-, but as already mentioned this is low confidence at present. MOSWOC REFM is currently close to the observed fluence values, but is considered to show too steep a decline in fluence levels in the short term, however the overall downward trend through the period is accepted.