Forecaster summary - Issued 2021-12-20T00:38:10

The high energy (greater than 2 MeV) electron flux as observed by GOES-16 is currently at background, but likely to increase as a result of recent fast wind enhancements from coronal hole 36. Once early geomagnetic activity on day 1 (20th) eases a gradual build of observed flux is likely, peaking at High levels (above 1000 pfu). Further enhancement from any arrival of fast wind from CH35 on day 2 and 3 could bring dropouts to the observed flux, before Moderate to High levels are expected to resume. This enhancement is currently uncertain however, giving low confidence to the forecast by day 3 and 4 (22nd and 23rd). 

The associated 24 hour fluence is expected to remain below the Active (1e8 integrated pfu) threshold until at least day 2 (21st) with a chance of then rising above. Whilst this risk increases through the period, it remains low confidence due to uncertainty around the strength of any enhancement from CH35. REFM is currently giving poor guidance as this currently doesn't take account of the solar wind enhancement that is ongoing at time of issue.