Forecaster summary - Issued 2021-09-18T00:17:13

Expected periodic enhancements in the period may occur from of negative coronal hole 01, and perhaps a southern hemisphere coronal hole-like feature visible at similar longitude. These alone are unlikely to significantly alter the Van Allen Belt electron populations, instead relying on the effects of the 13 September CME arrival to raise electron levels.

The chances of Active 24-hour integrated high energy electron fluence being realised rise slightly into the coming UTC weekend. This is counter to REFM output, with the rationale being the forecast's reliance on CME effects rather than coronal hole activity to achieve this outcome.