Forecaster summary - Issued 2026-05-26T00:16:56

High energy (>2MeV) electron flux at GOES19 dropped below the High threshold through the overnight UTC period 25-26 May, following a short spell of Quiet to Unsettled geomagnetic activity, and has subsequently persisted at Moderate levels. A return to high levels through the first half of the period, especially during the diurnal maxima, cannot be ruled out but is uncertain. Some coronal hole influences are possible through Days 1-3 (26-28 May), bringing the possibility of a reduction in flux levels. However, the coronal hole influences may be weak in which case it could have limited impact on the electron flux.

The 24 hour integrated fluence has dropped below the Active (1e8 integrated pfu) threshold, and is now most likely to remain below Active through the period, although with some uncertainty as to how far below. MOSWOC REFM shows a steady or slight rising trend initially, before a sharp reduction. These overall trends seem reasonable, although the magnitude of the predicted fluence levels is very uncertain.