FXXX12 KWNP 181231
DAYDIS

:Product: Forecast Discussion
:Issued: 2026 May 18 1230 UTC
# Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center
# Product description and SWPC contact on the Web
# http://www.swpc.noaa.gov/wwire.html
#
#             Forecast Discussion
#
Solar Activity

.24 hr Summary...
Solar activity was at low levels. The strongest flare of the period was
a C9.7/2n at 17/2053 UTC from Region 4436 (N19W45, Hsx/alpha). The event
produced an associated Tenflare (370 sfu). No ejecta was identified in
subsequent coronagraph imagery. Only minor changes were observed in the
six active regions on the visible disk.

.Forecast...
Solar activity is expected to be at low levels, with a chance for
additional M-class (R1-R2/Minor-Moderate) flares through 20 May. 

Energetic Particle

.24 hr Summary...
The greater than 2 MeV electron flux increased to high levels with a
peak flux of 6,120 pfu occurring at 17/1740 UTC. The greater than 10 MeV
proton flux was at background levels, though beginning to show
contamination signatures from the elevated electron flux.

.Forecast...
The greater than 2 MeV electron flux is expected to remain at moderate
to high levels through 18 May before possibly returning to normal to
moderate levels by late on 19 May with any CME glancing effects from the
16 May event. If this occurs, then electron flux in geostationary orbit
will likely remain at normal to moderate levels on 20 May. The greater
than 10 MeV proton flux is expected to stay at background levels through
20 May.

Solar Wind

.24 hr Summary...
The solar wind parameters reflected continued influence of a negative
polarity coronal hole. Total field averaged under 5 nT and no
significant periods of negative Bz were observed. Solar wind speeds
gradually decreased from ~650 km/s to ~550 km/s by the end of the
reporting period. The phi angle was predominantly negative.

.Forecast...
A negative polarity CH HSS regime is expected to gradually wane through
20 May. Additional enhancements are possible on 18 and 19 May due to
aforementioned glancing CME influences from the 16 May event.

Geospace

.24 hr Summary...
The geomagnetic field was at quiet levels.

.Forecast...
G1 (Minor) geomagnetic storming periods, with a chance for G2
(Moderate) levels, are likely on 18-19 May due to any glancing CME
effects from the 16 May event as modeling efforts suggest that a bulk of
the material should pass just north of Earth. Quiet to unsettled
conditions are expected on 20 May as negative polarity CH HSS effects
wane.