FXXX12 KWNP 190031 DAYDIS :Product: Forecast Discussion :Issued: 2026 May 19 0030 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 continued at low levels. The largest event of the period was a C1.9/1f flare at 18/1828 UTC from Region 4436 (N19W52, Hsx/alpha). This region was responsible for the vast majority of the otherwise occasional low-level B-class flaring observed throughout the period. There are currently six numbered regions on the visible disk, nearly all of which exhibited steady signs of decay and simplification. Region 4436 remained mostly stable, though it produced short-lived, transitory trailing pores. Region 4439 (N06E42, Dao/beta) underwent penumbral decay alongside flux submergence in its trailing spots. Region 4440 (N17E42, Hrx/alpha) showed a slight reduction in its overall penumbral extent. Region 4441 (N08W01, Dao/beta) was mostly stable in both area and magnetic complexity, despite some localized flux emergence. Region 4442 (S15E28, Bxo) continued in a state of decay, completely losing its rudimentary penumbra. Region 4443 (S16E47, Bxo/beta) experienced slight decay and minor flux submergence. No Earth-directed CMEs were observed in available coronagraph imagery. .Forecast... Solar activity is expected to be at low levels through 21 May, with a chance for isolated M-class flares (R1-R2/Minor-Moderate). This flare potential is driven primarily by the complexity of Region 4441 and the recent eruptive trends of Region 4436. Energetic Particle .24 hr Summary... The greater than 2 MeV electron flux at geosynchronous orbit remained at high levels, reaching a peak flux of 6,667 pfu observed at 18/1435 UTC. The greater than 10 MeV proton flux at geosynchronous orbit remained at background levels. .Forecast... The greater than 2 MeV electron flux is expected to drop to normal to moderate levels 19-20 May as high-speed stream influences continue to wane, likely returning to moderate to high levels on 21 May. The greater than 10 MeV proton flux is expected to remain at baseline background levels through 21 May. Solar Wind .24 hr Summary... Solar wind parameters reflected a very gradual decline back toward nominal conditions under the waning influence of a negative polarity coronal hole high-speed stream (-CH HSS). Total magnetic field (Bt) averaged around 4 nT. The north-south (Bz) component oscillated frequently with a maximum observed southward deviation of -5 nT. Solar wind speeds were variable between 500 and 575 km/s. The phi angle remained predominantly in the negative (towards the Sun) sector. .Forecast... Solar wind parameters are expected to continue trending toward background levels through 20 May, with isolated enhancements possible on 19 May due to glancing influences from a CME that left the Sun on 16 May event. Conditions are expected to become mildly enhanced again on 21 May from a solar sector boundary crossing ahead of an approaching positive polarity coronal hole high-speed stream (+CH HSS). Geospace .24 hr Summary... The geomagnetic field was quiet to unsettled. .Forecast... Isolated periods of up to G1 (Minor) geomagnetic storming are anticipated on 19 May due to glancing influences from the 16 May CME. The geomagnetic field is expected to return to quiet to unsettled levels on 20 and 21 May, due to lingering CME effects on 20 May and a projected solar sector boundary crossing on 21 May.