####018002212#### FXXX12 KWNP 261231 DAYDIS :Product: Forecast Discussion :Issued: 2025 Sep 26 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 largest event of the period was a C3.4 flare at 25/1401 UTC from Region 4217 (S18W80, Cso/beta). The remaining eight spotted regions were either quiet or only produced low-level C-class activity. No Earth-directed CMEs were observed in available coronagraph imagery. .Forecast... Solar activity is expected to be low, with a chance for isolated M-class flare activity (R1-R2/Minor-Moderate) over 26-28 Sep. Energetic Particle .24 hr Summary... The greater than 2 MeV electron flux remained at moderate levels. The greater than 10 MeV proton flux was at background. .Forecast... The greater than 2 MeV electron flux is expected to continue at moderate levels, with a chance for high levels, on 26-28 Sep as CH HSS influences wane. The greater than 10 MeV proton flux is expected to continue at background levels all three days. Solar Wind .24 hr Summary... Negative polarity CH HSS effects continued to decrease. Total magnetic field strength was at or below 6 nT. No significant periods of southward Bz were observed. Solar wind speeds declined from ~500 km/s to ~430 km/s over the past 24 hours. Phi angle was primarily oriented in the negative solar sector. .Forecast... Mostly nominal conditions are expected through the rest of 26 Sep. Relatively weak enhancements are anticipated by late on 27 Sep, lasting into 28 Sep, as influence from another negative polarity CH HSS is anticipated. Geospace .24 hr Summary... The geomagnetic field was at quiet to unsettled levels. .Forecast... Mostly quiet levels are expected through 26 Sep as CH influences diminish. Quiet to unsettled conditions are expected on 27 Sep, with active levels likely on 28 Sep, as a subsequent negative polarity CH HSS becomes geoeffective. ####018002124#### FXXX10 KWNP 261231 DAYTDF :Product: 3-Day Forecast :Issued: 2025 Sep 26 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 # # 3-Day Forecast # A. NOAA Geomagnetic Activity Observation and Forecast The greatest observed 3 hr Kp over the past 24 hours was 3 (below NOAA Scale levels). The greatest expected 3 hr Kp for Sep 26-Sep 28 2025 is 3.67 (below NOAA Scale levels). NOAA Kp index breakdown Sep 26-Sep 28 2025 Sep 26 Sep 27 Sep 28 00-03UT 2.33 2.33 2.33 03-06UT 2.33 2.00 2.00 06-09UT 1.00 2.00 2.00 09-12UT 2.33 1.67 2.00 12-15UT 1.33 2.00 2.00 15-18UT 1.33 2.00 3.00 18-21UT 1.67 2.00 3.33 21-00UT 1.67 3.00 3.67 Rationale: No G1 (Minor) or greater geomagnetic storms are expected. No significant transient or recurrent solar wind features are forecast. B. NOAA Solar Radiation Activity Observation and Forecast Solar radiation, as observed by NOAA GOES-18 over the past 24 hours, was below S-scale storm level thresholds. Solar Radiation Storm Forecast for Sep 26-Sep 28 2025 Sep 26 Sep 27 Sep 28 S1 or greater 1% 1% 1% Rationale: No S1 (Minor) or greater solar radiation storms are expected. No significant active region activity favorable for radiation storm production is forecast. C. NOAA Radio Blackout Activity and Forecast No radio blackouts were observed over the past 24 hours. Radio Blackout Forecast for Sep 26-Sep 28 2025 Sep 26 Sep 27 Sep 28 R1-R2 30% 30% 30% R3 or greater 5% 5% 5% Rationale: There is a chance for isolated R1-R2 (Minor-Moderate) radio blackouts over 26-28 Sep.