FXXX10 KWNP 260031 DAYTDF :Product: 3-Day Forecast :Issued: 2026 Apr 26 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 # # 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 Apr 26-Apr 28 2026 is 4.67 (NOAA Scale G1). NOAA Kp index breakdown Apr 26-Apr 28 2026 Apr 26 Apr 27 Apr 28 00-03UT 4.67 (G1) 3.67 2.33 03-06UT 4.33 3.00 2.00 06-09UT 3.33 2.67 2.00 09-12UT 3.33 2.33 2.00 12-15UT 2.33 2.00 2.33 15-18UT 2.33 2.33 2.00 18-21UT 3.00 3.33 2.00 21-00UT 3.33 3.33 2.00 Rationale: Isolated G1-G2 (Minor-Moderate) geomagnetic storming conditions are possible (G1 likely with a chance for G2)early 26 Apr in response to the arrival of the glancing CMEs. 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 Apr 26-Apr 28 2026 Apr 26 Apr 27 Apr 28 S1 or greater 10% 10% 10% Rationale: There is a chance to exceed the S1 (Minor) solar radiation storm thresholds due to the flare potential of Region 4419 further beyond the western limb, and Region 4420 near the central solar meridian. C. NOAA Radio Blackout Activity and Forecast Radio blackouts reaching the R1 levels were observed over the past 24 hours. The largest was at Apr 25 2026 0759 UTC. Radio Blackout Forecast for Apr 26-Apr 28 2026 Apr 26 Apr 27 Apr 28 R1-R2 55% 55% 55% R3 or greater 15% 15% 15% Rationale: R1-R2 (Minor-Moderate) radio blackouts are likely, with a slight chance for R3 (Strong or greater) events through 28 Apr, primarily driven by the complexity of Regions 4420, 4423, and 4425.