FXXX10 KWNP 191231 DAYTDF :Product: 3-Day Forecast :Issued: 2026 Apr 19 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 6 (NOAA Scale G2). The greatest expected 3 hr Kp for Apr 19-Apr 21 2026 is 5.67 (NOAA Scale G2). NOAA Kp index breakdown Apr 19-Apr 21 2026 Apr 19 Apr 20 Apr 21 00-03UT 3.67 3.67 3.33 03-06UT 4.67 (G1) 3.67 4.00 06-09UT 5.67 (G2) 3.33 3.00 09-12UT 3.67 3.33 2.67 12-15UT 5.67 (G2) 3.33 2.33 15-18UT 4.67 (G1) 2.00 3.00 18-21UT 3.00 3.33 2.67 21-00UT 4.00 3.33 2.33 Rationale: G1-G2 (Minor-Moderate) geomagnetic storm levels are expected on 19 Apr as negative polarity CH HSS geomagnetic conditions persist. 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 19-Apr 21 2026 Apr 19 Apr 20 Apr 21 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 Apr 19-Apr 21 2026 Apr 19 Apr 20 Apr 21 R1-R2 10% 10% 10% R3 or greater 1% 1% 1% Rationale: There is a slight chance for (R1-R2, Minor-Moderate) radio blackouts on 19-21 Apr, primarily due to the flare potential of Region 4419.