FXXX10 KWNP 211231 DAYTDF :Product: 3-Day Forecast :Issued: 2026 Mar 21 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 7 (NOAA Scale G3). The greatest expected 3 hr Kp for Mar 21-Mar 23 2026 is 7.00 (NOAA Scale G3). NOAA Kp index breakdown Mar 21-Mar 23 2026 Mar 21 Mar 22 Mar 23 00-03UT 7.00 (G3) 4.67 (G1) 3.33 03-06UT 6.00 (G2) 5.00 (G1) 4.33 06-09UT 5.00 (G1) 4.33 3.00 09-12UT 4.00 4.00 3.00 12-15UT 3.33 2.67 2.00 15-18UT 4.00 3.33 2.00 18-21UT 4.67 (G1) 4.33 3.33 21-00UT 4.33 4.33 3.00 Rationale: G1-G3 (Minor-Strong) geomagnetic storm conditions are expected on 21 Mar with G1 (Minor) conditions likely on 22 Mar due to persistent CME effects followed by HSS activity. 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 Mar 21-Mar 23 2026 Mar 21 Mar 22 Mar 23 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 Mar 21-Mar 23 2026 Mar 21 Mar 22 Mar 23 R1-R2 10% 10% 10% R3 or greater 1% 1% 1% Rationale: No R1 (Minor) or greater radio blackouts are expected. No significant active region flare activity is forecast.