:Product: 3-Day Forecast :Issued: 2024 Mar 19 0030 UTC # Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center # 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 Mar 19-Mar 21 2024 is 4.67 (NOAA Scale G1). NOAA Kp index breakdown Mar 19-Mar 21 2024 Mar 19 Mar 20 Mar 21 00-03UT 3.33 1.67 3.00 03-06UT 2.67 2.00 4.00 06-09UT 2.00 1.67 4.67 (G1) 09-12UT 1.67 3.00 3.00 12-15UT 0.67 3.67 4.00 15-18UT 0.67 3.67 3.00 18-21UT 1.67 4.00 3.00 21-00UT 1.67 4.67 (G1) 2.00 Rationale: G1 (Minor) storm levels are likely on 20-21 Mar due to the arrival of CMEs from 17 Mar. 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 19-Mar 21 2024 Mar 19 Mar 20 Mar 21 S1 or greater 5% 5% 5% 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 Radio blackouts reaching the R2 levels were observed over the past 24 hours. The largest was at Mar 18 2024 1919 UTC. Radio Blackout Forecast for Mar 19-Mar 21 2024 Mar 19 Mar 20 Mar 21 R1-R2 40% 40% 40% R3 or greater 5% 5% 5% Rationale: There is a chance for R1-R2 (Minor-Moderate) radio blackouts on 19-21 Mar.