:Product: 3-Day Forecast :Issued: 2026 Sep 14 1230 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 2 (below NOAA Scale levels). The greatest expected 3 hr Kp for Sep 14-Sep 16 2026 is 4.67 (NOAA Scale G1). NOAA Kp index breakdown Sep 14-Sep 16 2026 Sep 14 Sep 15 Sep 16 00-03UT 1.00 3.33 3.67 03-06UT 2.33 3.67 3.33 06-09UT 1.33 3.33 3.00 09-12UT 2.00 3.33 2.67 12-15UT 3.67 3.00 3.00 15-18UT 3.33 2.00 3.33 18-21UT 3.67 3.00 3.67 21-00UT 3.33 3.00 4.67 (G1) Rationale: The likelihood of G1 storming increases on 16 Sep as a subsequent -CH HSS moves into a geoeffective position. 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 14-Sep 16 2026 Sep 14 Sep 15 Sep 16 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 14-Sep 16 2026 Sep 14 Sep 15 Sep 16 R1-R2 5% 5% 5% R3 or greater 1% 1% 1% Rationale: No R1 (Minor) or greater radio blackouts are expected. No significant active region flare activity is forecast.