FXXX10 KWNP 130031 DAYTDF :Product: 3-Day Forecast :Issued: 2025 Dec 13 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 5 (NOAA Scale G1). The greatest expected 3 hr Kp for Dec 13-Dec 15 2025 is 4.67 (NOAA Scale G1). NOAA Kp index breakdown Dec 13-Dec 15 2025 Dec 13 Dec 14 Dec 15 00-03UT 4.33 3.67 2.33 03-06UT 4.33 3.00 2.00 06-09UT 4.67 (G1) 2.67 2.00 09-12UT 3.67 2.67 2.00 12-15UT 2.67 2.67 2.00 15-18UT 2.67 2.00 2.00 18-21UT 3.33 2.00 2.00 21-00UT 3.67 2.67 2.33 Rationale: G1 (Minor) geomagnetic storm levels are expected on 13 Dec due to ongoing CH HSS influence. 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 Dec 13-Dec 15 2025 Dec 13 Dec 14 Dec 15 S1 or greater 5% 5% 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 Radio blackouts reaching the R1 levels were observed over the past 24 hours. The largest was at Dec 12 2025 0505 UTC. Radio Blackout Forecast for Dec 13-Dec 15 2025 Dec 13 Dec 14 Dec 15 R1-R2 55% 45% 35% R3 or greater 5% 1% 1% Rationale: R1-R2 (Minor-Moderate) radio blackouts are likely on 13 Dec due to the potential of Region 4296 and 4294 near the W limb.