####018002166#### FXXX10 KWNP 101231 DAYTDF :Product: 3-Day Forecast :Issued: 2025 Dec 10 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 3 (below NOAA Scale levels). The greatest expected 3 hr Kp for Dec 10-Dec 12 2025 is 4.67 (NOAA Scale G1). NOAA Kp index breakdown Dec 10-Dec 12 2025 Dec 10 Dec 11 Dec 12 00-03UT 2.67 1.00 3.33 03-06UT 2.00 2.00 2.00 06-09UT 3.33 2.33 2.00 09-12UT 2.00 2.33 3.00 12-15UT 2.00 2.33 2.67 15-18UT 2.00 2.33 3.00 18-21UT 3.00 2.33 3.33 21-00UT 4.67 (G1) 2.67 3.33 Rationale: Isolated G1 (Minor) or greater geomagnetic storms are likely on 10 Dec, due to passage of a magnetic transient. 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 10-Dec 12 2025 Dec 10 Dec 11 Dec 12 S1 or greater 15% 15% 15% Rationale: There is a slight chance for S1 (Minor) or greater solar radiation storms on 10-12 Dec. 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 10 2025 0737 UTC. Radio Blackout Forecast for Dec 10-Dec 12 2025 Dec 10 Dec 11 Dec 12 R1-R2 75% 75% 65% R3 or greater 15% 15% 15% Rationale: R1-R2 (Minor-Moderate) radio blackouts are expected on 10-11 Dec and likely on 12 Dec. There is a slight chance of R3 (Strong) or greater events on 10-12 Dec. ####018003303#### FXXX12 KWNP 101231 DAYDIS :Product: Forecast Discussion :Issued: 2025 Dec 10 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 # # Forecast Discussion # Solar Activity .24 hr Summary... Solar activity was at moderate levels due to multiple low level M-class flares (R1-Minor), mostly from Region 4294 (S15W69, Ekc/beta-gamma-delta). The Region 4294 continues to show flux emergence in its leading spots creating instability and its activity. Region 4304 (N26W36, Cai/beta-gamma) experienced rapid growth and flux emergence, with the potential to develop a delta spot over the next few days. Newly numbered Region 4305 (S25E20, Cai/beta-gamma) also continued to grow rapidly. All other regions were stable or in decay. There were no Earth-directed CMEs in coronagraph imagery. .Forecast... R1-R2 (Minor-Moderate) flare activity is expected (75% chance), with a slight chance (15%) for R3 (Strong) activity. Probabilities remain elevated due to the large complex of the three regions in the southwest part of the disk. Energetic Particle .24 hr Summary... The greater than 2 MeV electron flux at geosynchronous orbit were at high levels, with a maximum of 1572 pfu at 09/1615 UTC. The greater than 10 MeV proton flux remained at background. .Forecast... Without the geoeffective positioning of any coronal hole high speed stream until 13 Dec, electrons will continue to trend towards moderate levels through 12 Dec. Due the growth of Region 4294 and its favorable positioning in the west, there remains a slight chance (15%) for an S1 (Minor) radiation storming event. Solar Wind .24 hr Summary... Solar wind parameters reflected a disturbed near-Earth environment throughout the reporting period. The total interplanetary magnetic field (Bt) averaged 7 nT until 10/0328 UTC, when a magnetic transient arrived and pushed it to 13 nT. The north-south (Bz) component was largely south (negative) for the reporting period, reaching a maximum of -7 nT at 10/0434 UTC. Solar wind speeds showed little reaction to the magnetic transient, averaging 375 km/s throughout the reporting period. The phi angle was oriented towards-the-Sun (negative) for the majority of the reporting period, then slowly rotated around to away-from-the-Sun (positive) 1.5 hours after the arrival of the transient. .Forecast... Solar wind environment is likely to slowly return to nominal levels by the end of 10 Dec as the transient moves through, with 11 Dec remaining quiet. Conditions may become elevated on 12 Dec due to a potential weak impact from a CME that left the Sun on 08 Dec. Geospace .24 hr Summary... The geomagnetic field was at quiet levels for the first half of the reporting period, and then was largely unsettled after the arrival of the transient. .Forecast... Isolated periods of G1 (Minor Storming) levels are possible on the later half of 10 Dec, due to the continued passage of the transient and a weak but favorable connection with Bz. 11-12 Dec are likely to return to largely unsettled levels.