Space Weather Message Code: ALTK08 Serial Number: 50 Issue Time: 2025 Apr 16 2054 UTC ALERT: Geomagnetic K-index of 8, 9- Threshold Reached: 2025 Apr 16 2055 UTC Synoptic Period: 1800-2100 UTC Active Warning: Yes NOAA Scale: G4 - Severe NOAA Space Weather Scale descriptions can be found at www.swpc.noaa.gov/noaa-scales-explanation Potential Impacts: Area of impact primarily poleward of 45 degrees Geomagnetic Latitude. Induced Currents - Possible widespread voltage control problems and some protective systems may mistakenly trip out key assets from the power grid. Induced pipeline currents intensify. Spacecraft - Systems may experience surface charging; increased drag on low earth orbit satellites, and tracking and orientation problems may occur. Navigation - Satellite navigation (GPS) degraded or inoperable for hours. Radio - HF (high frequency) radio propagation sporadic or blacked out. Aurora - Aurora may be seen as low as Alabama and northern California.
:Product: 3-Day Forecast :Issued: 2025 Apr 16 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 6 (NOAA Scale G2). The greatest expected 3 hr Kp for Apr 16-Apr 18 2025 is 6.67 (NOAA Scale G3). NOAA Kp index breakdown Apr 16-Apr 18 2025 Apr 16 Apr 17 Apr 18 00-03UT 5.33 (G1) 5.33 (G1) 3.67 03-06UT 3.33 4.67 (G1) 4.33 06-09UT 3.33 4.33 3.00 09-12UT 4.67 (G1) 4.33 3.00 12-15UT 4.67 (G1) 4.00 2.67 15-18UT 4.33 3.00 3.00 18-21UT 3.33 2.67 3.00 21-00UT 6.67 (G3) 4.00 3.00 Rationale: G3 (Strong) geomagnetic storming is likely on 16 Apr, followed by G1 (Minor) storming on 17 Apr. 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 Apr 16-Apr 18 2025 Apr 16 Apr 17 Apr 18 S1 or greater 10% 10% 5% Rationale: There is a slight chance for S1 (Minor) solar radiation storms on 16-17 Apr. C. NOAA Radio Blackout Activity and Forecast Radio blackouts reaching the R1 levels were observed over the past 24 hours. The largest was at Apr 15 2025 1813 UTC. Radio Blackout Forecast for Apr 16-Apr 18 2025 Apr 16 Apr 17 Apr 18 R1-R2 80% 75% 60% R3 or greater 15% 10% 10% Rationale: R1-R2 (Minor-Moderate) radio blackouts are expected 16-17 Apr. Probabilities decrease slightly on 18 Apr.
Map from NOAA titled showing North America and the North Pole with a color gradient overlay of aurora likelihood.
Map from NOAA titled showing North America and the North Pole with a color gradient overlay of aurora likelihood.
Aurora Forecast Update for 2025-04-16T21:00:09Z
ALERT: Geomagnetic K-index of 8, 9-
Threshold Reached: 2025 Apr 16 2055 UTC
Synoptic Period: 1800-2100 UTC
Active Warning: Yes
NOAA Scale: G4 - Severe
Additional Details Here.
