Product: 3-Day Forecast
- Issued: 2026 May 15 1230 UTC
Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center.
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 May 15-May 17 2026 is 5.67 (NOAA Scale G2).
| May 15 | May 16 | May 17 | |
|---|---|---|---|
| 00-03UT | 2.33 | 4.33 | 3.00 |
| 03-06UT | 1.67 | 5.00 (G1) | 4.67 (G1) |
| 06-09UT | 3.00 | 3.67 | 3.33 |
| 09-12UT | 3.33 | 3.33 | 3.00 |
| 12-15UT | 3.67 | 3.33 | 3.00 |
| 15-18UT | 4.33 | 3.33 | 3.67 |
| 18-21UT | 5.00 (G1) | 3.33 | 3.33 |
| 21-00UT | 5.67 (G2) | 3.33 | 2.67 |
Rationale: G1-G2 (Minor-Moderate) geomagnetic storms are likely on 15 May due to the CIR associated with a positive polarity CH HSS. G1 (Minor) storming levels are likely on 16-17 May due to the CH HSS persistence.
Solar Radiation Activity Observation and Forecast
Solar radiation, as observed by NOAA GOES-19 over the past 24 hours, was below S-scale storm level thresholds.
| May 15 | May 16 | May 17 | |
|---|---|---|---|
| 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.
Radio Blackout Activity and Forecast
No radio blackouts were observed over the past 24 hours.
| May 15 | May 16 | May 17 | |
|---|---|---|---|
| R1-R2 | 40% | 30% | 25% |
| R3 or greater | 5% | 5% | 5% |
Rationale: There is a chance for R1-R2 (Minor-Moderate) radio blackouts through 17 May due to the flare potential of the regions on disk.
Space Weather Overview
Credits
Space Weather Images and Information (excluded from copyright) courtesy of:
NOAA / NWS Space Weather Prediction Center
Mauna Loa Solar Observatory (HAO/NCAR)
SOHO (ESA & NASA)
Powered by Space Weather PHP script by Mike Challis of Long Beach Weather.
Additions by Ken True of Saratoga Weather and Jerry Wilkins of Southeast Lincoln Weather.