:Product: 3-Day Forecast
:Issued: 2026 Oct 17 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 4 (below NOAA
Scale levels).
The greatest expected 3 hr Kp for Oct 17-Oct 19 2026 is 2.67 (below NOAA
Scale levels).

NOAA Kp index breakdown Oct 17-Oct 19 2026

             Oct 17       Oct 18       Oct 19
00-03UT       2.00         1.67         1.67         
03-06UT       1.00         1.67         1.33         
06-09UT       0.67         1.33         1.33         
09-12UT       0.67         1.33         1.33         
12-15UT       1.33         1.33         1.33         
15-18UT       1.33         1.33         1.33         
18-21UT       2.00         1.33         1.67         
21-00UT       2.67         1.67         1.67         

Rationale: No G1 (Minor) or greater geomagnetic storms are expected. No
significant transient or recurrent solar wind features are forecast.

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 Oct 17-Oct 19 2026

              Oct 17  Oct 18  Oct 19
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.

C. NOAA Radio Blackout Activity and Forecast

Radio blackouts reaching the R1 levels were observed over the past 24
hours. The largest was at 16/1542Z UTC.

Radio Blackout Forecast for Oct 17-Oct 19 2026

              Oct 17        Oct 18        Oct 19
R1-R2           20%           20%           20%
R3 or greater    5%            5%            5%

Rationale: A slight chance for R1-R1 (Minor-Moderate) radio blackouts
will persist through 19 Oct due to the development exhibited by Region
4551 and current flare potential of 4557.