:Product: 3-Day Forecast
:Issued: 2026 Jun 26 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 Jun 26-Jun 28 2026 is 4.00 (below NOAA
Scale levels).

NOAA Kp index breakdown Jun 26-Jun 28 2026

             Jun 26       Jun 27       Jun 28
00-03UT       3.00         3.00         3.33     
03-06UT       2.33         3.67         3.67     
06-09UT       2.00         2.00         4.00     
09-12UT       1.67         2.67         3.00     
12-15UT       2.00         2.00         2.00     
15-18UT       2.33         2.00         1.67     
18-21UT       3.00         2.67         2.67     
21-00UT       3.00         3.00         2.67     

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 Jun 26-Jun 28 2026

              Jun 26  Jun 27  Jun 28
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

No radio blackouts were observed over the past 24 hours.

Radio Blackout Forecast for Jun 26-Jun 28 2026

              Jun 26        Jun 27        Jun 28
R1-R2           50%           50%           50%
R3 or greater   10%           10%           10%

Rationale: There is a high chance for R1-R2 (Minor-Moderate) radio
blackouts 26-28 Jun due primarily to the flare potential of Region 4478.