:Product: 3-Day Forecast
:Issued: 2026 Sep 06 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 1 (below NOAA
Scale levels).
The greatest expected 3 hr Kp for Sep 06-Sep 08 2026 is 4.67 (NOAA Scale
G1).

NOAA Kp index breakdown Sep 06-Sep 08 2026

             Sep 06       Sep 07       Sep 08
00-03UT       1.33         3.33         4.00     
03-06UT       1.33         2.00         4.00     
06-09UT       1.33         2.00         4.67 (G1)
09-12UT       1.33         3.00         4.67 (G1)
12-15UT       1.33         3.00         4.67 (G1)
15-18UT       1.33         3.33         4.00     
18-21UT       1.33         3.67         3.67     
21-00UT       1.67         4.00         3.33     

Rationale: Isolated G1 (Minor) periods are likely if the CMEs from 05
Sep impact Earth as forecast.

B. NOAA Solar Radiation Activity Observation and Forecast

Solar radiation, as observed by NOAA GOES-18 over the past 24 hours, was
above S-scale storm level thresholds.

Solar Radiation Storm Forecast for Sep 06-Sep 08 2026

              Sep 06  Sep 07  Sep 08
S1 or greater   75%     10%     10%

Rationale: The greater than 10 MeV proton flux is expected to continue
decreasing towards background levels through early 08 Sep, with a slight
chance for S1 (Minor) levels over the next three days.

C. NOAA Radio Blackout Activity and Forecast

Radio blackouts reaching the R1 levels were observed over the past 24
hours. The largest was at Sep 05 2026 1518 UTC.

Radio Blackout Forecast for Sep 06-Sep 08 2026

              Sep 06        Sep 07        Sep 08
R1-R2           20%           20%           20%
R3 or greater    5%            5%            5%

Rationale: There is a slight chance for R1-R2 (Minor-Moderate) radio
blackouts through 08 Sep.