roduct: 3-Day Forecast
:Issued: 2026 Sep 27 0030 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 Sep 27-Sep 29 2026 is 3.00 (below NOAA
Scale levels).

NOAA Kp index breakdown Sep 27-Sep 29 2026

             Sep 27       Sep 28       Sep 29
00-03UT       2.67         1.67         1.67     
03-06UT       3.00         2.00         1.33     
06-09UT       2.67         1.67         1.33     
09-12UT       2.67         1.67         1.00     
12-15UT       2.00         1.67         1.00     
15-18UT       1.67         0.67         1.33     
18-21UT       1.67         0.67         1.67     
21-00UT       2.00         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 Sep 27-Sep 29 2026

              Sep 27  Sep 28  Sep 29
S1 or greater    1%      1%      1%

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 Sep 27-Sep 29 2026

              Sep 27        Sep 28        Sep 29
R1-R2           10%           10%            5%
R3 or greater    1%            1%            1%

Rationale: There is a slight chance for R1-R2 (Minor-Moderate) radio
blackouts through 29 Sep.


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