Subj : 3 Day Space Weather Forecast
To   : All
From : Sean Dennis
Date : Sat Sep 12 2026 12:19 am

:Product: 3-Day Forecast
:Issued: 2026 Sep 12 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 3 (below NOAA
Scale levels).
The greatest expected 3 hr Kp for Sep 12-Sep 14 2026 is 3.67 (below NOAA
Scale levels).

NOAA Kp index breakdown Sep 12-Sep 14 2026

             Sep 12       Sep 13       Sep 14
00-03UT       2.33         2.33         3.33     
03-06UT       2.67         2.00         3.67     
06-09UT       2.67         2.33         3.00     
09-12UT       2.33         2.33         3.00     
12-15UT       1.33         2.33         3.00     
15-18UT       1.00         2.33         3.00     
18-21UT       2.00         2.67         3.67     
21-00UT       2.33         3.33         3.33     

Rationale: No G1 (Minor) or greater geomagnetic storms are expected
through 14 Sep, though a solar sector boundary crossing and CH HSS on
13-14 Sep are expected to create unsettled to active conditions.

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 12-Sep 14 2026

              Sep 12  Sep 13  Sep 14
S1 or greater    1%      1%      1%

Rationale: No S1 (Minor) or greater solar radiation storms are expected
through 14 Sep.

C. NOAA Radio Blackout Activity and Forecast

No radio blackouts were observed over the past 24 hours.

Radio Blackout Forecast for Sep 12-Sep 14 2026

              Sep 12        Sep 13        Sep 14
R1-R2           10%           10%           10%
R3 or greater    1%            1%            1%

Rationale: There is a slight chance for R1-R2 (Minor-Moderate) radio
blackouts through 14 Sep.


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