Subj : 3 Day Space Weather Forecast
To   : All
From : Sean Dennis
Date : Wed Sep 30 2026 12:19 am

:Product: 3-Day Forecast
:Issued: 2026 Sep 30 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 2 (below NOAA
Scale levels).
The greatest expected 3 hr Kp for Sep 30-Oct 02 2026 is 4.67 (NOAA Scale
G1).

NOAA Kp index breakdown Sep 30-Oct 02 2026

             Sep 30       Oct 01       Oct 02
00-03UT       1.67         1.67         2.33     
03-06UT       1.67         1.33         2.67     
06-09UT       1.67         1.33         2.67     
09-12UT       1.33         1.33         3.33     
12-15UT       1.33         1.33         3.67     
15-18UT       1.00         1.33         4.67 (G1)
18-21UT       1.00         1.67         4.00     
21-00UT       1.67         1.67         3.33     

Rationale: G1 (Minor) geomagnetic storming is likely on 02 Oct due to
glancing effects from a CME that left the Sun on 28 Sep.

B. NOAA Solar Radiation Activity Observation and Forecast

Solar radiation, as observed by NOAA GOES-19 over the past 24 hours, was
below S-scale storm level thresholds.

Solar Radiation Storm Forecast for Sep 30-Oct 02 2026

              Sep 30  Oct 01  Oct 02
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 30-Oct 02 2026

              Sep 30        Oct 01        Oct 02
R1-R2           10%           10%           10%
R3 or greater    1%            1%            1%

Rationale: A slight chance for R1-R2 (Minor-Moderate) radio blackouts
due to isolated M-class flare activity will persist through 02 Oct.


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