103
FXXX10 KWNP 151231
DAYTDF

:Product: 3-Day Forecast
:Issued: 2026 Sep 15 1230 UTC
# Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center
# Product description and SWPC contact on the Web
# http://www.swpc.noaa.gov/wwire.html
#
#             3-Day Forecast
#
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 15-Sep 17 2026 is 4.67 (NOAA Scale
G1).

NOAA Kp index breakdown Sep 15-Sep 17 2026

             Sep 15       Sep 16       Sep 17
00-03UT       3.00         3.67         3.67
03-06UT       2.33         3.33         3.00
06-09UT       0.33         3.00         2.00
09-12UT       0.67         2.67         2.67
12-15UT       3.00         3.00         2.67
15-18UT       3.00         3.33         2.67
18-21UT       3.00         3.67         2.00
21-00UT       4.67 (G1)    4.67 (G1)    2.67

Rationale: Active to G1 (Minor) geomagnetic storming is likely on 15 and
16 Sep, with a chance for G1 conditions persisting on 17 Sep, due to
combined negative polarity CH HSS and CME influences.

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 15-Sep 17 2026

              Sep 15  Sep 16  Sep 17
S1 or greater   20%     10%      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 15-Sep 17 2026

              Sep 15        Sep 16        Sep 17
R1-R2           10%           10%           10%
R3 or greater    1%            1%            1%

Rationale: There is a slight chance for R1-R2 (Minor-Moderate) radio
blackouts on 15-17 Sep period.