515
FXXX10 KWNP 241231
DAYTDF

:Product: 3-Day Forecast
:Issued: 2026 Sep 24 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 24-Sep 26 2026 is 4.67 (NOAA Scale
G1).

NOAA Kp index breakdown Sep 24-Sep 26 2026

             Sep 24       Sep 25       Sep 26
00-03UT       3.00         3.67         3.00
03-06UT       2.33         3.67         3.67
06-09UT       3.00         3.00         2.67
09-12UT       4.33         2.67         2.00
12-15UT       2.33         2.33         1.67
15-18UT       2.33         3.00         2.33
18-21UT       3.00         3.33         2.33
21-00UT       4.67 (G1)    3.00         2.67

Rationale: G1 (Minor) geomagnetic storming is likely on 24 Sep due to
positive polarity CH HSS influences. Unsettled to active levels are
expected to persist on 25 and 26 Sep as HSS effects gradually wane.

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 24-Sep 26 2026

              Sep 24  Sep 25  Sep 26
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 24-Sep 26 2026

              Sep 24        Sep 25        Sep 26
R1-R2           20%           20%           20%
R3 or greater    1%            1%            1%

Rationale: There is a slight chance for R1-R2 (Minor-Moderate) radio
blackouts through 26 Sep primarily due to the flare potential of Active
Regions 4536, 4538, and 4537.