697
FXXX10 KWNP 111231
DAYTDF

:Product: 3-Day Forecast
:Issued: 2026 May 11 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 2 (below NOAA
Scale levels).
The greatest expected 3 hr Kp for May 11-May 13 2026 is 4.33 (below NOAA
Scale levels).

NOAA Kp index breakdown May 11-May 13 2026

             May 11       May 12       May 13
00-03UT       2.00         1.67         4.33
03-06UT       1.67         1.67         3.67
06-09UT       1.00         1.33         2.33
09-12UT       1.00         1.33         2.33
12-15UT       1.33         1.33         2.00
15-18UT       1.33         0.67         2.33
18-21UT       2.00         2.33         2.67
21-00UT       2.67         4.00         3.00

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-19 over the past 24 hours, was
below S-scale storm level thresholds.

Solar Radiation Storm Forecast for May 11-May 13 2026

              May 11  May 12  May 13
S1 or greater   10%     15%     15%

Rationale: A slight chance for an S1 (Minor) solar radiation storm event
will persist through 13 May. Probabilities increase from 10% to 15% on
days two and three due to the possibility of shock arrival enhancement
from the 10 May CME event originating from AR 4436.

C. NOAA Radio Blackout Activity and Forecast

Radio blackouts reaching the R2 levels were observed over the past 24
hours. The largest was at May 10 2026 1339 UTC.

Radio Blackout Forecast for May 11-May 13 2026

              May 11        May 12        May 13
R1-R2           45%           45%           45%
R3 or greater   10%           10%           10%

Rationale: A high chance for R1-R2 (Minor-Moderate) radio blackouts,
with a slight chance for an isolated R3 (Strong) event, will persist
through 13 May due to the flare potential and histories of regions 4432
and 4436.