FXXX10 KWNP 191231
DAYTDF

:Product: 3-Day Forecast
:Issued: 2026 May 19 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 May 19-May 21 2026 is 4.67 (NOAA Scale
G1).

NOAA Kp index breakdown May 19-May 21 2026

             May 19       May 20       May 21
00-03UT       1.67         2.33         2.67     
03-06UT       3.00         2.33         2.00     
06-09UT       3.67         2.00         2.33     
09-12UT       4.00         2.00         2.33     
12-15UT       4.67 (G1)    2.00         2.33     
15-18UT       2.00         2.00         2.33     
18-21UT       3.00         2.00         2.33     
21-00UT       3.33         2.00         2.67     

Rationale: Isolated periods of up to G1 (Minor) geomagnetic storms are
possible on 19 May due to a potential glancing blow from a CME that left
the Sun on 16 May.

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 19-May 21 2026

              May 19  May 20  May 21
S1 or greater    5%      5%      5%

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 May 19-May 21 2026

              May 19        May 20        May 21
R1-R2           40%           40%           40%
R3 or greater    5%            5%            5%

Rationale: There is a chance for R1-R2 (Minor-Moderate) radio blackouts
through 21 May.