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

:Product: 3-Day Forecast
:Issued: 2026 Aug 19 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 5 (NOAA Scale
G1).
The greatest expected 3 hr Kp for Aug 19-Aug 21 2026 is 4.67 (NOAA Scale
G1).

NOAA Kp index breakdown Aug 19-Aug 21 2026

             Aug 19       Aug 20       Aug 21
00-03UT       4.33         4.00         4.00     
03-06UT       4.67 (G1)    3.33         2.00     
06-09UT       4.00         3.33         1.67     
09-12UT       4.67 (G1)    3.00         2.33     
12-15UT       4.00         2.33         2.33     
15-18UT       3.67         2.00         2.67     
18-21UT       3.33         2.33         2.67     
21-00UT       3.67         3.00         3.00     

Rationale: G1 (Minor) geomagnetic storms are likely on 19 Aug due to the
influences of a CME and/or CIR.

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 Aug 19-Aug 21 2026

              Aug 19  Aug 20  Aug 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 Aug 19-Aug 21 2026

              Aug 19        Aug 20        Aug 21
R1-R2           35%           35%           35%
R3 or greater    5%            5%            5%

Rationale: There is a chance for R1-R2 (Minor-Moderate) radio blackouts,
with a slight chance for R3 (Strong) events through 21 Aug.


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