Subj : 3 Day Space Weather Forecast
To   : All
From : Sean Dennis
Date : Fri Apr 17 2026 12:19 am

:Product: 3-Day Forecast
:Issued: 2026 Apr 16 1230 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 2 (below NOAA
Scale levels).
The greatest expected 3 hr Kp for Apr 16-Apr 18 2026 is 6.00 (NOAA Scale
G2).

NOAA Kp index breakdown Apr 16-Apr 18 2026

             Apr 16       Apr 17       Apr 18
00-03UT       0.67         2.33         6.00 (G2)
03-06UT       1.00         2.67         6.00 (G2)
06-09UT       1.00         2.67         5.00 (G1)
09-12UT       0.67         2.00         4.00     
12-15UT       1.67         1.33         3.67     
15-18UT       1.67         2.67         3.33     
18-21UT       1.67         4.33         3.00     
21-00UT       2.33         5.67 (G2)    4.33     

Rationale: G1-G2 (Minor-Moderate) geomagnetic storms are likely on 17-18
Apr due to the anticipated arrival of a negative polarity CH HSS 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 Apr 16-Apr 18 2026

              Apr 16  Apr 17  Apr 18
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 Apr 16-Apr 18 2026

              Apr 16        Apr 17        Apr 18
R1-R2           30%           30%           30%
R3 or greater    5%            5%            5%

Rationale: There is a chance for R1-R2 (Minor-Moderate) radio blackouts
through 18 Apr, mostly due to the flare potential of Region 4419.


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