Routine Space Environment Product (Daily)
Issued by NWS
Issued by NWS
335
FXXX10 KWNP 161231
DAYTDF
:Product: 3-Day Forecast
:Issued: 2025 May 16 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 3 (below NOAA
Scale levels).
The greatest expected 3 hr Kp for May 16-May 18 2025 is 4.67 (NOAA Scale
G1).
NOAA Kp index breakdown May 16-May 18 2025
May 16 May 17 May 18
00-03UT 2.33 3.33 3.67
03-06UT 3.00 2.00 3.67
06-09UT 3.00 2.00 4.00
09-12UT 2.00 3.00 4.67 (G1)
12-15UT 2.33 3.00 3.67
15-18UT 1.33 3.67 3.67
18-21UT 1.33 3.33 4.00
21-00UT 2.33 3.33 3.67
Rationale: G1 (Minor) geomagnetic storm conditions are likely on 18 May
due to CH HSS onset.
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 May 16-May 18 2025
May 16 May 17 May 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
Radio blackouts reaching the R1 levels were observed over the past 24
hours. The largest was at May 15 2025 1721 UTC.
Radio Blackout Forecast for May 16-May 18 2025
May 16 May 17 May 18
R1-R2 65% 65% 65%
R3 or greater 30% 30% 25%
Rationale: There remains a 65% chance that M-Class (R1-R2,
Minor-Moderate) level flare activity will occur through 18 May with a
30% chance for X-Class (R3-Strong) levels during the same time due to
the complex magnetic field within Region 4087.