Message 30181 in SPACWX.USA
From: N4SD
Date: Thu, 17 Sep 26 12:32:00 Z
Newsgroups: SPACWX.USA
Subject: Space Weather 3-Day Forecast
Message-ID: <22597_N4SD>
Path: N2MH4|WB4WPF|N3IP|KA3VSP|N4SD
R:260917/1307Z 37328@N2MH4.#SENC.NC.USA.NOAM LinBPQ6.0.24
R:260917/1307Z 20783@WB4WPF.#SFL.FL.USA.NOAM LinBPQ6.0.25
R:260917/1306Z 74837@N3IP.#SEPA.PA.USA.NOAM BPQK6.0.24
R:260917/1305Z 8240@KA3VSP.DE.USA.NOAM BPQ6.0.25
R:260917/1232Z 22597@N4SD.#TIDE.VA.USA.NOAM BPQ6.0.24
FXXX10 KWNP 171231
DAYTDF
:Product: 3-Day Forecast
:Issued: 2026 Sep 17 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 Sep 17-Sep 19 2026 is 4.67 (NOAA Scale
G1).
NOAA Kp index breakdown Sep 17-Sep 19 2026
Sep 17 Sep 18 Sep 19
00-03UT 3.00 3.67 2.67
03-06UT 1.67 2.00 2.00
06-09UT 1.67 2.00 2.33
09-12UT 1.67 2.67 2.33
12-15UT 3.33 2.67 2.33
15-18UT 3.33 2.67 2.33
18-21UT 3.33 2.67 2.33
21-00UT 4.67 (G1) 3.00 2.67
Rationale: Rationale: Active to G1 (Minor) geomagnetic storm conditions
are likely on 17 Sep due to combined negative polarity CH HSS and CME
influences. Unsettled to active levels are expected on 18 and 19 Sep as
enhancements wane.
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 Sep 17-Sep 19 2026
Sep 17 Sep 18 Sep 19
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 Sep 17-Sep 19 2026
Sep 17 Sep 18 Sep 19
R1-R2 5% 5% 1%
R3 or greater 1% 1% 1%
Rationale: No R1 (Minor) or greater radio blackouts are expected. No
significant active region flare activity is forecast.
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