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Space Weather Message Code: WARK04
Serial Number: 5325
Issue Time: 2026 Apr 21 0545 UTC
EXTENDED WARNING: Geomagnetic K-index of 4 expected
Extension to Serial Number: 5324
Valid From: 2026 Apr 20 0805 UTC
Now Valid Until: 2026 Apr 21 1800 UTC
Warning Condition: Persistence
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.
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Space Weather Message Code: WARK05
Serial Number: 2229
Issue Time: 2026 Apr 21 0544 UTC
EXTENDED WARNING: Geomagnetic K-index of 5 expected
Extension to Serial Number: 2228
Valid From: 2026 Apr 21 0110 UTC
Now Valid Until: 2026 Apr 21 1500 UTC
Warning Condition: Persistence
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Spacecraft - Minor impact on satellite operations possible.
Aurora - Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.
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Space Weather Message Code: ALTK05
Serial Number: 2012
Issue Time: 2026 Apr 21 0153 UTC
ALERT: Geomagnetic K-index of 5
Threshold Reached: 2026 Apr 21 0148 UTC
Synoptic Period: 0000-0300 UTC
Active Warning: Yes
NOAA Scale: G1 - Minor
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Spacecraft - Minor impact on satellite operations possible.
Aurora - Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.
______________________________________________________
Space Weather Message Code: WARK04
Serial Number: 5324
Issue Time: 2026 Apr 21 0110 UTC
EXTENDED WARNING: Geomagnetic K-index of 4 expected
Extension to Serial Number: 5323
Valid From: 2026 Apr 20 0805 UTC
Now Valid Until: 2026 Apr 21 1200 UTC
Warning Condition: Persistence
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.
______________________________________________________
Space Weather Message Code: WARK05
Serial Number: 2228
Issue Time: 2026 Apr 21 0110 UTC
WARNING: Geomagnetic K-index of 5 expected
Valid From: 2026 Apr 21 0110 UTC
Valid To: 2026 Apr 21 0600 UTC
Warning Condition: Persistence
NOAA Scale: G1 - Minor
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Spacecraft - Minor impact on satellite operations possible.
Aurora - Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.
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Space Weather Message Code: ALTEF3
Serial Number: 3680
Issue Time: 2026 Apr 20 2023 UTC
CONTINUED ALERT: Electron 2MeV Integral Flux exceeded 1000pfu
Continuation of Serial Number: 3679
Begin Time: 2026 Apr 19 1920 UTC
Yesterday Maximum 2MeV Flux: 1297 pfu
Potential Impacts: Satellite systems may experience significant charging resulting in increased risk to satellite systems.
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Space Weather Message Code: ALTK05
Serial Number: 1783
Issue Time: 2026-04-20T19:34:00
ALERT: Geomagnetic K-index of 5
THRESHOLD: 2026-04-20 19:34 UTC
ISSUED BY: Forecaster User
SYNOPTIC PERIOD: 1800-2100
ACTIVE WARNING: YES
NOAA SCALE: G1 - Minor
COMMENT:
G1 - Minor
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Space Weather Message Code: ALTK05
Serial Number: 1782
Issue Time: 2026-04-20T17:36:00
ALERT: Geomagnetic K-index of 5
THRESHOLD: 2026-04-20 17:34 UTC
ISSUED BY: Forecaster User
SYNOPTIC PERIOD: 1500-1800
ACTIVE WARNING: YES
NOAA SCALE: G1 - Minor
COMMENT:
G1 - Minor
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Space Weather Message Code: WARK04
Serial Number: 5001
Issue Time: 2026-04-20T17:21:00
EXTENDED WARNING: Geomagnetic K-index of 4 expected
Extension to Serial Number: 5323
Valid From: 2026-04-20T08:05:00
Now Valid Until: 2026-04-21 03:00
Warning Condition: Persistence
Extended 2026-04-20 17:21 by Forecaster User
Extended 2026-04-20 17:21 by Forecaster User
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Space Weather Message Code: WARK05
Serial Number: 2065
Issue Time: 2026-04-20T17:20:00
WARNING: Geomagnetic K-index of 5 expected
ISSUED BY: Forecaster User
VALID FROM: 2026-04-20 17:20 UTC
VALID TO: 2026-04-20 23:59 UTC
WARNING CONDITIONS: Onset
NOAA SCALE: G1 - Minor
COMMENT:
G1 - Minor
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Space Weather Message Code: WARK04
Serial Number: 5323
Issue Time: 2026 Apr 20 1420 UTC
EXTENDED WARNING: Geomagnetic K-index of 4 expected
Extension to Serial Number: 5322
Valid From: 2026 Apr 20 0805 UTC
Now Valid Until: 2026 Apr 20 2100 UTC
Warning Condition: Onset
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.
______________________________________________________
Space Weather Message Code: ALTK04
Serial Number: 2651
Issue Time: 2026 Apr 20 0819 UTC
ALERT: Geomagnetic K-index of 4
Threshold Reached: 2026 Apr 20 0820 UTC
Synoptic Period: 0600-0900 UTC
Active Warning: Yes
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.
______________________________________________________
Space Weather Message Code: WARK04
Serial Number: 5322
Issue Time: 2026 Apr 20 0805 UTC
WARNING: Geomagnetic K-index of 4 expected
Valid From: 2026 Apr 20 0805 UTC
Valid To: 2026 Apr 20 1500 UTC
Warning Condition: Onset
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.
______________________________________________________
Space Weather Message Code: ALTEF3
Serial Number: 3679
Issue Time: 2026 Apr 19 1947 UTC
ALERT: Electron 2MeV Integral Flux exceeded 1000pfu
Threshold Reached: 2026 Apr 19 1920 UTC
Station: GOES19
Potential Impacts: Satellite systems may experience significant charging resulting in increased risk to satellite systems.
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Space Weather Message Code: ALTK06
Serial Number: 714
Issue Time: 2026 Apr 19 0900 UTC
ALERT: Geomagnetic K-index of 6
Threshold Reached: 2026 Apr 19 0859 UTC
Synoptic Period: 0600-0900 UTC
Active Warning: Yes
NOAA Scale: G2 - Moderate
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 55 degrees Geomagnetic Latitude.
Induced Currents - Power grid fluctuations can occur. High-latitude power systems may experience voltage alarms.
Spacecraft - Satellite orientation irregularities may occur; increased drag on low Earth-orbit satellites is possible.
Radio - HF (high frequency) radio propagation can fade at higher latitudes.
Aurora - Aurora may be seen as low as New York to Wisconsin to Washington state.
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Space Weather Message Code: WARK05
Serial Number: 2227
Issue Time: 2026 Apr 19 0849 UTC
EXTENDED WARNING: Geomagnetic K-index of 5 expected
Extension to Serial Number: 2226
Valid From: 2026 Apr 18 2348 UTC
Now Valid Until: 2026 Apr 19 1800 UTC
Warning Condition: Persistence
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Spacecraft - Minor impact on satellite operations possible.
Aurora - Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.
______________________________________________________
Space Weather Message Code: WARK06
Serial Number: 655
Issue Time: 2026 Apr 19 0849 UTC
WARNING: Geomagnetic K-Index of 6 expected
Valid From: 2026 Apr 19 0848 UTC
Valid To: 2026 Apr 19 1500 UTC
Warning Condition: Onset
NOAA Scale: G2 - Moderate
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 55 degrees Geomagnetic Latitude.
Induced Currents - Power grid fluctuations can occur. High-latitude power systems may experience voltage alarms.
Spacecraft - Satellite orientation irregularities may occur; increased drag on low Earth-orbit satellites is possible.
Radio - HF (high frequency) radio propagation can fade at higher latitudes.
Aurora - Aurora may be seen as low as New York to Wisconsin to Washington state.
______________________________________________________
Space Weather Message Code: WARK04
Serial Number: 5321
Issue Time: 2026 Apr 19 0849 UTC
EXTENDED WARNING: Geomagnetic K-index of 4 expected
Extension to Serial Number: 5320
Valid From: 2026 Apr 18 0157 UTC
Now Valid Until: 2026 Apr 19 2359 UTC
Warning Condition: Persistence
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.
______________________________________________________
Space Weather Message Code: ALTK05
Serial Number: 2011
Issue Time: 2026 Apr 19 0650 UTC
ALERT: Geomagnetic K-index of 5
Threshold Reached: 2026 Apr 19 0650 UTC
Synoptic Period: 0600-0900 UTC
Active Warning: Yes
NOAA Scale: G1 - Minor
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Spacecraft - Minor impact on satellite operations possible.
Aurora - Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.
______________________________________________________
Space Weather Message Code: ALTK05
Serial Number: 2010
Issue Time: 2026 Apr 19 0604 UTC
ALERT: Geomagnetic K-index of 5
Threshold Reached: 2026 Apr 19 0559 UTC
Synoptic Period: 0300-0600 UTC
Active Warning: Yes
NOAA Scale: G1 - Minor
NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation
Potential Impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Spacecraft - Minor impact on satellite operations possible.
Aurora - Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.
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https://www.swpc.noaa.gov/products/alerts-watches-and-warnings