YOSEMITE · HORSETAIL FALL
Firefall Live
Should you go, which night is strongest, when should you arrive, and what could stop the glow?
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CURRENT OUTLOOK
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Connecting to the Firefall engine
THE DECISION
Best current Firefall attempt
Loading the water, sky and solar signals that control Firefall.
SEVEN-NIGHT VIEW
Compare upcoming evenings
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TRIP PLANNER
What do extra nights buy you?
Adjacent weather nights are correlated, so the model does not pretend each night is an independent lottery ticket.
ACCESS STATUS
Verify this season’s Yosemite rules
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Official NPS Horsetail Fall guidance ↗DATA HEALTH
What the engine is using
HOW IT WORKS
Three things must line up
Nearby Sierra snow-water measurements, snowpack change, temperature-driven melt and recent precipitation establish whether Horsetail has a plausible source. Merced River discharge is corroborating basin context only.
The engine samples the setting-sun corridor west-southwest of Yosemite rather than trusting a generic local cloud percentage. Near the event window, GOES-18 can replace forecast uncertainty with satellite evidence.
Sun position is calculated minute by minute. The score hard-stops outside the Firefall alignment envelope; a pretty weather forecast cannot overcome impossible geometry.
Independent experimental decision support. Probabilities are not guarantees.