When forecasts are issued

When we reference forecasts, there are a couple times to note:

• The initialization time refers to the start time of the forecast
• The issue time is when the forecast was published

HydroForecast's issue times are later than the initialization time because we rely on weather forecasts which take a few hours to be produced.

HydroForecast Short-term has two primary updates each day using the 00 and 12 UTC (GMT) weather forecasts. Every two hours between the two primary updates, HydroForecast Short-term makes smaller adjustments to the latest forecast based on near-real time flow observations. Here are the times of day the 00 and 12 UTC primary updates are first available.

00 UTC Forecast (the morning forecast in the US):

Initialization time: 00 UTC aka 16:00 PST/19:00 EST of the day before

Issue time: 08 UTC aka midnight PST/03:00 EST

12 UTC Forecast (the afternoon forecast in the US):

Initialization time: 12 UTC aka 04:00 PST/07:00 EST

Issue time: 20 UTC aka noon PST/15:00 EST

HydroForecast Seasonal forecasts are issued once per day:

Initialization time: 00 UTC aka 16:00 PST/19:00 EST of the day before

Issue time: 01 UTC aka 17:00 PST/20:00 EST