GribStream
Explore NOAA/SPC's parallel GREFS, REFSCT and GEFSCT probability guidance for a United States city. Use the city picker and time range to explore another city or forecast period.
Values are percentages from 0 to 100. Each point marks the end of a probability period: four hours for GREFS, one or four hours for REFSCT, and 24 hours for GEFSCT. The panels keep those periods separate. Overlapping windows must not be added together or divided into hourly probabilities.
The GEFS input control applies only to GREFS. For a 12 UTC REFS run, 0h uses the 12 UTC GEFS run and 6h uses the 06 UTC GEFS run. Both use the same REFS run. The lag is the age of the GEFS input, not a shift in forecast time or a publication delay; neither branch is inherently more accurate. The tables below the charts show when each forecast run was initialized and when each probability period ends. The charts use the latest available run for each interval end. Missing values are left blank. The ensemble information has already been combined into calibrated probabilities.
GREFS and REFSCT extend through 60 forecast hours. GEFSCT supplies eight daily periods ending at 12 UTC, through +204 hours for the 00 UTC run or +192 hours for the 12 UTC run. Full-period products are available through the model inventories and API; this dashboard uses fixed durations to keep each plotted series comparable.
NOAA schedules the operational transition on or after 14 October 2026. This dashboard uses NOAA’s parallel guidance. It is not an official warning service. See the NOAA implementation notice.
Read more about the new SPC probability datasets and the transition from older feeds.