GribStream

NOAA SPC HREF 4-hour Calibrated Hail Probability

GribStream Code: spchail4hr
SPC four-hour hail probability across its complete grid
SPC four-hour hail probability across the complete populated CONUS grid, with high-contrast light state and country boundaries. This plot was generated from the spchail4hr dataset.

Description

SPC HREF calibrated hail probability is a post-processed severe-weather product from the Storm Prediction Center. It is designed to translate storm-scale ensemble signals and larger-scale environmental support into a four-hour hail probability field over CONUS.

For calibrated severe hazards, SPC pairs HREF storm-attribute evidence, such as updraft helicity thresholds, with GEFS environmental ingredients. The historical frequency of reports near each grid point is then used to produce calibrated probabilities. For hail, the environmental side includes instability and effective shear, which are central ingredients in organized severe convection.

This dataset is useful for hail-aware alerting, insurance exposure, agriculture, fleet and vehicle protection, rooftop solar operations, utilities, and emergency-management dashboards. It works best as a probability layer, not as a deterministic hail-size forecast, and should be interpreted alongside HRRR, RAP, and SPC outlook context.

Detail

Parameters

HAILPROB –Hail probability (%)
1 variant

Hail probability (%).

Level Info Horizon Introduced Selector
surface prob >0 4h-36h 2 days ago
{"name":"HAILPROB","level":"surface","info":"prob >0"}