Thunderstorm probability (%).
GribStream
GribStream Code: spctstm4hr
Scheduled source retirement: NOAA plans to retire this HREF-based SPC product when SPC_POST v3 starts, on or after 14 October 2026 with the 12 UTC cycle. Significant weather can delay the change. SCN26-77.
Migration target: refsct · TSTM · 4 hour probability. The new products use different inputs and calibration. Select the replacement dataset and the appropriate probability period in your queries. Existing data expires under the current two-day retention policy.
SPC HREF 4-hour thunderstorm probability summarizes convective thunderstorm risk over a broader planning window than the one-hour product. It is useful when the exact minute of initiation is less important than knowing whether a location is likely to be affected during the next operational block.
The product uses SPC post-processing of High-Resolution Ensemble Forecast guidance to produce a probability field that can be compared across cities, assets, routes, and service territories. Four-hour probabilities are especially useful for outdoor events, school athletics, construction sites, utilities, aviation ground operations, and dispatch desks that need to plan staffing or safety posture before storms arrive.
Use it with SPC Thunderstorm 1h for shorter-term timing, SPC Lightning 4h for lightning-density context, and HRRR for storm-scale reflectivity and wind signals.
TSTMClick a parameter to reveal variants in a compact table with ready-to-copy JSON selectors.
Thunderstorm probability (%).
| Level | Info | Horizon | Introduced | Selector |
|---|---|---|---|---|
surface |
prob >0 |
4h-48h | 2 days ago |
{"name":"TSTM","level":"surface","info":"prob >0"}
|
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