The Day 4-8 Outlook doesn’t provide a categorical severe weather risk. Instead,
it shows severe probabilities of either 15% or 30%. For example, a 30% risk at a
given location means there’s a 30% chance that severe weather will occur within 25
miles of that location. Most of the time, the Day 4-8 forecast is either “Potential
Too Low” or “Predictability Too Low”. An outlook of “Potential Too Low” means that
the threat for a regional area of organized severe storms appears unlikely (i.e.,
less than 15%) for the forecast day. “Predictability Too Low” indicates that severe
storms may be possible based on some model scenarios. However, the location or occurrence
of severe storms are in doubt due to:
1) large differences in the deterministic model solutions,
2) large spread in the ensemble guidance, and/or
3) minimal run-to-run continuity.
For more information, visit http://www.spc.noaa.gov/misc/SPC_probotlk_info.html.
