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The Flash Flood Potential graphic on this page is an experimental product prepared using the National Weather Service's new "Interactive Forecasting Process System", or IFPS. Additional products generated from IFPS will be available to you over the coming months and years.
Please send any comments you have about the Flash Flood Potential Outlook to w-rev.webmaster@noaa.gov
This outlook is posted to the web by 6am each morning. It is NOT updated. Please click here for the latest National Weather Service watches, warnings, or advisories.
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Number |
Descriptor |
Discussion |
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1 |
Nil |
Stable and generally dry, or no heavy rain expected. High based convection is allowed with virga or no wetting rain. Any light stratiform rain does not affect the antecedent risk. |
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2 |
Low |
Some moisture and mostly high based thunderstorms are possible. Any convective rain is brief or mostly light. Prolonged heavy showers are unlikely. Considerable tropical cloud cover may be present but is without significant convection. Any light precipitation contributes little to current runoff potential and future antecedent conditions. High cell speed may contribute to the LOW designation. |
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3 |
Moderate |
Moisture is sufficient for at least local wetting rain, but generally below flash flood thresholds. There is a good chance of thunderstorms but they are mainly pulse type. There may be a transition from dry to wet down bursts. Local heavy rain is possible. Convection is generally not well organized but cells may interact as the event progresses. This risk may include events associated with heavy cloud cover and embedded convection in the remains of a tropical system. Risks vary considerably with terrain and cell speed. Training of cells may increase an area to a HIGH category. Flash flood prone areas are at greater risk than the area at large. |
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4 |
High |
Combined factors are at or approach flash flood thresholds. Thunderstorms are expected with at least local heavy rain. Local forcing is possible and convective interaction is likely. Antecedent conditions are possible but generally localized, if present. Cell speeds are usually low and training may push the risk to VERY HIGH. Terrain risks broaden and flash flood prone areas become a concern, even for relatively flat drainages. |
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5 |
Very High |
Flash Flood factors are at or above thresholds. Thunderstorms are expected. The character of any convection may change dramatically during the period. Local forcing and large scale dynamics are possible. Antecedent conditions may contribute to a faster reacting threat. All areas are at risk with any convection and or convection that breaks down into areas of heavy rain. Low cell speeds and or redevelopment are common. Flash flood prone areas are at an elevated risk and the risks are likely to increase through the course of a convective event. Persistent heavy rain could push a flood prone area to EXTREME. |
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6 |
Extreme |
All factors are at high levels. Thunderstorms are expected. Antecedent conditions are likely. Local forcing and or dynamics are likely. All areas are at risk but flash flood prone areas are at extreme risk. Unusually heavy, destructive flows are possible. Extreme conditions usually apply to smaller areas and are sparingly used. |
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