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You might know what a flash flood warning is, but what about a flash flood watch?
Here, we clarify what a flash flood is, how it differs from other flood types, and explain what a flash flood watch is, distinct from a flash flood warning.
As far as a flash flood watch is concerned, it describes a situation when a flash flood becomes possible and people are advised to prepare in case it does happen.
A Flash Flood
A flash flood is a flood that happens following a quick burst of rain, a sudden outburst rather than a normal dribble or trickle. Unlike areal flooding, it does not build up gradually, involve prolonged rainfall over a long time period, or cover a wide area. It is more localized and often unexpected, and a heavy downpour usually precedes it.
A flash flood can develop in a mere few minutes or within six hours to become a violent flood. In flood-prone areas, flash flooding results in the sudden accumulation of water and ponding. This makes it all the more necessary to issue a warning when it is likely to occur or advise a flash flood watch when conditions make it possible.
A Flash Flood Warning
A flash flood warning is issued when there is meteorological evidence to indicate that a flash flood is imminent. It is a warning to all those who may be affected by the flood to take immediate action to protect their life and property.
A Flash Flood Watch
We will now distinguish a flash flood watch from a flash flood warning. A flash flood watch is advised when there is meteorological evidence to suggest that a flash flood is possible in a particular area. It is advised because the conditions are ripe for it to occur.
The difference from a flash flood warning is only a matter of lesser likelihood. Both are equally caused for concern.
This is different from a flash flood warning because it is advice or recommendation. The developing conditions might or might not lead to an actual flood occurring. However, flash flood watchers are advised to be alert, prepared, and to plan for the eventuality. This advice is particularly critical if the flash flood watch was issued for those living in flood-prone areas, low-lying areas, or near the sea, rivers, or streams.
As shown in the image below, the possibility of a flash flood is often stated as a percentage and described as either a marginal, slight, or high risk.
This particular flash flood watch was put into effect for the Big Bend and most of North Florida on September 9, 2022 [1]. The condition that made it necessary was a surge of tropical moisture that was producing bouts of heavy rainfall, thus increasing the chances of flooding.
When a Flash Flood Watch is Advised
Whether a flash flood watch is put into effect or a flash flood warning is issued, the possible consequences are the same if the flood occurs. All floods are a potential threat to life and property, so take all necessary precautions. Although this article was focused on explaining what a flash flood watch is, i.e., an alert of possible flooding, here is a quick reminder of some things you can do to remain safe when such a watch is advised.
If you are indoors:
- Stay away from basements, tunnels, sewers, etc.
- Make arrangements to move your family, essential belongings, and valuables to higher ground.
If you are outdoors:
- Don’t attempt to cross low-water crossings or covered bridges.
- Never attempt to cross a flowing stream of water, even on foot. A person can be easily swept off their feet by only six inches of rapidly flowing water. Only walk in water if necessary, if the water is not flowing rapidly.
- Don’t stay in a car unless you are certain you can follow a safe escape route. Still, be wary of all puddles unless you know the roads and potholes. A car can easily lose control with only one foot of rapidly flowing water.
Further Reading
Read our article on ‘How to Prepare for a Flood’, particularly the section on what to do right before a flood watch is advised or when a warning is issued.
Take a look at some of our related articles below.
Reference
[1] Justin Ballard. A flash flood watch is in effect for the Big Bend and much of North Florida. WFSU, Storm Center. Retrieved from https://news.wfsu.org/wfsu-local-news/2022-09-09/a-flash-flood-watch-is-in-effect-for-the-big-bend-and-much-of-north-florida. September 9, 2022.
