Flash flood warnings and watches: What do they mean?

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Delran flood damage.

PHILADELPHIA - Flash flood warning, flood warning, flood advisory and flood watch. These alerts tend to pop up whenever severe weather hits, but what do they actually mean?

What we know:

Many people assume a "watch" and a "warning" are interchangeable — but knowing the distinction is critical.  

Watch vs. warning vs. advisory

• Warning: A flash flood warning or flood warning means it's time to take action, because the hazardous weather is imminent or already happening.
• Watch: A flood watch tells you to be prepared, because conditions are favorable for flooding to happen. A watch does not mean flooding will occur, but it is possible.
• Advisory: You should be aware if a flood advisory is issued. An advisory means that flooding is not expected to be bad enough for a warning, but may still cause significant inconvenience.

When You Shouldn’t Drive 

• If your area is under a warning, don’t gamble with flash floods or falling trees. Postpone driving, if you can.
• If visibility is low, heavy rain and wind can drastically reduce visibility and reaction time.
• If water is covering the road, try to avoid driving through flooded roads. Just six inches of water can stall a car, and 12 inches can carry it away.
• If the power is out in your neighborhood, that likely means traffic lights are too. Navigating intersections can become dangerous fast.

What you can do:

What to do after driving through floodwater

1. Don't start your car - Attempting to start a vehicle with water in the engine compartment could cause hydrolock and damage your engine.
2. Disconnect the battery - Water mixed with electrical current could cause failure of electrical items in your vehicle.
3. Roll down the windows.
4. Look for a high-water mark to give you an idea of the level of damage.
5. Get any residual water out of your vehicle
6. Drain and refill the engine oil, transmission oil and differential fluid
7. Remove spark plugs if the vehicle is in a high-water situation.
8. Check your vehicle's field system, along with other fluids.
9. Assess electrical damage by turning on electrical systems one-by-one.