The rain and wind from Hurricane Sandy is about to get worse, Arlington County said in an emergency alert this afternoon (below).

County officials compared the dangerous conditions Arlington will experience over the next 24 hours to the heavy winds of the June 29 derecho, which lasted 24 minutes.

Already some power problems and falling trees and power lines have been reported. Dominion reported 423 customers without power in Arlington earlier this afternoon, but power has since been restored to most. Firefighters are currently on the scene of a large tree that fell on to a house on the 2900 block of N. Oxford Street, in the Bellevue Forest neighborhood. The house was unoccupied at the time and nobody was hurt.

In the following Arlington Alert, the county says they’re starting to receive reports of flooded roads. Long Bridge Drive has already been closed due to flooding.

Hurricane Sandy is about to get worse.

Think of the derecho storm with high winds in June that lasted 24 minutes. The winds we’re about to experience beginning this afternoon are like the derecho, but they will last for 24 hours.

To paraphrase: Instead of 24 minutes of dangerous winds, it will be 24 hours of dangerous conditions.

We need you to stay off the roads and indoors as travel will become extremely dangerous with winds and heavy rain beginning this afternoon.

Several inches of rain and potential flooding could start happening. We’re beginning to get reports of flooded roads.

Have your battery-powered radio available and make sure your phone is fully charged if you lose power. We will share any shelter openings and other updates via our information channels such as our Emergency Management Blog, County Web Page and Arlington Alert.

Separately, the county is advising residents to secure loose items outside, if that can be done safely, and to avoid driving into high standing water. “Please exercise extreme caution” in the storm, the county said.

As high winds approach, exercise extreme caution. For the safety of our employees, Arlington County will implement its high-wind policy. As the wind approaches sustained speeds of 30-40-45 miles-per-hour, we will pull crews off the roads and in to a safe place. This includes Parks staff, who will suspend responding to downed tree calls during these dangerous wind conditions. As winds approach very high, sustained speeds, police and fire personnel will respond only to life-threatening calls.

Please exercise extreme caution; emergency managers urge you to go a safe place and stay there. We also encourage you to remove/secure loose items from your yard, balcony, deck, etc., as these could become dangerous projectiles in high wind. Do this if you can do so safely.

Monday & Tuesday trash and recycling services are delayed until Wednesday. Bring your trash carts and recycling bins into your house/garage; do not leave them outside, as they could become airborne and dangerous.

Also, it’s a good idea to remove or secure loose items from your yard, balcony, deck, etc., as these could become dangerous projectiles in high wind. Do this if you can do so safely.

We are receiving reports of ponding on some roads. Standing water is deceptive; do not drive into standing water. Do not go out onto the roads if at all possible; we urge you to get to a safe place and stay there.

• Do not drive into standing water. If floodwaters rise around your car, abandon the car and move to higher ground if you can do so safely. You and the vehicle can be quickly swept away.
• Six inches of water will reach the bottom of most passenger cars, causing loss of control and possible stalling.
• A foot of water will float many vehicles .
• Two feet of rushing water can carry away most vehicles including SUVs and pick-ups.