NOAA, National Weather Service Middle Atlantic River Forecast Center Briefing Thursday July 3, 2014

Key Message Arthur is now a Hurricane. MARFC began 24 hr operations at 6:30 this morning. We will remain open overnight tonight. We will be monitoring the rain and rivers and will update our precipitation forecasts at minimum of every 6 hours. River forecasts will be updated when needed. Although we are not currently forecasting mainstem inland river flooding, there remains a potential for heavy rain and possible flooding across the eastern Mid-Atlantic region today and Friday. Flash flooding is also possible. Stay alert and monitor weather.gov and your local media today and Friday. The rain should move out by Friday evening.

Rain already on the ground Although not related to Arthur, strong thunderstorms yesterday dumped some locally heavy rainfall. These areas that experienced heavy rain yesterday will be vulnerable to additional rainfall today and Friday. – Berks County, NJ 2.62” – Sussex County, NJ 2.47” – Wayne County, PA 2.29” – Sullivan County, NY 2.17” – Hunterdon County, NJ 2.10” – Pike County, PA 2.00” – Hudson County, NJ 1.98” – Burlington County, NJ 1.92”

Current Conditions Rain has already moved into the Mid Atlantic region from the west with a frontal system. NWS radars are showing the rains from Arthur in the Carolinas. NWS Radar 10am July 3, 2014

Current Stream Conditions This map from our friends at the USGS shows how our current river levels compare to normal values for this time of year. The blues are higher than normal stream levels and the greens are at normal.

Forecast for Arthur The area in white shows where the center of Arthur is expected to be. Rain can occur sooner and much further inland of this area.

Storm Surge Potential This is a new experimental product from the National Weather Service this hurricane season. The blue colors on this map of coastal Virginia, the Chesapeake Bay and the Delmarva show where there is a 1 in 10 chance (worst case scenario) of up to 3 ft of storm surge is possible. At this time this is the furthest north any storm surge is shown. This product is posted at: hics_at1+shtml/ shtml?inundati on#contents hics_at1+shtml/ shtml?inundati on#contents It will be updated again today at 2pm, 8pm, and Friday at 2am, 8am and 2pm, etc… as long as a hurricane watch is in effect for the United States.

Rainfall forecast for today & Friday Although Arthur will stay out to sea, a frontal system will bring us rain and may draw in some of Arthur’s deep tropical moisture. The purple colors are where we are forecasting the most rain. These rainfall amounts are in the 1.5 to 2.5” range. Blue shades are around 1”. Thunderstorms always have the potential to dump locally very heavy amounts of rain. Isolated amounts of 4” are not out of the question today and tonight. This is why we must carefully keep monitoring this situation and stay alert and aware of the flood threat.

MARFC Status MARFC began 24 hour operations at 6:30 this morning. Our morning forecasts have been completed and are now posted at water.weather.gov None of our forecasts indicate flooding at this time. MARFC will continue daily briefings until the threat of flooding from Arthur has ended.

Some things to keep in mind today and Friday Monitor for your river forecast. There may be frequent updates made today, tonight and Friday. Remember there is uncertainty in river forecasts. When winds are strong, our rain gages will measure less rain than is actually falling. Radar rainfall estimates may not be accurate when hail is occurring. MARFC graphics & info do not contain the entire flood threat. See info from your local NWS Weather Forecast Office and your local media for flash flooding, storm surge, river flooding in tidal reaches, etc..

Flood Safety Messages Have a plan. NEVER drive through flooded roadways. Do not camp or park your vehicle along streams or low areas. Evacuate when requested. If flooding occurs, go to higher ground. Be especially cautious at night when it is harder to recognize flood dangers. Avoid nighttime travel if you can. Monitor for your river forecast. Look for frequent updates. Realize there is uncertainty in river forecasts.

Turn Around Don’t Drown Over half of all flood-related drownings occur when a vehicle is driven into flood water. The next highest percentage of flood-related deaths is due to walking into or near flood waters. People underestimate the force and power of water. Many of the deaths occur in automobiles as they are swept downstream. 6” of fast-moving flood water can knock over an adult. It takes only two feet of rushing water to carry away most vehicles, including pickups and SUVs. Flood waters may hide the fact that the road bed has been washed away.

Need more info? Contact your local NWS Weather Forecast Office – Binghamton, NY – Blacksburg, VA – Mt Holly, NJ – State College, PA – New York City, NY – Sterling, VA – Wakefield, VA

MARFC is online at: Homepage: Facebook Twitter

The next MARFC Briefing will be between 11am and Noon, Friday, July 4 th.