MARFC River Ice Briefing Friday, February 7, 2014 NWS Middle Atlantic River Forecast Center Delaware River at Penns Landing, Philadelphia, PA February 5, 2014 Photo courtesy Hadas

Our Current Status Ice movement in the Potomac River basin produced isolated minor flooding yesterday. Overall, ice coverage has remained unchanged in PA, NJ & NY. The ice is more than has been experienced in recent years, but the ice is not unusually thick. With below freezing temperatures expected through next week, we do not anticipate any large scale river ice break-up or jamming. Isolated jams and flooding are always possible. But of course ice conditions can change rapidly and people should stay alert and continue to monitor their river and weather forecast. We'll know more next week, in the meantime, stay alert, monitor and share river ice observations with your local NWS office.

A Sample of some recent River Ice Photographs We continue to find many helpful photographs from Facebook and Twitter from across our area. The following are a good sample from across our service area from the past couple of days.

Delaware River at Trenton, NJ Photo by Michael Feb 4, 2014

Raritan River, New Brunswick, NJ, near Rutgers University Photo by Daniel Feb 4, 2014

Susquehanna River at Tunkhannock, PA Photo by Jon Meyer, Feb 5, 2014

Susquehanna River in Lancaster County, PA Photo by Wes Feb 6, 2014

Lehigh River at Jim Thorpe, PA Photo by M. L.

Potomac River Tidal Basin, Washington DC Photo by Geeky Girl

River Hydrographs – What’s going on? The following 3 slides help explain why you’ve been seeing some strange river readings on the NWS river forecast website Depending on where the ice is in relation to the stream gage, or the type of streamgage equipment, the river readings will behave differently. River forecasting is difficult enough, but with river ice, we cannot predict when these sharp quick rises or falls will occur. This is why we need to stay in communication with each other, share our river photos and news about river ice. We will update our river forecasts often while river ice is moving.

Rises of this magnitude are likely the result of "anchor ice" building up on the orifice of the streamgage equipment. The ice increases the pressure that is measured by the equipment and is interpreted as an increase in river stage. When these readings are noticed, both the USGS and the NWS will filter these out as soon as possible.

Temperature Forecast for Saturday Where we have river ice, High Temperatures will range from the low 20s to mid 30s during the day Saturday. Overnight low temperatures will be in the teens and 20s.

Temperature Forecast for Sunday High Temperatures Sunday will range 20s to mid 30s Overnight lows will be in the teens or single digits.

Precipitation Forecast through the weekend All of the precipitation in the Mid- Atlantic will be in the form of snow. Without any runoff to our rivers, there is nothing to help break up the ice.

Recent River Ice Photos & News Thank you to everyone who is sharing news and photos of the river ice with us. We are sharing these photos, plus any news we gather, through our Facebook and Twitter accounts, everyday. Following MARFC on Facebook & Twitter is the best way to stay up to date on the river ice because, as you know, conditions can change rapidly. If you notice anything urgent, such as a jam forming and flooding, please notify your local emergency management and your local National Weather Service office soon as possible.

How to stay updated 1.Monitor your river forecast at: Follow MARFC on Facebook herService.MARFC.gov herService.MARFC.gov 3.Follow MARFC on 4.Follow your local NWS Weather Forecast Offices too. They are also sharing photos and news about river ice.

Additional Resources NWS Middle Atlantic River Forecast Center Website: NWS Temperature Forecasts: NWS Precipitation Forecasts: NWS MARFC Water Temperature Observations (raw data - not quality controlled): NWS Susquehanna and Delaware River Basins River Ice Website

As long as conditions remain stable, the next MARFC River Ice Briefing will be Wednesday, February 12th. If you have any questions or concerns, please