Warming temperatures in the Red River of the North basin will begin melting ice and snowpack, setting the stage for a dangerous second crest in Fargo, N.D., and Moorhead, Minn., later this month, according to forecasters with NOAA’s National Weather Service.
After using all available forecast temperature information to assess its impact on the melt of snow and ice that remains in the Red River Basin, the National Weather Service updated the outlook for the second crest at Fargo. The current National Weather Service outlook indicates a high probability (75 percent chance) of reaching or exceeding 41 feet and a 25 percent chance of reaching or exceeding 42.8 feet. This second crest currently is expected to occur in the latter half of April.
Fargo saw a March record rainfall of 4.62 inches, topping the 1882 record of 2.83 inches, and a record March snowfall of 28.1 inches, topping the 1997 record of 26.2 inches. The current winter season (2008-09) snowfall through April 3 at Fargo-Moorhead was second only to 1996-97 totals. Frigid temperatures have kept this water frozen in place, and it will begin to flow into the river system in the coming weeks. Before the record March snowfall, water content in the region’s ice and snowpack was as much as 300 percent above normal.
“The collaborative effort of local, state and federal governments to protect Fargo last week paid off, but Fargo isn’t out of the woods yet,” said Scott Dummer, chief hydrologist of the North Central River Forecast Center. “It’s critical that we plan for the second crest now.”
Several factors create a high potential for additional significant flooding in the Red River of the North basin. These factors include:
- High flows. Local river levels have fallen after their recent record flows, but these drops are slowed by excessive downstream waters and the overall low-relief of the river valley, leaving a significant amount of water in the river.
- Saturated and/or frozen soils. Heavy rain last fall produced saturated soils before winter freeze-up. These soils remain saturated and/or frozen to a depth of 30 inches or more, causing any spring rains or snowmelt to rapidly runoff into the river.
- Widespread frozen surface water. Cold temperatures caused overland flow and local runoff to freeze on area fields. This water will quickly become runoff when the temperatures warm above freezing.
- Record precipitation and recent significant snowfall. Fargo saw all-time record precipitation over the past seven months, with significant precipitation throughout the basin, particularly upstream of Fargo. The recent March 30-April 1 snow storm brought an additional 10-20 inches of snow across broad sections of the basin, which will increase runoff into the river when melting begins.
- Reduced water storage. Area reservoirs are virtually full and currently have little or no additional storage capacity. Officials are releasing water from these reservoirs. Additional runoff will enhance the need for further releases.
- Spring warming. An inevitable warm-up through the spring combined with the threat of additional rainfall could exacerbate the potential for rapid runoff.
Concerns still remain about the first flood wave as it continues to slowly move downstream toward Drayton. Residents can monitor local conditions online.
NOAA urges residents of Fargo-Moorhead and Red River Valley communities to continue heeding orders issued by local officials. If told to evacuate, do so immediately.
NOAA understands and predicts changes in the Earth’s environment, from the depths of the ocean to the surface of the sun, and conserves and manages our coastal and marine resources.
21 April 2009
Debris-flows can occur quickly and trap or kill unsuspecting victims in their path.
High resolution (Credit: NOAA)
Many people living throughout much of the continental United States may not be too concerned about a wall of mud, water, and debris swallowing up their homes and potentially endangering their lives, but those living near wildfire burn areas in regions such as Southern California may tell another story.
In the United States, approximately 25 to 50 deaths a year can be attributed to the phenomenon of debris flow — or mudslides as they are more commonly known — with monetary losses exceeding $2 billion annually (National Resource Council, 2004).
These gravity-driven mixtures of sediment, water, and other dislodged objects are caused by heavy rainfall or rapid snowmelt, and weakened terrain, creating a deadly slurry of dislodged rocks, soil, and trees. These ingredients combine to resemble a wet concrete-like mass that can develop tremendous downhill force and leave a path of destruction in its wake.
27 January 2009
Weather Systems - Precipitation In The Making
By: Vince Paxton
For those who study weather on a daily basis, movement of air masses is at the heart of most changes in weather conditions. These huge areas of warm air or cold air (weather fronts) move up or down in the atmosphere, as well as horizontally, sometimes covering hundreds of miles in a short time. The sun does not heat the atmosphere on a consistent basis. Variations in temperature occur, depending on the location. The large masses of air move about, part of nature’s attempt to maintain balance.
But it is not just the movement of a single air mass that is key in determining the type of weather we experience. Instead, the confrontation between two masses of air often cause significant changes in conditions. A mass of air moving into a particular region will encounter another mass. The area where these two air masses meet, where the conflict occurs, is commonly called a front.
For general weather watching purposes, when a cold air mass moves in and attempts to replace a warmer mass, meteorologists and weather watchers call it a cold front. When the moving air mass is warm and it meets a cold air mass, the area of contact is called a warm front.
However, movement of these huge areas of air is not limited to straight-line, horizontal activity. A warm mass encountering a colder section of air will ride over the top of the cooler mass, causing clouds to be formed through condensation. Essentially, the difference in temperature between the two air masses triggers a reaction in the water vapor of the masses. Most of the time, an observer of this activity will see cirrus clouds high in the atmosphere, with clouds forming at a slightly lower level later. Heavy stratus clouds appear, generally producing precipitation and windy conditions.
Over long periods of time, there is some consistent frontal activity, which produces the various climate conditions found around the world. Scientists have learned that weather changes produced by a cold front will often be more volatile than the activity caused by a warmer mass of air. A cold front meeting a warm air mass forces the warmer up, quickly. This movement results in unstable conditions and convection. Massive cumulus clouds will result, with storms forming along the boundary between the two masses of air. In addition, the rising air produces a low-pressure area, with stronger winds resulting. Most of the time area residents will experience heavy rain. Precipitation tends to linger after the passage of this frontal activity.
Less common but still of interest is the overtaking of a slow-moving warm front by a cold air mass. The warm air is pushed to a higher elevation but the air masses continue to travel together. This front between two air masses, one above another, is known as an occluded front, which usually have stratus clouds and some rain as companions.
While displacement of one air mass by another is quite common, sometimes these two sections of the atmosphere have the same strength. When one cannot replace the other, meteorologists and weather watchers see a stationary front. Extended periods of cloudiness and precipitation are the features of this unique climate condition.
Article Source: http://www.articlesnatch.com
About the Author:
Vince Paxton published essentially for http://www.alicante-spain.com , a web publication on the topic of weather fronts and climate. His writings on weather forecast for benidorm spain are found on his site .
18 January 2009
Cold Weather Safety Tips:
* Dress in several layers of loose-fitting clothing to create pockets of insulating warm air.
* Wear wool or fleece fabrics, not cotton as it dries slowly; warm socks with a thermal sock liner; comfortable, closed shoes; a scarf, hat and earmuffs to prevent loss of body heat; a water repellent, hooded outer garment to add extra protection; and mittens instead of gloves to keep hands warm.
* Walk around or move in place to increase circulation and generate additional body heat.
* Drink warm beverages.
* Do not drink alcohol as it will cause a loss of body heat by dilating blood vessels.
* Seek shelter indoors periodically to warm up.
* Take extra precaution with the elderly and very young as they are most at-risk.
Cold Weather Dangers and Warning Signs:
* Frostbite is damage to body tissue caused by exposure to extreme cold. Warning signs include a loss of feeling and a white or pale appearance in extremities, such as fingers, toes, ear lobes or the tip of the nose.
* Hypothermia is a potentially fatal condition brought on when the body temperature drops to less than 95 degrees F. Warning signs include uncontrollable shivering, memory loss, disorientation, incoherence, slurred speech, drowsiness and apparent exhaustion.
If you experience any of the warning signs of frost bite or hypothermia, seek medical attention immediately.