Thursday, December 30, 2010

[FEMA]

Homeland Security Threat Level: YELLOW (ELEVATED)

Significant National Weather

WestÂ*
A major winter storm continues to affect much of the region. Higher elevations in the Four Corners states will receive up to two feet of new snow, while lighter snowfall will affect much of the Northern and Central Rockies. Showers will fall from coastal Oregon down through central California and light snow will fall as far south as areas of Southern California. Gusty winds are forecast for much of the Southwest. There are numerous Watches and Warnings in effect for much of the region including Blizzard and Winter Storm Warnings, see www.weather.gov/largemap.php for the latest information.
Midwest
An arctic front will bring cold temperatures (single digits) and gusty northeasterly winds to the Northern Plains. A wintry mix will spread out of the Rockies into the northern Plains and Upper Midwest and bring up to a foot of new snow in many areas. There are numerous Watches and Warnings in effect for much of the Northern and Central Plains including Blizzard and Winter Storm Warnings. See http://www.weather.gov/largemap.php for the latest information. The Mississippi Valley, Great Lakes and Ohio Valley areas will see light rain or freezing drizzle across parts of Michigan and Ohio.
South
The Lower Mississippi and Tennessee Valleys will see scattered showers and thunderstorms. Heavier precipitation, with rainfall up to two inches, is forecast for the central Gulf Coast and Louisiana. The remainder of the Southeast will be dry.
Northeast
Under high pressure, the East Coast will have mostly sunny skies and high temperatures around 40 degrees. Precipitation will be limited to freezing drizzle or light freezing rain over parts of western Pennsylvania and West Virginia.
(NOAA and various media sources)Â*
Snowmelt Flooding

According to the National Oceanic and Atmospheric Administration (NOAA), eight of the most significant floods of the 20th century (in terms of area affected, property damage, and deaths) were related to snowmelt. Snowmelt flooding can occur in both winter and spring and is identified when melting snow is the major source of the water involved in a flood. The Northeast and North Central U.S., and some areas of the Western U.S. are particularly susceptible to snowmelt flooding.
Snowpacks store water and unlike rainfall, which reaches the soil almost immediately, snow stores the water until it melts, for days, weeks, or even months. Once the melted water reaches the soil, the result is the same as rain as the water either infiltrates into the soil, runs off, or both. Flooding can occur whenever the rate of water input exceeds the ability of the soil to absorb it or when the amount of water exceeds natural storage capacities in soil, rivers, lakes and reservoirs.
Several factors contribute to snowmelt flooding including; high soil moisture conditions prior to snowmelt, frozen soil that prevents water from infiltrating the soil, heavy snow cover that stores and then yields even more water as snowmelt, widespread heavy rains melting snowpack causing them to melt earlier than expected, known as âRain-on-snowâ events, and finally ice jams. Ice jams are blocks of ice that act as dams on rivers, forcing water to build up behind them and can result in flooding. For additional information visit: www.floodsafety.noaa.gov/snowmelt.shtmlÂ*
(NOAA, USGS)Â*
Earthquake Activity

At 1:56 a.m. EST on Dec. 30, 2010, a magnitude 5.3 earthquake occurred in the Aleutian Islands, 77 miles west of Attu, Alaska at a depth of 14.4 miles. No damage or injuries were reported.
(USGS)

Disaster Declaration Activity

No new activity (FEMA HQ)
Stay informed of FEMA's activities online: videos and podcasts available at www.fema.gov/medialibrary and www.youtube.com/fema; follow us on Twitter at www.twitter.com/fema and on Facebook at www.facebook.com/fema.


More...