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National Situation Update: Wednesday, December 31, 2008

Homeland Security Threat Level: YELLOW (ELEVATED).

Significant National Weather

West:
A low pressure system moving ashore from the Pacific will produce precipitation in Washington, Oregon, northwest California and spread eastward into Idaho, Montana and Wyoming later today.  The Cascades and Olympics are forecast to receive one to two feet of snow by the end of the day.  The tight pressure gradient around the low pressure system will produce high winds in the coastal areas of Washington and northern Oregon.  The rest of the region will be mostly sunny and relatively mild.
Midwest:
Under a large high pressure system most of the region will remain cold and dry.  The cold air passing over the Great Lakes will produce a few inches of lake-effect snow east of Lake Michigan and southeast of Lake Erie.  Portions of Michigan and northeast Montana is forecast to received sub-zero temperatures.
South:
Under a dry cold front and building high pressure the region will remain dry but temperatures will be noticeably cooler.  The temperatures will range from below freezing in Tennessee and North Carolina to the 70s in southern Florida.
Northeast:
A low pressure system moving out of the Mid-Atlantic will produce snow over Pennsylvania, New York state and New England.  Some areas may see four to six inches of snow, with locally higher amounts.  New York City and Long Island will see rain changing to snow but amounts should stay in the one to two inch range.  With the wind chill factored in, temperatures will be below zero in Boston and in the single digits in New York City for the New Year's Eve celebrations.  The storm is forecast to deepen when it moves off the coast of New Jersey and over the relatively warm waters of the Gulf Stream. The tightening pressure gradient will produce strong northwesterly winds, decreasing temperatures and blowing and drifting snow on the backside of the storm.  (NOAA, NWS and Media Sources)

Region V: Winter Weather Update

Over the past weekend, thunderstorms and heavy rain, combined with ice melt, led to stream and river flooding over a large portion of the Midwest, although Flood Warnings continue for numerous rivers in Illinois and Michigan, there is no major flooding forecast for the Region.  Of the affected states, only Michigan has continuing power outages; DOE reports 54,000 customers remain without service.  Full power restoration is anticipated later today.  All major highways and Interstates are operational.  There has been no request for Federal assistance at this time. (Region V, DOE, DOT)

Region VIII: YELLOWSTONE VOLCANO

Current Situation
Region VIII: YELLOWSTONE VOLCANO
Volcano Alert Level: NORMAL
Aviation Color Code: GREEN

The University of Utah Seismograph Stations reports that a notable swarm of earthquakes has been underway since December 26 beneath Yellowstone Lake in Yellowstone National Park, three to six miles south-southeast of Fishing Bridge, Wyoming. This energetic sequence of events was most intense on December 27, when the largest number of events of magnitude 3 and larger occurred.

The largest of the earthquakes was a magnitude 3.9 at 10:15 pm MST on Dec. 27. The sequence has included nine events of magnitude 3 to 3.9 and approximately 49 of magnitude 2 to 3 at the time of this release. A total of more than 250 events large enough to be located have occurred in this swarm. Reliable depths of the larger events are up to a few miles. Visitors and National Park Service (NPS) employees in the Yellowstone Lake area reported feeling the largest of these earthquakes.

Background
Earthquakes are a common occurrence in the Yellowstone National Park area, an active volcanic-tectonic area averaging 1,000 to 2,000 earthquakes a year. Yellowstone's 10,000 geysers and hot springs are the result of this geologic activity.

The Yellowstone Caldera is located in the northwest corner of Wyoming extending into portions of Montana and Idaho. The major features of the caldera measure about 34 mi by 45 mi as determined by geological field work conducted by Bob Christiansen of the United States Geological Survey in the 1960s and 1970s.

The Yellowstone Supervolcano is the volcanic field which produced the latest three supereruptions. The three supereruptions occurred 2.1 million, 1.3 million and 640,000 years ago; forming the Island Park Caldera, the Henry's Fork Caldera, and Yellowstone calderas, respectively. The Island Park Caldera supereruption that produced the Huckleberry Ridge Tuff was the largest and produced 2,500 times as much ash as the 1980 Mount St. Helens eruption. The second largest supereruption formed the Yellowstone Caldera and produced the Lava Creek Tuff. The Henry's Fork Caldera produced the smaller Mesa Falls Tuff but is the only caldera that is visible today.

Non-explosive eruptions of lava and less violent explosive eruptions have occurred in and near the Yellowstone caldera since the last supereruption. The most recent lava flow occurred about 70,000 years ago while the largest violent eruption excavated the West Thumb of Lake Yellowstone around 150,000 years ago. Smaller steam explosions occur as well; an explosion 13,800 years ago left a 5 kilometer diameter crater at Mary Bay on the edge of Yellowstone Lake (located in the center of the caldera). Currently, volcanic activity is exhibited only via numerous geothermal vents scattered throughout the region, including the famous Old Faithful Geyser.

FEMA Region VIII is monitoring the situation and has not received any request for federal assistance.  (University of Utah Seismograph Stations, Yellowstone Volcano Observatory,   National Park Services, U.S. Geological Service, FEMA Region VIII)

Fire Management Assistance Grant (FMAG)

No activity.(FEMA HQ)

Tropical Weather Outlook

Western Pacific:
No activity affecting United States territories.(NOAA, HPC, National Hurricane Center, Central Pacific Hurricane Center and the Joint Typhoon Warning Center)

Earthquake Activity

The largest earthquake in the last 24 hours was a magnitude 4.2 event approximately 300 miles west-northwest of Fairbanks Alaska on Tuesday December 30, 2008 at 8:54 am EST at a depth of 3.1 miles. There were no reports of any damage.

As discussed in the article above, the swarm of small earthquakes continues in and around Yellowstone National Park (Wyoming, Montana, and Idaho).  (USGS, Earthquake Hazards Program, Alaska Earthquake Information Center)

Preliminary Damage Assessments

No new activity (FEMA HQ)

Disaster Declaration Activity

No new activity (FEMA HQ)