National Situation Update: Tuesday, December 2, 2008

Homeland Security Threat Level: YELLOW (ELEVATED).

National Weather

West:
A fast moving low ("Alberta Clipper") moving out of western Canada will produce precipitation in Montana, Idaho and Wyoming and south to the Four Corners area. The mountains of central Idaho, Bitterroots, Glacier peaks and Tetons may see 6 to 10 inches of new snow by tonight.  Cold air moving in with the system will result in temperatures dropping as much as 30 degrees from yesterday's record highs in parts of Montana. A Dense Fog Advisory for the northern Sacramento Valley is in effect  until 10 am PST.
Midwest:
The Alberta Clipper will bring widespread precipitation including light rain, snow and freezing rain across the Northern Plains and Upper Midwest.  High temperatures will vary widely, from the upper 20s over northeast Wisconsin and lower Michigan behind the cold front to near 70 in Kansas from gusty southerly winds.
South:
Under high pressure, much of the region will be partly cloudy with little or no weather except for a few light showers over parts of the coastal Carolinas and the central coast of Florida.
Northeast:
A series of low pressure troughs moving over the region will produce widespread cloudiness and snow showers from the Appalachians to northern New England. Significant accumulations (5 to 9 inches) are expected in the usual areas - east of Lakes Erie and Ontario. (NOAA, National Weather Service and Various Media Sources)

Tule Fog

California's Tule Fog season usually begins in November, after the first substantial rain and lasts until the end of March. Tule fog is a dense ground fog produced over land by the cooling of the lower atmosphere and is also known as radiation fog. Areas of dense fog can reduce visibility to less than 1/8 of a mile. Since the Central Valley of California has no air drainage other than mountain passes, day time heating or turbulent winds are required to break up the fog layer once it develops. Tule fog can be accompanied by drizzle and black ice. Accidents caused by Tule fog are the leading cause of weather related casualties in California. Examples of major accidents include:
  • December 1997 - 25 cars and 12 big rigs collided in fog near Elk Grove, south of Sacramento. 5 killed, 28 injured.
  • February 2002 - 80-plus car pileup on Hwy 99 near Kingsburg resulted in 2 killed.
  • November 2007 - a pileup involving 108 cars and 18 big rigs resulted in 2 deaths and 39 injuries.

During periods of dense fog the California Highway Patrol runs traffic breaks and pace cars on major highways to help slow traffic when visibility drops below 500 feet. Message signs provide information on changing conditions. (NOAA National Weather Service, FEMA Region IX)

Fire Management Assistance Grant (FMAG)

No significant activity.(FEMA HQ)

Tropical Weather Outlook

Western Pacific:
No current tropical cyclone warnings(NOAA, HPC, National Hurricane Center, Central Pacific Hurricane Center and the Joint Typhoon Warning Center)

Earthquake Activity

No new activity (FEMA HQ)

Preliminary Damage Assessments

No new activity (FEMA HQ)

Disaster Declaration Activity

No new activity (FEMA HQ)

Last Modified: Tuesday, 02-Dec-2008 08:21:33 EST