Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 2:11 PM GMT on December 08, 2010
A major winter storm powered ashore today in the Pacific Northwest, bringing heavy rain and snow to the Olympic Mountains. This storm dumped four inches of rain over the Olympics, bringing the Skokomish River to flood stage. Record warm temperatures ahead of the storm have surged northwards across the Pacific Northwest, with Seattle, Washington hitting a record high of 55°F yesterday. Snowfall amounts approaching 2 feet are expected in the Olympic Mountains from the storm, with 1 - 3 feet likely in the Cascade Mountains. This is typical sort of storm one expects to see during a La Niña winter.
Figure 1. Radar-estimated precipitation from the Seattle radar for the period Dec 7 - Dec 8. Precipitation amounts in excess of 4 inches have occurred over the Olympic Mountains. Mountains surrounding Seattle block the radar beam, leading to the streaky nature of the image.
As the storm tracks eastwards over the Central U.S. later this week, it will intensify and pull in a large amount of cold, Canadian air. The latest set of computer model runs have come into much better agreement on the track of the storm, and a band of heavy snow of 6 - 10 inches is likely to set up over Central Illinois on Saturday afternoon. The storm will move rapidly eastwards, with the heaviest snow likely to impact northern Indiana, northern Ohio, and southern Ontario on Sunday. The biggest cold blast of the season thus far will roar in behind the storm, causing widespread blowing and drifting of the snow, plus new heavy Lake-effect snows in the lee of the Great Lakes. Low temperatures approaching -20°F are likely in northern Minnesota Saturday and Sunday night after the storm passes. By Tuesday morning, much of the eastern half of the nation will shiver through one the coldest mornings on record for the first half of December, with below freezing temperatures expected to penetrate all the way into South Florida. Record lows were set across much of Southeast U.S. this morning, with 39°F at Fort Lauderdale, 16°F in Columbia SC, and 9°F in Lychburg, VA. Temperatures much colder than this are likely on Tuesday morning across the region.
Figure 2. Forecast surface temperature for 7am EST on Tuesday, December 14, as predicted by this morning's 1am EST run of the GFS model. The heavy red line running along the coast of Florida is the 0°C freezing line, and temperatures below freezing are expected across nearly all of the Southeast U.S.
I'll have a new post on Thursday, when I'll discuss the CSU and TSR forecasts for the 2011 hurricane season. The TSR forecast was released Monday, and the CSU forecast is due out later today.
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