The big weather story the next few days is going to be the two storms that will have a major impact across the country. The biggie will be the monster blizzard that will hit the New England area through Saturday. Snowfall amounts in excess of 2 feet are expected in local areas. The all time record snowfall for Boston from the President's Day storm of 27.6 inches may be broken. The computer model average is 23 inches, with three runs producing 30+ inches.
In several ways the New England blizzard is similar to superstorm Sandy. Both started out as a warm and wet system moving northeast just off the southeast coast, with a strong cold upper level system moving southeast from the Midwest. The two systems will have undergone intense cyclogenesis or "bomb" off the coast as the two systems merge. In the case of Sandy there was an upper block over Greenland so the system was forced northwest to the New Jersey coast. For this storm there is not block so the center will continue to move northeast just off the coast. Hurricance force wind gusts are expected along the New England coast.
The other storm is the strong upper level system that is now coming ashore along the California coast. Deep low pressure will form over eastern Colorado Saturday afternoon and then move to upper Michigan by Monday morning. Very heavy snow will fall northwest of the storm with rain and thunderstorms to the east. Severe storms with tornadoes are once again possible over Texas to the Gulf coast over the weekend. Thunderstorms as far north as central Illinois are possible.
For the metro Chicago area; ice, rain, and snow were all experienced during Thursday. As the upper level trough approached the area, dynamic cooling started to turn the rain to wet snow just south of the Wisconsin border midmorning. This rain to snow change then proceeded south during the day. The graphic shows the correlation coefficient product from the Chicago radar. The product is designed to show areas of mixed sized precipitation. The yellowish band running west-east is the changeover zone. As the zone moved over my house I experienced a mixture of rain, sleet, and snow before becoming all snow.
Snow amounts over the metro area varied greatly depending on location. From 6-8 inches far northeast in parts of Lake county to just a very little slush south sections. All the reports and a map can be found here and here. At least for the coming storm there will be no snow. A very brief window of freezing rain is possible west early Sunday morning before temperatures warm eventually into the mid to upper 40s during the day.
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