Tuesday 10 a.m.
It remains chilly in central and northern New England this morning. Farther south in New York City and Philadelphia, yesterday's snow has been replaced by temperatures in the 40s under cloudy skies. Meanwhile, it feels like May in parts of the Midwest. Just after daybreak, the Chicago temperature hit 60 degrees, breaking a record that had been in place for 99 years. The warmth was advancing on the strength of gusty southwest winds. Yesterday, the temperature soared to 77 in Topeka, Kan., burning the previous record of 74 for the warmest January reading in their history of record keeping.
A strong upper-air trough over New Mexico will move out over the Plains today, sponsoring development of a strong low pressure area at ground level. As that storm moves northeast and its attendant cold front whips around its south side, violent thunderstorms and potentially deadly tornadoes will be unleashed. The following map shows today's severe weather threat.
The storm system has already tapped into moisture streaming northward from the Gulf of Mexico. This will cause a period of torrential rain from the mid-Mississippi Valley into the Great Lakes. Virtually that entire needs rain, but the intensity will lead to local flooding. North of the path of the storm, there will be wind-whipped snow. This video has more:
By Thursday, the cold front will be off the East coast, and wintry winds will be generating snow showers from the Great Lakes into the Appalachians. Just a few flurries are likely east of the mountains Thursday night and Friday. Models have not come into agreement on this, but a patch of mostly light snow may moves from the southern Great Lakes and Ohio Valley regions to the Middle Atlantic coast during the coming weekend.
On this map from 10 a.m. ET Thanksgiving Day, you can see the high pressure area that is causing dry and mild weather in the East and the cold front farther west.
During the late afternoon and early evening hours, the cold front of a knife will slice through the turkey and cause it to accumulate 1-2 inches on plates...
This satellite picture shows clouds over parts New York and Pennsylvania, as well as areas of low clouds, fog and snow cover from Michigan to Illinois. Most of the Northeast should have at least some sunshine through Thanksgiving Day.
As we go through the week, the flow aloft over the East will become southwesterly. This will promote a major warmup. This map shows the projected upper-air flow for Thanksgiving afternoon:
A major snowstorm will affect the area from Iowa to Michigan tonight and tomorrow. At first, snow can melt on streets, but as it continues and the temperature drops, the area impacted by slippery conditions will increase dramatically. This map shows expected accumulations:
This map shows two cold fronts in the northeast quarter of the nation; 9 a.m. ET temperature are plotted. The isobars are closest together over the central and western Great Lakes, and this is where the strongest winds were occurring.