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 Farther south in New York City and Philadelphia, yesterday's snow has been replaced by temperatures in the 40s under cloudy skies.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.
This picture shows cloudiness surrounding a low pressure area off the Southeast coast. In the cloud zone, moist air rises and cools to the saturation point, and clouds form. Outside the storm, there is sinking air motion. This warms and dries the air, promoting sunshine.
A frontal zone separating cool to mild air to the north from really warm air to the south is becoming established from Illinois to New Jersey. An area of rain is moving east near and just north of the front. This map shows the setup.
Between yesterday morning and early this morning, quite a bit of lightning occurred. There can be some lightning all the way to the East Coast with this cold front, but the activity is likely to diminish. This map shows the distribution of lightning strikes in the (almost) 24-hour period ending at 7:30 ET this morning
The peak of the upcoming warmup should come on Monday for much of the Northeast. This map shows computer projections of temperatures at 4 p.m. ET Monday afternoon. Note the 80+ area in Pennsylvania. Cooler air will arrive by midweek.
As a storm slowly develops along the North Carolina coast, rain that was affecting areas of Michigan, Ohio and western Pennsylvania will tend to redevelop farther east and south. A flow from the east (see map) will keep it cool through tomorrow from New York City to Boston.
A sunny triangle is framed by a band of clouds moving southeast from Wisconsin, rain clouds over the Southeast and the western fringe of a North Atlantic storm.