Monday 9 a.m.
Very humid air is in place throughout the Northeast today, and a series of disturbances will move through the area from west to east during the next few days. Each of these can cause some showers and thunderstorms. A cold front approaching Wednesday may be strong enough to cause locally severe thunderstorms from the Ohio Valley to New York state and New England.
Once the front goes by, it is likely to become comfortable with low humidity across the Great Lakes and perhaps as far east as the Appalachians. Closer to the coast (and including the I95 corridor), the front could stall. This would increase the chance of more frequent rainfall, though the increased cloudiness would also hold temperatures down. This video has more:
This satellite picture with a radar overlay shows the most concentrated area of showers and thunderstorms this morning was over the western Great Lakes region.
map shows predicted rainfall between now and next Wednesday. This will need to be watched in order to assess the risk of flooding.
Looking farther ahead, it appears a summer version of THE POLAR VORTEX will send much cooler air into the Great Lakes and then the Northeast. The first map shows the flow aloft next Tuesday night. The second map shows what could be a heat wave a week and a half later!
There were numerous thunderstorms yesterday. This is the lightning stroke map covering the period from 8 ET yesterday morning to 7:30 ET this morning. Thunderstorms will be less numerous today, but any that do form can cause briefly strong and gusty winds.
One area of concern is Lake Erie, where unprepared boaters could suddenly be blasted by 60-mph winds. The National Weather Service Storm Prediction Center has outlined a large area where the threat of strong wind exists. The map is below today's forecast video.
Tomorrow, a cold front will cross the Great Lakes, then reach the Northeast by the end of Wednesday. Today, a southwesterly current of very warm air is evident on the surface pressure map.
The center of Arthur (shown here at noon ET) should pass less than 50 miles southeast of Nantucket this evening, causing heavy rain and gusty winds across much of eastern New England. Meanwhile, the Great Lakes and much of the Appalachian region have a lovely Fourth (but take a jacket or sweater as you head out to the fireworks).