Thursday 10 a.m.
With hot air in the middle of the country and a ridge building into the Great Lakes and Northeast, the main theme of the weather pattern is to expect midsummer warmth and uncomfortable for the holiday weekend from Chicago to New York City and on south.
So why is humility part of the headline? With a front separating very hot air from much cooler air meandering across the Great Lakes and Northeast... and a few disturbances embedded in the generally southwesterly flow aloft, certain details cannot be confidently predicted. It would be nice to say with confidence how the weather will turn out for each event on Memorial Day.
I view this as a situation where our service can be particularly helpful to you. By checking your accuweather app on your iphone or other mobile device, you can see in seconds whether there are showers or thunderstorms nearby. You can make a short animation showing where the showers have moved and whether they are increasing, decreasing or staying the same in terms of shape and intensity. Just like that, you have changed a forecast of partly sunny, hot and humid with a chance of a thunderstorm to something you can use directly for a short-term forecast. Combine that with satellite pictures, our weather stories and other information about both routine and threatening weather... and you have a very potentially valuable tool.
Here is the video from this morning.
We are quite concerned about the prospect of violent thunderstorms and life-threatening tornadoes in the Upper Midwest this afternoon and evening. This map shows lightning strikes between 8 a.m. and 10:15 a.m. EDT. There's nothing spectacular, but you can see the concentration of lightning in the region upstream from where the worst storms will be later today.
you can see clear skies out ahead of the cold front that is causing showers and thunderstorms from Michigan to Missouri. The resulting heating will add fuel for developing thunderstorms ahead of the front this afternoon. The National Weather Service Storm Prediction Center highlights this in its outlook
While the Northeast and Great Lakes regions had fine weather much of the Fourth of July weekend, thunderstorms were very common in other parts of the country. This map shows lightning strokes from 7 a.m. ET yesterday until 6 a.m. ET today:
Over the Ohio Valley, rain is starting nudge northward again, prodded by one of a series of upper air disturbances embedded in the flow. It appears the rain will advance across Pennsylvania overnight, reach the area from New York City to Boston tomorrow... then head out to sea.
Farther north, the area from Chicago to Boston looks most likely to have sunshine and dry weather. Cloud cover will vary during the weekend, and I focus on that aspect of the weekend forecast in this video.
A band of heavy rain and locally violent thunderstorms moved from the New York City area at 4 a.m. to just past Boston (distance: 188 miles) by 9:30 this morning. Note the stunning contrast between where it is pouring (dark red) and where it has dried out.
On the map, showers and thunderstorms were located along and ahead of the gray line that cuts through Pennsylvania and along/ahead of the blue line. Both should be off the East coast by Thursday. Drier air from the Upper Midwest should filter into the Northeast later in the week.