The storm that brought extreme rainfall to Detroit, then Baltimore, then Islip, New York, and Portland, Maine, is now moving northward through eastern Canada. In Monday's report I wrote, "As with other rain-producing systems this summer, this one is likely to include narrow bands of excessive rain capable of causing street flooding in a matter of minutes."
Of course, even if we know this well on advance, it is an entirely different story trying to pinpoint the exact wheres and whens until we are much closer to when it actually occurs. This is an important issue: how to get the message across that you may die or be injured in a particular area while telling folks elsewhere there is much less concern. Another storm system next week could move east from the Ohio Valley or southern Great Lakes to raise the same issues and questions. Here is my forecast video:
Looking beyond next week, we see signs of something that has been missing in the Great Lakes and Northeast just about all summer: hot weather. That may change. Here is a computer model prediction of the upper air flow on Sunday, Aug. 24. Note how the flow appears to run from Arizona all the way to north of New England.
After reaching the 80s today from NYC to Boston, it might not be that warm again through much of next week.
A noticeable push of cooler air will spread southward from Ontario and Quebec into the eastern Great Lakes and New England between tomorrow and Saturday.
A cold front from eastern Canada will slide southward along the East coast between late Friday and the end of the weekend. For the area from Philadelphia to Boston, where temperatures will reach the summery 80s each day through Friday, it will mean a noticeable change to cooler weather.
Average high temperatures in Chicago and New York City are in the mid-70s now, but for the next several days, temperatures will run 8-15 degrees above those long-term averages. Supporting this warmth is a flow aloft that originates over the Southwest:
Rain was common in the Northeast this morning, though Boston was still waiting as of 9 a.m. Their summer dry spell has continued.
There will be an increase in warmth and humidity in the Northeast that will not be reversed until the next cold front arrives.