Heavy Rain Expected Thursday, Some Flooding Quite Possible, Severe Weather Possible

Powerful storm churning across Ohio Valley right now


A powerful storm churning across the Ohio Valley Tuesday has spawned clusters of damaging thunderstorms in the Southeast United States, and is forecast to slowly move east in the coming days.  As the storm's large, coutner-clockwise circulation of wind nears New England, this will draw more warmth and moisture into our region, eventually leading to a confluence of wind and water over New England by Thursday.  In fact, so much moisture is forecast to move into the region that we will likely have about 200% of the normal water content in our air.  This will result in a humid feeling over the next few days, but will likely culminate in some significant rainfall totals Thursday for New England, with localized amounts of 3"-5"+ of rain not impossible.  Keep in mind that trees are no longer taking up much moisture as the leaves drop and they begin to go dormant, meaning much more runoff during a heavy rain event than would have been the result earlier in the season.

Here, note two rainfall forecasts (NAM left, GFS right) - while the axis of heaviest rainfall is still to-be-determined, both agree on rainfall measured in inches, backing up the thought posited above, and raising a moderate to high probability for at least localized flooding where heaviest rain falls:


It's worth noting, from a lifestyle perspective, that those interested in the Patriots game Thursday night at Gillette Stadium, no matter what precise solution verifies, should expect a wet evening - this is supported by looking at the same two-model scenario below, showing rainfall from 8 PM to 2 AM Thursday night - wet and wet:


 All the while, winds aloft will align from the south on Thursday, and this will promote strong wind gusts, capable not only of stirring up large waves (see previous post here), but also of scattered wind damage.  Note the surface wind gust forecasts below, valid overnight Thursday night...you still see the difference of timing and placement, to be determined as we near the event, but the theme, again, is easy to decipher - an area of surface wind gusts 45-50 knots (52-58 mph) in the corridor of highest wind...surely capable of downing some tree limbs and power lines where it hits:


Finally, there is the potential for embedded severe thunderstorms on Thursday into Thursday night.  Though it's early to give specifics on this, the bottom line is we will have a band of intense rain, ample dynamics to support thunderstorm growth, and the strong wind field mentioned above.  Though the lowest several thousand feet of the atmosphere will feature a rather uniform southerly wind, typically favoring straight-line wind gusts, tropically infused rainbands like these often end up featuring rotating storms embedded within them, further accentuated by the southeast wind that likely will blow right at ground level.  This all implies we will need to be on-guard for severe weather potential in the coming days.


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