Very Heavy Rain Tomorrow

Good evening! Update post regarding the multi-hazard system tomorrow. I may do an update on the Friday and weekend rain threats later this evening; HOWEVER, I felt it was necessary to get the more immediately important info out first.

Rain/Flooding

This will be a big rainmaker, and the big story among this mess as well, with an area of low pressure in the Mid-Atlantic and a cold front nearthe west edge of precipitation. Rain will continue to move into the region through the evening – current doppler:

Capture

The rain will continue throughout the day tomorrow, heaviest in the northern two thirds of New England, and continue overnight Wednesday night before tapering off early Thursday morning to scattered showers throughout Thursday. When all is said and done, expect a widespread 2-5″, with locally higher totals, especially in Maine. There may be less than 2″ in the southern half of Southern New England.

In the areas of high vertical velocity (pink), expect very heavy rain at times – map valid for 2 PM tomorrow:nam_rapid-vvelprs-700-nepoolnerc-24-C-000

This will likely lead to some urban flooding problems, as well as problems in poor drainage and low-lying areas. The smaller and faster-responding rivers and streams could also see some issues. I am not expecting any issues in the main stem rivers, such as the Merrimack River and the Connecticut River. Do not drive your vehicle into areas where water covers the road. Move to higher ground if necessary. An areal flood watch is in effect for much of New England:

Capture2

Additionally, with very heavy rainfall in some spots, there is a concern for some flash flooding, with the very heavy rain around midday (also in the morning). Combined with the morning commute, this could become a serious situation.

Thunderstorms/Severe Weather

This is not a huge concern. Even though there are still some good shear and helicity values, which would often indicate a strong risk for damaging winds and perhaps an isolated, brief tornado, instability is going to be quite low tomorrow, which should limit severe weather chances tomorrow, even with decent lapse rates modeled. However, there may be enough instability to fire off a few embedded thunderstorms, with very heavy rain which could lead to additional flash flooding. As noted, favorable shear and helicity values are there, meaning the potential for strong to damaging winds and maybe a very isolated, very short-lived and weak tornado somewhere. It’s not likely, though, considering things against it.

Wind

This storm, by itself, will not be much of a wind maker for much of the duration. Just a little on the windy side. Onshore winds 10-20 mph, gusts to 25 mph. Winds could become an issue in the evening, mainly near the coast, with gusts of 30-40 mph possible Wednesday evening through Friday as the bulk of the rain begins leaving. An exception to this would be within any thunderstorms or stronger showers, with strong winds possible, and MAYBE a localized damaging gust as noted in the severe section above.

Coastal Flooding

There could be minor coastal flooding issues at the time of astronomical high tide Wednesday morning, mainly along the coast of southeast Massachusetts and coastal Rhode Island as well as the NH/Maine coast, with increasing seas and wind. More coastal flooding issues are possible at the high tides Wednesday evening and Thursday. A coastal flood advisory is in effect for south coastal MA/coastal RI, and a coastal flood watch for the NH/Maine coast to near Portland.

Current NWS Alerts

Areal Flood Watch for NW CT/Far Western MA/Southern VT; Areal Flood Watch for Central VermontAreal Flood Watch for Western/Central/NE MA, and Northern CTAreal Flood Watch for NH and Western MaineAreal Flood Watch for Eastern Maine; Coastal Flood Watch for NH/Maine Coast to Just East of PortlandCoastal Flood Advisory for South Coastal Southeast MA and Coastal RI. Colors are clickable links.

Have a good evening!

-Nathan

Published by Nathan Coram

Hello! I'm Nathan Coram, a 19 year old meteorology student and weather geek, and am going into my junior year at UMass Lowell as a meteorology major. I am the current Vice President of the UML American Meteorological Society Local Student Chapter. Prior to at UML, I attended the Dracut school system for my K-12 years, having graduated from Dracut High in 2018. I first got into weather with the December 2008 ice storm, which knocked out my electricity for 4 days. I had no idea how it could be raining and becoming ice immediately, and how rain can knock out power. (Now I do - warm layer aloft, cold air at surface). But I didn't really get into it until the heat of July 2010 and specifically a few severe weather events during that month, followed by the year 2011, which featured several high profile weather events. Since then I have had a growing interest, and am hoping to make it into the meteorology field, preferably with NOAA/NWS. But for now, I'm blogging here, helping with the UML Weather Center social media, and tweeting about the weather on my own account as well. Thanks for visiting!

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