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Flood Watches up for New England as Long-Duration Rain Event Continues

The first stalled frontal boundary of the spring has arrived and will provide eastern New England with a washout today. An area of low pressure will slowly work up the east coast today, along the front. This will lead to a long-duration rain event as the front very slowly pushes through New England. This will provide eastern New England with a widespread 1-3 inches of rain.

Rainfall will generally come in waves as the front slowly pushes through and the main coastal system continues toward the region. The area of low pressure will be down near the Carolinas today, but a strong southerly flow in the upper levels will help transport deep moisture into the region, allowing rain to fall along the cold front well before the main system's arrival.

HRRR showing expected weather around 2pm today:

Rainfall rates will not be consistent all day long. It is more likely to come through in waves, meaning there will likely be periods of much lighter rains between the waves of steady to at times heavy rain. One such lull in the rain today may come around midday today before filling back in during the afternoon and evening. With that said, don't expect any truly dry periods today as moisture is deep.

Expected weather around midday, showing gaps in the rainfall:

The rain will continue all night long Thursday into Friday for eastern areas. The rainfall will shut off earlier and earlier the further west you go in New England. When all is said and done by Friday evening, much of eastern New England will have received at least an inch of rain with areas closer to the coast seeing 2-3 inches.

This will result in some minor flooding issues, mainly minor river flooding and ponding of roads and low-lying areas as well as potential basement flooding. Flash flooding is not a concern as all this rain will be falling over the course of 24+ hours, meaning rainfall rates likely won't get intense enough to create flash floods.

Snowmelt will add to the runoff in areas that saw a heavy snowfall last week. The snowpack is still new, so it won't melt out completely in places that have a deep snowpack, but it could add an additional 1-2 inches of runoff for northern New England.

As the system lifts into the Gulf of Maine on Friday, colder air will begin to wrap around the backside of the system. This could support a transition to snow by Friday morning for the White and Maine mountains. Some models are much more excited about the prospect of snow than others, but a couple inches will be possible across the mountains and northern Maine. The question will be if the transition can occur before the precipitation begins to shut off, especially for the White Mountains.

Probability of at least 2 inches of snow by Saturday morning:

This storm does clear out in time for Easter weekend. Saturday morning will see any leftover precipitation in eastern Maine clear out in the morning. Elsewhere will be dry and will see the return of the sun. It will be windy on Saturday, typical of post-storm days. Sunday will see less wind and an isolated rain or snow shower as a weak disturbance zips through.

Attention then turns to a potentially impactful storm for the middle of next week. Confidence is increasing that a storm will come into the vicinity of New England during this time. Whether it actually comes close enough to bring impactful weather remains to be seen. This storm will likely involve a primary low tracking to the north with a secondary low forming to the south.

This could support another round of impactful precipitation (rain, snow or both). Being a week out, it's impossible to go into details on when, where, what and how strong it will be as large spreads in the outcome naturally exist at this range. As always, we'll be watching.

Model roundup (Euro, GFS, CMC and GraphCast) for next week's potential storm:



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