Cutoff Low Keeps On Spinning Around New England

The cutoff low to New England's west will continue to very slowly meander its way eastward. As it does so, showers and downpours will continue to cycle into New England throughout the day. Multiple rounds of energy will ride across this system's frontal boundary, which remains draped across the south coast of New England. This boundary will provide additional lift and forcing for showers, so rainfall amounts will be highest near the front.

There won't be much of a rhyme or reason to the showers and downpours today. They will be scattered around seemingly at random. They will continue to rotate through New England from south to north around the cutoff low. After this morning's round, activity will likely be most widespread around mid to late morning, when energy will be at its height for showers to be produced.

Below: HRRR showing hourly weather from noon today to midnight tonight:

A widespread 1-3 inches of rain continues to look likely for much of southern and central New England through Thursday morning, with a majority of this falling today. Amounts will taper off moving northward in the region. The best lift and forcing for multiple rounds of rain will be closest to the system's frontal boundary and triple point. With these features remaining over southernmost New England and just to New England's west, it puts interior southern New England in the bull's eye for the most amount of rain.

A flood watch remains in effect for interior southern New England through this evening. The potential for river rises and minor river flooding remains the biggest threat. A handful of rivers in central and southern New England are expected to reach at least action stage with minor flood stage possible on a few of them. Any flooding from this system is expected to remain localized and minor.

Minor and localized street/flash flooding is also possible, but this threat remains on the lower end. The current threshold for flash flooding to occur sits at 1.5-2.5 inches in three hours for most of the region. Currently, rainfall rates may be able to reach up to 0.25-0.5 inches an hour within the downpours. This means rainfall rates will generally stay below the threat for flash flooding. With that said, should downpours happen to continuously run over the same areas throughout the day, some minor issues could arise.

Overall, this will be more beneficial than anything as central and southern New England continues to try to make up for the massive rainfall deficit from this past fall. Minor to moderate drought conditions are persisting across southern New England as of the last Drought Monitor update last Thursday. Basically, the rain will help in the long-term, but could create some minor short-term issues.

One other area to watch today will be the potential for some thunderstorms to be embedded within the downpours. The frontal boundary will provide additional lift this afternoon. With dew points running in the 50s and some building instability from limited daytime heating, some rumbles of thunder will certainly be possible. Moisture, instability and shear will all be limited, so the threat for any strong to severe storms is very low.

Below: HRRR showing potential weather around mid-afternoon today:

A dry slot looks to wrap into the region tonight, reducing showers and downpours from widespread to isolated beginning this evening. Overall, trends have been for a quicker eastward progression of the cutoff low on Wednesday. The low and cold pool will be overhead of New England by Wednesday morning.

This will provide the energy for another round of scattered showers. These showers will be most numerous across northern New England for Wednesday. Some non-severe thunderstorms will be possible once again. Overall, a quicker progression of the low has reduced the thunderstorm threat, especially for southern New England.

Below: FV3 showing potential weather around mid-afternoon Wednesday:

The cutoff low to our west will finally push to our east by Thursday. This will result in a much drier day across New England. The best chance for showers will be over eastern Maine, closer to the low. Elsewhere, plenty of clouds and spot showers will likely be around, but coverage should be much less than early this week. A cold front will dive into northern New England, resulting in a cooler day compared to Wednesday. For central and southern New England, temperatures will likely hang around levels seen on Wednesday.

Below: AIFS showing temperature departure from average Thursday afternoon:

By Friday, the cutoff low responsible for the Omega Block will have moved away from New England. This will likely be replaced with expansive ridging over the western and northern United States. Another trough will undercut the ridge over the northeast and cutoff.

Basically, another cutoff low will be replacing the current one here at the beginning of the week.

This will result in another day filled with showers. The exact coverage and intensity of these showers is very difficult to say at this point as cutoff lows are notoriously difficult to forecast. It could range from just a few showers to a near-washout. The trends will be watched through the week. What's much more certain is that Friday will be a chilly and raw day. Showers will likely continue into Saturday as well.

As of now, this trough looks to clear out in time for Mother's Day, resulting in a drier and possibly warmer Sunday. With that said, guidance also has a tendency to struggle with blocking patterns and often shows them breaking down quicker than they actually do. With that said, Sunday could absolutely trend cloudier, wetter and cooler throughout the week.