Multiple waves of low pressure will be coming to New England over the next several days, starting this evening. The most potent of these systems will be a coastal storm that is looking to arrive by Sunday. This system will have the potential to produce very heavy downpours overnight Sunday into Monday morning for much of New England.
SATURDAY NIGHT
A warm front will lift across New England starting on Saturday morning. Showers will fire across the region (except Maine) by early evening. There will be widespread showers to a steady rain. The most rain with this initial wave will be seen in southern New England with up to a quarter to half an inch falling.
A frontal boundary associated with a cutoff low will stall over New England, keeping unsettled weather around throughout the night. Widespread showers continue through the overnight hours. Maine will remain mostly dry on Saturday due to high pressure.
SUNDAY AND SUNDAY NIGHT
Over the past couple days, the coastal storm has been trending toward coming in earlier. This means that at least Sunday afternoon is looking to be a washout for nearly all of New England. Sunday morning will see scattered showers around for much of New England. Maine will remain dry Sunday morning. Steady rain will begin falling around mid morning and continue to increase in intensity from south to north throughout the day, reaching Maine by mid to late afternoon.
Early Monday morning, note the VERY heavy downpours over southeast New Hampshire and southwest Maine:
The most intense rain bands are still looking to impact New England from Sunday evening through early Monday morning as the coastal storm interacts with a cutoff low meandering over the Great Lakes. From about 4pm to 4am, very heavy downpours will be possible across southern and central New England, especially across eastern New Hampshire and the southern half of Maine. Several inches of rain will be possible along with gusty winds.
MONDAY
With the storm's earlier arrival, Monday has been trending drier and drier. Southern and central New England will likely see rain end by sunrise. Once the rain ends, clouds will begin clearing quickly. Southern New England will likely see a mostly sunny sky for much of the day. Maine, being further north and east, will hold onto the steadier rain during the morning. However, even eastern Maine will likely see rain end by midday and see some sun by mid afternoon.
Monday afternoon, southern New England completely cleared out (Note the cutoff low still hanging around the Great Lakes):
RAIN TOTALS AND FLOODING
Rain totals have trended upwards quite a bit overnight. When all is set and done with both systems,much of the region could see several inches of rain, a majority of New England will see at least one inch. The highest rain totals will likely be in eastern New Hampshire and western Maine, where up to three inches could fall, with isolated amounts up to four inches.
This much rain in a relatively short amount of time (a majority of the rainfall shown on the map will fall Sunday night to Monday morning) could lead to some flooding issues. Rivers and streams could reach flood stage by Monday. Isolated flash floods are possible across most of New England, especially in eastern New Hampshire and the southern half of Maine.
WIND
Being a coastal storm, there will be some strong winds. Earlier this week, I wrote that the wind threat would be something to watch as the week progressed. It is still looking like winds will not be too much of an issue, with gusts up to 40-45 mph possible. Gusts at this level are below the threshold for damage, but an isolated issue is always possible with these coastal storms.
COASTAL FLOODING
Fortunately, coastal flooding is looking increasingly likely to be a non-issue. Tides are astronomically low and, combined with the wind direction, will stop pretty much all coastal flooding. As with any coastal storm, some splashover could be possible during high tide.
BEYOND
That cutoff low will continue to hang around the Great Lakes throughout the coastal storm. After the coastal storm passes Monday night, the cutoff low will VERY slowly push eastward across New England. This will lead to a cool and showery week all week long. Next week is going very gloomy.