An area of low pressure will be moving to the north of New England over the next 36 hours. This system will drag its fronts across the region, leading to a period of widespread rainfall. Conditions are looking favorable for a period of steady rainfall with embedded bouts of scattered downpours within the system's warm sector. A bulk of the rainfall will move through tonight through Thursday.
After a bout of morning showers across northern New England this morning, showers will be few and far between for much of the day today. Lighter showers may break out across western New England in the mid afternoon to evening. The steadier, more widespread rainfall will arrive first to northern New England overnight tonight, likely early Thursday morning as the warm front approaches. Forcing for rainfall will be greatest near the center of the low pressure, which will be north of New England.
WRF-ARW showing potential weather early Thursday morning:
Once the warm front pushes through the region, conditions will remain unsettled as moisture increases within the warm sector of the system. By Thursday afternoon, all of New England will be under the gun for scattered showers. Activity will be more widespread across northern New England with generally more scattered activity in southern New England. The day is looking washed out across the north. There will be plenty of wet times in southern New England, but it may not quite amount to an all day wash out for everyone.
Also Thursday afternoon, the system's cold front will begin to push into western New England. This front will push southeastward through New England through the afternoon and into southern New England by Thursday evening. With ample moisture and some instability developing ahead of this front, a fine line of downpours and even some convection is possible. While full thunderstorms and severe weather is not likely, some rumbles of thunder will be possible and scattered downpours will be on the table.
GFS showing potential weather Thursday afternoon (1st image) and Thursday evening (2nd image):
The cold front will usher in a drier air mass and rapid drying trend is likely once the fine line of downpours moves through the region. This line does look progressive in nature. High pressure will build in behind this system, bringing an end to the wet weather by Friday morning for nearly all of New England. As usual, the mountains will still have some shower potential Friday afternoon.
When all is said and done, New England will be looking at a widespread dousing of rain, with the highest amounts across northern New England and dropping as you head south. Vermont, New Hampshire and Western Maine will likely be looking at a general 1-2 inches of rain.
Amounts will drop in southern New England as generally less time with downpours is expected, still a half inch to an inch of rain will be possible all the way to the south coast. A majority of this may fall as the cold front sweeps through. Rainfall amounts will not be uniform across the region due to the scattered nature of the downpours. Some areas will see a bit more while others see less.
This will be a moisture-rich system with the warm front ushering in a juicy atmosphere. Combined with deep warm cloud depths, periods of scattered downpours will be likely with this system. Overall, rainfall rates will not be consistent through the system. Sometimes it will be a lighter rain and other times it will be heavy. The line of showers along the cold front will be the most favorable time for heavier downpours as the lift of the front will interact with plenty of moisture and instability within the warm sector.
This is looking to be a mostly beneficial rainfall event for New England with very limited flooding potential as New England remains in a deficit for rainfall in September. Northern New England missed out on the coastal storm last week and has been very dry over the past several weeks. Despite the potential for heavy downpours, flash flooding potential remains low as the flash flood threshold is currently high, around 2-3 inches for most of New England and rivers are running low.
On the tropical front, Helene will likely make landfall as a category three hurricane in Florida's big bend region. The situation will be similar to what happened with Francine earlier this year as Helene moves inland. A large area of high pressure is looking to block the remnants from coming to New England. This will keep the storm in the south as it deteriorates. This will be a major flooding event for the south (both from storm surge and inland rainfall).
Below: Hurricane Helene's current forecast track and intensity and the current Weather Prediction Center three day rainfall forecast:
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