A cold front will begin to push into New England tonight. A weak wave of low pressure will likely form along the front, bringing a round of showers to the entire region. Unlike previous storms, this one will not bring a soaking rain with multiple inches falling. This storm will bring a round of rain and mountain snow showers on Wednesday.
Showers should break out in western parts of New England shortly after sunrise and push eastward throughout the morning. Showers will generally be more widespread the farther north you go in the region. These showers will generally be on the lighter side, but some steadier rain will be possible for a time across northern Vermont.
HRRR showing expected weather Wednesday morning:
Showers will begin to become more isolated as the morning transitions to the afternoon, especially for southern and central New England. Heading into the afternoon, colder air on the backside of the front will wrap around the system, allowing a transition to snow across the higher elevations of northern New England.
Snow showers may drop down to the valleys in northern Vermont and northern New Hampshire, but this will be short-lived and accumulations will be very light to none. There is some discrepancy among models on just how extensive any snow showers will be, but, in the end, we're talking about the possibility between just flurries or a very light accumulation.
HRRR showing expected weather around midday Wednesday:
Showers will generally come to an end from west to east during the afternoon hours. Some additional isolated showers or perhaps a thunderstorm may pop up in the afternoon outside of Maine. Maine itself will see continued rain and snow showers through much of the afternoon. Northern Maine will stand the best chance to see more widespread snow showers Wednesday afternoon into the evening.
HRRR showing expected weather around late-afternoon Wednesday:
The cold front clears the region by Wednesday night, leaving a drier and colder air mass in its wake. High temperatures for most of New England will likely be seen by midday with temperatures beginning to fall in the afternoon. Overnight will see temperatures fall into the 20s to low 30s region-wide.
As for this system, it's not moisture-rich like many of our previous storms over the past few months. PWAT values (basically the amount of moisture in the atmosphere that could become precipitation) will be below an inch. This does not support soaking downpours. The day is unlikely to get washed out for most.
The system is also rather progressive, so drier air on the backside will work in quickly. With that said, rainfall will generally be a quarter inch or less. There could also be some isolated thunderstorms in the afternoon, mainly in southern and central New England. A majority will not see a thunderstorm, but the potential is there.
Storm Prediction Center thunderstorm outlook for Wednesday:
As stated before, northern Maine will have the best shot at seeing more widespread snow. As you would expect in late-April, there are plenty of factors working against snow and not too many working for snow. The question will be how much precipitation is able to wrap around the backside of the system before the atmosphere becomes too dry to support it. An inch or two will be possible in the Green and White mountains with 1-3 inches possible in northern Maine.
Probability of snow accumulating at least 2 inches:
After this system, New England will see drier and sunnier weather return. There will also be a warming trend heading into the weekend as a southwest flow develops around an area of high pressure. Temperatures will likely peak on Sunday or Monday with highs well into the 60s and perhaps climbing into the 70s for the typical warm spots in the region.
Just how warm it gets will depend on whether or not a backdoor cold front moves into the region, which would steal the warmth, as they often do in the spring. There will also likely be a sea breeze to keep coastal areas cooler, as they often do in the spring as well. There could end up being a decent temperature gradient across New England with eastern areas much cooler than western areas.
Euro (1st image) and GFS (2nd image) temperature departure from average on Monday, April 29. Euro is favoring more widespread warmth while GFS shows the backdoor cold front and sea breeze looming large:
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