It's hard to come up with a single theme for this week as there'll be wet times and dry times along with mild times and cooler times throughout the week. There's also a chance for some flakes toward the end of the week for portions of New England. The best term for this week is: it's early Spring.
MONDAY
A shield of rain ahead of a cold front will continue to push through New England today. This cold front was progressive at first, but has since slowed down to an offshore ridge of high pressure. A secondary area of low pressure has formed along the front and will move across New England through the day. This will allow steady rain and showers to continue for much of the day.
The steadiest and most widespread of the rainfall today will be across the eastern half of New England, mainly near the coastal plain. Scattered showers will remain possible to the west of the front as the secondary area of low pressure keeps cyclonic flow in place. Conditions will gradually dry behind the front with falling temperatures. Should enough moisture linger behind the front, snow showers will be possible across the mountains as it winds down.
Below: HRRR showing potential weather early this afternoon:
The combination of this steady shield of rain and substantial snowmelt has led to some river flooding issues. Most rivers (seen below) are expected to crest in minor flood stage. The Missisquoi River and Otter Creek in Vermont are now expected to crest in minor flood stage after being forecast at moderate flood stage.
Below: River forecasts through Tuesday:
TUESDAY & WEDNESDAY
The cold front will clear New England Monday night, allowing for a drying trend from west to east. A few leftover showers will be possible early Tuesday morning across Cape Cod and Downeast Maine, but other than that, dry weather returns. Despite the passage of the cold front, it won't turn all that cooler behind this front. A narrow ridge of high pressure will build into New England.
This won't be a cool, Canadian high pressure, so temperatures will remain elevated. With that said, flow will be weaker under the high pressure, which will allow for sea breezes, which will likely cool off the coastal plain each afternoon. A southerly flow will increase Wednesday ahead of New England's next system, which will, again, keep temperatures on the warmer end.
Below: AIFS showing temperature departure for Wednesday afternoon. Note the decline in temperatures heading toward the coast:
THURSDAY & FRIDAY
The next system looks to enter the picture next Thursday into Friday. A primary looks to move north of New England with potential secondary low development near the Mid-Atlantic. This storm currently doesn't look as moisture-packed as tonight's storm. The main area to watch will be the potential secondary low development in regards to strength, track and timing.
While the overall setup is similar to the storm that's moving through New England now (in regards to an area of low pressure lifting north of New England, dragging a cold front across the region), the potential formation and strengthening of a secondary low in the Gulf of Maine leads to increased forecast uncertainty. This secondary low will allow for colder air to drain southward into New England during the cold front's passage. This may allow for a changeover to a mix or snowfall for a portion of New England after initial rainfall.
The system currently looks to enter New England later Thursday and last through Friday, though some guidance shows the system's precipitation breaking out earlier in the day Thursday. This will likely be rainfall for everyone as mild air initially pushes into New England. By Thursday night and into Friday, a sharp thermal gradient may set up along the system's cold front. The level of possible wintry precipitation will come down to the strength, timing and track of the secondary low. A weaker secondary low won't pull as much colder air down as a stronger one.
Confidence in any potential impacts remains very low as a significant spread in outcomes among guidance remains. These range from a few flakes mixing in at the end for the higher elevations to a period accumulating snowfall for interior northern New England. As we're now heading into late March, there will be increased uncertainty in wintry impacts as these events become more elevation-based in nature. For what it's worth, the Winter Storm Severity Index currently tops out at 30% for minor winter weather impacts in New England.
Below: Current Weather Prediction Center probability of impactful winter weather Friday:
The warmth preceding the potential switch could hinder any winter impacts greatly, so a trend toward a more wet outcome over white is plenty possible, but the trends will be watched over the coming days. We're reaching the point where it takes an increasingly strong low pressure to create colder impacts. Interior Maine would be the most likely to be affected by a switch to snow with lower chances moving west in the region.
WEEKEND
The timing of the aforementioned system will determine Saturday's weather/ The going forecast right now is for the region to dry out by Friday night, but a trend toward a more unsettled Saturday is possible.
Another quick disturbance may develop just south of New England on Sunday, bringing a round of showers at some point, but this should be a weak one, and its formation isn't a guarantee, so Sunday could end up completely dry. Overall, the weekend is a lower confidence than usual at this point due to the uncertainties around the late week storm.
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