September has been very kind to us…in fact, since the 10th of the month (18 days ago) we have only had rain on four days. That is about to change as we enter an unsettled stretch that will last the rest of the month.
A trough in Eastern Canada is in the process of digging into the Northeast and strengthening. This trough will enhance a vortmax moving out of the Ohio Valley late tonight and tomorrow. The lift from the vortmax is already producing solid rain over PA and will do the same here in New England. Rain will break out from west to east tomorrow morning…mostly afte the morning commute. By midday we all should be seeing raindrops, mostly light ones but by the end of the day and tomorrow night that should change as better dynamics pass overhead. This will be a solid soaking too…at least a half inch and maybe as much as an inch!
The storm should slide offshore by Saturday morning taking with it the heavier and steadier rain. Although Saturday won’t see heavy rain, it won’t exactly be dry…mist and drizzle will fall out of a solid low cloud deck and onshore winds will keep temps around 60 degrees.
Sunday will be a bit better as the upper level circulation retrogrades a bit to the west and surface flow takes on a more southerly component. This will inject some very moist and slightly unstable air into Southern New England and if the low clouds erode enough and we see some brightening or even a few sunny breaks convective precip could be initiated. This means that we may see a few downpours Sunday midday or afternoon.
The cut-off upper low will begin to move Sunday night and lift north…this will send the final surface low through early Monday morning with the final batch of rain and the start of a sunnier and warmer stretch.