It’s going to be a difficult week of forecasting, and you should be prepared for surprises in both precipitation and temperature. Eastern Canada is a source region for maritime polar air, which is cool and moist this time of the year. Even in the middle of summer if we get maritime polar air to push into New England, it often drops the temperatures by 20 degrees or more.
To start the week, we are going to have a frontal boundary draped across New England. One only needs to check out the map below for Tuesday afternoon indicating temperatures over portions of Maine in the 40s whereas down toward New York, it could be in the 70s. This dramatic temperature contrast is a forecast dilemma because the exact placement of the front determines just how warm the actual air temperature will be where most folks are reading this.
In addition to the frontal boundary, there’s going to be a couple of waves of energy helping to promote a few showers. After a few overnight showers on Sunday, there can be a few more showers later Monday afternoon and evening into early Tuesday and then another round of showers later Tuesday into Wednesday.
Monday itself should be mostly dry with the mildest air before noon and a slow cool-down from east to west this afternoon. You will need a jacket by the end of the day for sure. Sometimes when you get these situations you end up with a day with a lot of clouds and a little bit of drizzle, but you can still get outside without getting drenched. That is today.
There will be times when the rain comes down harder and it makes it more difficult to be outside, Monday night into very early Tuesday and perhaps again on Wednesday. Monday night’s showers are going to likely be heaviest south of Boston. The trend of the models has been to keep the steadiest rain over Cape Cod, and this would mean much less actual rainfall north of Boston.
We do see some more showers and perhaps even a thunderstorm on Wednesday as another frontal system pushes through the region. Behind this, high pressure will build in bringing what I think will be a few dry days.
The question mark for the upcoming weekend is whether or not low pressure developing in the ocean will come close enough to allow just clouds, showers, or a steady windswept rain into the area. Presently the trend has been to keep this nor’easter off the coastline but I’m not ready to write it off completely just yet. Obviously, there’s a lot of forecasting ahead.