Cool dry air is on the move from Canada. This will make for two excellent days of sunshine Sunday (nr 70) & Monday (nr 75) with overnight lows dropping into the 40′s. Pretty straight forward weather, so I am going to take the time to look indulge myself on the upcoming rainstorm heading our way this week…if you don’t mind.  On Monday, A deep trough will begin sliding into the Northern Plains from Canada. It will push even further south..close enough that it may even be able to tap into the Gulf of mexico to direct moisture up the east coast. This is a very strong trough for this early in the season and the beginning of a blocking pattern which will likely take hold for the rest of the month. This is going to bring unseasonably cool air into 2/3rds of the nation as evidenced by the 8-14 day temperature forecast by the Climate Prediction Center. With a ridge in the west and a ridge in the Atlantic, this trough will become stuck in place for a while with several pieces of energy spinning into and out of this trough to keep the weather active for September…This will also come with forecast complications…so extended forecasts should be eyed with caution.

In this kind of pattern all you can do is focus on the next coming wave, so that is what we will do. By Tuesday a broad trough will be fully in place extending from the midwest to the east coast. SW flow up the eastern US will mean increasing clouds, humidity and strengthening SW winds. High pressure off the coast will help to keep much of New England dry for much of the day Tuesday with clouds and breezy SW winds and temps in the 70′s.  Meanwhile a batch of rain will be merging with an approaching cold front and move right up through the Ohio Valley and into New England by late Tuesday…mainly Tuesday night. This will be an energized front with heavy downpours, strong SW winds and embedded storms as it pushes from west to east. Wind advisories and Flood Advisories may have to be posted with it’s passage. The heaviest rain appears to happen 10 PM Tues to 10 AM Wednesday. That could change slightly as we get closer.  The front will deliver heavy rain in the order of 1-3″ with the heaviest in Western New England. Below is the precipitation total forecast for the next 5 days. A very wet look huh?

Once this front is by building high pressure should provide dry seasonal air behind the front for Thursday & Friday. Hopefully it will be that easy. Unfortunately we are going to have to watch this trough closely. The front will stall off the coast…the question is how far off the coast?  SW flow up the east coast will continue with another piece of energy digging into the trough in place over the Great lakes. This will slow the pattern down where the front could just stall right off the coast and keep clouds and scattered showers at the coast going Thursday & Friday. The slower solution of the Euro is showing this….and so far this is the model of choice…with it’s slower solution and deeper trough. So when we talk of forecast complications in the extended range…this is definitely something to watch out for…It may not be a nice week at all if this pattern really digs in the way it could.