This week could end up being one of the wettest of the entire spring/summer.
The jetstream, which typically flows from west to east across the Country, has gotten all sorts of tangled up. This type of pattern is not all that unusual in the springtime, but when it occurs, you tend to get a lot of interesting weather. I would equate it to throwing a large boulder in the middle of a stream…the flow gets diverted and water flows in all sorts of unusual patterns in an attempt to normalize.
That is exactly what is going on in our atmosphere right now. We call this particular pattern an “Omega Block” because it resembles the Greek letter, Omega.
Your two “boulders” are low pressure areas in the upper levels of the atmosphere, one over the Desert Southwest and the other over the Ohio Valley.
This causes the weather to stall out for several days and what you see one day is typically what you get the next day… and the next… and the next.
So, if you end up under a ridge or high pressure area, you are in the clear and likely to have a prolonged stretch of terrific weather.
On the flip side, if you are located under a trough, or low-pressure area (see New England this week), you are likely in for a long, wet week.
You can clearly see the large scale atmospheric features in play on the current water vapor loop.
There is a large area of low pressure spinning around in the Ohio Valley and on its east side, a firehose of moisture streaming up the East Coast, right into New England.
At the moment, and through much of tonight, that plume of moisture will be aimed mostly into central and western Massachusetts. Therefore, the heaviest rain will fall in those areas initially. On Tuesday, the focus for the heaviest rainfall will shift eastward over eastern MA. That will bring waves of downpours into the Boston area, likely leading to several instances of localized flooding.
The National Weather Service has issued a flood watch for central and western MA through Tuesday night, but this may eventually be expanded to the east.
The flood watch is largely due to the concern for river and stream flooding. Currently, most of our rivers can easily take a few inches of water but, if totals were to climb as high as 4-5″, that could very well lead to some rivers overflowing their banks.
The greatest chance of achieving those higher end rainfall totals through Tuesday is indeed across western and southwestern New England.
Unfortunately, the wet weather this week does not end here.
On Wednesday we expect some additional pop-up showers and storms in the afternoon and evening.
Thursday looks like the driest day of the week, however we still cannot rule out a few stray showers.
On Friday, another large and hefty rainstorm is likely. This could bring another 1-2″ of water to most of the region.
The timing is still a bit in question, but there is hope that this system will clear out fairly early on Saturday, leaving us with a mainly dry Mother’s Day weekend!
