When the flow of these jet streams is fast or progressive there is nothing to slow them down so we end up with a boring weather pattern that tends to bring warmer pacific air into the pattern. That is what is currently going on. The image below shows the straight nature of the two jet streams shooting across the country..
Now even though the pattern is very progressive right now, there is still a lot of energy on the map due to that very active southern branch. The question now becomes how do we slow this flow down so these jet streams can potentially combine. The answer to that question is building a ridge out west and some sort of blocking in the Atlantic. Blocking is basically an area of high pressure that forces the jet stream to go around it. This amplifies the flow and slows everything down potentially resulting in the phasing of the two streams and big storms.
By the time we enter this weekend, things start to get a little more interesting as a ridge builds out west..
I pointed out a few things in the image above. Take a look at the the two red lines first. That represents each branch of the jet stream this weekend. Notice how the northern branch is now rising in the west which causes it to dip down stream. This dip allows the flow to slow down a little and the potential for two disturbances to combine in both branches. I circled the two disturbances in green.
As these two disturbances are closing in on each other lets take a look at things downstream in the Atlantic. Remember we want some sort of blocking or high pressure area there so a developing storm does not just skirt out to sea. The image below shows the pressure pattern by the time we get to early next week..
Now things are starting to get very interesting! Those two disturbances circled in green above are slowed down significantly due to high pressure surrounding them. Red is high pressure and blue is low pressure representing our developing storm. Notice how because of the high pressure to the north the energy can not simply escape and is forced to deepen and develop a major storm.
A storm is one thing but how about the cold air? That is the tricky part here. The key to this whole set up is now much down that northern jet stream digs and supplys cold air. The steeper the ridge out west the more the northern branch will dig and the more cold air we will have. Right now the models are struggling with this. Here is the predicted precipitation type on the Canadian model..
You can see it shows an impressive interior snowstorm and rain in areas closer to the coast. At this time, I do not even look at the surface printouts. What we need to monitor over the next few days is the projected interaction between those two disturbances. If you want snow closer to the coast, then you need to root for the northern disturbance to "dig" sharper than modeled all due to a bigger ridge out over the west coast.
If this storm materializes someone is going to get dumped on with impressive amounts of snow. As of now the models project the heaviest snow to be in interior New England. This can very well end up being the case but with so much going on you really can not trust any model outputs at this point.
And yes, in case anyone is wondering, the European is also showing storm development..
image above is WMO from weatherbell.com
So we got something to watch over the next few days! This could turn out to be very exciting. Keep checking in for updates!