Saturday, January 5, 2013

When Will The Snow Come Back?

Snow has dropped off the radar for a while now, and questions are arising- when will the snow be back?

The problem is something called zonal flow. The term zonal flow refers to when the jet stream is displaced north and moves in a monotonous west-to-east line. This monotonous jet stream formation then stirs up above normal temperatures in the East and Central US, and commonly stays until a new pattern comes along.  My weekly forecast for the next 7 days is shown above (see Week 1 and Week 2 explanations by clicking here), and I am expecting a zonal flow formation to set up during this time period. This comes as the Madden Julian Oscillation (MJO) moves into Phases 5-7, which are best known for being favorable for warm weather. So we can pretty much rule out the next 7 days for any snowstorms across the nation.

In Week 2, we see a significant change occur in the jet stream pattern. High pressure has formed in the Gulf of Alaska, leading to low pressure holding its ground in the West US and the Rocky Mountains. The jet stream accommodates this predicament by pulling the strongest upper level winds south, and then pushing them far north as high pressure builds across the East Coast. This is a good example of the negative phase of the Pacific North American (PNA) index. In the negative phase, low pressure builds over the West US and, as physics dictates, high pressure then forms in the East US to balance out the low pressure. The negative PNA pattern brings about cold weather in the West and warm weather in the East. This pattern is probably the most favorable for the Plains, and that is where I expect to see the next snowstorm.

I anticipate low pressure to enter the Southwest, eject into the Southern Plains and move northeast on a track known as a Great Lakes Cutter. This cutter gets its name for going through the Great Lakes region, hence Great Lakes Cutter. This system should move through Oklahoma to Wisconsin, giving snow to the Central Plains and Upper Midwest. Given the high moisture content of the storm system, heavy, flooding rains would be expected across the lower Midwest, Gulf Coast and Ohio Valley regions. I expect this storm to hit between the 11th and the 13th of January.

This negative PNA pattern continues for several days, with the trough responsible for below normal anomalies in the West beginning to slide east very slowly. When the trough breaks free, it should move northeast into Southern Canada, where a meeting with a piece of the polar vortex could be in order. A strong cold front could follow this trough, and that could very well be what kicks off the brutally-cold Late January into February. This would happen around the 20th of January.

So it's looking dry for the next week thanks to the infamous zonal flow pattern. A negative PNA pattern will then emerge in the wake of the zonal flow, and I expect heavy snow to hit the central Plains and Upper Midwest around the middle of the month, with flooding rains in the Lower Midwest and eastern Great Lakes into the Ohio Valley. Beyond that, things get unusually murky thanks to the incoming Arctic outbreak that will start in the West and bleed East.



Anonymous said...

given what you know and see happening for this next system in the central plains do you think it has the possiblites to make a good old fashioned blizzard with several inches or even a foot or two of snow for kansas (we need the moisture any way we can get it)
your best guess is all i ask

fivethousandoverlibor said...

Andrew - great work here. The 500MB anom maps days 6-15 are staring to look like an artists pallet - extreme color everywhere. It looks amazing. 570m high over Greenland in the 12z euro op at 240hrs. I don't know that I've ever seen it that anomalous. Massive -NAO building.

BUT - can the -PNA budge? Can the eastern pacific ridge get a bit east to make room for this air to get into the big population centers in the east? What do you see as the drivers for opening up this polar pig to the US Atlantic Coast? Many thanks in advance. Oh - and don't suffer the fools - I used to myself - difficult as it is - don't do it.

Anonymous said...

When do you expect the cold to get to the mid atlantiv region? The cold and snowy forecast looks like its coming together in a supriseing way for many peoople. Lots of people dont know about this.

Anonymous said...

will detroit michigan get the heavy snow or the rain for the january 11 system

Anonymous said...

Thanks Andrew for the update.. Typically, in the Shenandoah Valley, our best snow producing storms have to come up from the gulf. If they come from the West the mountains block the energy. If storms develop do you think there is a chance they will come up from the gulf region?

Anonymous said...

anything new information on next weekend storm track? how strong of a system is this going to be?