Weather It Is (Tuesday Evening Blizzard Update)

Good Evening:

The forecast map shows a phasing of the northern (Europe) and southern (Mediterranean) jet streams.  This is unusual, and in some years never happens at all. In the previous four years, this has occurred at least once, and last year with great intensity.

This year's storm at first glance is not as intense as last year, as the total moisture available to this storm is less. Moreover, it was thought that it would come in on Wednesday and be gone by Thursday.

However, temperatures will be quite cold as a massive front moves in off the coast tomorrow morning and sweeps through the coastal regions and up into the mountains. Hence, the precipitation will start as snow in the mountains and accumulate at the rate of two to three inches per hour over several hours, before moderating a bit.  However, even as the moisture flow moderates, the temperatures will be cooling to extremely cold levels aloft (-32 C at 500 mb), which will wring the atmosphere moisture in periodic convective bursts.  Hence, snow accumulations will be expected at night and will continue into a good part of Thursday.

This was suppose to be the end of story.  That is, the story would end when the phased trough would move off to the east and the northern jet stream decoupled from our southern stream (our cut-off low would weaken and dissipate).

Yet, an unusual weather pattern is forecast to develop where the cut-off low will move just off to our northeast east and start subsisting on and sending back our way frigid Siberian air.  This frigid air will slowly, but inexporably cool the lower atmosphere, and this cold layer will soon interact with another wave moving through the southern Jet stream to create another round of snow (likely accumulating) on Friday into Friday night.  Moreover, we're going to quite possibly repeat this pattern on Saturday night into Sunday, where moisture amounts may lead to an even more significant snow.

Lastly, our global ensemble suggest a 40% chance that another phasing of the north and southern streams may occur mid-next week.

Some might think that we're going from bad to worse, and then from worse to worst. Others might think this just a cap and a feather on their snowmen.

In either case: get ready for snow, high winds, and frigid temperatures that will make last year's storm seem a bit tame by comparison.

Please keep in mind that the snow won't announce itself, it will just come and come with a vengeance.

Barry Lynn