Happy New Year!

For all you winter weather lovers living in the East, winter will be on hold for a while after this weekend I’m afraid as mild air is coming. In saying that, 2013 starts with a very impressive 66.6% of the country covered by snow and that widespread snowpack and arctic air feeding down, has lead to these temperatures this morning.

Parts of Minnesota got down to -24 this morning and such cities as Minneapolis and Chicago as well as countless others started today with the coldest lows of the season.

Here is the current national snow cover. I believe this is the highest New Year’s day snow cover in at least 10 years. While impressive, what’s more impressive is that the snowpack was a mere 6% back on Dec 6, 33% on Dec 15 and now look.

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The current cold pattern, which kicked in about a week before Christmas will continue for the next 5 days and will in fact produce the coldest nights of the winter over New England and down into the Big Cities. Models were bold in the cold for late this week into the weekend but it’s not looking as cold. Models a few days ago showed lows down to 10 in NYC and PHL while Saranac Lake may have pushed 30 below. It’s unlikely to be this cold but we could see a few -20s show up over the 2ft snowpack over Maine. I recon 0 degree air can still creep into N. Pennsylvania and the Cities fall into the teens.

All this said, it’s going to warm over the East starting early next week, perhaps as early as Sunday. I must emphasize though that this warming won’t be nationwide. The stays cold West and over the next 5 days it will turn colder than it is now.

The pattern is turning from it’s current cold mode in the East, in part due to the AO flipping back positive. It is currently around -1 in the negative but in a few days it will go positive. As you can see from the below stratospheric temperature chart, there is plenty of cold over top of the pole so this strengthens the vortex and will raise heights over the mid-latitudes, therefore pulling back the cold.

Like I say, while much of the Lower 48 was warm during the first 15 days of December, the upcoming warmth won’t be US-wide, a trough will hold in the West and could allow a delivery of some exceptional cold down over the Rockies and Plains later next week. I wouldn’t be surprised if the potential cold shot dropping south, may be the coldest seen in quite some time.

A few days may see an area from Billings to Denver remain below zero while Salt Lake sees a few nights drop below zero. This will occur while the AO is positive.

Now, I want you to have a good look at that chart above and now look at the same chart below for 192 hours. Just look at how the arc of warmth at 10mb arcs from Asia over the arctic ocean and the pole. This splits apart a polar vortex which is strong at the moment.

By 240 hrs, there complete displacement of the arctic air with the entire polar stratosphere warm… If this happens, this could have major consequences to both the USA and Europe later in January with some potentially wild winter weather.

These kinds of full polar stratospheric warming events have lead to some of the great arctic outbreaks in past years. It will lead to a likely sharp flip from + back to – in both the AO and NAO and both ensembles show a return to negative around Jan 12.

Here is the US temp anomalies for the next 5 days off the GFS.

Day 8-16.

Note the warming over the East but the cold holding in the West.

Here is the full 16-day period and notice the warmth in the East. Any cold now and over the next 5 days will get washed out by the coming warmth starting early next week. The deeper the trough which drops into the West, the stronger a ridge could be further East but remember what may lie ahead from January 15 onwards!

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