SATURDAY UPDATE ON DEC 22–23 POSSIBLE EAST COAST WINTER STORM

Now that the big LOW on December 15–16 has cleared the New England coast. Northwest winds and seasonally cold air has moved into the East coast and the next few days look very good for snowmaking conditions across all the central Appalachians. All attention now turns to the concern or possibility of a significant East Coast winter snowstorm right before Christmas on December 22 -23.

Over the past two or three days the operational GFS or American weather model has been extremely aggressive or bullish on the development of a significant East Coast winter snowstorm December 22–23. Some of the model data has been showing large areas of 8 to 20 inches of snow across much of the Middle Atlantic with the heaviest snow east of the mountains. Some of the other models have at times supported the solution -if not quite that much snow — while at other times they have shown no big storm on the East Coast Specifically the European and Canadian models have gone back and forth with this potential winter storm situation on the East Coast for December 22nd 23rd. At times the European and Canadian models have shown a significant East Coast winter storm with a lot of cold air in place and producing a widespread moderate to significant snowfall. But at other times these models have done a complete reversal and if said no it is not going to be on the East Coast — the LOW is going track into the Midwest or Ohio Valley and bring those areas a snowstorm and it will be rain on the East Coast.

The key to the entire situation appears to be what is going to happen in eastern Canada with the Greenland Block or the negative phase of the NAO The GFS model has been developing an upper LOW in the jet stream across southeast Canada that parks itself underneath the Greenland Block. This configuration is referred to in the weather business as a REX BLOCK. And when it happens it is often a significant feature in the atmosphere and often causes an East Coast winter storm.

The problem is that the European and the Canadian models no longer have this REX BLOCK feature in eastern Canada and Greenland.

And because they don’t, the system that develops in the Plains does not go to the East coast and become a big winter storm. Instead, it becomes an Ohio Valley winter storm and rain on the East Coast with big snows in Chicago and Illinois, Missouri, Indiana, and Michigan.

If it sounds like I don’t know what solution is correct or how this is going to play out — that would be an accurate assessment. I do not know at this time which solution is going to be correct. Normally I would side with the majority of the model data which would be the European British and Canadian models. Last winter however the European model showed several major East Coast snowstorms at days 6 through 10…. only to have them disappear every time we got close to the event. Usually, the European model does not perform this badly but last winter it was really bad. Perhaps there has been an adjustment and the model is doing better. I just don’t know at this time.

The Saturday morning 12z GFS has come in and it now has the DEC 22–23 LOW taking a much further track to the west very much like the European and Canadian models.

So yes, it is Probably a non-event for the East coast.

Experienced meteorologists know that when you are dealing with extended and medium range forecasting there was often this barrier or this breakpoint between the medium range and the short-range that occurs sometime between the 60-to-84-hour time frame. Over the past 30 years there have been numerous instances where the Global models show what seem to be massive Low pressure areas or Hurricanes making Landfall or heat waves or what have you at 168 hours (day 7)….or at 144 hours… at 120 hours… or at 96 hours but when you get to 84 or 78 or 72 hours there can often be this significant jump where models often come up with a totally different solution from what everybody was looking at during the past 4 or 5 days. The term that some have used to describe the shift is known as the breakpoint -the barrier between medium range and the short range.

I raised this because I am going to wait until we get within 72–84 hours before the start of the possible event before I totally and completely kill this threat for the East Coast.

Yes, all the data as of Saturday really downplays this event and shows a big Midwest Winter storm and a lot of rain and Mild temperatures for 24 hrs on December 22nd on the East Coast. I am worried that when we get within the 72 hour barrier that the Rex Block 50/ 50 LOW in southeast Canada is suddenly going to reappear on the model data and things might slide back to the East coast. I do not think that is going to happen but there is a small chance (20%? 15%) it might so before I officially kill this entire event, I will wait until Monday. If on December 19, there is still NO /50 Low in southeast Canada, then I will completely y give up on this entire event.

There has also been a hint of another potential winter storm on the East Coast around December 26th or 27 but that possibility is dependent on DEC 22–23 event being at East Coast winter storm. So if the system coming up for December 22–23 is a Midwest Winter storm then the follow-up event doesn’t occur on the East Coast on December 26th-27.

if we assume for a second that the December 22 -23 winter storm is going to pass to our West and it will impact the Ohio Valley / the Midwest and it will bring rain that might end as snow in the mountains on December 23rd, the air mass coming in behind the system is cold and it will last for several days.