Monday, 11:00 a.m.
For the first time in a long, long while, I can finally point to warm period of weather of more than a day or two from the Plains to the East Coast. I've been pointing to the second week of April for quite some time now as the transition period from the persistently cold pattern to a much warmer one, and it looks as if that timing is going to be right. We'll suddenly go from being much below normal and dealing with snow, wind chills, frosts, freezes and record lows to spring time warmth, budding flowers, bees, mud, snowmelt flooding and prospects of severe weather.
I'm not sure I'm willing to go out on a limb and predict record warmth from this point. After all, some of the records I'm looking at for the second and third weeks of April are well into the 80s - and even some 90s. I do find it rather interesting, though, that two winters noted for their cold, 1975-76, and 1976-77, both ended up producing record highs in April once winter left for good. Again, I'm not ready to switch to shorts and flip-flops - yet. I will go figure out where there were placed for winter storage, though, and probably look for the air conditioners and fans while I'm at it.
The thing that really stood out to me this morning was an 8- to 14-day temperature anomaly forecast from the Canadian NAEFS. Friday afternoon, they began to switch from cold, cold, cold to something other than cold from New England to the Ohio Valley and points south. It has become consistent in that forecast ever since, including the 0z run:
In addition to that forecast, the NAO forecasts going forward are also showing signs of the breakdown of the Atlantic blocking:
Let's look at how this changes. Compare the GFS ensemble forecast of 500mb heights and anomalies, starting with Wednesday morning:
That figure shows an intense upper-level low over Atlantic Canada, with a strong ridge to its north. That ridge extends from the northeast Atlantic back to the west across Greenland. That orientation is driving some very mild air up from the Atlantic into the Arctic and into most of northeast Canada, while at the same time it is forcing another shot of very cold air out of central and northwest Canada right through the Midwest into the East.
You can also pick out a few other things, such as the upper level trough moving into Texas, and the distinct split in the jet stream across the country.
Let's fast forward this to Sunday evening:
Notice the upstream ridging east of Hawaii and how it forces troughing into the West. In turn, that should help raise the heights downstream. They will, to some degree, though you can see there is still a large blue area on that map from Hudson Bay eastward to the northwest Atlantic. The eastern 'appendage' of that upper-level low is really the upper-level low rolling into Texas Wednesday morning. It looks as if this storm will develop into a powerful storm Friday night and Saturday as it blasts through or by eastern New England. It may be that very storm that ultimately breaks down the long-lived block.
Now move ahead to next Thursday evening:
The downstream block is gone, with the upper-level low just southeast of Greenland. There's still a ridge east of Hawaii, though farther east, with the downstream trough now move over the eastern Rockies and Plains, with the other downstream ridge along or just off the East Coast.
It's been a long time in coming, but spring warmth is just around the corner. Time to get the yard cleaned, the gardens turned over, and the power wash to clean winter's grime off the house and windows. Spring fever is about to bust out all over.
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