Monday, 11:30 A.M.
As promised, the weekend brought forth some measurable snow to portions of the Rockies as well as the northern Plains and Upper Midwest. Over 10 inches of snow fell in Minneapolis, Minn., while parts of the state picked up 16 inches of the white stuff. Meanwhile, over a foot of snow fell at some of the ski resorts in western Colorado, though accumulating snow was generally lacking in Denver and the surrounding areas.
Following on the heels of the cold front and any snow, arctic air drilled southward into the Rockies, and flowed freely across the northern Plains into the Upper Midwest. Look at the early morning low temperatures today:
For this afternoon and tonight there will be little additional snow across the Northeast, as the cold air and moisture will largely be mutually exclusive. The exception to that will be in the northern half of Maine, where the cold air is offering sufficient resistance to the approach of the warm air to lead to snow, then some sleet and freezing rain. Even there, though, the snow will change to ice at some point before a front comes through later tonight to sweep the moisture out of the region. There can also be up to a few inches of lake-effect snow through tonight, but it will not be widespread.
One of the reasons for the lack of lake-effect snow is the quick moderation of the air mass. Look at the morning analysis of pressure and 500-1000 mb thickness across the country:
If you look at the northern Plains, there are some sub 510 dm thickness values. Compare that to Wednesday evening:
The values in that same neck of the woods is now above 530 dm, and the lowest you can find anywhere at that time is around 520dm in northern Maine. Furthermore, if you examine the corresponding 850 mb temperatures, they go from -15C in northern Minnesota now to only around -9 or -10C in northern Maine by Wednesday evening, with similar readings along the Montana-Saskatchewan border in the wake of another wave of low pressure.
So, in summary, it is clearly going to turn much colder behind the cold front in the next 24 hours across the remainder of the Deep South and up the Eastern Seaboard. However, when you look at how the chill corresponds to normal, it will barely get normal in the mid-Atlantic, and may not get that low in New England. The biggest area of departures will be from Texas to Georgia, and even over the Southeast, the values will be smaller than they are today over Texas.
In fact, with that wave of low pressure tracking across the northern Plains on Wednesday, there will be a nice surge of milder air back into the central and northern Plains and Midwest, boosting temperatures some 5 to 10 degrees above average for mid-December. Take a look at the ensemble forecast for Thursday:
Another storm will track from the Rockies toward the Great Lakes late this week and this weekend, and it should be able to dump more snow on its northwest flank. It could well end up in much of the same area where it fell with this past storm, and it will ultimately help to carry some milder air right back into the East late this week into the start of the weekend, erasing the coming chill tomorrow and Wednesday.
With the storm rolling away from the Southeast this afternoon and tonight, a more typical west-to-east flow pattern will take over in much of the nation heading into the middle of October.
Heavy rains are exiting the Northeast this afternoon, but more excessive rains will return to the mid-Atlantic later tomorrow and Friday. Hurricane Joaquin is lurking near the Bahamas, and may make the situation worse this weekend.
The system along the Southeast coast will spread heavy rain from parts of Georgia into Virginia heading into the weekend, while most of the rest of the country is dry and warm.
It may now be autumn, but much of the country will be warmer than average for the rest of the week and into the weekend.
Fall begins one week from today, but there's still plenty of warmth to go around the rest of this week, with more to follow again next week.
Record heat blistered the East yesterday, but it is about to end. Still, another surge of very warm weather is likely next week to extend summer a little while longer.