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.
A snow storm affecting the central Plains and Midwest into the Great Lakes this afternoon into tomorrow night will be followed by the first of two arctic outbreaks around the country before Thanksgiving.
Winter is six weeks away, and there will be a couple of signs this week of the approaching season as a storm develops on the western Plains and heads through the Great Lakes.
A warm pattern is setting up for much of the nation next week.
Tropical moisture associated with the one-time Hurricane Patricia will bring heavy rains to many areas east of the Mississippi Valley between now and Wednesday night.
Patricia, the strongest hurricane on record in the eastern Pacific, will make landfall this evening in Mexico. It will spread torrential rains into East Texas, and impact the weather all the way to the Northeast next week.