Friday, 11:55 a.m.
Fast-paced changes are the norm across the eastern two-thirds of the country right now, and they will be through Monday before the arctic blast finally has its way and takes over for the heart of next week. To get there, though, there will be a full roller-coaster ride of changes.
To give you an example of those changes, just look at the difference between Grand Forks, N.D., and Chicago early this morning. While the latter was checking in at 4 below zero, the former at one point reached 30 degrees overnight! The difference was being caused by the fact that a massive high pressure area stretching from Oklahoma to Tennessee was responsible for the frigid conditions across the Ohio and Tennessee valleys into the East. At the same time, a powerful storm on the north shores of Hudson Bay was pulling an incredibly mild air over the Canadian Rockies out into the Prairie Provinces, as well as across the northern Rockies into the northern Plains.
As that storm and its attendant upper-level low roll southeastward this afternoon and tonight, there will be a little impulse of low pressure along the cold front arcing out of the storm, and it will spread snow into the eastern Dakotas, Minnesota and Wisconsin into Michigan, Illinois, Indiana and Ohio. The snow won't be heavy, but some places could pick up a few inches of snow, especially in Michigan. In the process of this unfolding, temperatures will likely keep on rising in the Ohio Valley with clouds and snow moving in. Tomorrow will be a noticeably milder in the East despite plenty of clouds and even some snow.
In fact, there could well be a burst of snow marching across Pennsylvania, New York state and New Jersey tomorrow ahead of the arctic front that will race off the coast tomorrow night. Regardless, whatever is gained ahead of the front today and tonight in the Great Lakes, and later tonight and tomorrow in the mid-Atlantic and New England, will be wiped out behind the front, as arctic air pours in behind the front.
Look now at the upper-level pattern as it is being forecast Sunday morning by the 12s Jan. 24 NAM model:
That feature shown moving through southern Saskatchewan will induce surface low development along the boundary separating the arctic air to its north and east from very mild air to its south and west. As the low crosses the Midwest into Michigan Sunday, it will generate some snow. South of the track of the low, one more surge of mild air will be yanked across the Plains and Mississippi Valley into the Ohio and Tennessee valleys. The strongest warming will be in the Tennessee Valley where there will be more sunshine.
As cold as it gets in the East Saturday night and early Sunday, it will warm modestly Sunday night into Monday morning east of the Appalachians ahead of the arctic cold front. Look at the 12z Jan. 24 GFS surface map forecast for Monday early afternoon:
By then, the front will be moving off the coast, the winds will have picked up, and the air will be well mixed - and about as mild as it will be for the ensuing five days across the entire Eastern Seaboard! After that, the cold air drilling into the central Plains and Midwest Sunday afternoon will drive all the way over the Appalachians, and the deep freeze will have begun.
The weather may be most interesting around the Great Lakes through the weekend and into Monday. There will be a lot of wind at various times, a couple of disturbances and arctic air. That will translate into opportunities for snow and lake-effect snow, and the wind will only add to the challenges by causing a lot of blowing and drifting snow and enhancing some of the lake-effect snow bands. Look at what happened on I-94 in northwestern Indiana yesterday! Near whiteout conditions in a band of lake-effect snow with some wind resulted in a massive pileup and several fatalities. Those types of conditions should be expected around the Great Lakes, especially downwind of any lake, through Monday. Snowfall amounts may not be too excessive, especially outside those shifting lake effect snow bands, but enough to cause problems. Here's the 72-hour precipitation forecast from the latest GFS:
Once we get to early next week, though, it's game on - the time when a January thaw might be in order will instead be a time for a prolonged period of extreme cold across the eastern two-thirds of the nation. It will modify over the eastern Rockies and western plains Wednesday and Thursday, but it will probably wait until the weekend until there's any hint of a return toward normal in the East.
Two systems will delay the onset of warm weather in the Ohio Valley and the East over the next week or so, but then it should get warm all across the country heading into the Memorial Day weekend.
A turn to much colder air over the Northeast and mid-Atlantic states will set the stage for a rain and snow storm later this weekend before it turns much warmer later next week.
It's warm now, but will turn much colder this weekend, with a storm threat later Saturday into Sunday. Warmth will return by the second half of next week.
Though it is cold now east of the Mississippi, with a couple of opportunities for snow into the weekend, a blast of warmth is due for much of the country east of the Rockies next week.
Warm air will once again surge eastward from the Plains to the East Coast this weekend and early next week. A strong storm next Tuesday and Wednesday will then be followed by colder air later next week.
A storm in Southeast Texas will generate severe thunderstorms this afternoon and tonight, and some wet snow on its western flank as it heads into the Ohio Valley tomorrow.