Saturday, 8:30 A.M.
I continue to be fascinated by the intricacies of the weather pattern these days. And even though I am an avowed cold hater in my aging days, there's even a lot to be said for that for the rest of the month. One quick point before I go any farther. I am still of the opinion that model forecasts are not yet cold enough when the true arctic hits the fan. The GFS MOS guidance numbers are trending in the right direction, but I still believe it'll be colder yet when the core of the first bitter blast moves into place.
At stake is a temperature 'fight', if you will, in Chicago, where there may not be a day with a temperature staying below zero all day, but I'm convinced they'll get at least one and perhaps two days with highs in the single digits. Also at stake is the ending of a 4-year run of daily high temperatures of 0 and above in Minneapolis. That may end tomorrow, but if it doesn't, it's a virtual lock on Monday.
Since I posted Friday, little has changed, in my opinion. But for the sake of maybe some newer readers today, let's review:
1) Arctic air being routed from the Northeast today. Temperatures before sunrise were already higher in Boston and New York City than throughout the day Friday. Southwest winds are chasing the cold quickly away, and temperatures will jump into the 40s with varying amount of sun, more the farther south you go. Just as an example, look at the highs out in the middle of the country Friday:
2) First arctic press follows behind weak storm and its attendant cold front. Here's the NAM surface forecast for tonight:
Temperatures will drop like a stone today in North Dakota and northern Minnesota once the front passes, drilling into Chicago and Detroit overnight, and then spreading across the Lakes into the Ohio Valley and upstate New York and Pennsylvania into northern New England tomorrow.
3) Second surge of arctic air follows behind an upper level disturbance within 24 hours. Two thoughts on this. First, it has the effect of diminishing the intensity of the first push of arctic air as it moves into the Northeast tomorrow and tomorrow night. That does NOT mean it won't get much colder! What it does mean is that the depth of the cold air becomes much more shallow as more of it consolidates with the second surge. And that means temperatures, while at or below normal Monday from Boston to Philadelphia, won't be as cold as everyone thinks. And it also means that as cold as it gets tonight and tomorrow in the Midwest and northern and western Great Lakes, it will be that much colder Sunday night and Monday.
4) Said disturbance blows up a fluff bomb off the Northeast Coast. There will be little bits of snow with this feature along the way. It'll start in northeastern Montana and the Dakotas tonight with a dusting to an inch or two of high snow to liquid ratio snows - something like 30:1 (30 inches of snow melting down to 1 inch of liquid). There will be a little of that in the Midwest tomorrow, and a touch of it in the Great Lakes and Ohio Valley tomorrow night, then in the northern Mid-Atlantic Monday. But then that feature will run into the rich moisture source known as the Atlantic. The pressures will lower rather dramatically Monday night and Tuesday, the air aloft will get progressively cold, and even colder air will drawn into the circulation of the developing storm at the surface. The result? some windblown 'fluff' snows that will accumulate a few inches over southern and especially southeastern New England sometime Monday night into Tuesday morning. It will not be a prolific snow, but out on the Cape, it could be fierce on Tuesday with 50-mph winds and blinding snow and blowing snow for a time.
5) Cold sets in for 3-4 days. As stated in the opening, I don't think the machine-generated numbers have yet caught up to how cold it will actually be from the Midwest to New England, but they're getting closer. The worst of the of the cold will go from the Midwest to northern New England. Look at the projected temperature anomalies on Tuesday:
6) Storm follows later in the week. Here is where it gets really interesting. Typically arctic air, once it gets in across the low levels, is not easily moved if there's any sort of depth to it. The stuff that moved into the Northeast yesterday doesn't fit the mold, because it was very shallow, and is being routed rather easily. Later this coming week, it will offer up much greater resistance.
The storm that develops off the New England coast Tuesday may well play a role in what happens late this week with that storm. The models for three days now have been insisting that this storm blows up and rolls up toward the southern tip of Greenland. In so doing, it all but destroys any downstream blocking, and also pulls the polar vortex through Quebec to the northeast shores of Labrador. Here's the Canadian ensemble view of things next Thursday evening:
That will allow for room for this storm to end up farther north than you'd think given the strength of the cold. And that raises some real interesting questions about the weather that ensues with the storm.
Speaking of the Canadian model, let's show you the forecast for next Friday morning that it currently has:
That 'L' is up over Lake Huron. Now, for comparisons' sake, here's the GFS model forecast for Friday evening:
The European and JMA models are in between these two seeming extremes, if you will, and seems a pretty good compromise for the moment. Regardless, the concern is still every bit the same today as it has been for me since Thursday - the cold air retreats enough, and the polar vortex gets out of the way far enough to allow a storm to track into the Lakes or very near them. When that happens, you almost always see a surge of warmth up into the Ohio Valley as well as east of the mountains, bringing into question the form of precipitation in many areas.
If you examine the CURRENT 850mb temperature forecasts ahead of the storm, many bring that 0C isotherm to the southern New England coast and up to the southeast corner of Pennsylvania. In the Ohio Valley, some bring it up past I-70 in Indiana and Ohio. And if you really want to see a doomsday forecast, look at the 850mb temperature forecast from the JMA model next Saturday morning:
That seems too warm to me. Still, there's plenty of valid concerns to not go with a bitter cold then storm=snow forecast, which many seem to be doing. Or maybe 'wishcasting.' I'm not into that kind of nonsense! I only tell it as I see it, and I can snow going to ice over interior southern New England and back into Pennsylvania, with snow in the Great Lakes, some snow in the northern Ohio Valley, but snow to rain or just plain ice to rain farther south. And snow to rain from the southern New England Coast, including New York City, down the I-95 corridor. None of this is etched in stone, but it's been a pretty consistent idea the modeling is presenting over the past several runs.
Once the storm passes, regardless of the form of the precipitation, another surge of arctic air seems likely. It'll be a little farther west this time around, digging into Montana and the Dakotas next Thursday, then pushing farther and probably more forcefully down the Plains Friday into Saturday before sweeping to the East Coast next weekend. And it looks like it should last 2-3 days before it, too, starts to retreat.
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.
A major spring storm will move from Texas tonight to the eastern Great Lakes Wednesday night, producing heavy rain and severe thunderstorms, with a swath of heavy, wet snow on its western flank.