Wednesday, 11:30 a.m.
There are times when you feel really good about something in advance, but when it comes to pass, it simply blows your mind away. For over a week, it was pretty obvious there would be blast of heat coming out of the Rockies and spreading across the Plains, and that it will move into the Midwest on Tuesday before that heat surge would weaken today as it reached into the mid-Atlantic. Temperatures in the 90s were easy to forecast given the pattern and the expected temperatures aloft, so it came as no shock when that happened Monday over parts of the eastern Rockies and northern and central Plains. Nor yesterday as it spread from South Dakota into Minnesota and Iowa.
The problem was that it didn't stop there. No, this blow torch had other things in mind. Feast your eyes on this high temperature chart from Tuesday:
Yes, that was a 98 in Minneapolis-St. Paul... 91 in Chicago... 104 in Estherville, Iowa,... 101 in Omaha, Neb.,... and 106 in Sioux City, Iowa, their all-time May record. Records were incinerated all over the Plains, just a couple of days after frost was on the ground in some of these same communities! It was a case where mixing down from the 850mb level didn't quite do it justice. No, in many of these areas, I'm guessing the mixing layer was deeper, maybe up to 750 or even 700mb. And the air was dry, too, making it so much easier to squeeze every degree possible out of the air mass.
That blast furnace of heat is being stoked across the Ohio Valley today. Most places south of a frontal boundary currently stretching from southernmost Iowa to Lake Erie that have any kind of sunshine are already near or over 80 degrees, and with another five to six hours of heating to go, many will reach to and beyond 90.
The real debate this afternoon will be east of the Appalachians up into northern Virginia and Maryland, where the morning started with light southerly winds, lots of clouds and temperatures in the 50s. Will there be enough sunshine to boost temperatures into the lower 90s? Will the wind turn around from the south or southeast quickly enough to combine with that sunshine to mix down the heat from aloft? Or will a shower or thunderstorm cool it off to prevent it from getting that warm? Tough questions to answer!
I suspect that in the Shenandoah Valley, everything will work out to get to or even above 90. In the Washington, D.C., area, it will be close, but probably no. It would have to charge up 30 degrees in six hours, and I just don't think that can happen.
Regardless, one of the more interesting things coming out of this is how woefully inadequate the NAM and GFS-based MOS guidance has performed in this dramatic turnaround. The temperature busts have been averaging 5 to 7 degrees too low, with some in double digits. And that's not a day-two or day-three forecast, but rather a same-day forecast! The European model 6-hour maximum 2-meter temperatures were overall better, but still deficient. The NANO guidance has been better, but even it had its problems. Overall, the models could 'see' the heat coming, but just didn't fully capture just how hot it would get.
Oh, and lest you think winter has been completely erased, not so fast, my friend! Okay, I'm talking Alaska, so that sort of doesn't count in one regard. That said, snow is a real possibility for Anchorage Friday night. Not just some random snowflakes, but actual accumulating snowfall. The latest day for measurable snow in the city is May 22, 1964. This would be May 17-18 if it were to occur, so we're practically at that theoretical late limit. I say theoretical, as the atmosphere can do whatever it wants to do. Just look at the 100-degree heat on the Plains and in the Midwest yesterday as an example. Still, it is yet another sign that winter isn't going to die quietly. Ask the people who had their plants and trees singed by frost in the past few days.
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.