Tuesday, 11:35 a.m.
The Memorial Day weekend is behind us, and left behind is the cold, as well as some snow in the high ground of northeast New York state and northern New England. Skiing on Memorial Day? Who would have believed it! But such was the case this year. Now we're about to flip the switch and go from shivering in that late-winter cold to a full-fledged summer heat wave later this week.
As warm air masses go, this one is probably 'run of the mill' for the end of May and the beginning of June. Few records are likely to be set. The highest temperatures will likely be just a couple of degrees into the 90s in most instances. However, it will have come on the heels of a much below-normal air mass, and it will be the first heat of this length with a fairly high amount of humidity. And that will make it feel that much more uncomfortable. In fact, look at the 850mb temperatures being forecast for Thursday evening:
That's a sizable area with temperature of 15C or better, but not 20C. Translated with dry adiabatic lapse rates to the surface and sunshine, it would give you surface temperatures in the upper 80s to low 90s. Heat, yes. But hardly earth-shattering. The key will be in the rather dramatic change from Saturday, Sunday and Monday to Thursday, Friday and Saturday.
This is a heat that will not come without a price tag. With the added moisture to the atmosphere, and the fact it's not exactly warm to the north, there will be a zone of 'resistance,' shall we say, one rife with repeated showers and thunderstorms. And much of that will be in areas that have already been quite wet in the past couple of weeks with showers and thunderstorms.
Take a look at the 12z 28 May NAM model forecast of total accumulated precipitation from this morning through Friday evening:
I will immediately caution you that it is a computer-generated forecast, and that one of the worst things to pick off the model is the quantitative precipitation forecasts, or 'QPF' for short. The NAM model is notorious for 'convective feedback,' where it takes an area of thunderstorms and internally blows it up to make more of it than it should be. In addition to that, it is quite possible for the models to 'jump' on the wrong disturbance or make more of one than it should at the expense of another. And since many of these features are rather small in scale, it is hard for the models to get an accurate depiction of them with their limited grid spacing.
All that aside, the image does suggest it is going to be pretty wet across the northern Rockies and central and northern Plains to the middle and upper Mississippi Valley. There's also likely to be a fair amount of rain over the next three days across parts of the Great Lakes and upstate New York. Exactly just how much rain is hard to determine, but surely there will be enough to cause some flooding. There will also be severe weather, just like what we saw on Memorial Day in the heat of the Plains.
Another interesting thing to note is the plume or streamer of moisture from the southeastern Gulf of Mexico through the Florida Straits toward the southern Bahamas. It is associated with a large but unorganized area of moisture stretching from the Yucatan Peninsula and the northwest Caribbean up into the Bahamas and back toward Hispaniola. It is an area that the models have been repeatedly targeting for some sort of early season 'trouble,' shall we say. It is not at all certain if there will be any sort of development from this feature, but it is likely to slowly grow and drift in a general north to northeast direction late this week and this coming weekend.
Check back to AccuWeather.com com throughout the week for updates on the wild variety of weather - the heat, flooding rain, severe weather and, yes, the tropics. Our team of experts will be on top of the stories as they unfold while I take a few days away from work for the first time since early fall. I'm eager to see some family and friends, enjoying some long rides in preparation for the national 24-hour challenge coming up in 18 days, and some short runs in final preparation for the Skirt Sports Half Marathon on June 9! Back on Monday!
A building upper-level ridge of high pressure in the West will promote hot, dry weather in the Northwest, while a downstream trough brings cooling through the Midwest into the Great Lakes and Ohio Valley.
A pattern more typical of late July and early August is shaping up around the country, one with heat and humidity, but with fewer incidents of severe thunderstorms and flooding.
There will be plenty of heat and humidity from the southern Plains to the East Coast this week while much cooler air prevails for a time over the Northwest to the northern Plains.
Severe thunderstorms raked across the Midwest and Ohio Valley in the past 24 hours, with more on the way this afternoon. The pattern will repeat itself over the next week.