Tuesday, 11:50 a.m.
Fresh off a very rare three-day weekend of sorts, I am looking across the country at a weather pattern that doesn't favor much in the way of heat, especially for the southern tier of states and the East. It's not that it will be quite chilly with a late-season arctic air mass coming in from northern Canada. Instead, there's just not going to be much heat to go around. It is rather humid across the South and up into the mid-Atlantic, but a cold front advancing into this sticky air mass will bring with clouds, showers and some thunderstorms that will keep temperatures in check, especially starting tomorrow.
The only real heat in the country right now is in California. That is expanding into the interior Northwest ahead of the next cold front. As this front sweeps inland later tonight and tomorrow, the warmth will be pushed right back out of the Northwest and into the northern Rockies. Look at the thickness packing behind the front over western Montana into Washington (dashed lines) late tomorrow:
This will push temperatures into the 80s tomorrow over parts of Idaho and Montana into Wyoming and maybe the westernmost Dakotas. By Thursday, behind the front, it will turn much cooler across the entire region, with the warmth being squeezed out onto the northern Plains and into the Midwest, while it also warms nicely over southeastern Wyoming and Colorado out into the central Plans. Very few places, though, will reach 90 from Colorado to South Dakota.
Meanwhile, in the East, the deep upper level trough will be slow to exit the East Coast. Even Thursday, the trough axis has yet to clear the coast:
This will mean a cloudy, wet time of it through tomorrow and into tomorrow night along the Eastern Seaboard and on up into New England. This is coming after a lengthy period of pretty dry weather. By and large, then, it will be considered a welcome rain, especially since it will occur in the middle of the week and not on the weekend!
Behind the trough, a rather large high pressure area, now up over Montana, will reorganize over the Plains, then the Mississippi Valley tomorrow and tomorrow night into Thursday morning. Where it moves, look for cool nights with below normal temperatures. Most place will experience this over two consecutive nights with pretty light winds. Some farther to the east over the Ohio and Tennessee valleys and into the Appalachians may get it over three straight nights, helping to keep temperatures in check.
It will warm some later this week across the South and East, but if you look again at that 500 mb forecast up above, there is another upper level feature rolling out of the southern Rockies that will inch along across Texas. This, in turn, means more opportunities for clouds, rain, and thunderstorms. The net effect of this will be to keep temperatures near to below normal across the southern Plains through the rest of the week and into the weekend, and it will steadily cool off across the Lower Mississippi Valley and points east.
If there's any heat to come, it will be reserved for the West this weekend. Look at the projected temperature anomalies for Sunday:
With an upper level ridge re-establishing itself over the West, there may be some places that approach 90 by Sunday. That won't even be a though over the East for quite some time to come.
Blocking over the Atlantic and in Europe is buckling the jet stream over the central and eastern U.S. to extend the cool and wet weather the rest of the week and into the weekend.
More excessive wetness is in store from the mid-Mississippi Valley to the mid-Atlantic states, while the brutal heat continues in the West and especially the Northwest this week.
A cool season storm will bring flooding rains and very cool air to the Ohio Valley and Northeast tomorrow into the weekend, while the Northwest has record-setting heat with sunshine.
As the jet stream undergoes amplification late this week into the weekend, it will lead to extremes of heat in the Northwest and cool and wet weather in the Ohio Valley, mid-Atlantic and parts of New England.
Heat and humidity surging across the Mississippi Valley will spark severe thunderstorms in the next 24 hours. The pattern will remain wet from the northern Plains to the East Coast for a while.