Wednesday, 11:55 a.m.
A potent upper-level disturbance is already generating some heavy thunderstorms over East Texas, just north of Houston at this hour. With dew point temperatures into the mid-60s all the way into southeastern Kansas this morning, it's no wonder we're already seeing some severe thunderstorms erupt there, much closer to the boundary that separates this warm, sticky air mass from a much cooler one to the west. As low pressure gets better organized over Kansas this afternoon, the severe weather will become more of a concern over time:
The storm will head northeastward into the Great Lakes late tomorrow and tomorrow night, dragging the cold front across the Plains and Mississippi Valley into the Ohio and Tennessee valleys tomorrow into tomorrow night. Since the air mass is so moist ahead of the front, there will be a hefty amount of rain along with some thunderstorms that will likely become severe. Here's the look for tomorrow:
While severe thunderstorms mean a chance of damaging winds, hail and even an isolated tornado, heavy rain could end up being as big of a concern through tomorrow night. Look at the latest NAM forecast of total precipitation through Friday morning:
Heading through Friday, the storm will continue on an east-northeast trajectory through southern Quebec, pulling a weakening cold front to the New England coast, with that front stretching across the mid-Atlantic states into the Southeast. Drier air will follow into New England and a good bit of the mid-Atlantic states later Friday, but as it stalls, a wave of low pressure is likely to form along the front Friday night that will move off the mid-Atlantic coast Saturday. It's not going to be a potent storm, but one that can bring another period of rain to the mid-Atlantic coast for a time.
Finally, a trailing upper-level trough will come through the Midwest into the Great Lakes and Ohio Valley Saturday:
Scattered showers will accompany this feature around the Midwest and Great Lakes into the Ohio and Tennessee valleys, with some snowflakes in the higher ground that won't amount to too much. As the trough moves through the East on Saturday night, it will push that coastal wave offshore and away from the mid-Atlantic states and New England. At the same time, there will be a few spotty showers, mainly of rain, across the central Appalachians to the mid-Atlantic coast to New England to round out the weekend as the core of the chilly air aloft moves in.
The coldest night upcoming will likely be Sunday night as high pressure finally slides into place and clears the air mass out. Before then, however, it's going to be a west and stormy 48-hour period from Texas to the Ohio Valley.
Intense heat and oppressive humidity surging out of the central Plains will cause severe weather from the Midwest to the Ohio Valley in the next 72 hours, followed by much cooler weather next week.
Despite the heat and humidity in the East today and a surge of intense heat and humidity coming out of the central and southern Plains for a brief period of time, cool air will dominate the pattern through the end of July from the Plains to the Appalachians.
A pattern of extremes is once again unfolding across the country over the next week, with two shots of cool air interspersed with intense heat.
Despite the heat over the central and southern Rockies this week, an amplified pattern means cool air will dominate in much of the country for the rest of July.
Heat will resurface over the eastern Rockies and Plains this weekend and early next week, but the warming in the East will be much slower.
In the wake of the deep upper-level trough over the Great Lakes to the Tennessee Valley, a strong upper-level ridge is poised to blossom over the Rockies, one that will bring on the heat this weekend into the start of next week.