Volatile Pattern Far from Over
5/23/2011, 7:35:35 AM
Monday, 11:40 a.m.
The deadly tornado that ravaged Joplin, Mo., was part of another massive and destructive outbreak of severe weather Sunday that extended from the southern Plains to the Midwest and all the way into parts of the East:
There's a lot to blame for what happened yesterday, but it boils down to some of the same problems we've been dealing with all spring long: a jet stream still too far south for so late in the season, a strong storm or series of storms (low pressure areas) to help focus showers and thunderstorms, a surge of high dew point air coming north to meet the storm and its attendant cold front and a relatively cool air mass behind it all, but more so aloft. The tornadic aspect of all this also can be tied to a notable turning of the wind from the south to more of a westerly direction with height.
This afternoon, the overall severe threat is a little farther east, and with temperatures making a run at 90 in parts of Virginia this afternoon, the places getting the sun will be at risk. Here's the general outlook:
Already, as I type this, three separate severe thunderstorm watches are out - one for northeastern Oklahoma and southwestern Missouri yet again, a second for portions of Pennsylvania down into north-central Virginia and a third in north-central Texas. No doubt more boxes will fly this afternoon into tonight.
Even tomorrow, as the front now plowing through the Midwest toward the Great Lakes moves farther downstream, severe weather is still high on the list of concerns:
By Wednesday, the risk area really doesn't change much. It won't include the Northeast, as the front will have swept much of the moisture off the New England and mid-Atlantic coast, but the farther west you go, the less impact this front will have on 'cleaning out' the atmosphere. Therefore, with temperatures at least in the 70s, and probably 80s (if not a tick higher), and plenty of low-level moisture, there will again be thunderstorms with evil intent as a strong upper-level low rolls across the Plains to the middle Mississippi Valley:
That feature represents a pocket of cold air aloft, and given how the low levels are likely to be very warm AND moist, it won't take much for thunderstorms to develop, and for things such as destructive winds, large hail, and yes, even a few more tornadoes, to accompany many of those thunderstorms.
What is implied but not actually stated in all of this is the threat of flash flooding - and this in areas that are already waterlogged or only now trying to recover from recent flooding. Here's the latest NAM precipitation forecast from tomorrow morning through Thursday evening:
That's not over the lower Mississippi, thankfully, but areas from the central Plains up into South Dakota into the Ohio Valleyand portions of the Tennessee Valley may be looking at several inches of rain this week.
I do hold out some optimism that this stormy and volatile weather pattern may ease up as we go through the Memorial Day weekend into next week. More on that thought as the week progresses.
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