The kind of storms that have taken shape over the southern Plains in the past few weeks are what we call mesoscale convective systems — or “MCS” for short — and they tend to produce extreme rainfall totals over a large area, sweeping across multiple states over many hours. These systems often develop in the late evening and persist well into the dark of night, making the flooding that much more dangerous.
On Thursday, a flash flood warning was issued for portions of eastern Oklahoma as a large complex of storms pushed across the state. The rainfall is light compared with most storms over the past few weeks, but Oklahoma is just so saturated that “even a half to one inch of rain could result in enough runoff to cause flash flooding,” says the National Weather Service in Tulsa. Another area of heavy thunderstorms is pushing through the Texas panhandle on Thursday, and the National Weather Service in Lubbock expects this area will grow in size into the evening hours as it inches east.
Friday and Saturday will also bring heavy rainfall potential, and although it’s not certain exactly where storms will set up, the overall patterns seems to be favoring the wettest areas so far this month, in southern Oklahoma and northern Texas. A cold front will sweep through the region on Friday night into Saturday, which could provide the next round of potentially dangerous flash flooding. Flash flood watches are in effect from southern Kansas to south-central Texas through Saturday morning for widespread rainfall totals of one to three inches and locally higher amounts. Though the final totals might not be blockbuster, the soil, streams and rivers have already been pushed to their breaking points. It doesn’t take much rain anymore for these areas to flood.
All told, the National Weather Service is expecting up to three inches of rainfall across northern Texas and southern Oklahoma through Saturday. It’s highly likely that isolated areas will see much higher totals, but again, it’s difficult to pin down exactly where these systems will capitalize on the extremely moist environment.
Beyond Saturday, though, things will begin to dry out for the Southern states. An upper-level trough of low pressure is forecast to dip into the southern Plains on Sunday and stall over the Gulf of Mexico, placing Texas and Oklahoma in a nice, dry flow from the north. These winds will carry with it a plume of drier-than-average air — which is exactly what the flooded areas need.
While there still remains the potential for afternoon, garden-variety storms early next week, the overall pattern will not be the kind to generate the massive, widespread convective complexes that Oklahoma and Texas have become so accustomed to in May.
Breaking it down by model, the GFS and the European are mostly in agreement on magnitude of rainfall totals over the next week, if not on exact location. In general, Oklahoma east of the panhandle and most of northeast Texas have the potential for two to four inches of rain, depending on where the heaviest thunderstorms set up.
GFS (7-day total precipitation forecast through Wednesday):
Euro (7-day total precipitation forecast through Wednesday):
More Texas-Oklahoma flood coverage:
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