From Jeff:
A higher end severe weather threat will evolve over the region today into this evening.
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An active day of weather is on tap for the region as a weak cold front move into an increasingly unstable air mass. Widespread thunderstorms will erupt as surface heating removes weak capping in place by late morning into the early afternoon hours with then large clusters or lines moving southward across the region into the late afternoon and evening hours. Activity should reach the coast and push offshore around midnight.
There is a pronounced severe weather threat this afternoon given high levels of instability in the atmosphere and increasing shear. All severe modes will be possible with damaging winds to 70mph and large hail up to 1-2 inches in diameter being the main threats. SPC has upgraded much of the region into an enhanced (level 3 out of 5) risk for severe weather. While the tornado threat is low, it is not zero and low level boundary mergers could result in local enhanced low level shear and a brief tornado. This is a day you want to be paying attention to the weather!
Given the slow moving nature of the frontal boundary along with the potential for storms and storm clusters to repeatedly move over the same areas the flash flood threat will be increased this afternoon and evening. Areas north of I-10 have now experienced at least two rounds of storms in the last 48 hours with grounds becoming increasingly saturated while much of the metro area and points south have seen little rainfall. Given the moisture in place, good low level feed off the western Gulf, and potential for training thunderstorms flash flooding and urban flooding could quickly develop. Widespread rainfall amounts of 1-3 inches will be likely with isolated higher totals upwards of 4-5 inches in a few hours.
Storm clusters or a large complex will make its way across the region early this evening and offshore by late evening with a drier air mass filtering in early Saturday and left over showers ending by sunrise.
Timing: Storms look to begin to develop as early as noon-100pm north of I-10 with more significant development and coverage in the 100-300pm timeframe with activity lasting well into the late evening hours especially for locations south of I-10.
Dry air and weak ridging will result in a fair and somewhat cooler weekend, but southerly flow quickly returns by late Sunday and Gulf moisture comes rushing back northward ahead of what looks to be a slow moving storm system for the mid to late part of next week. Overall pattern will support several rounds of severe thunderstorms and heavy/flooding rainfall across the state. This looks to be an increasingly classic May severe and flash flood scenario, but the fine details on timing, rainfall amounts, and the severe weather will have to be worked out in the coming days.
Jeff Lindner
Director Hydrologic Operations Division/Meteorologist
Harris County Flood Control District
9900 Northwest Freeway | Houston, Texas 77092
346-286-4000 (main) | 346-286-4165 (direct) | 281-924-2091 (cell)
Jeff.Lindner@hcfcd.hctx.net | Twitter: @jefflindner1
