Period of active weather late Wednesday-Thursday.
A few severe thunderstorms including isolated tornadoes will be possible over SE TX on Thursday.
Southerly winds will return to the area later tonight into Wednesday with onset of moisture advection off the western Gulf of Mexico. An upper level trough will approach from the west late Wednesday with surface low pressure being forced to develop over north Texas Wednesday night and moving eastward toward northern Louisiana on Thursday. In response to the formation of lower pressures near the Red River, low and mid level wind fields will respond over SE TX. A low level jet of 35-45kts will develop from off the lower TX coast into central TX early Thursday with a broad region of warm air advection and gradual lift over the area. Significant low level air mass recovery will take place along the upper TX coast early Thursday with upper 60 to low 70 degree dewpoints moving inland across areas near and south of I-10.
By mid morning on Thursday wind profiles will become supportive of low level turning and increasing speed and vertical shear over the area. Stronger forcing arrives into the midday and early afternoon hours and expect an increase in widespread shower and thunderstorm development. A few of the showers or storms rooting near the surface will have favorable wind profiles for tornado production when overlaid with a very moist and somewhat unstable atmosphere. This looks to be a fairly common US Gulf coast cool season tornado potential with highly favorable wind fields but marginal instability. Additionally, 50kt southerly flow at 850mb will support gusty winds in showers and thunderstorms and even local gradient winds of 25-35mph will be possible on Thursday.
Overall the window for any severe weather is fairly narrow (900/1000am-200/300pm) on Thursday. Main threats will be damaging winds and isolated tornadoes. SPC has brought the entire area into a slight (2 out of 5) risk for severe weather on Thursday, but think the greatest risk will be along and south of HWY 105 where the highest moisture values will push inland. While moisture levels will be high fast storm motions should help to negate any flash flood threat with a general 1-2 inches of rainfall most likely with the highest amounts along and east of I-45.
Surface front sags to the coast on Friday and stalls across the coastal waters while El Nino enhanced sub-tropical jet stream aloft carves across the western Gulf and TX coast. This will likely keep clouds and at least some chance of light rain in the forecast over the weekend, but much of this will depend on how far north disturbances track out of Mexico.
Severe Weather Outlook (Thursday):

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.org | Twitter: @jefflindner1