Just a quick midnight update on the state-of-play with Houston’s storms…
A heavy round of showers has now pushed east of the metro region, moving along the coast and toward Beaumont. Behind that, the front (with much lower dewpoints) is pushing into southeast Houston. And behind the front, there’s another area of fairly heavy storms moving east-northeast. We think this is probably the last really burst-y area of storms that will affect Houston tonight. After this, from 2am or 3am onward, we should see some additional light to moderate rainfall, but this too should peter out by around sunrise or shortly thereafter.
Flooding state of play as of midnight Friday. (Intellicast/Space City Weather)
We’re still concerned about the West Fork of the San Jacinto River, which we mentioned earlier, and South Mayde Creek and Langham Creek in Western Harris County are out of their banks and spilling into nearby streets and parks, according to the Harris County Flood Control District. Elsewhere, bayous and creeks are holding.
This is almost over, so hang tight, and lets begin to dry out come sunrise.
Good evening. We’re continuing to monitor conditions across the metro area and rainfall totals remain manageable for most of the region. We have two main concerns: flooding along the West Fork of the San Jacinto River, and the potential for more heavy rainfall later tonight as a main line of at least semi-organized storms moves through. Overall, most of Houston will come through this just fine, we believe.
San Jacinto River
The West Fork of the San Jacinto River, which is downstream of some of the heaviest rainfall today, may potentially go into major flood stage on Saturday or Sunday. According to the Harris County Flood Control District, the following subdivisions may see impacts: Forest Cove, Rivercrest, Northshore, Belleau Woods. Kingwood and Atascocita appear unlikely to be affected at this time.
Potential major flooding along San Jacinto River. (National Weather Service)
Main line of storms
So far today, rainfall amounts for most of the metro area have remained near 2 inches or less (we’ve seen more than this up north, in some parts of Montgomery County and elsewhere). These are quite manageable for area bayous.
As of 8:45pm CT we are seeing storms get organized just west and north of Houston, and from now until about 3am CT we are likely to see the potential for additional heavy rainfall as this mass of storms moves through, from west to east along with the front. Conditions will likely deteriorate for much of Houston over the next hour or two, so now is the time to be wrapping up any activities and getting home.
Most areas may see an additional 1 to 3 inches of rainfall from now through 3am—which should be fine for most bayous—although a few areas may see a bit more than this. After 3am we should see a slackening in rainfall on the west side of the metro area, and then a gradual ending beginning shortly before sunrise from west to east.
Saturday will be gray, and chilly, with highs in the 50s and blustery northerly winds.
Rains so far today have stayed mostly to the north and west of the Houston metro area, as anticipated. As of 2pm CT, just south of Huntsville is the big “winner” with about 4 inches of rain falling so far. Not a whole lot has changed with our forecast, but I did want to call out a few things we’re watching as we get closer to heavier rainfall this evening and during the overnight hours.
Models not showing extreme totals: None of the high-resolution models are really bombing out huge rain totals with this event. So while some forecasts have been calling for up to 10 inches of rainfall during the next 12 to 24 hours. We’re feeling more comfortable with 7 or 8 inches as an upper limit, with most of the area seeing 2 to 5 inches of rainfall.
Heavier rains more likely north: Some of the models suggest the heavier rain totals (5 inches or more) will generally fall north of Harris County, with most of the metro area remaining under that threshold. Other models show the rainfall pretty well dispersed, so we’re not overly confident with this part of the forecast.
Line of storms timing: The point at which the front (and a line of strong thunderstorms) moves through Houston has moved up somewhat, and now appears likely to sweep through the region, from west to east, between around midnight and 3am. This is the time when you definitely won’t want to be out and about due to the potential for heavy rainfall, flooded streets, and strong thunderstorms.
HRRR model forecast for line of storms as of 1am CT Saturday. (Weather Bell)
Flooding potential: Because some of the heaviest rainfall will occur well inland, we’ll have to watch for potential flooding along the Trinity, San Jacinto, Brazos, Navasota, San Bernard, and Colorado river basins. In terms of bayous, Jeff Lindner of Harris County said he’s most concerned about bayous and creeks across the northern, northwestern, and northeastern parts of the county: Cypress, Willow, Little Cypress, Cedar, West and East Forks of the San Jacinto, South Mayde, Langham, Bear. We think most of these will probably remain within their banks.
Event will end: We are not overly concerned about Friday night’s event, because it’s going to come to a pretty abrupt end by or before sunrise on Saturday. This will be kind of a nasty rain event for December, but if this were July or August, it wouldn’t be considered all that extreme. Our bottom line is that, if you’re overly anxious about this event, it’s probably not going to be as bad as you think.
We’ll be back this evening with an updated forecast.
The sunny weather we’ve enjoyed this week is now gone, as high pressure has been firmly supplanted by an onshore flow. We’ll see a steady diet of cloud cover through Saturday, with moisture moving onshore that will culminate in the potential for heavy rain on Friday night and Saturday morning. To mark this threat, the National Weather Service has issued a Flash Flood Watch for the region from Friday afternoon through Saturday morning. We discuss this threat below.
Green area denotes extent of National Weather Service Flash Flood Watch for Friday and Saturday. (Pivotal Weather)
Thursday
After a start in the 50s, highs today will climb into the upper 60s under mostly cloudy skies. Southeasterly winds will transport moisture inland throughout the day, and although we can’t rule out a few isolated showers we don’t expect anything significant. Low temperatures Thursday night won’t fall much below the mid-60s for most of the area.
Friday
The upper-level low pressure system will be moving down through Texas, approaching the Houston region from the north-northwest. We expect some light- to moderate rainfall on Friday in the Houston metro area during the daytime, but for the most part, heavier showers should remain west of Harris County until around sunset or so. Highs Friday should climb to near 70 degrees under mostly cloudy skies.
