Good morning, and I hope we all managed okay overnight. The worst of the rain is long past, though we will still have rain chances for a few more hours this morning. Then, we are just setup for a chilly weekend. Let’s walk through things here.

This morning

Radar as of 6:20 this morning shows sporadic showers across the region, with heavier rain marching east into Louisiana. We have one additional batch of heavy rain that stretches from near Victoria southwest to Beeville down in South Texas.

This batch of showers will push through the southeast half of the Houston area over the next 2-3 hours. Once that clears, steady rain should end. I can’t rule out lingering light rain or drizzle the rest of today. But the risk for moderate to heavy rain ends with this last batch pushing through.

Travel

As of 6:45 this morning, there were just shy of 20 high water locations on area roadways indicated by Houston TranStar

The high water locations are pretty evenly dispersed across the region. If you’re out and about early this morning, just keep that in mind and drive carefully. Never go around barricades.

Flooding

Overnight, we saw Keegans Bayou, Halls Bayou, Greens Bayou, Armand Bayou, Little Cypress Creek, and South Mayde Creek come out of their banks. As of 6 AM, several were still out of banks or at bankfull and slowly receding. Cypress Creek, Spring Creek, and Cedar Bayou are all rising but expected to stay within their banks.

The exception to this will be the West Fork of the San Jacinto River.

Because of heavy upstream rains and heavy rains in the area, all that runoff is filtering into the San Jacinto River, and it is expected to crest sometime by Monday or Tuesday in major flood stage at Humble. With the forecast of a 53.9 foot crest, major lowland flooding is expected with several subdivisions impacted. You can see the expected impacts at each level on the NWS website for this particular gage. For reference, this particular location crested just shy of 51.7 feet back in March. So this will be a bit higher.

Rain Totals

Houston officially had 4.31″ of rain on Friday, making December 7, 2018 the 5th wettest December day on record in the city, going back to the late 1800s. It was also our wettest single day since August of 2017, which we all know was during Hurricane Harvey.

Per the Harris County Flood Control website, most of the Houston area received essentially what was forecast. Most places saw 3-5″ of rain, with a few spots seeing more.

With rain totals like this, it’s never how much falls, it’s how much of it falls quickly that really matters and is always the challenge for us in forecasting. Hopefully we made that clear in the runup to this storm. Fortunately, we’ve now got a few days to dry out, with our next rain chance not in the forecast until at least Wednesday night or Thursday.

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.

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.

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.

We will update later tonight if warranted.

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.

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.