Matt Lanza

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.

Good morning. Let’s get right into the forecast here, as a significant winter rainstorm begins to bear down on Southeast Texas.

First off, Flash Flood Watches will go into effect for the entire region today and tonight.

This means conditions will be favorable for flash flooding, street flooding, and some substantial rises in area creeks, rivers, and bayous. If you’ll be out and about tonight, you will want to have a way to receive updated weather information. Space City Weather will be updated through the night as well, but make sure you have a couple sources of the latest information and a way to see radar.

Also, something that’s occasionally underappreciated: If possible, please make sure your neighborhood storm drains are free of leaves and debris. We are “past peak” fall foliage in Houston now, and many leaves have found their way to storm drains and gutters.

Reminder: before the rain, please clear your drain!#ThursdayThoughts #weatheraware
You can adopt your drain at https://t.co/V9XMMXl3yZ pic.twitter.com/Z3hVsqsETv

— Houston Public Works (@HouPublicWorks) December 6, 2018

Clearing these areas allows water to drain more effectively and will often mitigate some street flooding issues.

This morning

Radar this morning is quiet in Houston, but scattered showers have developed northwest of the city.

Expect scattered showers and the possibility of some thunder to continue through the morning hours north and west of Houston. This area should advance closer to Houston as well, bringing some rain chance to the city by late morning.

This afternoon

Expect showers and thunderstorms to become more numerous and widespread as we go through the afternoon, especially along and northwest of US-59. We will want to watch this to see if rain can advance farther southeast than expected, as this could push the steadier rains more into the central part of the Houston metro, rather than it being skewed northwest. Regardless, I don’t anticipate that we’re going to see a lot of flooding issues around the region through afternoon. That risk ramps up tonight (read more below).

But still, I would expect that we could see on the order of a half inch to two inches of rain on average during the daytime today from the city of Houston to the north and west, with lesser amounts south and east. However, we will need to watch southern and eastern areas later this afternoon for some isolated potentially strong to severe storms.

This evening

Steady rain could taper to scattered showers in spots, but in general, expect occasional showers, downpours, and thunderstorms through midnight, with the greatest concentration from the city of Houston to the northwest.

The image above is a forecast radar for 9 PM this evening. You get a sense of the patchy nature of things. Not everyone will be in downpours constantly, but some areas will get hit more often than others. If you get into a lull in the rain, just be advised that the event isn’t over and heavier rain will be incoming overnight from the west.

Overnight

This will be the main event. A strong, slow moving line of thunderstorms will plow across the entire region around or after midnight. This band of storms will be capable of producing 1-3″ of additional rain, or more, in short order as it moves west to east across the area. After today’s rains, grounds will be saturated, and runoff will be quicker than usual. This will be the band of rain most capable of producing widespread street flooding and leading to rises on bayous in the area. The areas most vulnerable to flooding will be those that see the most rain during the day today and in the early evening. Our assumption is that we’ll see this occur along and northwest of US-59. But we will obviously know more this afternoon as this event begins to setup.

Once all is said and done, we expect two to five inches of rainfall across the area, with a few locations perhaps seeing as much as five to ten inches of rain. That will not be the case in most of the area, but there will be dollops of some of those bigger ticket totals in parts of the region. As noted, where those occur will determine who exactly is at highest risk of flooding. Obviously, use extreme caution if you’ll be travelling tonight and never drive through flooded roadways, especially at night, when it’s extremely difficult to judge how deep that water is that’s covering the road. Eric will have an update on how things are progressing later today.

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After a mostly pleasant holiday weekend, a cold front came plowing through on Sunday and has brought us back to early winter as we start a new week. The good news is that it won’t be too cold for too long, nor will we have a lot of significant weather to discuss this week. Let’s get into the details.

Today & tonight

We’re starting off chilly this morning. We didn’t drop below the mid-60s on Sunday morning. But this morning, temperatures running a good 20 degrees or more colder than 24 hours ago.

It will eventually be a nice day today, albeit cool and breezy still. There’s an area of cloud cover that will be moving through the region this morning. It could perhaps have some showers or light rain with it as it passes through.

Once this passes by, we’ll see clearing this afternoon. So we’ll call it mostly cloudy with a chance of showers through about midday, then becoming mostly sunny. Winds will gradually subside through the afternoon. As long as skies clear out around midday, we should manage 50 degrees or lower-50s. If we stay locked in cloud cover into mid-afternoon, look for a struggle through the upper-40s.

Clearer skies and lighter winds tonight will make it the coldest of the next several. Low temperatures will range from the low-30s north of Houston to the mid-to upper-30s in town and low-40s along the coast.

A light freeze is possible for places like Conroe or Huntsville tonight.

Tuesday

Look for another cool day Tuesday but with less wind and plenty of sunshine. We’ll do a few degrees warmer tomorrow than today, with highs topping off in the upper-50s.

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Well, we sure didn’t start the holiday week on a bright and cheerful note, as Monday was a December or January-like gray Southeast Texas day. We will have a much brighter day today before we head into the holiday weekend with some low-impact unsettled weather to discuss post-Thanksgiving.

Today & tonight

Skies have mostly cleared out across the area, with the exception of a few spots south of I-10, as of about 5:30 AM. Expect those locations to clear out also, and we’ll have a mix of sun and just a few clouds in the area today. It will feel world’s warmer versus yesterday. Monday struggled to hit 50°, but today we should have no issues getting into the low-60s for high temperatures. Clear skies will continue tonight. Look for overnight lows to range from the low-40s northwest of Houston to the mid-40s in Houston and the upper-40s southeast of town.

Wednesday

The good news: If you’re traveling around the region on Wednesday, it should be mostly uneventful. There will be some low clouds or light rain and drizzle that materializes in the afternoon, mainly in East Texas. So just be prepared for some wet roads if traveling anywhere from Houston late. But any meaningfully significant rain will develop overnight and mainly over the open offshore waters of the Gulf of Mexico or east into Louisiana.

If you’ll be traveling outside of the region on Wednesday, there shouldn’t be a ton of issues to deal with.

There will be snow showers and some gusty winds in the Northeast, so if you’re flying toward New England or the New York City airports, that could give you a delay. Atlanta and Chicago both look good Wednesday, so a couple trouble-free hubs will help matters. There will be no issues in Denver, but a storm bringing much needed rains to California may cause some issues at San Francisco or Sacramento. Overall, this is an acceptable travel day forecast.

Bringing it back locally, we’ll see clouds gradually increase during the daytime. Some light rain, drizzle, or a few showers may develop toward evening and that would continue into Wednesday night.

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