Plan for significant rainfall on Friday night, Houston

We’re continuing to track the potential for heavy rainfall on Friday, Friday night, and Saturday morning as a strong front moves through the region. Unfortunately, the models remain highly consistent in forecasting a wet night, with the potential for widespread totals of 2 to 5 inches of rainfall, and some bullseyes of up to 6 to 8 inches. The atmosphere won’t be too favorable toward severe weather, so the primary threat is heavy rainfall and the potential for some light to moderate flooding.

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Wednesday

Conditions today will be a lot like those on Tuesday, which is to say a cold start, followed by a sunny warm up into the low 60s. However, a subtle wind shift from the northeast to the east later today will allow for a few clouds to develop later tonight, and should moderate low temperatures to around 50 degrees in Houston—colder up north, a bit warmer along the coast.

High temperatures on Wednesday. (National Weather Service)

Thursday

Winds will shift to come from the southeast on Thursday, and this will represent the return of a moist, onshore flow from the Gulf of Mexico. This will help ramp up moisture levels ahead of the front, but it won’t manifest in rainfall immediately. Instead, Thursday will be a mostly cloudy affair, with highs in the mid- to upper-60s, and those southeasterly winds.

Friday night into Saturday morning

The main event will occur as an upper-level low pressure system slides down into Texas on Friday, bringing the best focus for rainfall Friday night in the Houston area. Heavy rains will be possible before midnight Friday, and after sunrise on Saturday, but we expect most of the region to see most of its rainfall during these nighttime hours.

The latest modeling guidance suggests the path of this system will favor heavier rainfall for Harris County and points north, rather than the coast. But beyond that there’s not much to say. To give you a sense of some of the uncertainty, here is the forecast map for rain accumulation from the 00z operational run of the European model:

5-day rainfall forecast from the European model. (Weather Bell)

And the same map from the 06z GFS model:

5-day precipitation forecast from the GFS model. (Weather Bell)

As you can see, both models show significant bullseyes of rainfall in the 7-to-8 inch range. But the European model has the heaviest rains immediately north and northwest of Harris County, while the GFS model has them much further to the north, near Crockett.

Thus, while we continue to have high confidence in significant rains coming to southeast Texas late this week, we can’t say where the greatest amounts are going to fall. We may not know this Friday, and even then we will have some uncertainty.

Saturday afternoon and beyond

Rains should end before noon on Saturday, and a colder, drier air mass will move into the region. Highs Sunday and Monday probably won’t get much above the mid-50s, and overnight lows will drop down to around 40 degrees in the city. Sunny skies will prevail from Sunday morning onward.

19 thoughts on “Plan for significant rainfall on Friday night, Houston

  1. Louie

    I have an outdoor event to coordinate Friday evening in the Tomball/Cypress area from about 6pm – 8pm. Any idea if the HEAVY rain will hold off until after that time frame?

    Thanks!

  2. Arianda

    Should we expect a repeat of 2016..Tax Day and/or Memorial Day floods? Checking resources, many of the same rain totals exist….

  3. Steve

    Am planning to drive to Dallas Friday afternoon. Is heavy rain expected between here and Dallas, enough to make travel unsafe?

      1. Arianda

        Actually, i was thinking closer to Memorial Day Floods, here are the stats:

        Max Totals across Harris County for various flood events:

        Date 15-min 1-hr 3-hr 6-hr 12-hr 24-hr

        May 12-13, 2015 1.2 3.4 6.2 7.8 8.2 8.4
        May 25-16, 2015 2.1 4.8 8.3 10.1 11.0 11.0
        Oct. 31, 2016 1.6 4.1 7.4 8.5 11.8 11.9
        April 17-18, 2016 2.2 4.7 8.3 13.9 16.7 17.4
        May 26-27, 2016 1.4 3.6 6.2 7.4 8.1 13.4

        Granted the current prediction is 3-6″ widespread, but the isolated (which looks more condensed than isolated to me) is supposed to be upwards of 8-10″ or more. So, match that fact pattern to the above stats (from NOAA).

        This missing link is whether the rain rates will be per hour or total…..if that 3-6″ is in an hour, we are in trouble. Regardless, NOAA has already said the flooding of rivers will be minor-moderate with certain ones reaching major flood stage.

        The bottom line: watch very closely and prepare.

  4. Susan

    Flying from San Antonio to Hobby at 5:40 pm Friday…do you think the weather will impact my ability to get to Houston?

    1. dcrawshaw1

      Thank you soooo very very much, Eric and Matt………..you truly are the Walter Cronkite(s) of the Weather! Thank you for your passion, we are so very fortunate to have you!

    2. FoxTesla

      The county in the center of the map is Harris County (the county with the black 1.9 inside it on the lower map).

  5. Blackhawks Fan

    Oh, dear… do I have to go through my “how much rain will fall in the NE corner of my back yard at precisely 2:31:20 AM” rant again?

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