Please don’t freak out about tonight’s storms, Houston

Earlier today, I did a short telephone interview with The Weather Channel. Nice people. But they were really playing up the potential for serious flooding in Houston tonight. I offered a mild correction—that this was kind of a characteristic spring storm, and not something too worrisome—but that message seems to be getting lost. So let me reiterate it: Yes, some heavy rains are coming to the region this evening, and during the overnight hours, probably widespread accumulations of 1 to 4 inches, with higher isolated totals. No, we don’t expect widespread mayhem.

Rainfall accumulation forecast for now through the weekend. (NOAA)

The setup for heavy rainfall is clear; a slow-moving cold front is moving toward Houston and lifting the warm, moist air at the surface. Some training of heavy thunderstorms is possible as the convective activity feeds off of the warm Gulf of Mexico moisture. Fortunately, the front itself should move off the coast on Thursday, taking this mess with it. Here’s the outlook for Houston until then.

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Tornado Watch for Houston through 9 PM Wednesday

Just want to give everyone a quick update this early afternoon.

The National Weather Service has issued a Tornado Watch for most of the region through 9 PM tonight. This means that the environment over Houston is favorable for severe thunderstorms and possibly tornadoes.

Showers and thunderstorms are focused mostly north and west of Houston this afternoon. With some breaks in the clouds south and east of Houston, the atmosphere is becoming a bit more unstable. For that reason we expect a few more showers and thunderstorms to develop across the region. The environment over Houston is favorable for storms today to become strong or severe if they can get going.

A Tornado Watch means conditions are favorable for the development of severe storms and possible tornadoes. (NWS)

The main threats are isolated hail and damaging winds (we’ve already had some wind damage reported from a storm up near Lake Livingston earlier). Isolated tornadoes are possible, though we don’t expect things to get too out of control here today.

The rest of the forecast as described by Eric earlier is mostly on track. We’re still toying around with specifics on timing of the heavier rains (which should be tonight). Some of you may not see much rain at all during the day today. But others will see heavy rains at times. We don’t see any reason to change our thinking on flooding concerns: 1-3 inches of rain widespread, with pockets of 3-5″+ and street flooding in spots. Bayous and creeks still look to be able to handle this event fairly well, and we are not too concerned about issues with any of them right now.

Eric will have another update for you later this afternoon.

Timing of rainfall today, tonight remains big question for Houston

Last night Matt provided a solid overview of the reasoning behind Houston’s flash flood watch for Wednesday, and truthfully not much has changed. Wednesday and (especially, we think) Wednesday night have the potential for widespread, heavy rainfall with possibly some severe thunderstorms. We’re not expecting anything too extreme, rain-wise, but some street flooding is possible later tonight.

Wednesday

The big question for today is timing. As of about 7am, a fairly robust line of strong rain showers extends along a line almost half way between San Antonio at Houston. It’s not clear when the bulk of the rainfall will arrive. It could be as early as just before noon for western parts of the city, but not until afternoon, or even evening for most of the city. (Note: If you haven’t seen much or any rain by sunset, it doesn’t mean that the forecast is a bust, or the rain “missed” us. Hold on.) We’ll be watching closely, and update this site as necessary. Highs today should reach about 80 degrees under mostly cloudy skies.

Radar as of 6:55am CT on Wednesday. Click to enlarge. (Intellicast)

Wednesday night

Sometime later tonight, probably about 9 to 11 pm, the forecast models move a boundary into the Houston region, and this should serve as a focusing point for heavy rainfall between that point and perhaps 2 to 4am on Thursday morning. This is the period during which we think the heaviest rain showers will move into Houston, along with the potential for some inclement weather like hail. Most of the area will probably see 1 to 3 inches of rain, but depending on where this boundary sets up—perhaps along the US-59 corridor, perhaps closer to the coast—we could see higher amounts than this. Either way, if you’re a light sleeper, thunder and lightning will probably wake you at some point tonight.

Severe weather outlook for Wednesday and Wednesday night. (NOAA)

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Flash flood watch Wednesday: What you need to know

Good evening all. We wanted to give you an evening update on the incoming rain event for Wednesday. Truthfully, not much has changed from Eric’s synopsis and outlook this morning. But we want to freshen up some thoughts around timing, amounts, severe weather, and so forth.

Quick Summary

  • Flash Flood Watch begins at 1 AM Wednesday north & west of Houston and 7 AM in Houston and points south & east.
  • Heavier rains stay north & west of Houston later tonight and Wednesday morning. Isolated strong to severe storms are possible tomorrow afternoon, especially along and southeast of US-59/I-69. Widespread heavy rain and storms moves through with the front later Wednesday evening.
  • We still believe 1-3″ of rain on average will fall with a few pockets of 3-5″ or a little more not out of the question.
  • Street flooding is the primary form of flooding we are concerning ourselves with. Though bayous and creeks could rise, they should be able to handle tomorrow’s rains.

Flash Flood Watch

The National Weather Service has posted a Flash Flood Watch for almost the entire region (Edit to add: As of 8 PM, only Jackson & Matagorda Counties are excluded from the watch). The watch begins at 1 AM for areas north and west of Houston and at 7 AM for Houston and points south and east.

A large area of flash flood watches extends from just west of Houston all the way into the Mississippi Valley. (Pivotal Weather/NWS)

Timing

This is the one that I think might throw some folks for a loop. Much of Wednesday in Houston will actually be a lot like today. We do expect heavier rains in the morning northwest of the Houston metro area (up toward College Station, perhaps drifting as far south and east as Sealy through The Woodlands, which is why the flash flood watch begins at 1 AM there and not in Houston). But isolated showers and maybe a downpour with heavier rain well northwest should be the M.O. through early afternoon Wednesday.

We then have two parts to the stormy weather show. Part one is from early afternoon through early evening, when we’ll watch for scattered strong to severe thunderstorms. Not everyone will see rain, but if you do, it could be heavy. More on the severe weather threat below. Part two will be the main event tomorrow night. The cold front will be ushered slowly southeast from about 10 PM through 3-4 AM Thursday by a vigorous upper level disturbance. Look for the majority of tomorrow’s rain to fall from early evening into the early overnight.

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