Friday storms winding down, round two expected later tonight

The most intense storms that developed early Friday morning have been winding down as we approach the middle of the day, and this general weakening trend should continue through the afternoon.

For most of us, the rains have been more than manageable so far, with 1 to 2 inches across much of the region. But areas north and northwest of central Houston, including northern Waller County and western Montgomery County, have received 4 to 6 inches. While bayous remain mostly within their banks, these rains have saturated soils in the region.

24-hour estimated rain totals from 11am Thursday through 11am Friday. (NOAA)

Given the unpredictability of this kind of weather system, we still have lots of questions about the forecast. As a best guess, the next area to watch later today will be the Matagorda Bay region, and the potential for storms that develop there to migrate into the Houston area overnight and on Saturday.

Matt did an excellent job of summarizing things in this morning’s post, but the bottom line is that we still expect a situation where some area roadways may see high water during heavy rains. However, we’re not concerned about flooding of homes and businesses at this time, and think bayous are well positioned to handle these rains. For this reason we remain solidly in a Stage 2 flood alert, and don’t anticipate the need to increase this.

There may be some let up in storms on Saturday afternoon or evening, before a final round of storms pulses through the area on Saturday night and Sunday morning. Again, we think this will be mostly manageable for the area’s floodways, but you should be aware of the potential for moderate travel disruptions through Sunday morning.

We will post our update no later than 9 pm CT on Friday evening.

Strong storms possible early Friday, so we’re issuing a Stage 1 flood alert

Good evening. We’re getting closer to the first of two rounds of potentially heavy rainfall for the Houston area, and we’ve seen enough data from the high resolution models to raise our concerns. Therefore we’re issuing a Stage 1 flood alert for the greater Houston region. Such a Flood Scale alert, effectively, means to expect the potential for street flooding in the Houston area.

The first period of heavy rainfall will begin after midnight tonight across the Houston area, and the atmosphere is moist enough to produce rainfall rates of 1 to 2 inches per hour, which can begin to back up roadways. Conditions for heavy rainfall will persist into the morning hours on Friday, and possibly into the early afternoon. Our general expectation for rainfall totals during this first round is 1 to 2 inches for most areas, but there will very likely be some bullseyes that receive up to 5 inches or more.

Then we expect to see something of a lull in rainfall from Friday evening into Saturday morning, before round two begins. Storms will probably get spun back up from Saturday afternoon through Sunday morning, when there may be another 1 to 2 inches of widespread rainfall, with more bullseyes. This is all being driven by a slow-moving upper-level low pressure system that is difficult to predict.

NOAA rain accumulation forecast for now through Sunday. (Weather Bell)

We’ve issued this Flood Scale alert tonight, because we think some areas may see heavy rainfall before sunrise on Friday morning. Matt will have a full update for you early on Friday, and will reevaluate our Flood Scale status at that time. Then, of course, we’ll keep tabs on this system over the weekend as needed.

Storm chances increasing for Friday through Sunday, with a wet weekend on tap

Good morning. The forecast for this weekend continues to evolve and now looks considerably wetter than we anticipated a couple of days ago. This is a dynamic forecast with the kind of weather system that forecasters struggle with. So please be patient with our rainfall predictions over the next few days.

Thursday

Fairly vigorous storms associated with a cold front moved across Central Texas last night, but they are weakening as they move westward toward Houston this morning. So is the front. As a result, today is likely to be warm, with highs in the low 80s, and mostly cloudy skies for much of the region. There will be some scattered showers, but the better rain chances will come after midnight as the front sags into the area and stalls. Low temperatures will not fall below 70 degrees.

NAM model for dewpoints suggests the “front” will get to about Interstate 10 on Friday evening. (Weather Bell)

Friday

Cloudy skies and showers should limit highs to the upper 70s. Rains should become more widespread on Friday morning across the region, with accumulations of 0.5 to 1.5 inches likely throughout the day. The storms for Friday through the weekend will be driven largely by an upper-level low pressure system, and these are notoriously difficult to predict in terms of rainfall output. This can lead to a boom-or-bust forecast. Some areas of the region may see very little rain, and others enough to flood streets with slow-moving storms. So bear that in mind with regard to this forecast, and the potential for change. Matt and I will be watching this closely, and updating the forecast as needed and as our confidence improves. Lows Friday night will again drop to around 70 degrees as at least some slight to moderate rain chances persist.

Saturday and Sunday

The upper-level low will move more directly over head this weekend and continue to drive the potential for showers on Saturday morning, and then again Saturday night into Sunday. Depending upon how much rainfall the region gets on Friday, these additional rounds of showers may lead to some flash flooding of streets. Overall accumulations from Thursday morning through Sunday will likely be in the range of 2 to 3 inches of rain for most areas, but there almost certainly will be higher bullseyes.

NOAA rain accumulation forecast for now through Sunday. (Weather Bell)

So what does this mean for weekend plans? I know the Bike MS Texas is on Saturday, and at least light to moderate rain is likely along the route. Will there be thunderstorms? I’m less certain about that but it’s a possibility. The bottom line is that, after a string of sunny weekends with sedate weather, we’ll need to pay attention to Mother Nature this weekend. Sunday afternoon offers the best opportunity for clearing skies and lower rain chances, if that helps.

Next week

Rains end and temperatures rise to start next week, with highs likely reaching the upper 80s to even 90 degrees for inland parts of the area. Our next front could push through by late Tuesday or Wednesday, and let’s hope this one makes a clean passage into the Gulf of Mexico, rather than getting hung up over Houston. Right now that seems the most likely scenario.

Houston’s weekend forecast turn cloudy, with a chance of showers

Good morning. After several partly to mostly sunny days, Houston’s weather will turn cloudy today. And beginning Thursday, we’ll see at least low rain chances daily through the weekend.

Wednesday

Today will be warm, mostly cloudy, and quite breezy. In response to a low pressure system over central Texas, onshore winds will blow at about 15 to 20 mph, with gusts up to 30 mph. A wind advisory is in effect for areas just west as southwest of Houston, including Brazoria and Fort Bend counties from 11 am to 7 pm. It will be a rather warm day, with highs in the mid- to upper-80s, and the mercury could go a bit higher still for areas that see snippets of sunshine this afternoon. Rain chances are near zero, with a capping inversion in place, but we can’t entirely preclude a few sprinkles. Lows tonight will not drop below 70 degrees.

Look for strong southerly winds on Wednesday, with higher gusts. (Weather Bell)

Thursday

A cold front will be pushing through Central Texas overnight, and this will send a line of showers and possibly thunderstorms toward the Houston area. This line, which likely will be weakening as it moves into a more stable air mass, should reach College Station by around sunrise, and the Houston area itself during the afternoon hours. As for accumulations, its sort of a crap shoot, but I’d estimate most areas will see one to two tenths of an inch of rain.

It now appears that this line of showers, and an attendant weak front, will move off the coast Thursday evening. Daytime highs will be in the low 80s, with cloudy skies. Overnight lows will probably drop into the upper 60s.

Friday

At this point Friday looks mostly dry, but we can’t entirely rule out at least some scattered showers in the wake of the weak front. Skies will be mostly cloudy with highs likely somewhere in the upper 70s for most areas. Lows Friday night should again drop into the upper 60s, but my confidence in temperatures is not great.

Saturday and Sunday

Both weekend days should see mostly cloudy skies, and highs of around 80 degrees. The bigger question concerns rain chances, as a few disturbances pass across the area. I think both days will have about a 40 percent chance of at least light rain showers. For those participating in the Bike MS Texas on Saturday, that’s the bad news. The good news is that winds will have shifted to come from the south and southeast on Saturday, so there are very good odds that riders will have a tailwind going from Houston to College Station. Overnight lows will probably be in the upper 60s to 70 degrees.

NOAA rain accumulation forecast for now through Sunday. (Weather Bell)

By Monday, with sunnier weather on the way, highs should start to push into the mid- to upper-80s. Most of next week looks fairly warm, as one would expect for early May.