In brief: An unexpectedly intense flooding event has engulfed areas north of Houston this week. We discuss that, and the ongoing forecast for the weekend, which could see an additional round of storms on Sunday before things start to dry out next week.

If you live south of Interstate 10, you may be wondering what the fuss is all about in regards to heavy rains this week. Much of this area has received 2 inches or less over the last five days, and certainly not experienced anything remotely close to flooding conditions. However, looking at the rainfall accumulation map below, we can see that eastern Montgomery County got rocked with 12 inches of rain, and further to the north, Walker and San Jacinto counties recorded 15 to 20 inches of rainfall. Some of this came very quickly, with high rainfall rates.

And so we have a situation where much of the region is just fine, but there is terrible flooding ongoing along the San Jacinto and Trinity river basins. The most dangerous flooding is occurring along the East Fork of the Jacinto River, but the entire north and northeastern parts of the Houston metro area are dealing with significant and ongoing flooding.

What’s next

So what happens next? After today’s showers, we should see a reprieve for the rest of this afternoon and evening. Our record for predictions this week has been pretty shoddy, but at this point I only expect development of sporadic showers on Saturday morning. And most of Saturday, frankly, looks mostly rain free. At this time I think we’re unlikely to see more than scattered showers and thunderstorms, with accumulations not amounting to much.

Unfortunately, it does appear as though a final storm system will work its way toward the area later on Saturday night, or Sunday morning. This atmospheric disturbance will likely bring widespread showers and thunderstorms on Sunday morning-ish, and perhaps throughout much of the day. As a rough guess we’re looking at additional accumulations of 1 to 3 inches, with the potential for higher totals. This will, unfortunately, only exacerbate ongoing river flooding.

By Sunday night high pressure really should begin to assert itself, and most of next week looks sunnier, and hotter. Rain chances look lower for most of the week, although perhaps not zero.

Given the unpredictability of the storms we’ve seen this week, and the threat of additional rain on Sunday, we’re going to continue with posts each morning this weekend to keep you updated. Thanks as always for reading, and for your patience as we have struggled to grapple with a challenging forecast that has been more miss than hit.

In brief: Flash flood warnings are in effect for Montgomery, far northern Harris, and Liberty Counties this morning, as an additional 1 to 4 inches of rain has fallen. River flooding will continue in those areas as well, with numerous evacuation orders and road closures in effect. Major rain should hopefully exit this morning with more intermittent, scattered downpours through the day. Additional storm chances exist tonight and especially Sunday before the heat sets in next week.

A flash flood warning is in effect north of Houston through 8 AM, as another batch of heavy rain fired up overnight dropping 1 to 4 inches of rain between southern Montgomery, northeast Harris, and northern Liberty Counties.

This is not where we wanted to see the rain this morning. We do expect that this will actually move along at a better clip than yesterday’s rain did. Hopefully that leads to some quicker improvement, but all this water will help further swell the river systems up there. You can view flood gauge information on rivers, creeks, and bayous at the National Weather Service or at Harris County Flood Control. Please follow the advice of your local officials, and never drive around barricades.

A Flood Watch remains in effect along and north of I-10, extended through Saturday, and we will maintain our Stage 1 flood alert for Houston.

The San Jacinto and Trinity Rivers remain the two most serious issues at this time. There will continue to be rises and damaging flooding within both systems. Additionally, the Navasota River is expected to crest at record levels north of Bryan. That feeds the Brazos, and we’re likely to see high water or minor flooding begin in that river too as we head into next week. Thankfully, we aren’t expecting a whole lot worse in that system. A lot happening, and we’ll keep you posted on any significant changes with at least one more update later today.

Today

The rest of this morning is expected to see this very heavy stuff north of Houston exit east and be replaced by more in the way of scattered thunderstorms.

If we can pop more in the way of scattered storms, yes, that will lead to isolated heavy downpours, but more often than not it wouldn’t rain over one place hard for more than 15-20 minutes at a time. Even a few rounds of that is more manageable than the deluge and 2 to 6 inch per hour rates we’ve seen this week. We’ll continue watching and keep you posted. Have an umbrella and an indoor backup plan anywhere in the area today just in case. Highs will range from the upper-70s in places it rains persistently to low-80s. Showers should diminish in coverage this evening.

Saturday

Do we expect more showers and storms to fire up overnight tonight and Saturday morning? It’s NBA playoff season, so in the words of Marv Albert, “Yes!” Unfortunately we will probably see additional rains in saturated and flood-impacted areas north of Houston. There is a chance that this ends up being a little less rain than today, so hopefully that’s the case. Otherwise, sun, clouds, and 80s.

Sunday

The back half of the weekend looks to remain unsettled. Another wave of storms could pass through the area in the morning or afternoon hours, especially north of I-10, again. Rainfall could again be heavy, and right now I am a little more concerned about Sunday than Saturday in terms of rain and impacts. Outside of any storms, expect clouds, some sun, and highs in the 80s.

Next week

I wouldn’t be shocked to see one more round of showers or storms on Monday or Tuesday, but then the heat cranks up. Expect upper 80s on Monday, low-90s by Tuesday, and low to mid-90s on Wednesday and Thursday.

It will feel uncomfortably hot, given this is first real heat of the summer season, so take it easy. Morning lows will generally be in the mid-70s. We may see rain chances return toward the weekend but for now that’s mostly speculation, and I wouldn’t be changing any Mother’s Day plans at this time.

In brief: The heavy rainfall has exited the Houston area, for now at least. The thunderstorms dropped 1 to 3 inches of rain across the southern half of the region, but some whopping totals of up to 8 inches near locations such as Spring and Kingwood during a few hours today. We may see some additional rains tonight and on Friday, but we are confident that the worst is over.

As of about 4:30 pm this afternoon, the mass of showers and thunderstorms that brought widespread rain to Houston today has exited to the east. The atmosphere is now pretty worked over, so we should see fairly calm conditions for the rest of this afternoon and evening. And after that? There is the possibility of scattered showers and thunderstorms returning after midnight, especially for areas south of Interstate 10. Overall these areas have not been particularly hard hit, so I’m not particularly concerned about these storms in terms of flooding. Because the worst is likely over, we are stepping back our flood alert to Stage 1.

We may see another round of showers develop during the morning hours on Friday and persist into the afternoon. Given the messy forecast today, I’m not particularly confident in anything tomorrow. However I don’t anticipate it being nearly so potent as the system we saw today. Matt will have all the details first thing on Friday morning, when we should have the forecast better in hand.

The big story now is river flooding due to the incredible amounts of rain that fell north of Houston this week, including Wednesday night. Lakes Conroe and Livingston were particularly inundated. The National Weather Service has a map where you can find detailed flooding forecasts for various rivers in the greater Southeast Texas area here.

River flooding

Among the biggest concerns are the East and West Forks of the San Jacinto River. Already a mandatory evacuation is in effect for the eastern side of the river, from FM 1485 to Lake Houston. According to Jeff Lindner of the Harris County Flood Control District, forecasted water levels on the East Fork will rise 7 to 8 feet higher than earlier this week. Structures on the ground will be flooded to rooftops levels. Elevated structures will be flooded. For reference, the forecasted water level is only 3 feet below those of Hurricane Harvey.

Conditions are also serious along the West Fork of the river. Lindner says the river is rapidly rising from upstream inflows, and will rise to near 62 feet on Saturday. Widespread low land flooding will occur impacting the following subdivisions: Belleau Woods, Rivercrest, Northshore, Forest Cove, Kings Point, and Atascocita Shores. Flooding of streets in Kingwood, as well as lower structures near the river will also be possible.

If you live in flood-affected areas please do not drive into high water.

In brief: Due to the unanticipated escalation in storm activity this morning, it now appears as though the city of Houston will see intense showers and thunderstorms during the next several hours, through Thursday afternoon. We are issuing a Stage 2 flood alert for the entire area due to the high rainfall rates and timing of street flooding.

We were wrong. Just hours ago, in this morning’s post, it looked as though a band of showers north of the region would slowly wane through the morning hours. However, as we’ve been monitoring radar trends, that clearly has not happened. Instead we’ve seen this band thicken and slowly progress southward toward central Houston. Already in locations such as Spring, Humble, and Atascocita have picked up in excess of 5 inches in just a couple of hours this morning. That is a lot of water in a little time.

Although there remains considerable uncertainty, it now appears as though this line of storms will continue to sag southward this morning before reaching the coast by late afternoon. It is likely to have significant impacts in the city of Houston and surrounding areas, including street flooding. Of particular immediate concern is the high rainfall rates associated with these storms, which will back roads up quickly. For this reason we are escalating to a Stage 2 flood alert for the entire region. Conditions should hopefully improve late this afternoon or evening.

All of this activity should have an impact on the atmosphere, and because of this it no longer appears as though the region will see a round of stronger storms overnight, into Friday morning. But given the unpredictability of this system so far, that is not an entirely confident prediction.

Please stay safe today and do not drive into high water.