(This post, first published early Saturday morning, was updated throughout the day.)

Harvey, which made landfall as a Category 4 hurricane in Southeast Texas Friday night, weakened to a tropical storm Saturday. But the flood threat was only just beginning. The storm stalled over Southeast Texas and is forecast to remain there through the middle of the week unloading tremendous rainfall.

Through Saturday evening, 6 to 12 inches of rain had already fallen over much of Southeast Texas with isolated pockets of up to 18-20 inches.

Overnight Saturday, a deluge was unfolding over Houston as an extremely intense band of rain pivoted through the area. A flash flood emergency, the highest level flood alert, was issued for large parts of the Houston area into the predawn hours. The National Weather Service warned rainfall could come down at a rate of three to four inches per hour. “This is a PARTICULARLY DANGEROUS SITUATION. SEEK HIGHER GROUND NOW!,” the Weather Service said.

Pearland, Texas, which is located about 8 miles south pf Houston’s Hobby Airport, received 9.92 inches in just 90 minutes late Saturday night – a phenomenal amount of rain in such a short amount of time. Local media reported water rescues needed all over the Houston area due to stranded vehicles.

Through Thursday, most locations in Southeast, Texas can expect an additional one to three feet of rain.

Inland rivers are rising and the storm’s first flood evacuation orders have been issued for residents near the San Bernard and Brazos rivers. Specifically, officials in Fort Bend County have issued a mandatory evacuation for residents in low-lying areas. This is the same region that was flooded by persistent rain in 2016.

“Harvey has placed us in a familiar position,” said Fort Bend County Robert Judge Hebert in a news release. “Last year’s floods showed how quickly the Brazos River can impact lives and property in our County and this powerful storm is threatening many of our residents in the same areas.”

In the immediate Houston Metro, the Buffalo Bayou could crest at a record as early as Sunday morning — perhaps more than four feet higher than its previous record, set in 1992.

All in all, around 50 river gauges across Southeast Texas are predicted to crest in major flood stage, according to the National Weather Service.

Where is Harvey now?

Harvey had weakened to a tropical storm, with 50 mph winds as of 11 p.m., Saturday. It is basically stationary — no longer moving in any direction. It is centered about 40 miles northwest of Victoria, Tex, where an 83 mph gust was reported at 9 a.m.

Friday night, Hurricane Hunters reported a pressure as low as 938 millibars — exceptionally low when compared to average pressure around 1,000 millibars. The eye of the storm is filling in and the winds are weakening, but its outer rain bands are dealing a blow to Southeast Texas and southwest Louisiana.

At least 15 tornadoes have been reported to the National Weather Service on Friday and Saturday, including one that flipped a camper in Hackberry, La.

Where is Harvey going?

The short answer is that the storm isn’t going anywhere. Harvey is expected to stall for the better part of the upcoming week, penetrating inland perhaps 20 or 30 miles from its current position before finally jogging northeast around Thursday. This is essentially a worst-case scenario for already-waterlogged areas from Port Lavaca, Tex., up toward Houston, where between one and three feet of additional rain will fall in the days ahead.

Make no mistake: Even though Harvey’s wind threat has largely diminished, this is a disaster in the making. By Sunday afternoon, many areas may be inaccessible due to floodwaters, isolated to all but those traveling by boat. Now is the time to move to higher ground or evacuate if at all possible.

Meanwhile, attention also turns to a tornado risk. Circulations within the spiral rain bands on the outer edge of tropical cyclones often derive wind shear from their parent circulations, sometimes spinning up tornadoes by the dozen. These quick-hitting twisters appear most likely along the coastline near Galveston, Tex., on Saturday, before the threat expands inland in areal coverage Saturday night. Have a way to get notified if warnings are issued.

Where has Harvey been?

Hurricane Harvey meandered ashore just north of Port Aransas, Tex., on Friday night and early Saturday, lashing many coastal communities with sustained winds of 110 mph and gusts topping 130 mph. The slow-moving nature of the storm meant an extended beating for many coastal communities, collapsing buildings and inundating shorelines with its storm surge.

Harvey is only the fourth landfalling Category 4 or 5 hurricane in the United States since 1970, joining the elite ranks of Andrew, Hugo and Charley, and far surpassing Katrina and Sandy in power upon moving ashore. The incredible strength of Harvey’s winds even prompted the issuance of the second-ever Extreme Wind Warning, a revamped product forecasters dusted off to warn residents of imminent “tornado-like winds” at the tempest’s core.

Even many seasoned meteorologists and storm chasers were taken aback by Harvey’s raw force, provoking renewed discussion into the ethics of storm chasing. Extreme storm chaser Jeff Piotrowski worried viewers when his live stream suddenly went black amid 125 mph winds in the eyewall, while a National Geographic reporter crashed nearby and was told by sheltered first responders he was “on his own” (he was later rescued).

Meanwhile the Fairfield Inn and Suites, where more than 100 media personnel had converged to document the storm, experienced a partial building collapse, forcing chasers to relocate to a hurricane center as the eye passed overhead.

South Texas prepares for expected landfall of Hurricane Harvey

Thia NOAA-NASA GOES Project satellite image taken at 1737 UTC on August 24, 2017 shows storm activity off the south east coast of the US. A major storm, Harvey, was upgraded to hurricane status on August 24, 2017, as it targeted hundreds of miles of coastline in Texas and Louisiana. The US National Hurricane Center (NHC) warned of a potential for "life threatening" floods from the storm, which was due to make landfall sometime on August 25, 2017.The NHC said the category one hurricane could hit land as a much more powerful category three, with winds of 130 miles (209 kilometers) per hour. / AFP PHOTO / NOAA-NASA GOES Project / Handout / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO /NOAA-NASA GOES PROJECT/HANDOUT" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS HANDOUT/AFP/Getty Images (Handout/AFP/Getty Images)