The April 2016 North American storm complex was a major storm system that resulted from an

upper-level low A cold-core low, also known as an upper level low or cold-core cyclone, is a cyclone aloft which has an associated cold pool of air residing at high altitude within the Earth's troposphere, without a frontal structure. It is a low pressure syste ...

in the United States stalling and producing record-breaking rain in and around

Houston Houston (; ) is the most populous city in Texas, the most populous city in the Southern United States, the fourth-most populous city in the United States, and the sixth-most populous city in North America, with a population of 2,304,580 i ...

, Texas, resulting in severe

flood A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrol ...

ing, as well as a major snowstorm in the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico ...

. There were more than 17 inches of rain in one day in parts of the city, and up to 4 inches of

rain Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water ...

per hour that morning at

George Bush Intercontinental Airport George Bush Intercontinental Airport is an international airport in Houston, Texas, United States, serving the Greater Houston metropolitan area. Located about north of Downtown Houston between Interstate 45 and Interstate 69/U.S. Highway 5 ...

. It is described as the wettest April in the city on record. As the most widespread flood event there since

Tropical Storm Allison Tropical Storm Allison was a tropical storm that devastated southeast Texas in June of the 2001 Atlantic hurricane season. An arguable example of the " brown ocean effect", Allison lasted unusually long for a June storm, remaining tropical or s ...

in 2001, it caused a state of emergency to be declared in nine

counties A county is a geographic region of a country used for administrative or other purposesChambers Dictionary, L. Brookes (ed.), 2005, Chambers Harrap Publishers Ltd, Edinburgh in certain modern nations. The term is derived from the Old French ...

. __TOC__

Meteorological history

In mid-April 2016, a large, slow-moving

emerged from the Four Corners region in

over the

Central United States The Central United States is sometimes conceived as between the Eastern and Western as part of a three-region model, roughly coincident with the U.S. Census' definition of the Midwestern United States plus the western and central portions o ...

. Simultaneously, a ridge became anchored over the

Eastern United States The Eastern United States, commonly referred to as the American East, Eastern America, or simply the East, is the region of the United States to the east of the Mississippi River. In some cases the term may refer to a smaller area or the East C ...

with another low to the east, creating an

omega block Blocks in meteorology are large-scale patterns in the atmospheric pressure field that are nearly stationary, effectively "blocking" or redirecting migratory cyclones. They are also known as blocking highs or blocking anticyclones.Glossary of Mete ...

—a stagnant weather pattern. The low near the Rockies pulled large quantities of moisture north from the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...

, leading to both heavy snow in the mountains and widespread heavy rain to the plains. During the overnight hours of April 15–18, a nearly stationary

mesoscale convective system A mesoscale convective system (MCS) is a complex of thunderstorms that becomes organized on a scale larger than the individual thunderstorms but smaller than extratropical cyclones, and normally persists for several hours or more. A mesoscale con ...

developed over the Houston Metropolitan Area. Southeasterly flow from a

low level jet Jet streams are fast flowing, narrow, meandering air currents in the atmospheres of some planets, including Earth. On Earth, the main jet streams are located near the altitude of the tropopause and are westerly winds (flowing west to east) ...

fueled the system with ample moisture, leading to widespread rainfall rates of per hour. Rainfall intensified throughout the night into the morning of April 18 with rainfall rates reaching per hour, leading to a life-threatening situation. At 4:39 a.m. CDT, a

flash flood emergency A flash flood warning ( SAME code: FFW) is an hazardous weather statement issued by national weather forecasting agencies throughout the world to alert the public that a flash flood is imminent or occurring in the warned area. A flash flood is a ...

was declared for parts of

Colorado Colorado (, other variants) is a state in the Mountain states, Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the wes ...

, Waller,

Grimes Claire Elise Boucher (; born March 17, 1988), known professionally as Grimes, is a Canadian musician, singer, songwriter, and record producer. Her early work has been described as extending from "lo-fi R&B" to futuristic dance-pop, and has i ...

, Montgomery,

Harris Harris may refer to: Places Canada * Harris, Ontario * Northland Pyrite Mine (also known as Harris Mine) * Harris, Saskatchewan * Rural Municipality of Harris No. 316, Saskatchewan Scotland * Harris, Outer Hebrides (sometimes called the Isle of ...

, and Austin counties, later expanding to Fort Bend. Accumulations peaked at along Little Mound Creek at Mathis Road to the northwest of Houston. Other significant totals include along Cypress Creek at Sharp Road, along Langham Creek at Longenbaugh, and in Monaville.

saw , bringing the monthly rainfall total to . This marked the wettest April on record for Houston. At the same time, the upper low produced a major

snowstorm A winter storm is an event in which wind coincides with varieties of precipitation that only occur at freezing temperatures, such as snow, mixed snow and rain, or freezing rain. In temperate continental climates, these storms are not necessar ...

in the

and

High Plains High Plains refers to one of two distinct land regions: * High Plains (United States), land region of the western Great Plains *High Plains (Australia) The High Plains of south-eastern Australia are a sub-region, or more strictly a string of adja ...

from April 16–17. Due to the omega block, snowfall remained concentrated around the Denver metropolitan areas. Because of this, some snowfall totals ranged up to in some areas. This definitely led to areas coming close to breaking their top-snowiest days in April. A climate study analyzing the 2015 flood in Texas and Oklahoma has found an intensified El Niño effect on the climatologically wet season of spring, and th
intensification
has a trace of anthropogenic climate warming. The upper low began to move eastward on April 19, as the omega block began to break down. It was expected to reach the East Coast by April 22, with much less rainfall totals as it began to accelerate.

Impact

Over 47,000 customers lost power in

, and to the west of

Denver Denver () is a consolidated city and county, the capital, and most populous city of the U.S. state of Colorado. Its population was 715,522 at the 2020 census, a 19.22% increase since 2010. It is the 19th-most populous city in the Unit ...

, portions of

Interstate 70 Interstate 70 (I-70) is a major east–west Interstate Highway in the United States that runs from I-15 near Cove Fort, Utah, to a park and ride lot just east of I-695 in Baltimore, Maryland, and is the fifth-longest Interstate in the co ...

closed. In addition, portions of Interstate 80 closed in southeastern

Wyoming Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to the s ...

. The torrential rains resulted in widespread, severe flooding across Houston and surrounding suburbs—the worst since

in 2001. 5 people died in flood-related incidents. In Harris County alone, more than 1,800 high water rescues were conducted; 744 homes and 400 apartments were inundated with water. School districts across the county suspended activities for two days to three days. Immediately after the storm, property damage was estimated at $5 billion.

References

{{United States winter storms 2016 floods in the United States 2016 in Texas Floods in Texas History of Houston 2016 meteorology April 2016 events in the United States Natural disasters in Colorado