Dangerous Flood Threat, Severe Weather Continue in South-Central States Through Midweek (FORECAST)

Chris Dolce
Published: April 18,2016
The threat of flooding rainfall and severe storms will continue into midweek ahead of a slow-moving low pressure system pushing from the Rockies into the nation's midsection.
NOAA's Storm Prediction Center has issued a severe thunderstorm watch valid until 11 p.m. CDT for portions of southern Texas, including Laredo and Brownsville.

Map showing the heaviest rainfall totals in the Houston area in the 24 hours through Monday morning.

Torrential rainfall caused major flash flooding in parts of southeast Texas Monday morning. The Houston area was particularly hard hit with 10 to 20 inches of rain measured on the northwest and north side of the city, according to the Harris County Flood Control District. Dozens of water rescues have been reported and numerous of subdivisions have seen flooding. The governor of Texas has also declared a state of emergency in nine counties due to the deadly flooding. For the latest on impacts from the flooding, see our full news story at the link below.
(LATEST NEWS: Destructive, Deadly Flooding Hits Houston)
Major flooding has been reported on bayous, creeks and rivers in the Houston area, including: White Oak Bayou at Houston, Cypress Creek near Westfield and Hockley, West Fork of the San Jacinto River near Humble.
Below are more details on the severe weather and flood threats the next few days. At the bottom of this article you can find a full recap on the severe weather caused by this same storm system since Friday.

Current Radar with Watches and Warnings

(MORE: View National Interactive Radar Map | Difference Between a Watch and a Warning)

Severe Weather and Flooding Forecast

Monday Night

• Flood watches have been issued for periods of heavy rainfall for parts of the central states, from southern and eastern Texas to western Louisiana. The heavy rain will cause roads, as well as streams and rivers to flood, especially in flood prone areas. Do not attempt to drive through flooded roadways should you encounter one. 
• The best chance of severe t-storms will be in parts of south and southeast Texas, with hail, high winds and perhaps a brief tornado or two possible.
• Cities: San Antonio | Houston | Corpus Christi

(INTERACTIVE: Get Your 7-Day Severe Weather Outlook)

Monday Night's Thunderstorm Forecast

Flood Alerts

Tuesday

• Pockets of locally heavy rain may continue to impact the south-central states, from Missouri to Arkansas, Louisiana, eastern Oklahoma and eastern Texas.
• The chance for a few severe storms may also linger in central and southern Texas.
• That said, the overall threat of flooding and severe weather will be less than previous days.

Wednesday

• As low pressure aloft moves out of the Rockies and into the central states, scattered severe storms are possible in the southern Plains, from southern and central Texas into southern Oklahoma, northwestern Louisiana and southwestern Arkansas.
• Isolated large and damaging wind gusts will be most likely over parts of northern and central Texas.
• Locally heavy rain could cause some additional flash flooding from east Texas to the lower Ohio Valley.

The map below is a general view of the area where we're expecting the heaviest rain through Wednesday.

Rainfall Outlook Through Wednesday

Friday's Storm Reports

As of Friday night, tornadoes have been reported by storm spotters in Eads, Colorado and near Guymon, Oklahoma. Storm chasers reported multiple additional tornadoes in the Oklahoma panhandle. There were 10 reports of tornadoes, according to NOAA's Storm Prediction Center.

Hail to the size of tennis balls (2.5 inch diameter) were also reported near Dalhart, Texas and Burlington, Colorado Friday evening.
A helicopter for WSVN 7 News also captured video of an apparent dust devil or possible tornado in West Miami-Dade, Florida on Friday.

Saturday's Storm Reports

Late Saturday afternoon, a storm spotter reported a brief tornado in northwestern Kent County, Texas. A second tornado was also reported near Hermleigh, Texas Saturday evening.
Severe thunderstorms even produced large hail to the size of golf balls in Texas on Saturday, including in Big Spring and near Clarendon.

Sunday's Storm Reports

On Sunday, a brief rain wrapped tornado was reported southwest of Fowlerton, Texas and there were a few reports of quarter size hail in Charlotte, Texas and near Pearsall, Texas.

Rainfall Totals So Far

In some parts of the High Plains, the average rainfall for April has been doubled in just a couple of days. This includes Dodge City, Kansas, which picked up 4.77 inches of rain Saturday into Sunday afternoon, more than doubling their April average of 1.82 inches. Northeast of Dodge City in Ellis County, a few roads were washed out by flooding.
Numerous reports of roads flooded in Texas and Kansas have already been received. Here is a list of notable rainfall totals by state through Monday evening:

• Kansas: 5.31 inches near Plainville
• Nebraska: 6.25 inches near Riverdale; 5.50 inches in Kearney
• Oklahoma: 7.00 inches in Frederick; 6.02 inches in Tipton
• Texas: 10-20 inches on north and west side of the Houston metro; over 10 inches of rain was also reported west of the Austin metro in Fayette county

What's Causing the Heavy Rain?

Sometimes, winds at jet-stream level don't simply flow generally west to east (in the northern hemisphere), but rather take large north-south (or south-north) meanders. When this happens, weather systems producing rain or snow slow down.

Upper-level pattern forecast for Sunday, April 17, 2016, featuring an omega block in the East, trapped low in the Rockies, and deep moisture into the Plains states.

A southward dip in the jet stream over the Rockies has become trapped for a while from a so-called "omega block" of high pressure over the East and Great Lakes, responsible for a much-welcomed warm-up in those areas.
(MET 101: "Omega Block" Brings Welcomed Warm-Up)
With high pressure both to the northwest and northeast of the stuck low, there's nowhere for the closed low to go fast.
On the east side of that swirling, slow-moving low, deep moisture is in place in the central states.
In general, the slower the trapped upper low moves, the greater the potential for heavy rain over the same areas over multiple days.
This stagnant pattern with a deep plume of moisture in place is a prime setup for flooding rainfall, even despite parts of the Plains being rather dry, recently (more on that below).

MORE: Flooding Hits Houston Metro