Omega Block Breaks Down; Drier Conditions Return To Texas Late Week

Tom Moore
Published: April 20,2016
An exaggerated jet stream pattern over the U.S. has led to some extreme rain and snow totals over the past several days, but there are finally changes on the way.
This pattern, known as an "omega block", established itself last weekend.
The jet stream took a big southward plunge over the Intermountain West as a large ridge of high pressure bulged over the eastern U.S. The jet stream dipped again off of the Eastern Seaboard (forming the Greek letter Omega).
A good analogy would be to place a wooden block in the middle of a running stream of water. The water is blocked from moving along and builds up on the left (or west) edge of the block. Storm systems caught in this type of pattern are often memorable. In the current situation a storm system swung into the Rockies and was blocked from moving eastward, causing the storm to stall.

Omega block pattern this past weekend prevented the storm system across the West from progressing, resulting in high rain and snow amounts.

Moisture feeding into the storm fell as heavy, wet snow over a significant period of time across a section of the Rockies resulting in snowfall totals exceeding 4 feet in parts of Colorado.
Areas farther to the southeast, like central and southeast Texas, were inundated with torrential rain that created deadly flash flooding and the need for water rescues, especially in the Houston area.
(RECAPS: Deadly Houston Flood | Winter Storm Vexo)
There is some better news in the days ahead, however.
The "blocking" pattern will slowly lose its tenacious grip and the ridge of high pressure aloft will slide slowly eastward. At the same time, the storm system responsible for all of the heavy rain and snow will move slowly northeastward into the central and northern Plains.
The associated moisture will be slow to move, however. Although significant rainfall remains likely across parts of Texas through Thursday, rainfall rates will be much lower than what we saw Monday morning, so any flooding will be more scattered in nature.
(MORE: More Flooding Possible)
If you are driving, do not attempt to navigate through flooded roadways. Even a foot of water can cause vehicles to float. Remember "Turn around, don't drown".
In the latter part of the week, the storm system will continue to progress northeastward into Canada and it will weaken considerably while the attending cold front will progress eastward.
This will bring a few days of dry weather to the southern Plains, including Houston and other parts of Texas. However, there are signs that a new storm system could bring more rain to the south-central states early next week, but details are uncertain.
(MORE: 7-Day National Forecast Maps)

Friday's Forecast

Meanwhile, this pattern is creating relatively warm and dry conditions in the eastern U.S. Late in the week, parts of the Great Lakes will encounter more rain showers and slightly cooler temperatures. The cold front will move offshore by the weekend. Rainfall totals in these areas will be light, so no flooding is expected.

PHOTOS: Photos of the Houston Flooding