Over the last several days, a longwave trough has remained in place across the western U.S., while a ridge has dominated the pattern across the eastern third of the U.S. Between these two larger-scale features, smaller shortwave impulses have generated favorable conditions for excessive rainfall amounts across parts of the Southern Plains and mid-south.
weekend, a northern stream shortwave trough will dig into the Northern Plains
and move into the Great Lakes by late weekend. This feature will usher in a pattern
change and begin breaking down the ridge that has been placed across the
Southeast and Mid-Atlantic. Before the cold front associated with the northern
system pushes through the Gulf Coast and East Coast states early next week, a
period of widespread moderate to heavy rain will fall across a large region of
the southern U.S. and extend into parts of the Mid-Atlantic.
Since the northern stream system will begin flattening and weakening the ridge, there will be an eastward expansion of the rainfall and potential flooding risk. Deep, tropical moisture will advect northward and northeastward throughout the weekend; thus, any rain that falls could be heavy and tropical in nature. The next three graphics outline the flash flooding risk for today (Friday), Saturday, and Sunday. Notice how the flash flooding risk will begin shifting eastward with time.
additional rainfall that occurs across southeast Texas and southern Louisiana today
will become problematic given recent heavy rain over the last 24 hours. This
includes the Houston and Baton Rouge areas. States east and north of Alabama
have remained relatively dry compared to the region just west. Even though soils
are quite a bit drier east of the mid-south, high rainfall rates will still
result in localized flash flooding farther east. By Sunday, lower rainfall
rates will be necessary to cause flash flooding concerns, due to prior rainfall
today and Saturday.
though I didn’t explicitly mention all regions under a flash flooding risk,
please refer to any maps included in this article and future maps we post on social
media. The purpose of this article is mainly to give you a heads up on this wet
and stormy pattern, especially with Mother’s Day being this Sunday.
Matthew Holliday (Curriculum Vitae - Resume) is a graduate of the University of Oklahoma, where he completed a B.S. in Meteorology and a B.S. in Geographic Information Science. He is currently pursing his master's degree in meteorology and climatology at Mississippi State University. Matthew founded Firsthand Weather in 2010.