It looks quite interesting across the Southeast U.S. this weekend as a strong winter weather system moves over the region. I thought I’d point out some key hydrometeorological aspects regarding this event. First, let’s take a look at a Water Vapor satellite image. This shows mid and upper level atmospheric moisture. You can track an upper level moisture plume originating from the Pacific. I have also circled a pooling of deep-seeded moisture in the Gulf of Mexico. I start to get concerned about heavy rain when a system taps into both Pacific moisture at upper levels and low or mid level Gulf moisture.

The next image (below) shows lower-level parameters forecast as of midday Saturday. You can see that an area of low pressure is expected to develop in Texas. The blue arrows indicate that this low will easily pull in low-level moisture from the Gulf of Mexico. Heaviest rain is typically aligned along and near the warm front (indicated in red).

I often take a quick look at Precipitable Water (PW) — a good indicator of the total amount of vertical moisture. This image shows PW values of 1.5 inch or greater late Saturday. Note how this deep moisture has been transported well into Mississippi, Alabama, and Georgia. This represents a value within or exceeding the 75th percentile for this time of year.

Thus, it looks like there is a high confidence that there will be plenty of deep-seeded moisture and lift to produce heavy rainfall over the Southeast U.S. this weekend. The final image today is from a weather model that shows the best chances for rainfall of 1″ or more over a 24-hour period. This looks reasonable to me as it is generally aligned along the warm front and the trajectory of the surface low. Take note how the alignment of the heaviest rain is similar to the core of the exceptional drought. Right now, the forecast calls for the axis of heavy rain to be just north of the exceptional drought area, perhaps eroding the northern edge. It the axis of heaviest rain drops a bit south it could result in more significant drought relief. Likewise, if it forms just a bit further north, the drought region could receive much less rainfall.