Thanks to an upper air pattern characterized as a western (southwest) trench, below an omega block over the Pacific Northwest (Rex Block) and a ridge to the east – this pattern specifically generates a favorable environment for heavy rainfall and ocean waves of moisture between troughs and mountain slopes throughout the Plains and Deep South. Over the past 14 days, we can simply see where precipitation has accumulated relative to the rest of the US. We’re adding more this week!
First, identify the key features involved that will lead to the wet pattern. We have a higher level trench that will shift from the Eastern Pacific and rotate in the vicinity of Baja, CA. This will open up moisture from the Pacific, as we see the jet stream heading north. To the north, a polar jet feature will pass through the Rockies and the Northern Plains. As it does so, we will see a manifestation of the higher-level difference resulting with the right rear quadrant of a jet trail superimposed on itself over the outlined area of interest. exacerbating a previously favorable environment.
When we found our way down to 500mb, we not only saw the polar trench deepening and pushing north and east, but also a few short waves or small pulses emanating from the ULL off Baja Ca. peninsula, but there is also some active eddy entering the back of the polar trench creating a push to go up.
On the surface, we really have two boundaries; a fixed front ran from NM through the TX panhandle into OK, while a remarkably cold front (due to extreme trench excavation) headed south. With forward generalization scaling and “crossing the boundary” shortwave, we create a very favorable environment for precipitation, and the components are all there to allow heavy rainfall to occur, along with with the development of several thunderstorm clusters with over 1000 J CAPE forecast to build with all that moisture advancement.
From a humidity perspective, notice there’s no shortage of that with the PWAT exceeding 1.2″ over a large area across the Plains, resulting in heavy rainfall.
Not to mention, we are looking at a convection training case with the cutting direction more parallel to the front. When we put all of our components together, we got a consensus on rainfall exceeding 2” across CO, NM, panhandles north of TX and into south of KS before entering. MO and AR.
Unfortunately, for this area, the pattern still seems to work as we head into the last week of May before we start to see changes.
About the author
Armando Salvador
Hello! My name is Armando Salvadore and I am a Mississippi State graduate with a Bachelor of Professional Meteorology and an Activity Meteorologist working in the Private Sector. Stay tuned if you like technical, exotic, and general weather tweets! Also big on long-range forecasting as well! Twitter: @KaptMands
