1:10PM Friday Update... I posted this on twitter this afternoon.
The question isn’t, “if it will rain?” , but “HOW MUCH?” Euro a bit more realistic… hopefully
Both the Euro and GFS show the rain, but differ greatly on how this plays out. The GFS closes the low off west of the state and keeps it west of us for quite awhile and high rainfall amounts result. The Euro is more progressive. It brings rain, then shoots the low northeast. The answer? It's a wait and see thing. The Euro has been known to handle these things better, but if the low does close off, typically they are slow moving. I'm taking the middle of the road approach at this time.
|Here's the Euro next Wednesday at 6AM at 500 mb (about 20K feet up) . The low is opening up and shooting northwest. It's located near the borders of Missouri, Iowa, and Illinois.|
If you watched the video yesterday, I pointed out the differences between the GFS and the Euro. The GFS closes the low off and keeps it west of the state while the Euro closes the low and moves it more rapidly to the east. History tells us closed lows often do not move fast at all giving the GFS a bit more credibility. Usually the answer is somewhere in the middle.
The end result is in rainfall amounts and timing differences at to when the system leaves. If you believe the GFS, our rainfall amounts could be extreme. The Euro is nothing to brush off though. It shows heavy rain, but not nearly as much as the GFS.
The position and movement of the low is crucial. The circulation around the low will entrain dry air from the southwest and shut down precip, but the question is where and when. This entrainment of dry air is very typical in these systems and we refer to them as a "dry slot". When that arrives and shuts down the rainfall is what needs to be answered. That will be slower if you believe the GFS and faster if you believe the Euro.
|This is the European rainfall amounts through Wednesday morning at 5AM. Believe it or not, this is the lightest between the two main models. It's very possible to have at least 3-4 inches of rainfall.|
|Since the GFS is slower, it makes sense rainfall amounts are heavier with 4-6 inches possible. I think the answer is somewhere in the middle. Nevertheless, significant rainfall is likely.|
|This is 500mb from the GFS valid late Wednesday. You see that closed line over southeast CO? That's the upper level low. The GFS is much slower compared to the Euro. That's why rainfall amounts are heavier with this particular model.|