11:10 AM Monday Update... This is why you can't hang your hat on any particular model run when you're dealing with a long term forecast. The latest version of the GFS is not as strong with the energy coming out of the southwestern United States next week and therefore develops a weaker surface low and moves it on through. This model continues to show the potential for significant rainfall though with more than 1-2 inches or more. Like I said in the earlier post, this will change several more times between now and then, but I thought I would just update you and show you why forecasting this based on a model that's run 4 times a day with 4 different solutions is impossible at this point.
|The upper energy is pulling out of the southwest and isn't as impressive compared to earlier model runs.|
|Here's the surface chart showing the low moving through with heavy rain the big threat late next Monday into Tuesday.|
|The GFS run this morning shows 1-2 inches with higher amounts possible. This will vary with each model run, but notice it has been consistent with the corridor right through the gut of Arkansas.|
It finally appears the pattern is changing, but details are still to be sorted out. I thought it would be by the middle of the month at the earliest, but it's coming a few days before that. I don't hear many complaints about that though.
With all that said, this is more than likely going to happen next Monday, December 10th, so this is still very much considered the long range period and much can and will change.
It's very tough to go from highs in the 70s to near 80 degrees in December to colder weather without something significant happening. Without sounding like a President or politician, I hope we can do this peacefully.
However, the overnight run of the Global Forecasting System (GFS) stalls a strong boundary right through Arkansas with waves of rain on it this weekend. The flow aloft is parallel to the front not allowing it to move. A strong upper level storm system will dig into the southwestern United States. Once THIS feature pulls out, strong surface low pressure will develop along the front and sweep it to the east.
So here are the questions that remain in regards to the GFS solution: where does the front stall? ( this will be the focus for the heaviest rainfall ). Also, where does the surface low pressure develop? How much instability develops ahead of the front? How fast will this feature move? As you can see, details are sketchy this far in advance. If you believe the overnight run of the model, the biggest potential is heavy rainfall and some severe weather can't be ruled out.
Then there's the Euro model which offered a faster solution yesterday (Monday) blasting the system through here Sunday. As I look at the new run Tuesday morning, it now looks more like the GFS so there is some agreement. However, it does keep the front north of Arkansas most of the weekend, but brings it south Sunday night into Monday with rain (some heavy) with the surface low tracking right through Arkansas late Monday. So there are still some differences, but they both agree on a significant storm system.
Both models agree temperatures will return to average behind the front or even below average! FINALLY.
Here are the maps below which explain the set up.
|This is the GFS early next Monday morning. You can clearly see the green blobs, precipitation fields) along the stalled front from NE TX through AR into the Ohio River Valley.|