So the pattern appears to look pretty bleak and best way to describe it would be subtle. Synoptically there appears to be no real evidence of a descent stretch of active weather across the plains until near the end of May which I will get into momentarily. But it appears as the bulk of the flow remains in the northern portion of the plains and up into Canada the wobble and weaker troughs near the base of the flow could prove to be the hidden gems I mentioned in the previous post. Here we see the GFS, NAM, ECMWF respectively all indicating the first potential active day for May 16. The NAM/ECMWF are slightly slower with the trough and the Canadian GLB model barely even shows it anymore. The GFS a little on the fast side, let’s hope that the NAM/ECMWF are more right since the slower solution may allow for more moisture return and little more instability. Another extra bit of comfort here are the GEFS ensemble solutions which show rather good convergence on the trough actually being there with a slight spread in the timing.

What does have me concerned is; I believe Dave Lewison termed it perfectly, saying that this initial trough is more of a "sacrificial trough" to help moisture return into the plains. Here are the 00Z GFS and 12Z NAM sfc Td and streamlines. I had to pull the 00Z GFS as the 12Z run did not fully load onto the Nexlab page. So I also included the GFS sfc chart to get a feel of the low level flow for the same time frame. The NAM looks pretty scary and shows hardly any moisture return at all with the GFS showing some promise and even breaking out some QPF along the CO/NE border. Thus leading me to conclude that possibly the slower solution of the ECMWF/NAM may start to render little more moisture return as the situation continues to unfold, or Dave's theory is bang on. None the less with the time we have out there looks like we may chance it and hope from some upslope magic.

May 17 also holds some merit as the GFS and the GEFS ensembles have the trough lingering into the south central NE and north central KS area as seen on the 500 mb charts showing the GFS, GEFS ensembles and ECMWF. As the trough does render a weakly cyclonic sfc flow this day here may be a little better allowing some better moisture return. The ECMWF also shows a subtle hint that the trough will linger as well as the GLB. However the GLB keeps the trough down in southwest KS near the OK panhandle which is a little out of sync with the other models thus I’m going to reject it here.

With the how weak the upper pattern is here I am really just hoping for some sort of mesoscale accident. There does seem to be enough dynamical energy to render the sfc slightly more cyclonic as seen here in the GFS and ECMWF sfc pressure charts. I've also included the GFS 850mb chart as the ECMWF chart shows 850 winds. They both to appear to agree on a axis of stronger 850 flow through the central plains but the ECWMF orientation of the axis is not ideal and may prove to be more harmful than good. What also has me concerned is these weak lingering upper lows can cause low cloud to linger killing any instability that may be able to build up.

The days to really look over here are May 18/19 as things looks to get going a little more in terms of the overall synoptic pattern. What is odd though examining the 500 mb charts below where the GFS opp. run shows barely any real trough over the southern plains and the GEFS spaghetti plot, and ECMWF seem to agree more on having a slightly deeper trough. With the weaker impulse that will have passed in the previous two days the moisture return should be sufficient here to provide something noteworthy. Another positive aspect to take from this particular setup is the general tilt of the trough axis. It’s not overly negative, but is showing more of a negative tilt rather than a positive one which should help with any capping issues, if any do present themselves.

The disconnect between the upper flow with the GFS and the general sfc pattern is interesting. Here the top panel is the 850 mb flow from the GFS and the bottom from the ECMWF. With how subtle the GFS opp. run is with the upper trough you would think the sfc/low levels would not render such a strong cyclonic feature and low level flow, but the ECWMF seems to backup this solution as well. Thus is makes it a little more difficult to conclude whether or not the ECWMF or GFS pattern is more correct. Looking at what the GFS lower level say the ECMWF may be the better solution but there cannot be any real distinct conclusion. 

May 19 is where things start to diverge some with the ECMWF continuing with a more aggressive 500 mb trough and the GFS showing a more zonal flow. The GEFS ensembles actually show a midpoint solution, I find, giving a subtle trough with a little more amplitude than the GFS but not as aggressive as the ECMWF upper air charts show.

But again with descent flow at 850 mb there appears that there could be some extreme western plains action along the dryline. The other option if it pans out more like the GFS, could possibly be in for some more upslope events in S CO or even some baroclinic instability along what could be a stationary front or pseudo stationary warm front.

After this run of active weather the flow appears to jump north again with some weak ridging taking over. There appear to be some noise along the base of the upper flow which could give a few chase days of marginal convection but tough to pin point anything at the moment. There real kicker comes near the end of the 12Z GFS run with what is shown below. The first panel shows the GFS 500 mb vorticy and the second is the 250 mb flow. This is promising to see because 1. What was to be a DEATH RIDGE appears to have had its axis gradually shifted ESE. The GFS begins to break it down completely giving a deep trough and a more synoptically driven setup that may prove to be descent. Even better is finally we get the polar jet dipping south into the southern U.S. If this can pan out, with the return of some much needed Jet dynamics this can prove to be very active last few chase days. Were not in the clear yet but the trend seems promising.

Granted this isn’t all glory yet, as the ECWMF is not as aggressive with this trough and not all members of the GEFS ensemble are on board with this solution showing a pretty large spread, but at the same time not indicating a death ridge. The NAEFS also is not too bad, again no as aggressive with the trough but trending away from the ridge that has been forecasted the past few runs.

So to wrap this up, not much has changed from the previous post; a departure on Tuesday May 15 is a go. Now depending on how the models play out the May 16 potential, we may put in a few extra hours of driving on the 15 to put us into striking distance if need be for May 16 so that we can drive right to a target area if needed. If not we will be in position to play on the May 17-20 opportunities in the central plains. This season looks to be tough forecasting and will have to find those hidden gems that are out there which should be little easier to do once the high resolution and mesoscale models can come into play, but for now going to have to really study the subtle hints and play on those.