|Posted by Near Zero Probability Chasers on April 15, 2016 at 4:40 PM|
The "omega blocking pattern" currently in place in the US should dominate the weather pattern until around mid week next week where it should slowly move east and out of the Plains but not before delivering several rounds of severe weather to the Plains as well as very heavy rain. Once it moves out, more robust severe weather should take place as the peak of the tornado season arrives. As it sits right now, there seems to be two major troughs ejecting almost one after the other behind this omega pattern.
"Omega blocking pattern" depicted below:
WHAT WE KNOW:
There seems to be a pretty potent and significant severe weather event in the latter part of April. Right now, it seems to have been pushed back later than we previously thought due to the slow progression of the omega blocking pattern set to affect the central Plains this weekend and linger up until early next week. Once this trough finally moves out of the CONUS, another more potent trough should eject (see images below) in the west sometime around mid next week and ramp up near next weekend. The omega pattern this weekend isn't as favorable due to relatively stationary feature of the front giving lots of clouds and favoring heavy rain events, therefore limiting instability and the general severity of the event. However, should see some tors regardless. Next weekends trough looks very different.
WHAT WE DON'T KNOW:
The exact timing of next week's omega pattern moving out of the CONUS and the second major trough ejecting is still relatively unknown at this time. Too many variables can affect which days this big severe weather event will occur (if it even occurs). The biggest concern is the flow aloft and the timing of the trough which is too far out to know with certainty with using only medium-range models (GFS/ECMWF/ensembles). High CAPE values depicted could very well mean strong cap inversion preventing storm development as well, it's not because high CAPE & high dews that storms will occur.
GENERAL SETUP DISCUSSION (from what we know):
As previously mentioned, the significant trough seems to eject later than previous thought. It seems to start to appear on the west coast around the 21st or 22nd of April. So why are we looking at this weekend if it will be near the west coast or deserts? Well pre-frontal instability and moisture return ahead of the trough should build up to (it seems like) pretty significant numbers as early as the 22nd (Friday). This could eject multiple dryline/warm front setups as well as pre-frontal troughs into the central Plains regions allowing for a multi-day event before the actual trough itself reaches the Plains allowing for kinematics to be maximized. Whether these will have enough forcing to initiate convection in the high-CAPE & dewpoints environment is less certain, but if storms do form in this environment you're looking at some pretty impressive storms. High-CAPE'd environments usually favor photogenic supercells and very large hail, however, as I have witnessed in Simla, it can always spawn multiple tornadoes as well due to high updraft and dews (4500J & 20kts of shear day).
As it sits right now, we're looking at the April 22nd to April 25th time range for chase days, with April 21st possibly a less "big" day but also a possibility. Like I said, these days will most likely fluctuate since it's a week out. Also, there might be another significant trough ejecting after this one near the 25th time range. More info soon!