It’s going to be…well it’s going to be a week on the Central and Southern Plains into the South and all the way back into the Southwest. Expect severe weather chances to ramp up on Wednesday, with snow possible through the workweek and rain also likely for many. There’s so much to dissect so let’s do it day-by-day.

Tuesday

Tuesday will feature our first storm system of the week. Gulf moisture will stream northwards and will interact with the lift from this incoming system to generate widespread precipitation.

  • At the present time, instability looks to be limited with this system, so expect only a few rumbles of thunder amidst the heavy rain.
  • Snow will be possible with this initial system, but atmospheric temperatures are pretty warm. Thus, expect only the highest elevations across New Mexico and Colorado to see a lot of snow.
Simulated radar shows widespread rain across the Southern Plains into the Central Plains on Tuesday morning.
The rain should end quickly from west to east as the storm system departs to the northeast. Typically this time of year that wraparound area in Nebraska and Kansas would be ground zero for a major winter storm — but it’s too warm for that this time.
Snowfall totals from this first system will be very healthy over the highlands of New Mexico and Colorado. This is a key thing for the upcoming storm season — the snowpack in these areas is actually somewhat above normal. Just keep that in the back of your head.
The airmass behind this system isn’t terribly dry. This means that the next storm system coming out Wednesday can return enough moisture for active weather once again.

Wednesday

And thus, we arrive at Wednesday. This is a day that will feature several weather stories at once. There will certainly be a severe weather risk over the Southern Plains and into the South — but could we see winter rampaging across the region as well? Let’s take a look.

  • The first thing you’ll notice when you wake up Wednesday morning (at least for most people) is a cool and crisp airmass with strong southerly winds.
  • A storm system will be approaching from the west, drawing the warm/moist airmass north.
  • This is a much colder system so on the north and west side of our eventual storm system track, a widespread snow event will almost certainly occur.
Moisture return throughout the day on Tuesday reveals a ‘just-in-time’ moisture regime. For drylines to convect, you need two very important things: strong convergence along the boundary (usually from well established drylines) and upper-air lift. The latter can get it done with newer moisture regimes, but it’s more rare.

Dryline Convergence

Convergence increases on a dryline usually in response to what is happening aloft. It’s all part of the same system. The middle frame and right frame above shows the evolution of the dryline from 21z to 0z on Wednesday on the Euro.

  • The dryline is diffuse because the upper-air forcing is still a bit west at 21z. It sharpens up by 0z in response to the upper wave, but that is also sunset when the atmosphere will be rapidly cooling.
  • Because of this, storms don’t want to get going too widespread until after dark on most all models. Some models are even less bullish on moisture return, as the NBM shows the 60 isoderm well south of both the GFS and Euro’s location.
The system is still west a bit by Wednesday afternoon. Of course, a bit more progressive (faster) ejection would be a huge difference maker.
The environment along the dryline on Wednesday afternoon is initially pretty meager. The surface heating doesn’t look particularly robust, and thus this combination leads to a bit of convective inhibition along the dryline. The -106 MLCINH is pretty significant.
From 21-0z the atmosphere quickly evolves into one that could possibly support storm development. I think the key to getting a storm on the dryline on Wednesday will be dewpoints at or above 60. If you don’t have a storm up by 0z, it will almost certainly not happen until the front overtakes the dryline.
There will likely be a few zones of storm development on Wednesday evening. The first is in Northeast Texas as a cold front overtakes the dryline. The second is further east as warm ascent interacts with a warm/moist airmass.
The shear/instability parameter space will be highly supportive of severe weather with any terms that form after dark. The tornado risk also seems apparent, especially with any isolated cells that can sustain themselves over Northeast Texas. 0-1km SRH of greater than 220 m2/s2 will favor low-level rotation with any sustained supercells or QLCS segments.
  • The chances of a storm going up on the dryline in the late afternoon in Wednesday right now cannot be ruled out — but it is probably pretty unlikely.
  • Any storms that form after dark will have the capability of producing large hail and tornadoes. Damaging winds will also be possible, especially with a possible linear complex along a quickly advancing front.
  • The threat should persist into Thursday across the South.

Snow, Snow, Snow

The snow forecast for this system seems relatively straightforward. Take the path of the upper low and anywhere on the north and west half of that track will see snow.

  • 3-6” or possibly even higher local amounts are likely in a very broad swath.
  • Many of the areas that will see snow are in an exceptional drought situation, this is incredible news for these areas.
Let us all cross our fingers that this snowfall map for Wednesday -> Thursday comes to pass.