Northeast Colorado or the OK-TX Panhandles?
I’ve got a difficult chase forecast ahead of me this morning. Fortunately, either target is about 3-4 hours drive, so I’ve got about 5 hours to make up my mind. Roger Edwards 6z SPC disc was a good one, as always, highlighting my thinking at least from a storm chasing perspective. Yesterday, I was not really thinking much about a TX-OK PH dryline scenario… but now, I’m trying to find a reason NOT to chase south today. Morning obs suggest mid 50s dewpoints in place. It looks like a fairly classic "Day before the big day" dryline setup with convergence increasing towards 00z. There should be no problem reaching peak heating potential today, and the NAM shows highs in the lower 80s along and west of the dryline over W TX PH. Farther north over NE CO/NW KS… there will be more of a low level baroclinic zone with that retreating boundary so there will probably be a frontogenetic enhancement to upward vertical motion and subsequent initiation.
One thing I usually look at in the NAM model are 700mb RH/Omega clues from the NAM, especially with potential dryline initation… I think you get a good idea how much dryline upward motion from boundary layer convergence, etc you are getting for potential initiation. Another clue is 700-775mb temps. Usually the NAM will show a tongue of lower (roughly 1 to 1.5C) temps in this layer due to enhanced dryline lifting. Even though the 12km NAM convective parameterization schemes don’t show QPF along the dryline, the signals are shown that it’s trying hard to force convection from roughly Elkhart KS down to perhaps as far south as Plainview, TX. I went and checked the 00z explicit 4km NAM (http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/cent4km/v2/) and it indeed shows one isolated storm forming along the dryline over the western OK Panhandle.
24hr forecast of 1-hr convective precipitation from the 4km NAM model valid 7pm CDT 4/20. This is suggesting isolated severe thunderstorm development along the dryline.