Thursday, July 13, 2017

More Storms Today?

Above is my subjective 500 mb analysis of the 12 UTC upper-air data. While the ridge seems full of weak troughs, the anticyclone of interest is northeast of Tucson. There is a pronounced, upper-tropospheric cyclone/inverted trough over the Big Bend country and north-central Mexico - this feature is moving slowly westward and will help keep things interesting in southeast Arizona into the weekend. There will be substantial difluence ahead of this feature affecting our part of the state.

The morning sounding is more unstable than yesterday's and it appears that BL heating can produce an afternoon sounding that needs little lift to trigger storms. There is decent steering flow from the northeast to east, so some organized lines are likely. The 9:00 am MST visible image shows mostly clear skies our part of state.

The forecast 06 UTC WRF-GFS sounding valid at 5:00 pm today (above) indicates some advection of a mountain layer  providing a bit of a cap over the moist, surface-based BL. Forecast steering flow is from the northeast. So that may delay storms. However, storms in low elevations should develop easily with some outflow kick and with cloud bases around 700 mb could produce severe, hybrid downbursts.

The composite radar forecast below from the WRF-GFS is valid at 6:00 pm and forecast at bottom is for total precipitation through 11:00 am next Sunday. So a number of interesting days appear to be on tap.

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