Friday, April 12, 2019

Heavy Clouds And Bit Of Chill In Air

Heavy middle clouds cover sky this morning - north view from Kitt Peak (above) is from about 8:00 am MST. Visible satellite image below (from 7:00 am) shows bubbly clouds extending across all of southern Arizona.

When I walked this morning, there were some very light sprinkles around - one slight shower came by that was distinctly colder and with of burst of outflow winds of 30 to 40 mph. The heavy cloud-cover will keep temperatures today in the 60s.

The short wave discussed yesterday has indeed dug south to Arizona and northern Mexico this morning Above analysis is for 250 mb this morning (from SPC). Of main interest is the strong northerly jet with speeds reaching to 150 kts (purple) on northwest side of system. This will continue to force the highest vorticity at base of trough on into Mexico. The 12 UTC NAM 500 mb forecast (below - valid at midnight tonight) indicates a long streamer of vorticity from the Canadian border southward into north-central Mexico. The vorticity streamer is associated with the strong jet in upper-levels.  

The 12z skew-T plot of the TWC upper-air data (above from SPC)  indicates no CAPE this morning, and that PW has reached 0.39" with the thick cloud deck that extends from around 600 mb to 400 mb. Quick look at WRF-RR from 12 UTC indicates forecast measurable precipitation to mostly stay to our south, with some development of thunderstorms over Santa Cruz County possible  - first below shows composite radar echoes valid at 3:00 pm this afternoon and second below is model forecast of precipitation totals through 6:00 am tomorrow morning. Most of the precipitation impacts northern Mexico - note that light green indicates amounts of just over 0.50".

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