Saturday, September 24, 2016

Definitely Bit More Than Sprinkle Showers

More on the satellite question later today.

Moisture hung in through the afternoon yesterday and several bands of showers affected parts of the metro area and the Catalinas, as per ALERT data above for past 24-hours shows.We had 0.02" here with two periods of winds gusting 30 to 35 mph. TUS had 0.01" and DM had 0.02". Two sites in the Catalinas had nearly half an inch.

The WRF-GFS forecasts from 06 UTC continue to forecast very low PW, with values falling to 8 mm in metro by 7:00 pm MST this evening. However, the dry-out is short-lived in the model forecasts, with moist air returning from the east on Monday. The forecast below is valid at noon on Monday.

The evolution of features at 500 mb continues to be intriguing. Shown here are 500 mb forecasts (again from 06 UTC WRF-GFS, but on the 5.4 km grid) valid at 6:00 am - above on the 25th, below on the 26th, and bottom on the 27th. The closed low that develops just to our east digs southwestward over the GoC, but then moves northward toward southwestern Arizona. There will undoubtedly be showers and thunderstorms around parts of southern Arizona as all this evolves - but the details are certainly not clear at this time. The color bar has changed and is apparently one for winter - temperatures over us at 500 mb are forecast to be colder than -15C on the 27th, which could be very interesting.

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