South view from Kitt Peak this morning (above) shows considerable heavy, low cloud around, as well as some snow cover from early yesterday morning. The early run of the Atmo WRF-GFS this morning forecasts a wetter storm early tomorrow morning (Monday, November 7th, 2011), as the next 500 mb short-wave trough swings across Arizona. The WRF forecast of composite radar echo for 4 am MST tomorrow morning is shown below. Note that echoes are stronger in the new storm, with intensities indicating some thunderstorms embedded in the precipitation bands. If the model is on track, it should be interesting after midnight tonight.
The WRF surface forecast for 6 am MST tomorrow morning (above) indicates a cold and wet Tucson metro area at sunrise. Total WRF accumulated precipitation through noon tomorrow is shown below. Model forecasts more than an inch in some places. So, it would be good idea to check the WRF morning runs at the Atmo page later today.
Long term: Can't resist talking a bit about the long range GFS ensemble forecasts from 00 UTC last evening. All the members are fairly consistent at 168-hours, forecasting a wet system into the Southwest next weekend. The ensemble-mean forecast 500 mb chart and spaghetti plot at 168-hours are shown below. The very strong ridge in the Pacific north of Hawaii is controlling the pattern, with a downstream trough over the western US. The ensembles have a nice connection to lower-latitude moisture in their precipitation forecasts: 9 of 12 members have precipitation over southeastern Arizona for the 12-hours ending 5 am next Saturday (12 November); 11 of 12 for the 12-hours ending Saturday at 5 pm; and 11 of 12 for the 12-hours ending Sunday at 5 am. This long-term consistency is similar to several events that occurred during winter before last. Will be interesting to watch!
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