The closed low off the California coast is moving slowly southeastward this morning, much as various models have been forecasting the last several days. The issue continues to be how much lower-tropospheric moisture can this system pick up before it ejects northeastward? Slower movement is good, and it would help if it moved further south than models currently predict. The above graphic is the 12 UTC 500 mb analysis this morning from NCAR RAL.
The system is now within the forecast range of Atmo's early WRF-GFS. The run from 11 pm last evening forecasts the precipitation with this system will skirt by most of southern Arizona. The model forecast of PW at 5 pm MST tomorrow afternoon (Thursday, 11 October) is shown below. The model forecasts values to increase to around an inch from the Tucson area eastward, certainly not a very wet system in the current forecast. The NWS NAM model run at the same time last night kept rainfall east of Tucson.
The WRF-GFS forecasts one light streak of rainfall across eastern Pima County, but keeps more significant rainfall off to the east and northeast (below is total rainfall forecast from WRF-GFS through 7 am MST on Friday morning. I see that the new NWS NAM forecast is quite similar. So, a system to watch carefully, but clearly it will produce more weather across northern Arizona than it does down here in the south.
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