Model Differences at 84-Hours

The weather situation for next Monday (April 12th) continues to be quite interesting and the NWS models forecast considerably different solutions for Arizona at 84-hours. The GFS (top) forecasts (at 500 mb) a negatively-tilted S/W into northwestern Arizona, with a voticity maxima near Las Vegas. In contrast the NAM (bottom panel) forecast for the same time indicates a much sharper, and negatively-tilted, S/W to be over southern California and northern Baja, with a vorticity maxima over northern Baja. Note that 500 mb heghts are 50 to 100 m lower over southwestern Arizona, southern California, and northern Baja in the NAM forecast. Winds in both model's forecasts are strong at 850 and 700 mb but much more southerly in the NAM forecasts. The NAM hints at moisture inflow from the south, while the GFS is quite dry, with its southwesterly fetch from the Pacific. So, it looks like a windy start to the week no matter which forecast is more accurate, but the NAM solution would be much more interesting for southeastern Arizona with a stronger frontal passage and perhaps some showers and thunderstorms.