Looking Ahead

Several things of interest happening that will affect southeastern Arizona next few days and also next week.

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Out east in the Plains, high pressure dominates, extending from western Canada south across much of north and central Mexico. A re-inforcing push of cool, dry air today and tonight will be followed by a stronger push over the weekend and early next week, as a strong 500 mb trough digs toward the central Mississippi Valley. The top image shows the NAM forecast from this morning for 5 am Sunday morning, indicating that a strong backdoor front will have pushed into southern Arizona with gusty east winds. The easterly flow into Arizona will be quite dry, as the air over the Plains will be cool with low dewpoint temperatures - i.e., it's definitely a Fall regime.
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Later in the week a fairly strong 500 mb trough is forecast to dig into the Southwest, and this trough will have the potential to pick up some lower-latitude moisture, depending on where exactly it tracks, and how far north the old cutoff west of San Diego is kicked out. The bottom two images show the 168-hour forecasts at 500 mb from last evening's GFS and ECMWF runs (both are from the operational version forecasts). The eastern US cutoff low is very much stronger in the ECMWF, which results in a position further west for the cutoff in the Southwest. The ECMWF has a more moist trajectory for the Southwest cutoff than does the GFS, which tends to keep it on an over-land track. Thus, it will be interesting to watch to see which global model does best at mid-week next week. Note also that GFS has an Atlantic Tropical Storm in it's forecast.