The figure above indicates the forecasted high in orange (with error bar denoting the range of ensemble forecast members), average high for this time of year in orange (dashed line), forecasted low in blue (with error bar), average low this time of year in blue (dashed line), and forecasted wind speed in purple. Note that the wind speed forecast is sustained wind (not gusts), and it is based on only one model (not an ensemble).
Overnight lows this morning and for the next few mornings will be below normal as a dry and cool air mass has moved into Arizona behind the previous disturbance that exited to our east earlier this week. As autumn approaches, the nights are getting longer, and this combined with dry air and clear skies leads to a greater temperature difference between day and night.
A weak upper-level trough will cut-off from the jet stream and become situated along the California Coast by next Monday. The counter-clockwise rotation around the low will circulate a deep layer of more humid southerly wind into Arizona, with sufficient energy to create isolated to scattered showers or thunderstorms each day Monday – Thursday.
The moisture surge next Monday is expected to bring morning lows back up into the lower 50s.
Met Mail is an unofficial weather discussion and forecast transmitted once or twice a week via e-mail by the Embry-Riddle Department of Meteorology (http://meteo.pr.erau.edu/). Embry-Riddle offers an undergraduate bachelor-of-science degree program in Applied Meteorology. Please spread the word to all potential qualified candidates!
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Official National Weather Service forecast