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).
Happy autumn! Yesterday was the autumnal equinox, when sunlight impinges on the earth perpendicularly at the equator and all locations on earth have 12 hours of daylight and 12 hours of night (except at the poles, where sunrise or sunset lasts for 24 hours).<
Enjoy the blue skies today and tomorrow, because more clouds and showers are expected later this week. An approaching Pacific trough will create a surge of unstable, humid air across Arizona on Thursday – Sunday. As a result, scattered showers and thunderstorms are expected to return to the Prescott area. The approaching trough will create moist, deep southerly flow starting Thursday afternoon/evening. Friday – Saturday a fairly moist air mass will be in place for a chance of thunderstorms each day. Expect cooler, breezy conditions as well, making it seem a bit more like fall. Southwest winds will gust up to 20 or 25 mph on Friday and Saturday, with stronger gusts possible.<
On Saturday, the vertical wind shear will become stronger as a subtropical jet stream around the upper-atmospheric low pressure system shift across Arizona. As a result, isolated severe thunderstorms could occur, capable of producing large hail or damaging wind gusts.<
Thunderstorms will become less likely by Sunday as drier air begins to move in from the west, and by Monday skies will be clear again. Very dry westerly wind will spread across the state and winds will relax, allowing morning lows to drop into the 40s. From next week onward, westerly winds will likely prevail for the rest of this year. Monsoonal flow is not likely to set up again until next summer.<
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