Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000 FXUS65 KPSR 300902 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 202 AM MST Tue May 30 2017 .SYNOPSIS... Warm conditions with temperatures roughly five degrees above normal will affect the area Tuesday. Scattered mountain storms across far eastern Arizona will be possible, mostly for Tuesday and Wednesday. Temperatures cool somewhat into the end of this week with overall readings ending up near seasonal normals. Another minor warming trend this weekend into early next week will push lower desert highs closer to 105 degrees by next Monday. && .DISCUSSION... A trough progressing eastward into California will deliver a change to the weather for Arizona and throughout the southwest. Regional H5 heights will begin to decrease over the next few days to near 578 to 580dm. In addition, increased moisture and occasional thicker clouds will help moderate temperatures keeping the daily highs closer to seasonal normals. The higher terrain north and east of Phoenix will have a chance for thunderstorms today and Wednesday. For today, increased southeasterly winds in the lowest half of the atmosphere will draw additional moisture into the area which will usher dew points into the mid to upper 40s. Model soundings also suggest quite a bit of CAPE over Gila county. The GFS is at the conservative end with near 800 j/kg while the NAM and RAP indicate CAPE values over 1500 j/kg. While the higher values seem a little too aggressive, a number of the convective allowing models (CAMs) depict at least some isolated showers and thunderstorms over central Gila County, the Mogollon Rim and White Mountains. Given that any thunderstorms are going to be high based, much of the precipitation is likely to evaporate before reaching the surface. As such, the precipitation amounts leave much to be desired with most models indicating nearly zero measurable rain totals. Therefore, the chance for the existence of thunderstorms is probably greater than what the PoPs suggest. Any thunderstorms that do develop will have the potential for lightning strikes and producing outflow winds that may pose fire weather concerns for ongoing fire suppression operations and ignition of new fires. Wednesday`s forecast is not all that dissimilar from Tuesday except that the amount of moisture remaining over the mountains is in doubt. Coverage for storms Wednesday afternoon looks less than inspiring with the best chances for storms on the eastern fringe of Gila County and beyond. Thunderstorms aside, Wednesday afternoon looks to be breezy, especially for the Lower Colorado River area and over the higher terrain in Gila County, with gusts 15 to 25 mph. While weak troughing over the Western United States Wednesday and Thursday will allow for temperatures to drop to near seasonal normals, H5 heights will soon recover. The GEFS indicates H5 heights will return to the 582-586dm range by the weekend. As such, the temperature forecast was weighted more towards the upper half of the available guidance. && .AVIATION... South-Central Arizona including KPHX, KIWA, and KSDL, and Southeast California/Southwest Arizona including KIPL and KBLH: Light surface winds will continue overnight and through the day Tuesday favoring familiar diurnal patterns. However, there will be a period from about 15Z-19Z over south-central AZ (including metro Phoenix) where stronger than average southeasterly winds are anticipated before slowly becoming southwesterly in the afternoon. Thick cirrus will continue overnight before starting to thin from west to east during the day Tuesday. Aviation discussion not updated for amended TAFs. && .FIRE WEATHER... Thursday through Monday: Near normal temperatures will last into early next week under weak high pressure. Drier air will move back over the districts starting Thursday ending the thunderstorm/lightning threat. Winds will obtain the typical late afternoon breeziness on Thursday with somewhat lighter winds through the weekend. Minimum humidity levels will fall to around 10% except in a 15-20% range over higher terrain of Gila County, as well as lower elevations of southeast California. Overnight recovery will generally be fair. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook, Twitter, and at weather.gov/phoenix DISCUSSION...Deemer/Kulhman AVIATION...AJ FIRE WEATHER...Kulhman

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