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Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
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529 FXUS65 KPSR 060913 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 213 AM MST Sat Jul 6 2024 .SYNOPSIS... Extreme heat will continue region-wide through most, if not all of, next week with strong high pressure over the region. Temperatures will be near daily records with lower desert highs reaching 115 to 120 degrees. Some moisture return will bring increased thunderstorm chances back to the Arizona high terrain and southeast Arizona by the middle of next week. && .DISCUSSION... Deep mixing, record-level 850mb temperatures, around 32-33C, and low specific heat capacity with the dry air likely helped contribute to high temperatures overperforming by a few degrees Friday afternoon. Several records were broken across the region yesterday. There is every reason to believe something similar may happen again in the following days, with very little change in the environment as strong high pressure continues to dominate the region. However, model soundings do indicate a slight cooling, by 1-2C, of the 850mb temps heading into this weekend. So, this weekend`s highs are not forecast to be quite as hot as Friday, but still within a couple degrees of daily records. The forecast temperatures were blended with the NBM 75th percentile to nudge highs up a degree or two, following the NBM deterministic`s underforecast Friday. An Excessive Heat Warning remains in effect through Tuesday afternoon with no changes made during this morning`s forecast. However, it is hard not to acknowledge the latest forecast which has lower desert high temperatures remaining as high as 115-120F each day through Friday next week. Through all of next week global ensembles show little to no change in the height field over the Desert Southwest, with H5 heights remaining in the 594-597dm range, along with 850mb temps remaining near 30-33C each day. The uncertainty in the temperature forecast, primarily in AZ, remains tied to the gradual moisture return and subsequent increase in storm activity anticipated beginning early next week. A shortwave trough passing around the high pressure Monday is expected to increase storm activity in NM and West TX, which should in turn aid in low to mid level evening/overnight moisture fluxes back into AZ. NBM PoPs steadily increase day to day through next week, but most activity will likely remain isolated to Southeast AZ and higher terrain spots like the White Mtns and along the Rim. It will take some time for the South-Central lower deserts, including the Phoenix area, to see better chances if at all, with PWAT forecast to return to around 1.0" during the second half of next week. While the South-Central lower deserts may not see much thunderstorm activity, the potential for strong, long-traveling, outflow boundaries will be there as the environment will be ripe for strong downbursts. It is uncertain this far out how much influence regional thunderstorm activity, the moisture, and other mesoscale influences will have on temperatures, but the synoptic pattern, with the center of the high slowly trekking east across Southern NV and along the AZ/UT border, will likely still support extreme heat through next week. && .AVIATION...Updated at 0504Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation concerns are expected during the TAF period. Winds will follow typical diurnal trends, with occasional gusts upwards of 15-20 kts Saturday afternoon. Mostly clear skies will persist through the TAF period. Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns are expected during the TAF period. Winds at IPL will favor an E to SSE component, while winds at BLH will favor a S to SW component. Winds will overall remain light, aob 10 kts, outside of a few afternoon gusts Saturday upwards of 15-20 kts. Mostly clear skies are expected through the period. && .FIRE WEATHER... Hot and dry conditions will prevail across the area through much of next week as strong high pressure dominates. Excessively hot temperatures with highs generally between 112-120 degrees are expected across the lower deserts each day. Daily MinRH values through next week will fall to or below 15% across the lower deserts, while higher terrain areas in Arizona will mostly see 10-20%. Overnight recoveries will mostly fall in the 30-50% range. Winds will be fairly light most days and follow diurnal trends, occasionally gusting to 20 mph during the afternoon hours. The breeziest day looks to be Sunday, primarily across eastern districts, with afternoon wind gusts up to 20-30 mph. The combination of the very hot and dry conditions will lead to an increased fire danger threat. && .CLIMATE... Record Highs Phoenix Yuma El Centro --------- ------- ----------- July 6 116 (1942) 117 (2018) 118 (1966) July 7 118 (2017) 118 (2017) 121 (2017) July 8 115 (1985) 118 (1958) 117 (1942) July 9 116 (1958) 119 (1958) 117 (1958) July 10 115 (1958) 118 (1959) 116 (2021) && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Excessive Heat Warning until 8 PM MST Tuesday for AZZ530>555-559. CA...Excessive Heat Warning until 8 PM PDT Tuesday for CAZ560>570. && $$ DISCUSSION...Benedict AVIATION...Smith FIRE WEATHER...Benedict CLIMATE...Kuhlman