Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
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437 FXUS65 KPSR 051938 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 1238 PM MST Fri Jul 5 2024 .SYNOPSIS... Strong high pressure over the region will result in excessive heat conditions and mainly dry conditions through at least the first half of next week and possibly longer. Most of the lower desert locations are expected to see daily highs approach or even exceed 115 degrees. Some moisture return will bring increased thunderstorm chances back to the Arizona high terrain by the middle of next week. && .DISCUSSION... A strong ridge of high pressure is currently centered just off the northern CA coastline with a northerly flow encompassing the region. 500 mb height fields through the weekend and heading into all of next week will generally range between 594-597dm with a slow drift of the ridge towards Great Basin and Desert Southwest heading into the middle of next week. The northerly flow will continue to advect dry air into the region with PWAT values this weekend falling to as a low 0.6-0.7". Thus the dry air along with the subsidence from the high pressure will result in mostly clear skies and consequently hinder thunderstorm activity through at least the first half of next week. The combination of the enhanced 500 mb heights and the mostly clear skies will result in a several day stretch of extreme heat conditions, which will likely carryover through most if not all of next week. Lower desert high temperatures are expected to range between 112-120 degrees, with the highest readings expected across the western deserts with very little overnight relief as lows are expected to range between lower 80s to lower 90s. Multiple daily record high and warm low temperatures may be tied or broken. The extreme temperatures will lead to widespread major to locally extreme HeatRisk to materialize and thus Excessive Heat Warnings remain in effect through at least Tuesday. It is probable that the warning will need to be extended through the latter half of next week given that the forecast high temperatures will likely remain steady state. Given the prolonged nature of this extreme heat episode, it is crucial that people take all the necessary heat precautions such frequently hydrating, wear light-loose fit clothing, seek frequent breaks in the shade, and avoid strenuous outdoor activities during the hottest part of the day. Remember, heat is the number one weather-related killer in the country! As the center of the high pressure gradually shifts eastward into northern AZ and southern UT by the middle to latter half of next week, moisture levels will improve just enough that storm chances will increase across the higher terrain areas of eastern AZ towards portions of southeast AZ as well as the White Mountains and Mogollon Rim. However, across the south-central AZ lower deserts it will likely still remain mostly dry, which is why there is a good potential for the excessive heat conditions to continue through the end of next week. It looks like once the center of the high moves over the Four Corners Region by next weekend, a deeper push of monsoonal moisture will move in, which will help with increasing storm chances across the lower deserts as well as result in cooler temperatures. && .AVIATION...Updated at 1730Z. 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 this afternoon in the mid-teens, upwards of 20 kts. Other than a FEW mid-level clouds popping up over high-terrain areas, skies should be mostly clear through Saturday morning. Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns are expected during the TAF period. Winds at IPL will favor an E`rly component, with extended periods of variability through this evening. Winds may briefly try to switch out of the SW early tonight, but confidence in that shift is low at this time. At BLH, winds will favor a E/NE direction during the afternoon, before more diurnal trends take over by the evening hours. Mostly clear skies are expected through Saturday morning. && .FIRE WEATHER... Hot and mainly dry conditions will prevail across the area through the weekend and into the first half of next week as strong high pressure settles in from the northwest. Excessively hot temperatures with highs generally between 112-120 degrees are expected across the lower deserts each day through at least early next week. Daily MinRH values through early next week will fall between 5-15% across the lower deserts, while higher terrain areas in Arizona will mostly see 10-20%. Winds will be fairly light and follow diurnal trends, occasionally gusting to 20 mph during the afternoon hours. 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 5 116 (1983) 116 (1905) 115 (2007) 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...Lojero AVIATION...RW FIRE WEATHER...Benedict/Lojero CLIMATE...Kuhlman