Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
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488 FXUS65 KPSR 032310 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 410 PM MST Wed Jul 3 2024 .UPDATE... Updated Aviation && .SYNOPSIS... Strong high pressure system building across the region through the end of the week will result in drying conditions and hotter temperatures. This will result in excessive heat conditions building across the majority of the region starting on Thursday and likely lasting through at least the first half of next week as high temperatures across the majority of the lower desert locations approach 115+ degrees. && .DISCUSSION... A strong high pressure system, currently sitting just off the California coast, will gradually increase the northerly flow across throughout the day, with drier air being advected into the region. Latest SPC mesoanalysis shows PWATs across south-central AZ ranging between 1.0-1.2" and it is expected that these values continue to drop during the next couple of days. In terms of storm chances this afternoon, with the drier surge of air, activity will be very isolated with a slight chance of a thunderstorm developing across southern Gila County. Otherwise, a fairly tranquil weather day is expected throughout the region. The main concern heading through the next several days will continue to be the excessive heat that is expected to materialize across the majority of the region. As high pressure just off the west coast of California continues to gradually shift eastward into the Great Basin Region through the end of the week and the upcoming weekend, northerly flow will continue to maintain a fairly dry air mass in place with mostly clear skies and near zero storm activity. The mostly clear skies along with 500 mb height fields across the region increasing to 594-597dm will cause surface temperatures to increase. Highs across most of the lower desert communities will likely approach 115 degrees with the potential that some of the deserts of southeast CA approach 120 degrees. Temperatures this high will increase the HeatRisk into the major category with some localized areas reaching the extreme category. This signifies that most of the general population will be at risk of heat-related impacts if the proper precautions are not taken. As a result of the extreme heat expected to materialize, Excessive Heat Warnings are in effect through at least next Tuesday. Heading into next week, ensemble guidance continues to be in excellent agreement in showing the ridge of high pressure remaining parked over the Great Basin at least through the first half of the week with not much change in the overall temperatures. Thereafter, there are signs that by the middle to latter half of next week the ridge axis will gradually migrate eastward to the point that a more favorable moisture return pattern will more likely set up across the region. Timing out when this will occur is still a bit uncertain at this time. However, once the moisture increases and storm activity in concert picks up, we should see some cooling in the overall high temperatures. If the overall moisture return is delayed until the end of the week, then there is the potential that the Excessive Heat Warnings that are currently in effect through next Tuesday could be extended another day or two next week. && .AVIATION...Updated at 2310Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: No large weather issues will exist through Thursday afternoon with only afternoon cloud decks hovering over mountains well east of the terminals. West winds should predominate over the metro for the vast majority of the TAF period with only a brief period of easterly or light and variable winds around sunrise. Gusts up to 20kt will be possible during the late afternoon/early evening, and there could even be some speed enhancement arriving late evening before weakening again late night. Southeast California/Southwest Arizona including KIPL and KBLH: No major weather concerns will exist through Thursday afternoon under clear skies. A SE wind component will be preferred at KIPL with some variation between SE and SW at KBLH. Occasional afternoon/early evening gusts to 20kt should be expected. && .FIRE WEATHER... Drier conditions will continue to filter into the region through Thursday leaving only slight chances for some showers and maybe a weak thunderstorm across the eastern Arizona high terrain this afternoon. Rain chances will generally come to an end altogether starting Thursday. As conditions continue to dry out, hotter temperatures are expected with excessive heat spreading eastward through much of Arizona. MinRH values across the lower deserts will fall to around 15% today, while higher terrain areas east of Phoenix see 20-25%. Winds will follow diurnal trends, occasionally gusting to 20 mph during the afternoon hours. MinRHs starting Thursday will mostly be between 10-15% over the lower deserts to 15-20% over higher terrain areas. Temperatures by Thursday and through early next week are expected to be well above normal with lower desert highs over the eastern districts up to around 115 degrees and even hotter over some of the western districts. The combination of the very hot and dry conditions through the next several days will to an increased fire danger threat. && .CLIMATE... Record Highs Phoenix Yuma El Centro --------- ------- ------------ July 4 118 (1989) 117 (1957) 117 (1969) 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. Excessive Heat Warning from 10 AM Thursday to 8 PM MST Tuesday for AZZ531>555-559. CA...Excessive Heat Warning until 8 PM PDT Tuesday for CAZ562-566-567- 569-570. Excessive Heat Warning from 10 AM Thursday to 8 PM PDT Tuesday for CAZ560-561-563>565-568. && $$ DISCUSSION...Lojero AVIATION...18 FIRE WEATHER...Kuhlman/Lojero CLIMATE...Kuhlman