Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
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717 FXUS65 KPSR 031005 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 305 AM MST Wed Jul 3 2024 .SYNOPSIS... Drying conditions will continue over the next couple of days with limited shower activity mainly over higher terrain areas. Strong high pressure will also build into the region through the end of the week leading to even hotter temperatures and expanding excessive heat over all of the lower deserts starting Thursday. Excessive heat conditions are expected to prevail through the weekend into next week with highs across the lower deserts likely topping 115 degrees in some locations. && .DISCUSSION... The excessive heat conditions remain the main forecast concern through at least early next week as a current record strong high center off the California coast gradually shifts eastward into our region over the next several days. Dry air has worked its way into much of the region over the past day and half, but modest monsoon moisture still remains in place across southeast Arizona. In fact, we are currently seeing some shallow moisture advection working its way into the Phoenix area with more moisture seeping off the GoC into southwest Arizona later this morning. This increase in shallow moisture will be short-lived however as northerly flow increases west to east today bringing in another surge of dry air. Through this afternoon some mostly isolated light showers will continue to be possible south and east of Phoenix where there is enough lingering moisture present. Temperatures will continue to inch upward over the next several days as the high pressure ridge overtakes the region. The slight boost in moisture today should keep temperatures similar to yesterday`s highs, but it still means most lower desert areas will top 110 degrees this afternoon to as high as 115 degrees across southeast California. Scouring out whats left of the boundary layer moisture Thursday into Friday will make it easier for temperatures to climb, while also having heights rise due to the increasing influence of the ridge currently off the West Coast. High temperatures are expected to climb a degree or two per day through Friday with readings on the 4th of July ranging from 111-115 degrees in the Phoenix area to 113-118 degrees over the western deserts. Due to this expected rise in temperatures starting Thursday, Excessive Heat Warnings will go in effect for the majority of the area. From Friday through at least next Tuesday, the ridge center is forecast to gradually shift eastward reaching southern California and western Arizona by early next week. Luckily, guidance shows the ridge weakening some as it comes onshore with the core of the high dropping to around 596dm. However, during this entire period our region will see H5 heights ranging from 593dm across eastern Arizona to 596dm in southeast California. For some prospective, these heights are fairly common for our region during the summer and barely even make it into the 90th percentile of climatology. However, because we lose our moisture temperatures will more easily climb upward with these increasing heights, likely flirting with daily record highs starting Friday and lasting through a good portion of next week. NBM forecast highs starting Friday rise to 112-116 degrees across the south-central Arizona lower deserts to 115-120 degrees across far southwest Arizona and southeast California. At the moment, there is very little variation in forecast highs from Friday through the middle of next week, so it`s quite likely the current Excessive Heat Warning which goes through next Tuesday will end up getting extended. This heat will increase the HeatRisk into the Major category for much of the area from Phoenix westward by Friday with even portions of southeast California bumping up into the Extreme category. Model guidance does start to indicate some potential monsoon moisture returning into southern Arizona at some point late next week or the following weekend, but that will all depend on how long it takes for the ridge center to shift far enough east of the area. && .AVIATION...Updated at 0505Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: No significant weather issues will exist through Wednesday night with cloud decks concentrated mainly over higher terrain areas east of the terminals. A long traveling outflow will induce an easterly component across the metro around midnight with good confidence that directions will revert back to a westerly direction much earlier than usual mid/late Wednesday morning. Occasional gusts 15-20kt will be common again during the afternoon/early evening. Storms and outflow winds should not be an issue for the metro aerodromes Wednesday. Southeast California/Southwest Arizona including KIPL and KBLH: No major weather issues will exist through Wednesday night under clear skies. Confidence is good that winds should revert to a S/SE direction overnight with variability likely becoming more common towards sunrise. Only modest occasional afternoon/evening gusts should be experienced Wednesday with typical veering to a SW direction during the evening. && .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. && .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...Kuhlman AVIATION...18 FIRE WEATHER...Kuhlman CLIMATE...Kuhlman