415 FXUS65 KPSR 071140 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 440 AM MST Mon Jul 7 2025 .UPDATE...Updated 12z Aviation Discussion. && .KEY MESSAGES... -Generally dry conditions and hotter temperatures are expected this week with highs potentially exceeding 115 degrees across many of the lower desert communities by Wednesday -The hotter temperatures will result in widespread Major HeatRisk with Extreme Heat Warnings in effect for much of the region between Tuesday through Thursday -Slightly cooler temperatures expected by the end of the week through next weekend but still remaining above normal && .SHORT TERM /TODAY THROUGH TUESDAY/... Latest objective analysis depicts the subtropical high near the International Border with a cutoff low centered just off the central CA coast. The cutoff low will continue to limit the westward migration of the subtropical high for today and as a result high temperatures this afternoon are likely to be rather similar to what they were yesterday as readings will top out near 110 degrees on average across the lower deserts. By Tuesday, the cutoff low is projected to weaken allowing the subtropical high to migrate westward and become stationed on top of Arizona and strengthen in the process as 500 mb height fields increase to 596-598dm. This will translate to hotter temperatures with afternoon highs across the lower deserts ranging between 109-113 degrees with the hottest temperatures across the lower deserts of south-central AZ, including the Phoenix Metro. As a result, areas of Major HeatRisk show up across the majority of the south-central AZ lower deserts with Extreme Heat Warnings in effect. Any storm activity through Tuesday will be limited to portions of the High Country as well as portions of southeast AZ as meager moisture profiles and increasing subsidence from the strengthening high will hinder any potential for more widespread convection. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Wednesday is expected to be peak of the extreme heat episode as the subtropical high becomes more expansive across the Desert Southwest and strengthens slightly. This will translate to widespread high temperatures of 115+ degrees across the lower deserts with the latest NBM showing a greater than 80% of occurrence. Temperatures of this magnitude will result in widespread Major HeatRisk across the majority of the region with Extreme Heat Warnings in effect across virtually the entire CWA with exception of the elevations above 4000 feet east of Phoenix where Heat Advisories are effect. Both Phoenix and El Centro have a 70% chance of at least tying a daily record high. The subtropical high is expected to weaken slightly heading into Thursday as what is leftover from the aforementioned cutoff low moves eastward through the Great Basin and Intermountain West Regions, resulting in a suppression of the high. Temperatures are expected to cooldown slightly but still hot enough for areas of Major HeatRisk to remain in place with Extreme Heat Warnings in effect for all of the lower deserts. Heading into the end of the week and next weekend, the high will continue to slowly migrate westward towards the southern CA coastline and as a result heights aloft will continue to decrease slightly. This will translate to slightly cooler temperatures, enough to drop readings below extreme heat thresholds but still remaining above normal as afternoon highs will hover around 110 degrees across the lower deserts. With the subtropical high stationed over the region and the flow pattern not favorable for deeper moisture advection into the region, conditions are expected to remain mostly dry for the next several days across the majority of the region with any storm potential to be confined across the White Mountains through the southeastern third of AZ. In fact, virtually all of the EPS and GEFS ensemble members do not indicate any measurable rain potential for the lower deserts until at the earliest the middle of next week when potentially the subtropical high migrates into the Four Corners Region, resulting in a more favorable flow pattern for deeper moisture advection and thus more widespread storm chances. && .AVIATION...Updated at 1140Z. South Central Arizona including KPHX, KIWA, KSDL, KDVT: No major weather issues will exist through Tuesday morning under mid/high cloud decks that will be primarily relegated to the mountains east of the terminals by the afternoon. Winds will generally follow diurnal patterns, with current light east winds switching west by late morning. Confidence is moderate to good that the typical nocturnal switch to east winds will not take place at KPHX tonight. Southeast California/Southwest Arizona including KIPL and KBLH: No major weather issues will exist through the next 24 hours under clear skies. Winds will mostly favor SE to S at both terminals, with a relatively short period of SW winds during the evening and slightly stronger speeds (10-15 kts sustained) anticipated at KBLH this afternoon compared to yesterday. && .FIRE WEATHER... Above normal temperatures will persist throughout the week as lower deserts highs exceed 110 degrees. MinRH values will generally be in the low to mid teens with MaxRH values ranging between 25-45% for most of the area, with the exception across Imperial and southern Yuma Counties where periodic gulf surges will result in MaxRH values to exceed 50%. The overall wind pattern will follow the familiar diurnal trends, with some afternoon/early evening breeziness. Very minimal rain chances will exist throughout the week with CWR <10% through at least next weekend. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Extreme Heat Warning from 10 AM Wednesday to 8 PM MST Thursday for AZZ530>533-535-536. Extreme Heat Warning from 10 AM Tuesday to 8 PM MST Thursday for AZZ534-537>540-542>544-546-548-550-551-553>555-559-560. Heat Advisory from 10 AM to 8 PM MST Wednesday for AZZ557-558- 563. Extreme Heat Warning from 10 AM to 8 PM MST Wednesday for AZZ541- 545-547-549-552-556-561-562. CA...Extreme Heat Warning from 10 AM Wednesday to 8 PM PDT Thursday for CAZ560>570. && $$ SHORT TERM...Lojero LONG TERM...Lojero AVIATION...Whittock FIRE WEATHER...Lojero