074 FXUS65 KPSR 162327 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 427 PM MST Mon Jun 16 2025 .UPDATE...Updated 00z Aviation Discussion. && .KEY MESSAGES... - Hot and dry weather is forecast throughout the entire week with the hottest day expected to be Thursday. - Extreme Heat Warnings have been issued or extended through much of the workweek across south-central Arizona for high temperatures ranging from 108 to 116 degrees across the south- central Arizona lower deserts. - Widespread Moderate HeatRisk will be seen throughout the week before widespread Major HeatRisk prevails Thursday across south- central Arizona. && .DISCUSSION... Hot and dry weather with extreme heat conditions continue as the subtropical ridge of high pressure remains the dominant weather feature over the region. Latest look at objective analysis this afternoon shows the center of the high near the AZ/NM/MX border, keeping heights over our area around 592-594 dm. With the ridge persisting over the region, temperatures remain above normal with afternoon temperatures so far today reaching or exceeding 110 degrees in many areas across the lower deserts. Areas of Major HeatRisk continue today with an Extreme Heat Warning in effect through this evening for much of the area. Meanwhile, a shortwave trough currently pushing into northern California will continue to propagate eastward through the Great Basin and into Utah/northern Arizona going into early Tuesday. While this disturbance will be weak, it will help to flatten the subtropical ridge and somewhat push it to the south, leading to height falls and a slight drop in temperatures for Tuesday. Guidance show 500 mb heights decreasing to around 590 dm with afternoon highs slightly decreasing ~2-3 degrees to 108-113 degrees across the lower deserts Tuesday. Temperatures then begin to trend back up Wednesday following the passage of the trough as the subtropical ridge builds back over the Desert Southwest. Ensemble guidance show 500 mb heights rising for the middle part of the week before peaking around 592-594 dm by Thursday. Thursday will be the hottest day for most areas later this week as forecast highs rise to around 112-116 degrees. This will lead to widespread Major HeatRisk across south-central Arizona Thursday. Thus, new Extreme Heat Warnings have been issued. Despite the absence of Major HeatRisk on Tuesday, have decided to go ahead and extend the Extreme Heat Warning for the Phoenix metro through Friday as temperatures don`t lower much and will remain near Major HeatRisk thresholds. Temperatures Wednesday and Friday will be quite similar to each other and will flirt with Major HeatRisk thresholds. Thus, after Tuesday the Extreme Heat Warning will expand to include most of south-central Arizona Wednesday through Friday. Temperatures begin to trend down Friday as a potent Pacific trough pushes into the western CONUS. By Saturday, forecast highs drop below 110 degrees for most lower desert locales. This trough should continue to keep lower heights over our region into early next week with temperatures eventually dropping to around or even a few degrees below normals. Models have been trending toward a stronger trough as well as a slower progression, likely keeping dry air over most if not all of our region. Modest monsoon moisture over Mexico still tries to push northward into far southeast Arizona by early next week, but with the trough providing southwesterly dry flow this moisture will have a hard time gaining any foothold within our region. && .AVIATION...Updated at 2330Z. South Central Arizona including KPHX, KIWA, KSDL, KDVT: No major aviation concerns through the TAF period under clear skies. Winds will follow typical diurnal patterns with periods of variability between transition periods. Afternoon and early evening gustiness 15-20 kts out of the westerly direction will continue to be common through the period. Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns will exist through the TAF period under clear skies. Winds at KIPL favor the SE until a shift to the W this evening 10-15 kts before subsiding late tonight. KBLH will maintain a S to SW component into tonight before a W wind tomorrow. && .FIRE WEATHER... Hot and dry conditions with some afternoon breeziness will continue early this week. Temperatures will remain above normal with highs near or above 110 degrees each day across the lower deserts. Wind patterns will continue to follow diurnal trends (upslope and downvalley) with afternoon gusts up to around 20-25 mph, particularly across the higher terrain east of Phoenix. Humidities will stay low with MinRHs between 5-10% and overnight MaxRHs only between 15-30%. Afternoon gusts combined with the dry conditions may lead to some elevated fire weather conditions, especially across the higher terrain east of Phoenix. High pressure will remain the dominant weather feature through the rest of the week with temperatures remaining above normal through at least Friday and afternoon MinRHs likely staying between 5-10% each day. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Extreme Heat Warning until 8 PM MST this evening for AZZ530>536- 538-539-547-552>556-559>562. Extreme Heat Warning until 8 PM MST Friday for AZZ537-540>544- 546-548>551. Extreme Heat Warning from 10 AM Wednesday to 8 PM MST Friday for AZZ534-538-539-547-552>556-559>562. CA...Extreme Heat Warning until 8 PM PDT this evening for CAZ562>567- 569-570. && $$ DISCUSSION...Smith/Kuhlman AVIATION...Young FIRE WEATHER...Smith/Kuhlman