000 FXUS65 KPSR 202020 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 120 PM MST Mon May 20 2024 .SYNOPSIS... After a fast moving weather disturbance clears the region this evening, dry conditions with temperatures not far from the seasonal normal will prevail the remainder of the week. As is typical during late May, gusty winds during the afternoon and early evening hours will be common across the region. && .DISCUSSION... Early afternoon WV imagery and objective analysis depicts a compact negative PV anomaly and subtropical jet segment moving over the northern Baja in the process of phasing with northern stream energy deepening towards the Great Basin. This southern shortwave has entrained a notable plume of moisture with IVT in excess of 500 kg/m/s focused into southern AZ, however the totality of this advection is occurring above the H7 layer precluding any more than a few sprinkles/light showers along a decaying cold front through this evening. Evaporational effects with boundary layer T/Td spreads exceeding 50F and mechanical momentum transfer associated with elevated precipitation echoes along the cold front will support scattered outflows and strong, gusty winds into early this evening before activity shifts out of the forecast area. Conceptually and considering past historical cases along with 12Z HREF output, there is around a 50% chance of 40+ mph gusts later this afternoon around the Phoenix metro yielding isolated instances of blowing dust (based largely on nearby land use practices) and significant complications for ongoing wildfires. Conditions will dry out quickly with wind speeds gradually weakening following the frontal passage this evening. Ensemble members remain in excellent agreement with respect to the overall Conus flow pattern the remainder of the week highlighted by broad longwave troughing covering the western half of the United States. With H5 heights trapped in a 576-580dm range across the CWA, forecast guidance spread is extremely narrow resulting in excellent confidence of a near persistence forecast throughout the week with temperatures hovering not far from climatology. Several low amplitude shortwaves will be embedded in the larger western Conus cyclonic flow regime, mostly propagating over the Great Basin, although with a subtle reflection in the southern stream as the jet configuration still remains partially split. Current indications suggest Wednesday and Saturday as the best opportunities for modest height falls associated with the shortwave passage where afternoon/early evening wind gusts could be enhanced slightly, albeit with limited impacts. && .AVIATION...Updated at 1815Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: The main aviation weather concern today will be the potential for strong gusty winds mid afternoon as a line of mostly virga showers and some light rain is likely to push through the Phoenix Metro. West winds will start to gust 20-25 kt around 19Z out ahead of the approaching cold front. Confidence is good that virga showers and some light rain showers will form along the cold front that will move through the Metro between 20-22Z. With this cold front winds will gust, out of the west/southwest, up around 35 kt, with some periodic gusts up around 40 kt also possible. After the cold front and virga/light showers exit the Metro ~22Z, westerly winds will start to diminish, but stay elevated (25-35 kt) through sunset. After sunset westerly winds will quickly die off with speeds around 5-10 kt. Winds will then switch back to the east during the overnight hours. SCT-BKN clouds with bases aoa 10-12 kft will quickly clear out this evening behind the cold front. Southeast California/Southwest Arizona including KIPL and KBLH: The main aviation weather concern today will be gusty southwest to west winds. Winds at KIPL will predominately be out of the west and at KBLH will predominately be out of the southwest through the TAF period. At both terminals current gusts of 20-25 kt will pick up around 20-21Z with gusts of 30-35 kt. Winds will then lessen a little bit this evening with gusts going back down to 20-25 kt. Wind speeds will then lessen even more, down to around 5-10 kt for the overnight and early morning hours tomorrow. High clouds currently overhead will clear out this afternoon, with clear skies for the remainder of the TAF period. && .FIRE WEATHER... Very typical mid/late May weather will prevail the remainder of the week highlighted by seasonably warm temperatures, dry conditions, and frequently breezy afternoon/early evenings. Minimum afternoon humidity levels will mostly fall into the single digits with some modest improvement into a 10-20% level towards the end of the week. This will follow generally poor to fair overnight recovery of 20- 40%. Wind gusts 15-25 mph will be common through the week with some daily enhancement during the latter half of the week near terrain features resulting in an elevated fire danger. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...18 AVIATION...Berislavich FIRE WEATHER...18