Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
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742 FXUS65 KPSR 110810 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 110 AM MST Sat May 11 2024 .SYNOPSIS... Temperatures will steadily warm through early next week with many lower desert communities flirting with the 100 degree mark throughout much of the week. Seasonably dry conditions with typical afternoon spring breezes will also be common across the local area with showers and storms relegated to mountain locations of northern and eastern Arizona. && .DISCUSSION... Early morning WV satellite imagery reveals a closed circulation continuing to spin over the Great Basin comprising the eastern foot of an expansive omega block. The central portion of this blocking ridge was covering much of the northeast Pacific basin with anomalously high heights folded into the Pacific NW. However, this blocking regime is already showing signs of decay with strong upstream wave energy breaking into and dampening the high pressure axis. This upstream kicker wave in combination with an enhancement in subtropical jet energy will also act to eject the aforementioned Great Basin circulation, resulting in steady height rises over the SW Conus through the next 72 hours. Excellent forecast confidence exists the next several days characterized by minimal ensemble spread and a very narrow range of guidance within the NBM. Near normal temperature again today will warm decidedly early next week as H5 heights increase to around 578dm. With this midlevel height forecast not particularly anomalous, surface temperatures will warm into an above normal category, but nothing unusual for mid May. At this time, Monday appears to be the warmest day with better than a 75% chance of widespread 100F readings through the lower elevations of western zones, and greater than a 60% chance of KPHX breaching this threshold. Otherwise, seasonably deep mixing juxtaposed with jet energy situated on the southern flank of the circulation center will support frequent afternoon wind gust 20-30 mph the next couple days. By the middle of the week, ensemble output remains consistent in translating the dampened ridge eastward with an extension of the original upstream kicker wave descending into southern California. H5 heights should be eroded closer to 572dm allowing temperatures to recede somewhat closer to the climatological normal. Although NBM guidance spread remains narrow during this time frame, feel a trend towards the lower end of the guidance envelop is warranted given the synoptic pattern. Regardless, this modest cooling will only be temporary as lower heights should quickly be absorbed into downstream flow by the end of the week. While dry weather should persist across the CWA, evidence is growing in support of afternoon deep convection over the mountains of northern AZ with flow trajectories favorable towards bringing gusty outflow winds into lower desert locations (Wednesday and Thursday most supportive of this outcome). NAEFS members continue to suggest some form of high pressure ridging returning to the region towards the end of next week forcing another distinct warming trend. Some uncertainty regarding the magnitude of ridging and height rises still exists, however the preponderance of model output suggests H5 heights rebounding above 582dm next weekend with some individual members highlighting readings above 585dm. Based on these trends among ensemble membership, confidence and probabilities are growing regarding a more pronounced warming event and expansive 100F+ temperatures next weekend. && .AVIATION...Updated at 0554Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Typical Spring diurnal wind patterns are favored through Saturday at all terminals. West winds should shift east by 10-11Z. Winds shift back west by 17-18Z. Wind gusts Saturday afternoon will pick up by 20-21Z, peaking up to 20-25 kts. Skies will remain mostly clear, with FEW 12K ft cumulus in the afternoon. There will be convection a ways north Saturday afternoon, and not an impact to the metro area. However, there are indications an outflow, with mainly a wind shift, could move south toward the metro area in the evening. Southeast California/Southwest Arizona including KIPL and KBLH: Light winds will prevail through tonight at both terminals. Winds will remain light at KIPL through the day Saturday, while N to NW winds increase at KBLH in the afternoon with gusts to around 20 kts. Sundowner winds at KIPL Saturday evening will be capable of gusting up to 20 kts. Skies will remain mostly clear, with FEW 12-14K ft cumulus tonight and Saturday afternoon. && .FIRE WEATHER... Temperatures will continue warming through early next week, reaching and maintaining an above normal threshold. Seasonably dry weather should also persist across the districts with minimum afternoon humidity levels around 10% at lower desert elevations and in the teens over higher terrain areas. Overnight recovery will range widely from poor to fair in a 20-50% range. Typical afternoon spring breezes 20-25 mph will be common over most areas, though it should be noted there is at least a 25% chance of enhanced gusts and erratic directions at times during the middle of next week from outflows resulting from showers and storms over the mountains of northern AZ. Nevertheless, the combination of periodically gusty winds, dry fine fuels, and low humidity levels will yield an occasionally elevated fire danger throughout the week. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...18 AVIATION...Benedict FIRE WEATHER...18