textproduct: NWS Phoenix

KEY MESSAGES

- Extreme Heat Warnings remain in effect through Saturday with daily Major to Extreme Heat Risk.

- Lower desert highs are likely to reach or exceed 110 degrees through the rest of the work week and even into the weekend, peaking around daily records during the middle of the week.

- Monsoon storm chances will essentially come to an end starting today before slowly returning this coming weekend.

SHORT TERM /TODAY THROUGH THURSDAY/

GOES mid-level WV imagery and RAP40 500mb analysis show southerly flow aloft with dry air being advected into the region. The subtropical high is currently positioned over southeastern NM and western TX, but over the course of this week the core of the high will push westwards and sit over southeastern AZ/ southwestern NM. This will lead to winds aloft shifting out of the south to southwest, further drying the atmosphere. Ensembles show PWATs falling to near 80% of normal, additionally 1000- 700mb mixing rations are also forecasted to fall to between 6-7 g/kg. H5 heights associated with the high will most likely peak by Wednesday between 594-597 dam, or near climatological maximum for late August. This will correlate to afternoon highs in across the lower deserts to be between 110F-115F (5F-10F above normal). Overnight lows will offer very little relief from this heat, with lows throughout the week continuing to be in the upper 80s to lower 90s. These conditions has lead to widespread Major to Extreme HeatRisk across the region and as a result an Extreme Heat Warning will remain in effect through Saturday for the lower deserts, and has been expanded to include JTNP, Globe, and Tonto Basin through Friday evening.

LONG TERM /FRIDAY THROUGH SUNDAY/

Ensembles continue to point towards the subtropical high shifting back eastwards starting Friday as a troughing feature moves into the Northwestern U.S./ Canadian boarder. As the trough pushes eastwards PWATs begin to improve, being back above normal, near 1.5"-1.7" by Saturday, and is expected to remain through at least the weekend. 1000-700MB mixing ratios are forecasted to be generally back above 10 g/kg which should be enough for rain chances to return to the region as the NBM/WPC PoPs are currently reflecting a 20-30% chance. This is a decent increase from previous runs but still several days out so models are still subject to change, but currently looks promising for at least the eastern high terrain. Temperatures will notably reduce by Sunday for most of the region, falling to near normal.

AVIATION

Updated at 0505Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

No aviation concerns under FEW-SCT mid/high cloud decks can be expected throughout the TAF period. The overall wind pattern will follow the typical diurnal tendencies with speeds aob 10 kts. Periods of light variability can be expected, especially during diurnal transitions.

Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation concerns under FEW-SCT mid/high cloud decks can be expected throughout the TAF period. Winds will generally fluctuate between the southeast to southwest with speeds aob 10 kts along with periods of light variability during the morning hours.

FIRE WEATHER

Hot and seasonally dry conditions will prevail for much if not all of the coming week. Strong high pressure will settle over the region by midweek with gradual drying conditions. Minimum RHs will mostly fall into the teens starting today. Temperatures will be around 5-10 degrees above normal, with lower desert highs eclipsing 110 degrees nearly every afternoon. Outside of distant thunderstorm outflows, expect overall light winds following typical diurnal tendencies with some modest afternoon upslope gustiness.

CLIMATE

Record highs:

Date Phoenix Yuma El Centro ---- ------- ---- --------- Aug 25 113 in 2011 116 in 1962 117 in 1962 Aug 26 117 in 2011 115 in 2020 115 in 1981 Aug 27 114 in 2023 120 in 1981 117 in 1981 Aug 28 117 in 2023 118 in 2023 117 in 2009 Aug 29 116 in 2023 117 in 1954 117 in 2005

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Extreme Heat Warning until 8 PM MST Saturday for AZZ530>555-559- 560.

Extreme Heat Warning from 10 AM this morning to 8 PM MST Friday for AZZ556-561-562.

CA...Extreme Heat Warning until 8 PM PDT Saturday for CAZ562-565>567- 569-570.

Extreme Heat Warning from 10 AM this morning to 8 PM PDT Friday for CAZ561-563-564-568.