textproduct: NWS Phoenix

UPDATE...UPDATED 00z Aviation Discussion

KEY MESSAGES

- Unusually warm temperatures will continue to challenge daily records through the week resulting in pockets of moderate HeatRisk.

- The unseasonably hot conditions may be dangerous, especially for any strenuous outdoor activities without proper hydration and frequent breaks in the shade, or air conditioning.

- Temperatures should retreat from record levels early next week as the weather pattern shifts away from stagnant high pressure.

SHORT TERM /Today through Wednesday/

Longwave features over North American remain quasi-stationary this afternoon with mean troughing over the east and ridging across the west. While the amplitude of these features driving sensible weather has decreased somewhat, the magnitude of the anomalies has only been partially dampened. Over the local forecast area, robust positive height anomalies continue with objective analysis indicating H5 heights around 586dm, and only recently reduced due to the proximity of a cutoff low meandering off the northern Baja coast. All global and high resolution output show midtropospheric anti-cyclonic ridging re-intensifying over the next 48 hours such that H5 heights near 590dm return to SE Arizona starting another warming cycle. Ensemble guidance spread remains narrow yielding excellent forecast confidence of high temperatures ~20F above normal, and breaking records for the next several days. Due to more efficient nocturnal cooling and limited magnitude of these afternoon readings, only spotty and marginal moderate HeatRisk will be reached.

LONG TERM /Thursday through Sunday/

The H5 ridge will remain the dominant feature over the Desert Southwest through the weekend, keeping any noticeable relief out of sight through at least the next 6 days. Once the thermal profile fully catches up to the amplification of the ridge, widespread triple digits will make their return to lower elevations during this timeframe. Lower desert highs Thursday-Friday will range between 99- 103 degrees, continuing the record-trend for the forecast area. In fact, current forecast highs for Phoenix Sky Harbor would break each daily record high from now until Saturday. Having already eclipsed five consecutive daily records, it appears likely that this streak will reach at least 11 days before all is said and done. The only noticeable weather change projected during the week is perhaps some breezy conditions Thursday as the Baja trough cycles around the periphery of high's center before ejecting over the Great Basin.

Not to get everyone's hopes up, but there may be at least some relief on the near horizon. Global ensembles are in decent agreement regarding the center of the ridge migrating eastward toward the Plains by the weekend, imparting southerly flow over the region. This would set up a quasi-monsoon pattern as the southerly flow would tap into sub-tropical moisture, potentially pushing PWATs toward 200-250% of normal. This would, at a minimum, push considerable cloud cover overhead, limiting diurnal heating resulting in relatively cooler temperatures. Depending on the depth of the moisture profile, it may also create a favorable environment for showers and thunderstorms for parts of the forecast area. As of now, any rain potential is focused over the high terrain of eastern Arizona as orographic influences create a better setup for precipitation. The overall synoptic lift profile doesn't look all that promising currently, so any rainfall coverage would likely be limited, but a fair amount of uncertainty remains so this will be something to keep an eye on in the coming days.

AVIATION

Updated at 2335Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation weather concerns under some passing high clouds can be expected throughout the TAF period. Winds will continue to exhibit the typical diurnal tendencies with speeds generally under 10 kts.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather concerns under some passing high clouds can be expected throughout the TAF period. Southeasterly winds are expected at KIPL while southerly winds are expected at KBLH. Overall wind speeds will generally remain aob 10 kts, with periods of light variability expected, especially during the overnight and early morning hours.

FIRE WEATHER

Record heat along with dry conditions will persist through this week. MinRHs will generally range between 5-10%, with portions of the western districts being the exception during the next few afternoons, as an increase in Gulf of California moisture will push MinRH values for these areas closer to 15-20%. MaxRH values will follow a similar pattern with readings generally between 20-40% for the eastern districts as higher readings closer to 50-70% are observed for western districts locales the next couple of mornings. Winds will be generally light and follow diurnal trends with typical afternoon upslope breeziness through Wednesday. More widespread and stronger gusts may come into play during the latter portion of the week and into the weekend. With very dry air in place, any stronger winds would result in periods of elevated fire weather conditions.

CLIMATE

Daily record highs through this week:

Date Phoenix Yuma El Centro ---- ------- ---- --------- 3/23 93 in 1990 96 in 1990 93 in 1990 3/24 96 in 2025 97 in 2025 96 in 2025 3/25 99 in 2025 99 in 1896 99 in 2025 3/26 100 in 1988 99 in 1988 98 in 1988 3/27 98 in 1986 100 in 1986 99 in 1988 3/28 95 in 2015 98 in 2015 98 in 2015

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...None.