textproduct: NWS Phoenix

KEY MESSAGES

- Extreme heat will build over the region during the next few days and last through at least the weekend. Near record high temperatures can be expected Friday through Sunday.

- In response to the very hot conditions, Extreme Heat Warnings are in effect regionwide now until Monday.

- Drier air over the region will confine any chances for showers and thunderstorms over far eastern Arizona high terrain areas through at least Sunday.

SHORT TERM /Today through Friday/

Current objective analysis reveals the center of the sub-tropical high continuing to hover over New Mexico as it begins to strengthen. 500mb RAP analysis suggests peak heights have reached around 597dm, but further amplification is expected through the end of the work week. Ensembles continue to suggest that heights aloft will peak around 598-600dm by Friday, which would be near climatological records for this time of year, to put how strong this area of high pressure will be into perspective. This setup will translate to very hot conditions regionwide, with afternoon highs between 108-116 degrees being common across the lower desert today and once again Friday. In response, Extreme Heat Warnings have gone into effect and will continue into at least the start of next week.

The presence of weak troughing over the western CONUS helped pull in some relatively dry air (at least for this time of year), which has greatly limited monsoonal activity potential. Dew points have fallen into the lower and middle 50s for a good chunk of our forecast area, with some locations even seeing readings in the middle 40s. This is much lower compared to where we were 48 hours ago, when middle 60s and lower 70s were more common. Taking a look at the atmospheric columns as whole, PWATs have taken a decent hit too, now ranging between 0.5" over far western portions of our CWA, to around 1.2-1.3" across south-central Arizona. Moisture profiles do no support much in the way of showers and thunderstorms, both today and tomorrow, even across the vast majority of Arizona but a few convective cells cannot be completely ruled out for southeastern portions of the state and the White Mountains, but coverage will be very limited.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Model ensembles have changed little from yesterday's runs showing the peak of the ridge and temperatures occurring on Saturday before the ridge weakens Sunday into Monday. NBM foreast highs have come down a degree or so from yesterday, but it is hard to find a good reason why. Forecast confidence remains high that some daily heat records are likely to be broken this weekend with southeast CA lower deserts reaching 115-120 degrees to 113-117 degrees across the Arizona lower deserts. To give some prospective, Phoenix has only reached 116 degrees or higher 18 times after July 30th, half of which occurred since 2023 and only reached 117 degrees or higher 6 times. The probability of KPHX hitting at least 116 degrees Friday-Sunday is 20%, 67%, and 35% respectively. For Saturday, the NBM also shows a 20-25% probability of tying the all-time hottest temperature in August of 118 degrees which occurred August 7, 2025. We will have some relief from the extreme heat at night, more so across the western deserts where lows should still dip into the mid to upper 80s. The bulk of the Phoenix metro should have lows only in a 90-95 degree range Friday-Sunday.

Any potential rain chances over the weekend are trending even lower with guidance mostly showing any decent moisture advection holding off until late Sunday into Monday. Some members still show some improved chances over the eastern Arizona high terrain convection as early as Sunday with potential for outflows into the Phoenix area Sunday evening, but it seems more likely that will not occur until Monday at the earliest. Guidance does agree on the ridge noticeably weakening by Monday with H5 heights dropping to 594-596dm, but the residual heat over the region is expected to keep extreme heat conditions around through Monday. The ridge center should also begin to drift back to the northeast, closer to the Four Corners area by around next Tuesday. If and when this happens, it should open up portions of the region for better moisture advection out of the southeast. Monsoon storm chances are expected to gradually improve going into the middle of next week, while NBM forecast highs drop back to within a few degrees of normals.

AVIATION

Updated at 1720Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation concerns are expected through Friday afternoon under FEW-SCT and at times BKN mid to high cloud decks. Winds will continue to favor westerly directions through much of the period with afternoon/evening gusts into the middle to upper teens at times. There is a potential for a distant outflow boundary to pass into the Phoenix area from the S/SE late evening into the overnight hours but confidence is too low to include in the TAFs. Confidence is also low on a full easterly wind shift Friday morning, but regardless, winds should be light (generally AOB 6 kts) Friday morning. A slightly earlier than usual west wind shift is then expected across the terminals by late Friday morning.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns are expected through the next 24 hours under mostly clear skies. Trends in winds should be very similar to the past 24 hours featuring a preference towards a southerly direction at KBLH and southeasterly at KIPL before shifting SW this evening. Speeds are expected to be mostly AOB 10 kts, but with some gusts into the mid teens possible this afternoon at KBLH and this evening at KIPL.

FIRE WEATHER

Strong high pressure will gradually build over the region through the rest of the week while increasingly dry air confines any rain chances to over far eastern Arizona. Expect humidities to continue to lower over the next couple of days with MinRHs settling at 10-15% by Friday, while falling overnight RHs offer only little to modest relief. Record to near record temperatures are also forecast for Friday and through the upcoming weekend. Winds will mostly follow diurnal patterns, but west southwesterly winds will be dominant much of the time with afternoon gusts of 15-20 mph at times.

CLIMATE

Record high temperatures:

Date Phoenix Yuma El Centro ---- ------- ---- --------- Jul 31 116 in 2020 119 in 1957 119 in 2020 Aug 1 116 in 1972 117 in 1993 118 in 1993 Aug 2 114 in 2025 117 in 1918 117 in 1969 Aug 3 116 in 2024 116 in 1998 117 in 2021

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Extreme Heat Warning until 8 PM MST Monday for AZZ530>563.

CA...Extreme Heat Warning until 8 PM PDT Monday for CAZ560>570.