textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion.

KEY MESSAGES

- Above normal temperatures will be common during the next several days, with some lower desert locations approaching 110 degrees over the weekend.

- An increase in moisture by the end of the week and weekend will lead to slight chances of showers and storms.

SHORT TERM /Today through Friday/

Current objective analysis depicts longwave troughing in place from the Pacific northwest through the central and northern Rockies, with weak ridging over the Desert Southwest. With the upper-level height fields on the rise as a result of this weak ridging pattern in place, afternoon high temperatures will be about 3-6 degrees warmer compared to yesterday as readings top out in the mid to upper 100s across the lower deserts under mostly clear skies.

Heading into the latter half of the week, as the aforementioned longwave trough finally ejects east-northeastward into the upper Midwest and south-central Canada, it will allow the subtropical ridge, currently centered near Gulf Coast region, to expand westward. At the same time a weak upper-level low will move northward off the coast of the Baja Peninsula. These two features will cause the flow aloft to shift out of the south, allowing moisture to gradually increase later Thursday through Friday as PWATs increase above 1.0" across much central and southern AZ. As the moisture advection is ongoing late Thursday into Friday, a lobe of vorticity, providing upper-level ascent, is projected to move through the area. This will result in an area of isolated to widely scattered elevated showers to break out across portions of southwest and south-central AZ Friday morning, where NBM PoPs range between 15-25%. Given the lack of deep moisture in place, most of the showers that do develop will high-based and thus rainfall accumulations will be very minimal. Afternoon high temperatures both Thursday and Friday will remain steady state, in the mid to upper 100s across the lower deserts.

LONG TERM /Saturday through Tuesday/

Moisture levels will remain well-above normal (200-250% of normal), with PWATs hovering between 1.0-1.4", during the weekend. The combination of the moisture and daytime heating will favor afternoon convection across the AZ high terrain. The limited instability with large T/Td spreads and dry sub-cloud layer will favor dry lightning and gusty outflow winds versus heavy rainfall, as is typical with convective activity in June. There are some indications from guidance of some elevated showers and isolated storms materializing and affecting portions of the lower deserts Saturday morning, likely due to another lobe of upper-level vorticity moving through. Heading into early next week, as another longwave trough builds across much of the central CONUS, west to northwest flow will usher in much drier air into the region and scour out most of the moisture.

With upper-level heights remaining stagnant throughout the weekend and early next week, temperatures are expected to remain steady state with afternoon highs each day in the upper 100s across most of the lower desert communities, with some areas, especially the western deserts, touching 110 degrees. Overnight lows will be above normal with most locations bottoming out in the upper 70s and low 80s.

AVIATION

Updated at 1704Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT; and Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation weather concerns will exist through Thursday afternoon under mostly clear skies. Winds will continue to favor diurnal tendencies with a few afternoon gusts up to 15-20 kts. Light and variable winds will be possible throughout the period.

FIRE WEATHER

Seasonably hot conditions with temperatures in an above normal category will continue during the next several days. The overall winds through the end of the week will be on the lighter side with limited afternoon upslope gustiness. MinRHs will bottom out in the single digits today and increase into the lower teens on Thursday. MinRHs will increase even further into the 15-20% range beginning on Friday and continuing through the weekend as moisture increases. With the increasing moisture will also come increasing chances for at least isolated thunderstorms across the AZ high terrain over the weekend, with gusty outflow winds and dry lightning potentially leading to natural fire starts being the main hazards.

PSR WATCHES/WARNINGS/ADVISORIES

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