textproduct: NWS Phoenix

UPDATE

Updated Aviation

KEY MESSAGES

- Well above normal temperatures will persist through Tuesday resulting in areas of minor HeatRisk across the lower elevations.

- A pattern change mid to late week will lead to cooler temperatures and increasing rain chances, particularly across the eastern half of Arizona.

- Weather conditions will briefly turn more tranquil over the upcoming weekend before becoming more unsettled once again early next week as another storm system potentially impacts the region.

SHORT TERM /Today through Wednesday/

Early morning water vapor satellite imagery shows a cutoff low well to the south near the central/southern Baja peninsula while across the region, ridging continues to hold with 500 mb height fields near 580dm. The overall upper-air pattern for today will remain unchanged with ridging prevailing over the region as the cutoff remains nearly stationary over the central/southern Baja Peninsula. With 850 mb temperatures expected to remain around 15-16C across the region, afternoon high temperatures will once again reach the middle 80s across most of the lower desert communities, with a 40% chance of Phoenix Sky Harbor once again potentially tying a daily high, which is 86 degrees last set in 2016. On Tuesday, the pattern begins to shift as an upper trough begins to encroach the west coast, which will allow the cutoff low over the Baja Peninsula to finally eject more quickly to the east-northeast through northern Mexico and into western Texas. The approaching upper trough will also begin to lower heights aloft and increase mid to upper-level clouds, which will lower afternoon highs by about 5 degrees from today with readings near 80 degrees across the lower deserts. With the well-above normal afternoon high temperatures continuing through Tuesday, Minor HeatRisk will be common across the lower deserts. As a result, if spending time outdoors for a prolonged stretch, make sure to frequently hydrate and take breaks in the shade.

The upper trough will move onshore into central CA late Tuesday night through Wednesday while on a weakening phase with most of the associated PVA moving through the Great Basin. While most of the forcing associated with the trough is expected to remain to the north of the region, moisture levels are expected to increase in the mid to upper-levels and thus a few showers with the upslope flow may be squeezed out late Tuesday night into early Wednesday across the higher terrain areas north and east of Phoenix. This scenario is supported by some of the hi-res models, with NBM PoPs around 20%. Nevertheless, any showers that do develop should be short-lived with little to no accumulations. Afternoon high temperatures on Wednesday will lower a bit more but still remain above normal with readings in the middle to upper 70s across the lower deserts.

LONG TERM /Thursday through Sunday/

Weather conditions will remain unsettled heading towards the end of the week as another troughing feature affects the region. The latest model guidance shows the trough moving through late Thursday into Friday. There is still some uncertainty in terms of the overall strength of the trough as it passes by, however, the latest trends from the guidance does show the trough rather progressive and positively tilted, which is not an ideal setup for good moisture advection and thus widespread rain potential. Therefore, any precipitation potential will be mainly confined across the eastern AZ higher terrain areas, where NBM PoPs are between 30-60% during the day Friday. With the trough passage, afternoon high temperatures on Friday will cool down to around 70 degrees across the south- central AZ lower deserts (which is right around seasonal norms) to the middle 70s across the western deserts.

After the trough exits to the east, more tranquil weather settles in over the weekend as a transient ridge moves overhead with dry conditions and temperatures slightly warming up. The tranquil weather will likely be short-lived as both the deterministic and ensemble model suite continue to be consistent in indicating a more potent troughing feature setting up early next week across the western CONUS, which if the overall trajectory is ideal, could lead to more widespread precipitation chances across the Desert Southwest. Given that this potential storm system is still about a week out, there is a good deal of uncertainty on how things will play out with the precipitation potential and is something that will have to be monitored throughout the week.

AVIATION

Updated at 1700Z.

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

No major weather issues will exist through Tuesday afternoon mid/high clouds replace clear skies late in the period. Confidence is moderate regarding timing of the typical afternoon westerly wind shift around the Phoenix metro with the transition likely occurring later than usual. A W/NW wind component will be favored across SE California. Extended periods of nearly calm conditions will be common across the region.

FIRE WEATHER

Well-above normal temperatures and dry conditions will persist early this week. MinRH values will range between 10-20% today before increasing to 20-35% on Tuesday. By mid to late week, a pattern change is expected that will cool temperatures several degrees (although remaining above normal) and maintain MinRHs above 20%. Winds will remain very light today, with occasional breeziness expected the rest of the week. A weather system late in the week will bring a 20-50% chance of wetting rains over the higher terrain areas of the eastern districts.

PSR WATCHES/WARNINGS/ADVISORIES

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