textproduct: NWS Phoenix

KEY MESSAGES

- A Flood Warning is in effect through at least early next week along the Gila River between Painted Rock Dam and Dateland, Arizona due to water released from the dam.

- Dry and tranquil weather with slightly above normal temperatures will continue through middle of the week.

- A more unsettled pattern is expected by the weekend through early next week with increasing rain chances and cooler temperatures as a series of weather systems move through the Desert Southwest.

SHORT TERM /TODAY THROUGH THURSDAY/

Latest objective analysis shows upper-level ridging prevailing over the Desert Southwest. This ridging pattern will remain in place through the middle of the week before the pattern shifts by the end of the week. As a result, expect a continuation of dry and tranquil weather conditions along with mostly clear skies. Temperatures through Thursday will solidly be around 5 degrees above normal as afternoon highs across much of the lower desert communities top out in the mid 80s. Overnight and early morning lows will also be mild with readings in the mid 50s to around 60 degrees.

LONG TERM /FRIDAY THROUGH MONDAY/

A clear pattern shift later this week is likely to lead to a quasi-blocking flow regime as the flow becoming highly amplified over the eastern Pacific through the entire CONUS and Canada. The ridge over the Intermountain West is expected to extend into southern Canada by Thursday with deep troughing developing off the West Coast and over the Northeastern U.S. Despite the highly amplified flow, the upstream trough to our northwest should be enough to kick the ridge just to the east of our region later Thursday into Friday as a modest shortwave trough peels off from the parent large scale trough. Model guidance is still struggling to come to a full consensus on the track and the strength of the incoming disturbance for Friday into Saturday. Trends over the past couple of days have shifted the system more over Baja and Sonora Mexico while also showing some noticeable weakening as it tracks by just to our south on Friday. A second shortwave trough may also track by just to our north on Saturday.

Despite the lingering model uncertainty later this week, we are nearly assured to have increasing higher level clouds early on Friday followed by some weak lower level moisture advection out of the south during the latter half of Friday. Ensemble mean PWATs are shown to increase to between 175-200% of normal starting Friday, but due to the bulk of the system energy likely bypassing to the south on Friday and to the north on Saturday we are not anticipating widespread rainfall. NBM PoPs are still mostly between 10-25% for the Arizona lower deserts to 20-35% for the higher terrain north and east of the Phoenix area from midday Friday through much of Saturday. Rainfall is expected to be light with total amounts of a trace to at most 0.10" across the lower deserts to localized amounts of 0.10-0.20" over the high terrain. We also can't completely rule out a weak thunderstorm or two on Friday focused across far southern Arizona since forecast MUCAPE does increase to 200-300 J/kg. Temperatures will start to drop on Friday with lower desert highs falling back into the upper 70s to around 80 degrees followed by mid to upper 70s over the weekend. The unsettled weather pattern is expected to continue into next week with even better rain chances by around next Tuesday.

AVIATION

Updated at 1710Z.

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

No major aviation concerns are expected through Wednesday afternoon under periods of FEW-SCT high cirrus. Winds will remain light, AOB 10 kts, and follow diurnal tendencies across the Phoenix area terminals, with a weak W/NW switch anticipated by 21-23Z this afternoon. Across Southeast CA terminals, winds will generally favor a northerly component today and back out of the NW-W this evening. Extended periods of light (below 5 kts) and VRB winds to nearly calm conditions are anticipated.

FIRE WEATHER

Dry conditions and slightly above normal temperatures will prevail through at least Thursday. Minimum humidity values will hover near 25-40% across eastern districts and 20-30% in western districts. This follows fair to good overnight recovery near 30-60% in western areas and good to excellent levels 50-80% in eastern areas. Expect overall light winds, but also some marginally breezy conditions across ridge tops and terrain gaps of eastern districts during the morning hours. A more unsettled weather pattern is expected to settle over the region by the weekend increasing moisture and rain chances and dropping temperatures.

HYDROLOGY

Lower Salt: Water releases above 1000 cfs continue from the Bartlett to Granite Reef Dams. Therefore, a Flood Warning remains in effect through Wednesday morning between Granite Reef Dam and Tempe Town Lake with low-water crossings impacted.

Gila: A Flood Warning is in effect from Painted Rock Dam through the Dateland area through at least early next week due to water released from the dam. Water release levels are expected to increase during the next couple of days, peaking at 3000 cfs. These increased releases will have the potential to flood farm fields and low-water crossings along the river downstream from the dam.

PSR WATCHES/WARNINGS/ADVISORIES

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