textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion.

KEY MESSAGES

- Flooding of several area streams and rivers continues to subside, while major waterways like the Salt River and Gila River will likely continue to experience flooding through the week due to dam releases. - Dry weather with seasonable temperatures will continue the next several days with lower desert highs warming into upper 70s to middle 80s by the end of the week.

SHORT TERM /TODAY THROUGH THURSDAY/

A considerable volume of water continues to flow downhill through many of the major waterways in south-central AZ early this morning, especially in the Salt and Verde systems. Salt River Project releases from the Bartlett Dam into the Verde River and Granite Reef Dam into the Salt River, remain very high, over 30000 cfs and over 55000 cfs respectively. Streamflow gauges were also reading between 30000-60000 cfs downstream from Tempe Town Lake heading into the Gila River. The last time there were major releases this high was in the Spring of 2023 and the Granite Reef Dam releases peaked at just under 40000 cfs and the runoff lasted for 2-3 months before fully emptying into the Colorado River near Yuma. That event in 2023 involved snow melt. So, there was a more prolonged runoff, but this event has a larger volume of water. Water levels and flow of this magnitude will continue to impact several low water crossings and any settlements, structures, and camps immediately near the banks. Very strong currents will also be very dangerous and deadly. There have been multiple fatalities by people recreating in the Salt and Verde with past events. So, it is strongly encouraged to avoid entering the water and please obey any closures. Also, be prepared for significant flood water continuing through the Gila River to Painted Rock Dam in Maricopa County. From there it may take a few days before water is released from Painted Rock into the lower Gila in Yuma County.

With clear skies and very light winds this morning, and with the lingering saturated grounds, there is potential for some patchy fog to develop this morning. Many areas are just too dry for development, but following cross-over temperature analysis, the best shot at fog development looks to be in parts of Pinal County, along the Gila River in Maricopa and Yuma Counties, and parts of eastern La Paz County.

Besides the flooding and potential fog, weather will remain dry and pleasant through the middle of the week. Water vapor satellite this morning shows shortwave ridging moving over the area ahead of a deep Pacific low just off the NorCal coast. Model guidance remains in excellent agreement showing this Pacific low tracking through NV, UT, and CO today through tomorrow, staying far enough north to have minimal impact on the local weather, besides suppressing heights again following the shortwave ridge. Comfortable afternoon temperatures are expected each day, with highs in the 70s to near 80, and mornings will start out seasonally cool, mostly in the low to mid 50s across the lower deserts to mid to upper 40s in the typically cooler spots.

LONG TERM /FRIDAY THROUGH MONDAY/

The long term forecast remains dry and seasonal. Ensemble guidance continues to show a dry positively-tilted trough dropping through the area at the end of the week, ahead of a strong ridge spreading into much of the west. Guidance also shows a cutoff low forming south of the ridge over the eastern Pacific, west of the Baja Peninsula. From here the models diverge a bit. A majority of the GEFS members bring the cutoff low up into the Desert Southwest, drawing some moisture up with it. However, the rest of the global ensemble guidance leans toward a much weaker cutoff low, with the Desert Southwest remaining dominated by ridging. Latest NBM PoPs through the long term forecast remain under 5% across the local area. Temperatures late-week through this weekend should warm a few degrees, back to around normal as the ridge builds over the West. Lower desert highs are forecast to be in the upper 70s to lower 80s. Breezy northerly winds are likely to develop heading into the end of this week and weekend as surface high pressure builds over the Great Basin and Rockies, below the upper level ridge, but wind magnitudes do not look to reach advisory level.

AVIATION

Updated at 1120Z.

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 Wednesday morning under a few passing high cirrus decks. Confidence is excellent that light east winds will prevail across the Phoenix area through mid afternoon before attempting to become W/NW by sunset. However, directions may only become variable, albeit with speeds remaining below 8kt before reverting back to an east component mid/late evening. Across SE California, light W/NW winds will be preferred during the evening and overnight with prolonged periods of light and variable winds during daylight hours.

FIRE WEATHER

Dry seasonal conditions can be expected through the next 7 days, with lingering flooding in major waterways like the Salt and Gila Rivers. Saturated grounds will help keep surface humidity levels somewhat elevated. Afternoon minimum RHs today will be around 40-55% across AZ and 20-30% across southeast CA. Despite gradual drying through the week, the minimum RHs will only fall to around 30-40% across AZ and 17-25% across southeast CA by the end of the week. Overnight recoveries will remain good through the week, with around 60-80% max RHs most nights. Winds through the next 7 days will mostly follow typical diurnal trends with light speeds and modest afternoon upslope gusts. Breezier north to northeast winds are anticipated late week into this weekend with gusts up to 20-30 mph forecast at this time.

PSR WATCHES/WARNINGS/ADVISORIES

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