textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion.

KEY MESSAGES

- Above normal temperatures will be common through much of the week as high pressure prevails over the area.

- A fairly strong weather system will affect the region over the weekend leading to breezy conditions, cooler temperatures, and increasing rain chances.

SHORT TERM /Today through Wednesday/

A compact shortwave and associated jet streak were propagating through southern California early this afternoon thrusting expansive mid/high cloud cover inland along with increasing ascent. While total column PWAT exceeding 0.75" and above the 95th percentile of climatology have advected over much of the CWA, the saturated layer remains confined above H7 with only 5 g/kg mixing ratios in the sfc- H7 layer. This stratification incurs substantial dry air in the sub- cloud layer essentially precluding little more than virga over lower desert communities and sprinkles/light rain over mountainous locations. The aforementioned shortwave will quickly progress into New Mexico overnight with midlevel flow becoming NW and introducing a much drier atmospheric column into Arizona.

Forecast confidence over the next 72 hours is excellent as both ensemble solutions and numerical guidance exhibits very narrow spread featuring low amplitude ridging temporarily building into the SW Conus behind the exiting shortwave. With H5 heights steady within a 576-579dm range, temperatures should warm into a +10F to +15F anomaly with readings peaking on Wednesday under the ridge axis and widespread subsidence.

LONG TERM /Thursday through Sunday/

High pressure will continue to encompass the region on Thursday resulting in continued dry conditions and well above normal temperatures. Temperatures Thursday will be similar to Wednesday with afternoon highs in the low to mid 90s (mid to upper 80s) across the lower deserts (higher terrain), which is around 10 degrees above normal.

By the end of the week, ensembles continue to point towards a pattern change for our region. Ensembles show a closed low pressure system moving onshore of central CA on Friday, which will result in heights starting to lower across AZ. Ensembles show H5 heights going from 576-579 dm on Thursday to 573-576 dm on Friday. With lowering heights, temperatures will also start to cool with afternoon high temperatures falling into the upper 80s to low 90s (low to mid 80s) across the lower deserts (higher terrain). The low pressure system looks to weaken as it moves onshore this weekend and eventually get wrapped up into a trough digging out of the Pacific NW and eventually slowly progress eastward into our region by the end of the weekend.

However, there remains a decent amount of uncertainty within the ensemble members in the exact track and strength of this system as it moves onshore. If the system is stronger and deeper than precipitation chances will increase across the region as the system will bring in more moisture. However, if the system is weaker and shallower than precipitation chances may be confined to the higher terrain areas. Additionally this system could bring breezy conditions to the region. Either way temperatures will decrease and look to fall back into the 80s (upper 60s to mid 70s) across the lower deserts (higher terrain) this weekend. Temperatures on Sunday look to fall back to near to even slightly below normal.

AVIATION

Updated at 0019Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: E/NE winds are favored this evening through Tuesday morning. However, light variability is expected as well and wind directions may locally shift SW at just KPHX after 07Z tonight. Winds will shift westerly Tuesday by 19-20Z, with lighter speeds than today (mostly below 10 kts). Vicinity virga showers will come to an end over the next couple hours and skies will clear gradually clear through the night.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation weather concerns are expected over the next 24 hours. Winds at KIPL will favor a W'rly component, with perhaps a few gusts 20-25 kt during the evening, while KBLH should see extended periods of VRB conditions through Wednesday morning. KIPL will also see extended periods of light variability through the day Tuesday and may see a light easterly wind develop in the afternoon. Skies will clear this evening and remain SKC through Tuesday.

FIRE WEATHER

Generally dry weather and above normal temperatures will persist during the upcoming work week. MinRHs will be in the 10-20% range across the lower deserts today and in the 20-40% range across the higher terrain areas. Lower RH values return for the remainder of the workweek with minRH falling to 10-20% region wide. Overnight recoveries will be good to excellent overnight tonight (40-60% across lower elevations and 60-100% across the higher terrain). Overnight recoveries then fall to 25-60% for the remainder of the workweek. The increase in moisture today will result in some scattered showers and isolated thunderstorm chances across the higher terrain in northern and eastern AZ this afternoon. Elevated winds are once again expected during the mid and late morning hours today with gusts of 25-35 mph possible across the higher terrain and 15-25 mph possible across the lower deserts in eastern Maricopa and NW Pinal Counties. Lighter winds are then expected for the remainder of the workweek. This weekend a weather system will start to move into the region bringing breezy conditions, chances for precipitation, and cooler temperatures to the region.

PSR WATCHES/WARNINGS/ADVISORIES

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