textproduct: NWS Phoenix

UPDATE

00Z Aviation Discussion.

KEY MESSAGES

- Dry and tranquil weather conditions with near zero rain chances can be expected through this weekend.

- Near to slightly above normal temperatures will persist through the next several days.

- A low pressure system and moisture return early next week will bring a return of rain chances to at least the high terrain of northern and eastern Arizona.

SHORT TERM /TODAY THROUGH SUNDAY/

Latest water vapor satellite imagery depicts an upper-level low traversing the northern Great Basin, with southwest flow along the southern periphery injecting a much drier air mass into the region. Latest SPC mesoanalysis shows precipitable water values noticeably lower compared to the last 24-48 hours with values ranging between 0.8-1.1" across south-central AZ to between 0.5-0.8" across the western deserts, with even lower values expected heading into this weekend. Even though much drier air has been advected aloft, surface moisture remains abundant with dewpoints in the mid to upper 60s still hanging on across the lower deserts of south-central AZ. However, this drier air aloft is expected to eventually scour out the surface moisture as dewpoints are projected to drop into the 50s and even into 40s across some areas by this evening with dewpoints mostly in the 30s and 40s heading into the weekend. Therefore, given the abundance of dry air, generally clear skies with zero rain/storm chances are expected throughout the weekend. Temperatures will remain near steady state through the weekend with afternoon highs generally in the upper 90s to low 100s and early morning lows generally in the 70s across much of the lower deserts along with Minor HeatRisk.

LONG TERM /MONDAY THROUGH THURSDAY/

Heading into early next week, there is good confidence that a Pacific low will move to the central/southern coast of California by the end of the day Monday. Exactly how this low evolves once reaching the coast is still a little uncertain, but latest model consensus suggests the low will track ENE inland staying mostly north of the local area and driving a chance for showers and storms across northern AZ. Conceptually this is not a bad setup for a transitional severe weather event with potential frontogenetical forcing and a moderately strong upper level jet with higher shear, but rebounding quickly from the very dry air this weekend and getting sufficient moisture in here to support any lower desert rain chance will be tough. Model guidance does at least support a slow return of moisture Monday through next week, more so coming from the southeast like typical early stages of the monsoon.

Model guidance is also pointing toward a strong ridge developing through the middle of the U.S. with the subtropical high restrengthening near/over Texas by mid to late week. This would keep the Desert Southwest under predominant southwest flow which is not the most ideal setup for lower desert storm chances, especially not for southeast CA and southwest AZ. Latest NBM forecast has PoPs focused primarily across northern and eastern AZ each day next week with only minor (10-20%) PoPs for south-central AZ lower deserts in the evenings. The one thing this pattern does open the door for, the longer it persists, is potential Eastern Pacific tropical moisture advecting north.

Temperatures through next week will mostly stay the same day-to-day, with highs in the upper 90s to lower 100s, which will be around 2-5 degrees above normal, and lows remaining mostly in the 70s. The temperatures will lead to widespread Minor HeatRisk through at least the first half of the week with a trend toward areas of Moderate HeatRisk by the second half of the week as morning low temperatures creep back up.

AVIATION

Updated at 2320Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation weather concerns are anticipated through the forecast period with gradually clearing skies. Winds have been slow to come around to the W-SW, but have finally settled into a westerly direction. West winds will continue through late tonight before returning to the ESE. Speeds should remain light, generally aob 8 kts through the period.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather concerns will exist at the SE California terminals under clear skies. Winds will favor diurnal patterns at both terminals. Speeds should remain around 10 kts or less with limited gusts, and extended periods nearly calm conditions or light northerly at KBLH in the morning.

FIRE WEATHER

Overall there are no fire weather concerns through the next week. A drying trend will continue today through this weekend with no rain expected through at least the start of next week. Minimum RH values this afternoon will be around 20-35% across south-central AZ to 10- 20% across southeast CA and southwest AZ. The minimum RHs will then dip to 10-20% for nearly all areas this weekend. Overnight recoveries across south-central AZ will still be good tonight at 45- 75%, but then falls lower this weekend. There will be a gradual return of moisture next week, best across eastern AZ and there will be an increase in rain chances again, but as of now rain chances look to primarily favor northern and eastern AZ high terrain. Besides a potential increase in breeziness early next week with a weather system, winds will mostly follow typical diurnal patterns with modest afternoon upslope/upvalley gustiness (15-25 mph).

PSR WATCHES/WARNINGS/ADVISORIES

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