textproduct: NWS Phoenix

UPDATE

12Z Aviation Discussion.

KEY MESSAGES

- High pressure will persist across the region through at least midweek leading to above normal temperatures and dry conditions.

- Unsettled weather may affect the region late this week into the weekend with rain chances potentially returning and temperatures dropping closer to normal.

SHORT TERM /TODAY THROUGH WEDNESDAY/

A blocking pattern remains in tact across the eastern Pacific and the CONUS with high amplitude ridging persisting from southwest Canada throughout the Western U.S. into northern Mexico. There is also a weak disturbance west of Baja which is helping to bring some high clouds into our region, but this feature is expected to dissipate over the next 24-48 hours. Upper level ridging will remain the dominant feature across the Desert Southwest over the next few days despite heights falling from what we had seen since the middle of last week. The latest NBM forecast temperatures shows lower desert highs topping out between 73-79 degrees today and Tuesday before dropping to between 71-76 degrees Wednesday.

LONG TERM /THURSDAY THROUGH SUNDAY/

The weather pattern is expected to become more unsettled late this week into the weekend as a Pacific trough is likely to become cut off from the main flow on Tuesday and Wednesday and reach the coast of California on Thursday. The evolution of the system thereafter is still somewhat uncertain, but there is at least some model consensus of the low tracking southeastward just off the coast of southern California into northern Baja area on Friday. The track of the low over the weekend could be anywhere across northern Mexico to over southern portions of our region, but guidance mostly agrees it will be in a weakening phase as this happens.

Forecast moisture for late this week into the weekend is also not all that impressive with PWAT anomalies currently topping out around 150% of normal, but they have been trending higher over the past day or two of model runs. The current forecast shows the uncertainty by only having 10-30% PoPs across southern and central Arizona on Friday and Saturday. A more direct hit of the system along with even higher than forecast moisture would bring more widespread higher PoPs, while a more southerly track would likely bring little if any rainfall. Either way this system is not expected to bring impactful weather to the region.

AVIATION

Updated at 0950Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT and Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather concerns are expected through the forecast period. Winds will follow light and diurnal trends with speeds remaining aob 7 kts at all terminals. Period of calm and vrb winds will also be common, especially prior to the onset of diurnal wind shifts. FEW-SCT high cirrus decks will be present over the region through this evening.

FIRE WEATHER

High pressure will remain over the region through midweek keeping temperatures above normal and dry conditions in place. Daily MinRH values will remain stable, falling to 15-20% each day with overnight recoveries of 30-50%. Winds will overall be light through the period with only some periodic light breeziness across the Lower CO River Valley and over the Arizona high terrain. The weather pattern should eventually shift enough by next weekend to allow for cooler temperatures, an increase in humidities and possibly a period of light rainfall.

PSR WATCHES/WARNINGS/ADVISORIES

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