textproduct: NWS Phoenix

UPDATE

12Z Aviation Discussion

KEY MESSAGES

- Dry weather is expected over the next couple of days with temperatures warming to near normal starting Thursday. - Locally windy conditions will impact the western deserts starting Thursday before spreading across the rest of southern and central Arizona by Friday.

- Wind advisories have been posted for portions of southern Arizona into the Lower Colorado River Valley on Friday with wind gusts in excess of 40 miles per hour expected.

SHORT TERM /TODAY THROUGH THURSDAY/

The weather system that brought periods of showers over the past couple of days is finally exiting the region to the northeast leaving behind drying conditions. A fairly cool air mass will remain in place today, even as heights aloft slowly rise, keeping daytime highs in the 70s across the south-central Arizona lower deserts to the upper 70s and lower 80s across southeast California and southwest Arizona.

The main forecast concern then shifts toward windy conditions developing Thursday into Friday as a strong pressure gradient sets up between a developing cut-off low just to our southwest and a ridge moving into the Great Basin. Northerly breezy conditions will first develop across the Lower CO River Valley today before strengthening further on Thursday. The rising heights today into Thursday will also push temperatures higher for Thursday with highs mostly in the mid to upper 80s across the lower deserts.

LONG TERM /FRIDAY THROUGH TUESDAY/

Strong easterly winds are expected to develop across southern and central Arizona by Friday morning with guidance showing H8 winds of 30-45 kts across southern and much of central Arizona. The best corridor for strong winds looks to be across southeast Arizona into southern Gila County and through Pinal, southern Maricopa, and Yuma Counties. Occasional gusty winds of 25-40 mph are expected before sunrise in this area before increasing to advisory level around or just after sunrise Friday morning. Wind Advisories have been issued for the aforementioned areas for Friday morning into the afternoon with wind gusts in excess of 40 mph at times. The peak of the winds should occur mid to late morning Friday with some gusts up to 50 mph possible. Areas to the north, including Phoenix, should stay below advisory level but gusts of 30-40 mph will be likely during the latter half of the morning Friday. Patchy blowing dust will also be a concern on Friday, particularly across Pinal County. Winds should eventually drop off some for most areas during the afternoon hours Friday, but advisory levels winds should continue to be a concern through the rest of Friday and even into Saturday across higher terrain areas east and southeast of Phoenix.

Winds Saturday will again be elevated with gusts of 25-35 mph for much of southern and central Arizona, but any advisory level winds are likely to be limited southeast Arizona. Aside from the wind concern, guidance is suggesting some lower end shower potential later Friday through Saturday. The placement of the cut-off low to our southwest starting Friday is expected to advect a good amount of mid and upper level moisture into the area. Some high-based light showers may become possible across southern Arizona as early as Friday afternoon, but little if any measurable rainfall is expected. These low-end (10-20%) light shower chances may stick around through Saturday as the cut-off low begins to drift back through our region, but most locations will struggle to get anything more than a trace to a few hundredths of an inch.

Early next week is likely to be a transition period with weak upper level ridging briefly taking over and overall dry conditions. After a brief dip in temperatures on Saturday, daytime highs should trend closer to normal for early next week. Looking out even further, ensemble guidance is hinting at another deep Pacific trough moving into the Western U.S. early next week and potentially reaching our region during the middle part of next week. This next weather system could bring more rain chances and another cool down during the latter half of next week.

AVIATION

Updated at 1015Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

No major aviation weather concerns are anticipated through the TAF period. Winds are expected to be light (aob 8 kts), following a typical diurnal trend, however slightly more northwesterly with extended periods of VRB during directional changes. Winds tomorrow morning are currently projected to see an easterly shift tomorrow at Sky Harbor, but confidence is low. Otherwise, clear skies will persist throughout the period.

Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation weather concerns are anticipated through the TAF period under clear skies. Winds at KIPL will fluctuate between W'rly and N'rly with speeds aob 8 kt. At KBLH, winds will be northwesterly most of the TAF period with gusts up around 20 kt starting by 18Z through the evening before relaxing.

FIRE WEATHER

Drier air will work into the region over the next couple of days leaving mostly clear skies and lowering humidities. MinRHs will drop to 20-25% across the western districts today to 30-45% for the eastern districts before lowering to 20-35% areawide Thursday. Northerly breezy winds will affect southeast CA and southwest AZ today before increasing to around advisory level Thursday into Friday. The eastern districts will keep overall light winds today before windy conditions settle in Thursday night into Friday. Some moisture return Friday into Saturday may bring low-end rain chances, but wetting rains chances should remain below 10%.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Wind Advisory from 5 AM to 3 PM MST Friday for AZZ531-532-536- 538-539-554-559.

Wind Advisory from 5 AM Friday to 11 AM MST Saturday for AZZ552- 553-555-558-560>562.

Wind Advisory from 5 AM to 6 AM MST Friday for AZZ530.

CA...Wind Advisory from 5 AM to 6 AM PDT Friday for CAZ564-565-569- 570.