textproduct: NWS Phoenix

UPDATE

00Z Aviation Discussion

KEY MESSAGES

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

- 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/

Skies have cleared after days of clouds and rain and this morning was the coldest since March. Low temperatures this morning were in the 50s across the lower deserts which is around 5-10 degrees below normal. The temperatures were cooler thanks to a cold front associated with the low pressure system that moved through northern AZ overnight. This low is no leaving the area and moving through CO this afternoon. High temperatures this afternoon, under the clear skies, will be in the middle 70s across south- central AZ lower deserts to around 80 degrees in southwest AZ and southeast CA.

With the departure of the upper low and rising H5 heights, temperatures will warm several degrees heading into tomorrow. The morning will still be cool in the 50s to around 60 degrees, thanks in part to the clear skies, but afternoon high temperatures will warm back into the middle 80s across the lower deserts. There is even a low chance (10-20%) Phoenix reaches 90 degrees. Average high temperature for mid-October is still around 90 degrees.

Wind will become the main focus of the forecast starting tomorrow as the pressure gradient across the area strengthens in response to strong surface high pressure developing to the north and strong high pressure aloft also spreading into the Great Basin in the wake of the departing upper low. A shortwave trough moving down on the backside of the departing low will actually help induce a weak cutoff low just to the west-southwest of the local area by the end of the day tomorrow. Initially tomorrow the greatest surface pressure rises will be to the northeast with a 1040mb high centered in MT and WY, which will induce breezy northerlies and northeasterlies across the area. Strongest breezes (25-35 mph) tomorrow will be focused across northern AZ and across portions of southeast CA, including the lower Colorado River Valley. The gradient winds will become stronger and the orientation will shift more E-W heading into Friday.

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. Latest NAEFS and ENS show H8 winds reaching near record magnitudes compared to climatology. 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 50-55 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 late 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 2300Z.

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

No major aviation concerns are expected during the TAF period under mostly clear skies. Outside of a slightly northerly tilt to the winds, typical diurnal trends will be favored, with some periods of VRB conditions during the overnight hours. Breezy conditions will develop by late Thursday morning, with northeasterly gusts around 20 kt continuing toward the end of the forecast window.

Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation concerns are expected through tonight as generally light winds and clear skies prevail. Northerly breeziness will develop during the back half of the TAF period, with gusts around 20-25 kt at each terminal.

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 tomorrow. Northerly breezy winds will affect southeast CA and southwest AZ today before increasing to around advisory level tomorrow into Friday. The eastern districts will keep overall light winds today before windy conditions settle in Thursday night into Friday. Easterly wind gusts as high as 40-50 mph are expected 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 8 PM to 11 PM MST Thursday for AZZ530.

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 2 PM MST Friday for AZZ530.

CA...Wind Advisory from 8 PM to 11 PM PDT Thursday for CAZ564-565-569- 570.

Wind Advisory from 5 AM to 2 PM PDT Friday for CAZ564-565-569- 570.