textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion.

KEY MESSAGES

- Temperatures into early next week will fluctuate up and down with readings cooling into the 70s by Friday, warming back up over the weekend before cooling briefly again early next week. - A dry weather system will bring widespread breezy to windy conditions on Thursday and lingering into Saturday across the western deserts.

- A stronger and slower moving weather system may bring some chances for rain showers Sunday into Monday.

SHORT TERM /TODAY THROUGH THURSDAY/

A slightly cooler airmass continues to move into the area which will help keep afternoon highs in the mid-80s this afternoon, still about 10 degrees above normal.

Strong height falls Thursday will lead to increased winds throughout much of the daytime hours, especially across southeast California where Advisory level winds are expected in some areas. A Wind Advisory has been posted for eastern Riverside County through northern parts of Imperial County for Thursday morning and afternoon. Wind gusts outside of the Advisory area may also reach 25-35 mph during the afternoon hours. Drier air will also surge southward on Thursday behind an advancing cold front dropping surface dew points into the teens by early afternoon. The cold front will keep daytime highs mostly in the upper 70s across the lower deserts.

LONG TERM /FRIDAY THROUGH TUESDAY/

Models are finally starting to agree on the expected cut-off low development by Saturday and its slow progression from northern/central Baja across northern Mexico early next week. Even with better agreement on the track and the timing, there are still differences with how much moisture will advect into our region and the exact placement of the moisture axis. The second shortwave trough is shown to dive southward into the base of the trough somewhere across southern California and/or western Arizona on Friday triggering the development of a closed low. Continued height falls on Friday and the core of the colder air aloft should lead to highs only reaching into the low to mid 70s across the lower deserts. Despite the low developing overhead, there will be so much dry air in place skies should remain clear on Friday. Winds will also continue to be quite breezy to at times windy across southeast California into the Lower CO River Valley.

As the low continues to deepen Friday night into Saturday, guidance agrees it will dig farther to the the southwest before stalling out just off the central Baja coast Saturday night. Mid level winds will also increase during this time leading to moisture starting to advect northwestward into our region from northern Mexico. The amount of moisture advecting into our area does not look all that impressive, but ensemble mean PWATs are shown increasing to between 150-180% of normal by Sunday evening. The moisture will also be more elevated in nature with boundary layer moisture likely be quite limited. Models have pushed up the time line for potential rain chances with low end chances starting as early as Sunday morning. The placement of the low well to our south Sunday into Monday will also somewhat limit the amount of forcing our region will have available. The best chances for rain showers currently looks to occur from Sunday evening through Monday afternoon with the highest PoPs of 30-40% over the eastern Arizona high terrain. Ensemble QPF amounts remain quite low across the region with lower desert amounts of around 0.05-0.15" to possibly 0.25" across much of southeast Arizona into the higher terrain east of Phoenix. Models mostly agree on ejecting the low to our east southeast Monday night into Tuesday, likely ending any rain chances.

Temperatures late this week through early next week will be on a bit of a roller coaster ride with highs warming back into the 80s over the weekend, dipping back into the 70s Monday, before warming back well into the 80s again by the middle of next week. Models then favor further warming through the latter half of next week with highs potentially topping 90 degrees again at some point.

AVIATION

Updated at 0533Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Winds will continue to follow diurnal tendencies with speeds generally AOB 8 kts through Thursday mid morning. Confidence is good that winds will then quickly shift out of the west between 16-18Z Thursday morning and become gusty by the afternoon across the terminals. Gusts around 20-30 kts are expected Thursday afternoon, likely peaking between 22-02Z. Expect a few periods of passing high clouds through tonight followed by SKC skies most of the day Thursday. Some slantwise visibility impacts from lofted dust cannot be ruled out in the mid-afternoon through sunset Thursday.

Southeast California/Southwest Arizona including KIPL and KBLH: The primary aviation weather concerns during the period will be the potential for brief LLWS conditions at KBLH early Thursday morning followed by gusty northerly winds beginning Thursday mid morning at both terminals. Confidence is low that LLWS criteria will be met at KBLH, but the best timing for LLWS conditions will be 11-15Z Thursday. Winds will remain light (under 10 kts) and generally contain a westerly component until Thursday mid morning, with periods of variability likely. Afternoon wind gusts up to 25-35 kts are expected at KBLH, which may also bring with it some blowing dust and brief reductions in surface visibility. Afternoon gusts will not be as strong at KIPL, mostly around 20-25 kts. Anticipate mostly clear skies other than some passing high clouds tonight.

FIRE WEATHER

The weather pattern will become increasingly active through the rest of the week as a series of dry disturbances cross the Southwest. The current passing system continues to bring light diurnal winds which will begin to strengthen bringing breezy to windy conditions tomorrow. Dry conditions will persist across the region with minimum relative humidity values staying entrenched between 10-15% through Saturday, while overnight recoveries will only reach the 30-50% range. Winds are expected to strengthen significantly after sunrise Thursday, with west gusts of 25-35 mph in the Phoenix area and peak WNW gusts of 30-45 mph across southeast California, leading to elevated fire weather concerns before a potential slight increase in moisture arrives Sunday into Monday.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...Wind Advisory from 7 AM to 6 PM PST Thursday for CAZ560-561-564- 568>570.