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 more progressive weather pattern has briefly settled into the region with shortwave ridging currently moving into the region from the west as the first disturbance exits through Colorado. A slightly cooler air mass is now in place and this will help to keep highs mostly in the mid 80s today, but still 10 degrees above normal for early March.

The next weather system will come in two separate pieces with the first shortwave moving across the Great Basin later today and tonight before moving through northern portions of our region on Thursday. 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 1750Z.

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 shift out of the west between 16-18Z Thursday and become gusty by the afternoon across the terminals. Gusts into a 20-25 kt range may become common Thursday afternoon. Expect a few periods of passing high clouds through tonight followed by SKC skies most of the day 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, so it is not included in the TAF, but a front is expected to sweep the area within a few hours of sunrise Thursday morning. If the surface remains sufficiently decoupled, the best timing for LLWS conditions would 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. Anticipate mostly clear skies other than some passing high clouds this evening into the overnight hours.

FIRE WEATHER

The weather pattern will be a bit more active through the rest of the week with an initial passing disturbance bringing breezy to windy conditions starting Thursday. Dry conditions will remain in place over the next several days with MinRHs staying between 10-15%. After light winds today, winds are expected to become gusty after sunrise Thursday with the strongest gusts of 30-40 mph across southeast California late morning through the afternoon. The combination of the gusty winds and low RHs Thursday should result in elevated fire weather concerns across much of the western districts. Another disturbance is likely to develop across the region Friday into the weekend leading to more locally windy conditions and eventually some potential rain chances by around Sunday.

PSR WATCHES/WARNINGS/ADVISORIES

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