textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion.

KEY MESSAGES

- Fluctuating temperatures along with breezy to locally windy conditions will accompany a few weather systems as they traverse the region.

- The stronger and slower moving area of low pressure will present rain chances to the region into the start of next week

- High pressure, along with consistent above-normal temperatures, make their return by the middle portion of next week

SHORT TERM /TODAY THROUGH SATURDAY/

Current WV imagery shows the trough, that was positioned over Northern Nevada yesterday, now to the east digging down the Four Corners region and extending into Northern Arizona. This troughing feature will continue to extend down the Desert SW today lowering heights aloft, this will result in afternoon highs in the low to mid 70s across the lower deserts, or a few degrees below normal for the day. Below normal temperatures will be short lived as this trough will break off and develop into a cut-off low just off the NW coast of the Baja Peninsula by Saturday afternoon. This cut-off low will be too far SW from the region to keep temperatures down, leading to temperatures increasing into the mid to high 70s by Saturday afternoon, swinging to back above normal for the day.

Portions of Southeast California, into the Chocolate Mountains and Joshua Tree National Park will continue to experience breezy to locally windy conditions today and Saturday, especially during the afternoon hours. However, speeds will be lighter than Thursday, so no wind advisory is in effect, but wind gusts can still be in between 25-35 mph in those areas, with mountain peaks potentially reaching 40 mph.

LONG TERM /SUNDAY THROUGH THURSDAY/

Models remain in agreement that the cut-off low will be positioned over the Northern Baja Peninsula by Saturday afternoon and will stall in that position throughout the weekend. As this cut-off remains stationary to the region's SW, it will allow H5 heights aloft to increase to around 570-573 dam over the lower deserts on Sunday. This will cause temperatures to increase further into the mid to upper 80s Sunday afternoon, with little relief as skies will also remain clear. Resulting in Minor HeatRisk across the lower deserts on Sunday. By Monday afternoon the cut-off low will begin to progress eastwards over Northern Mexico/Southern Arizona. Uncertainty remains in the amount of moisture likely to be advected into the region during the system's movement, with many models now pushing the best moisture advection and precipitation chances to Monday afternoon into early Tuesday morning, compared to previous runs projecting Sunday night through Monday afternoon. Most precipitation chances remain low (20-30%) with expected QPF totals anywhere from 0.00-0.05" across the lower deserts and 0.05-0.15" in the higher terrain. Continued monitoring of this system will be needed over the next several day.

As mentioned earlier, the core of the cut-off low will begin to progress eastwards over Northern Mexico/ Southern Arizona starting Monday, leading to temperatures cooling into the upper 70s - high 80s. By Tuesday evening, the cut-off low will be ejecting into Western Texas and into the Plains. Afterwards the Desert SW H5 heights will then be able to steadily climb, leading to a steady increase in temperatures with highs back in the mid to high 80s by Wednesday and likely into the low 90s by late next week.

AVIATION

Updated at 1755Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: The only weather issue that will exist during the TAF period will be occasionally gusty winds during the daytime hours today and Saturday. Winds will continue to favor a westerly direction through early this evening. Wind speeds between 6-10 kts sustained and occasional higher gusts will be common through early this evening, followed by generally lighter winds establishing out of the east overnight, then easterly winds will pick up a few hours after sunrise Saturday. Anticipate easterly gusts to develop between 16-19Z across the terminals, with low confidence on exact magnitudes of the gusts but at least reaching a 15-20 kt range for a time. SKC skies will give way to periods of FEW-SCT mid to high clouds decks this evening into Saturday.

Southeast California/Southwest Arizona including KIPL and KBLH: Gusty northerly winds will be the primary aviation weather issue under periods of FEW-SCT mid to high cloud decks and otherwise mostly clear skies. Northerly gusts have already developed at the terminals and are expected to be stronger at KBLH (20-25 kts) than KIPL (15-20 kts) through this afternoon. Confidence is moderate that gusts will subside overnight before picking back up out of the north northeast Saturday mid morning. If a sufficient amount of decoupling occurs overnight into early Saturday morning, modest LLWS conditions may once again develop, though confidence remains very low on LLWS meeting criteria for including in the TAF. During periods of stronger northerly winds, hazy conditions may develop due to lofted dust, briefly reducing VIS below 10SM.

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 today and Saturday, especially during the afternoon hours. Dry conditions will persist across the region with minimum relative humidity values staying entrenched between 10-15% through Sunday, while overnight recoveries will only reach the 30-50% range. Peak wind gusts of 25-35 mph across southeast California and into the high elevations will continue, leading to elevated fire weather concerns before a potential slight increase in moisture arrives Monday.

PSR WATCHES/WARNINGS/ADVISORIES

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