textproduct: NWS Phoenix

UPDATE

06Z Aviation Discussion.

KEY MESSAGES

- Lingering low pressure will help keep breezy to locally windy conditions in the forecast through Saturday.

- A weather system continues to meander near the region through the start of next week, allowing for an increase in rain potential for Monday

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

SHORT TERM /TODAY THROUGH SATURDAY/

Current objective analysis reveals troughing centered over the Rockies with a high amplitude ridge over the Eastern Pacific. Meanwhile, the Desert Southwest finds itself in a bit of a transition zone as the previosuly-mentioned weather system starts to eject eastward. However, as this disturbance migrates away from the region, a piece of shortwave energy is expected to break off from the main flow and dig further to the south, eventually settling as a cut-off low. Due to the presence of a relatively enhanced pressure gradient, breezy to locally windy conditions will remain in the forecast through Saturday, mainly for areas around the Lower Colorado River Valley and westward. Gusts 25- 35 mph will be common across these areas, with locally higher gusts focused over enhanced terrain features. Given the high likelihood of achieving gusts greater than 40 mph, a Wind Advisory has been posted for portions of SE California for Saturday morning hours.

In terms of temperatures, this afternoon looks likely to be the coolest day for at least the next week as the above-mentioned trough and its associated cooler air sit in close proximity. Lower desert highs this afternoon will range between the lower to middle 70s, right around and even a few degrees cooler than normal for this time of year. As the cut-off low develops and sags further south, heights aloft will rebound slightly, allowing for a bum up in temperatures for Saturday when middle 70s to around 80 degree readings will be common for much of the region.

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 0540Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Aside from a brief period of gusty winds developing mid-morning Saturday, aviation weather concerns will remain minimal through the TAF period. Winds will shift out of the east overnight and become more elevated after sunrise Saturday morning. Gusts in the teens to around 20 kts will become common by mid-morning, but are expected to slacken by the late afternoon. Guidance does indicate winds will attempt to switch out of the west Saturday evening. FEW-SCT high clouds will progress through the region overnight.

Southeast California/Southwest Arizona including KIPL and KBLH: Gusty N-NNE winds will be the primary aviation weather concern at both terminals Saturday morning through Saturday afternoon. Light W-NW flow will continue overnight with speeds remaining aob 8 kts. Confidence is high that gusts up to 20-25 kts will materialize at both sites Saturday morning and persist through mid afternoon. Periods of FEW-SCT mid to high cloud decks will pass over the region, but skies will become mostly clear early Saturday.

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...Wind Advisory from 2 AM to noon PST Saturday for CAZ560-561-564- 568>570.