textproduct: NWS Phoenix

UPDATE

Updated 18Z Aviation Discussion.

KEY MESSAGES

- An unseasonably strong ridge of high pressure will boost temperatures around 3-5 degrees above normal this weekend and eventually into a well above normal range by the middle of next week as lower desert highs reach up to 98-105 degrees.

- Periods of breezy to locally windy conditions can be expected across southcentral and southwestern AZ through Monday with gusts reaching 20-30 mph at times.

- Dry weather with zero rain chances will persist through this weekend and into much of next week.

SHORT TERM /TODAY THROUGH SUNDAY/

Latest GOES mid-lvl wv imagery and 500 mb objective analysis reveals a strong area of high pressure building over N AZ while a cutoff low remains entrenched over far W TX and SE NM. Our forecast area lies between both of these features, resulting in continued dry NE flow aloft. The unseasonably strong ridge is expected to remain the predominant feature through this weekend as hghts aloft peak around 590-591 dam which is near the 97th percent of climatology for early October. Due to expansive positive hght anomalies, temperatures are expected to reach up to 3-5 degrees above normal with lower desert highs in the upper 90s to low 100s today and Sunday. The hottest temperatures will reside along and west of the Lower Colorado River valley where highs will peak in the 100-103 degree range. Overnight lows will also remain on the warmer side, mainly in the mid 70s to around 80 degrees through at least Monday morning which can be attributed to elevated winds that will occur prior to sunrise. These above normal low/high temperatures will result in a Moderate HeatRisk across the western deserts. Due to an increased sfc pressure gradient, winds will continue to remain breezy with gusts reaching 20-30 mph at times across southcentral and southwest AZ. The strongest gusts look to be from early morning through the mid afternoon time period. It is also possible that locally higher gusts up to 35 mph could materialize for a few hours across the higher terrain of E And SE AZ as well as in southwestern AZ as winds become channeled through terrain features. Therefore, patchy blowing dust will be possible, especially around the Yuma area.

LONG TERM /SUNDAY THROUGH THURSDAY/

Heading into next week, deterministic and ensemble guidance show the unseasonably strong ridge weaken and retrograde wwd as an upper-lvl trough progresses through the Intermountain West. This will allow temperatures to dip a few degrees on Monday afternoon, although highs will still remain slightly above normal. The aforementioned trough will provide a temporary weakness in 500 mb hghts over southcentral AZ early next week, however positive hght anomalies will still exist over SE CA and SW AZ which will maintain highs in the low 100s. As ridging aloft begins to expand back over N AZ by mid-week, significant warming is progged to arrive with highs across the western deserts topping out around 100-105 degrees and approaching 100 degrees for the central AZ deserts on Wednesday and Thursday. These will likely be the hottest days of the forecast period before another trough potentially arrives onto the west coast by Friday into next weekend. Overall, subsidence aloft coupled with N-NE flow in the mid-lvls will maintain a dry forecast with near zero rain chances each day next week.

AVIATION

Updated at 1744Z.

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

Gusty easterly winds will prevail through Sunday with mostly clear skies. Winds will be strongest in the morning hours through early afternoon, with speeds mostly around 10-15 kts and gusts around 20-25 kts. Winds will be slightly stronger Sunday morning, with gusts briefly reaching up as high as 30-35 kts between 15-18Z. Winds will stay elevated through the overnight hours around 7-11 kts with an occasional gust. Minor LLWS impacts may develop overnight with 1000-2000 ft AGL winds increasing to 30-35 kts, but shear magnitudes are expected to remain below TAF threshold.

Southeast California/Southwest Arizona including KIPL and KBLH:

No significant aviation weather impacts expected under clear skies. E-NE winds are expected through most of the TAF period at both terminals with speeds mostly at or below 7-12 kts, and occasional gusts to 15-20 kts at KBLH this afternoon. Lighter speeds, with VRB conditions, are expected during the overnight hours.

FIRE WEATHER

Dry conditions with slightly above normal temperatures are anticipated through this weekend before further warming occurs into the middle of next week. MinRHs will mostly range from 15-25% over the western districts to 25-35% for the eastern districts with fair to good overnight recovery area-wide. A persistent breezy easterly gradient wind will continue through at least Monday. Expect winds to remain elevated around 8-12 mph with early morning and afternoon gusts up to 20-30 mph.

PSR WATCHES/WARNINGS/ADVISORIES

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