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FXUS65 KPSR 231157 AFDPSR

Area Forecast Discussion National Weather Service Phoenix AZ 457 AM MST Sat Sep 23 2023

UPDATE
Updated 12z Aviation Discussion.

SYNOPSIS
After a fairly cloudy early part of today, skies will clear out this afternoon allowing for temperatures to warm up into the mid to upper nineties across the lower deserts. Weak high pressure will then dominate across the region through at least the middle of next week bringing slightly above normal temperatures, dry conditions, and generally clear skies.

DISCUSSION
Current satellite imagery shows expansive clouds across southern California and western Arizona early this morning with relatively clear skies for areas east and southeast of Phoenix. These clouds are all associated with remnant moisture from what was TC Kenneth and a weak shortwave trough tracking east northeastward through southern California. Very dry air within the boundary layer is prohibiting anything other than sprinkles or at most very light rain from occurring across the lower deserts west of Phoenix early this morning. These very light showers are forecast to track into the Arizona high country later this morning before the shortwave trough enters northern Arizona. Skies will quickly begin to clear out from southwest to northeast later this morning with sunny skies likely over the lower deserts by mid afternoon. The increased insolation today will help to boost temperatures as highs are expected to reach into the mid to upper 90s across the lower deserts.

As the shortwave trough exits well to the northeast of the region on Sunday, upper level ridging from the subtropical high centered over Mexico will spread over the region. This will boost H5 heights from around 585dm today to 588dm on Sunday, before finally peaking around 591dm on Tuesday and Wednesday. Drier air will overtake the entire region Sunday into early next week with PWATs lowering to around 40-60% of normals and surface dew points gradually dropping into the 20s and 30s. Temperatures will also continue to warm up through early next week with highs reaching to around 100 degrees over most of the lower deserts by Monday before peaking at 100-103 degrees on Tuesday and Wednesday, or right around 5 degrees above normal. Fortunately, the dry air and clear skies will allow for very efficient nocturnal cooling and overnight lows staying right around normal. At some point later next week, with ensembles favoring closer the next weekend, a deep upper level trough will sag southward across much of the Western U.S. This trough should eventually lower heights across our region, increase winds, and bring cooling temperatures. The latest NBM run shows high temperatures finally dipping fully below 100 degrees across the lower deserts around next Saturday.

AVIATION
Updated at 1200Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation weather concerns are expected through the TAF period. BKN to OVC mid to high level clouds aoa 10 kft will become SCT to SKC by mid to late afternoon. Virga associated with these cloud decks may cause periods of gustier winds upwards of 15-20 kts before subsiding in the evening. Otherwise, winds will follow typical diurnal tendencies going into the overnight hours tonight.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation weather concerns are expected through the next 24 hours. Light W to NW winds are favored at KIPL through the period, while winds at KBLH predominantly favor the SSW with extended periods of variability through the morning and again into the overnight hours. A few passing virga showers will remain possible into the early morning hours, which could create some erratic breezy winds at times. SCT-BKN mid and high clouds aoa 10 kft will continue before clearing out going into tomorrow afternoon.

FIRE WEATHER
Tranquil and dry conditions will prevail this weekend into next week. Temperatures will warm up this weekend into early next week with highs eventually at or just over 100 degrees across much of the lower deserts during the first half of next week. Afternoon minimum humidity levels will be the teens today, but then gradually drop into the single digits by early next week.
Overnight MaxRHs will mostly range between 30-50% through Sunday before lowering to 20-40% on Monday. Winds will continue to be on the lighter side over the next several days, though some afternoon upslope gusts remain possible.

PSR WATCHES/WARNINGS/ADVISORIES
AZ...None.
CA...None.

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