textproduct: NWS Phoenix

UPDATE

18Z Aviation Discussion

KEY MESSAGES

- A gradual warming trend is anticipated through the remainder of this week and into this weekend. Lower desert highs will return to near normal across southcentral AZ and slightly above normal for areas a long and west of the Lower Colorado River Valley.

- Aside from lingering isolated shower activity in southern Gila County today, dry conditions will return to the region through early next week as high pressure takes hold over the region.

SHORT TERM /TODAY THROUGH FRIDAY/

Latest GOES satellite wv imagery and 500 mb streamline analysis reveals a deep cutoff low which is centered directly over Gila County. This low has been responsible for periods of showers and storms across the Desert Southwest during the last 48 hours with some locations receiving over 2.00" of rainfall. A good chunk of southcentral AZ received around 0.25"-1.00" of rain with the highest totals residing over northern and western Maricopa County and S Gila County. A few wrap around showers and storms are currently developing within the proximity of the upper-low and this will likely continue through the rest of this morning and into the early afternoon as the low center slowly migrates ewd. These showers may produce an additional few hundredths to a tenth of an inch of rainfall. Dry air will gradual filter in behind this system as PWAT values fall below 1.00" late this afternoon and evening, ultimately ending rain chances region-wide. Dry conditions will prevail through the remainder of this week with essentially no rain chances expected across the entire Desert Southwest.

Due to the presence of negative 500 mb hght anomalies and elevated soil moisture from yesterday's widespread rainfall, sfc temperatures are expected to remain well below normal across southcentral AZ this afternoon. Lower desert highs will mainly range from the low to mid 80s with temperatures across the higher elevations in the low to mid 70s. For areas along and west of the Lower Colorado River Valley, clear skies and a drier airmass will allow temperatures to climb to around normal mainly in the low to mid 90s. Upper-lvl ridging will begin to build in behind the departing weather system Thursday and Friday, causing temperatures to steadily climb around 3-5 degrees each day. Lower desert highs should return to the mid 90s to around 100 degrees by Friday.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Model guidance shows upper-lvl ridging migrating over the Four Corners region by this weekend with 500 mb hght fields increasing to around 588-590 dam. As this occurs, global models show a weak upper- low developing over N MX and far W TX which will induce easterly flow aloft over our forecast area. The increased pressure gradient between both features will bring breezy conditions to southeastern and southcentral AZ from Saturday through Monday. Elevated winds will likely develop each morning and persist into the early afternoon with gusts reaching 30-35 mph over the high terrain and 20- 25 mph across the lower deserts. This sfc easterly flow will help keep high temperatures near normal across southcentral AZ, but overnight lows will be elevated in the low to mid 70s. The 500 mb ridge axis looks to shift back to the over SoCal and the Great Basin early next week as a weak trough passes through the Intermountain West. This pattern should maintain temperatures in a near normal range across central and eastern portions of the region, but allow highs to warm around 3-5 degrees above normal across the western deserts where highs will likely reach the low 100s each afternoon.

AVIATION

Updated at 1710Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation concerns are expected during the TAF period. Winds will be very light with extended periods of VRB conditions. The typical westerly shift is not anticipated this afternoon, though some occasional observations are still likely. Cloud decks as low as 6-8 kft will linger through early this afternoon ahead of clear skies through the remainder of the forecast.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns are expected during the next 24 hours under clear skies. Outside of extended periods of VRB conditions, southerly/southeasterly flow will be common at bother terminals, with speeds generally aob 10 kt.

FIRE WEATHER

After the last couple days of abundant wetting rainfall, drier conditions are expected to return today as a weather system departs the region. Temperatures will remain well below normal across southcentral AZ and near normal for areas along and west of the Colorado River Valley through the rest of this week with gradual warming anticipated by this weekend. Relative humidity will bottom out around 15-30% across the western districts and remain above 40% across the eastern districts today and Thursday. Good to excellent overnight recoveries can be expected through the remainder of this week. Winds will return to light and diurnal patterns with speeds remaining predominantly 10 mph or less over the next few days before a stronger easterly gradient wind sets in by this weekend.

PSR WATCHES/WARNINGS/ADVISORIES

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