textproduct: NWS Phoenix

KEY MESSAGES

- Isolated showers and thunderstorms will be possible across South Central Arizona late this afternoon.

- Tropical moisture will arrive into the region tonight into Friday, further increasing rain chances mainly across the foothills and high terrain areas east of Phoenix before chances shift into Southwest Arizona and Southeast California this weekend.

- Temperatures remain in a near to below normal category for the rest of this week and into the weekend, resulting in widespread Minor Heat Risk and localized areas of Moderate Heat Risk.

SHORT TERM /TODAY THROUGH FRIDAY/

Latest GOES-18 mid-lvl wv imagery and 500 mb streamline analysis reveals a broad trough of low pressure encompassing the Pacific NW and Intermountain West while a ridge of high pressure extends from the Southern Plains into the southeastern U.S. Our forecast area is situated between both of these features under a prominent fetch of dry SW flow aloft. Meanwhile, now Cat 2 Hurricane Marie is churning over the E Pacific, well southwest of the tip of the Baja Peninsula. Moisture advection is ongoing well out ahead of the main circulation into N Sonora MX and beginning to encroach on southern AZ. Moisture will continue to be transported nwd into central AZ with PWAT values expected to climb to around 1.5-1.7" later today through early Friday, however there is expected to be a well defined moisture gradient from E to W across AZ. Much drier air associated with the troughing to the NW of our region will extend into SE California and southwest AZ through Friday which will really limit rain chances across the western half of the forecast area until better moisture arrives this weekend. NBM PoPs have continued to shift ewd with each subsequent run and the main focus for shower and storm activity now looks to be east of Phoenix, mainly in the foothills of Maricopa County and S Gila County. This aligns with the latest WPC ERO for Day 2 (Friday) with an eastward shift in the slight risk which mostly encompasses the TWC forecast area and clips S Gila County. Nonetheless, CAMs still indicate a few pop up isolated showers and storms in central Maricopa County including the Phoenix Metro area late today through early Friday and again Friday afternoon/evening. Some storms could produce gusty wind and localized flash flooding.

Due to the presence of troughing to our west maintaining 500 mb hghts within a 587-590 dam range, temperatures will be within a degree or two of daily normals through the end of this week. Lower desert highs will generally range from the upper 90s to around 105 degrees each afternoon, following morning lows from the upper 70s to middle 80s. The West Coast trough will also promote a tighter mid lvl pressure gradient over southeast CA and western AZ which will lead to continued breezy to locally windy conditions across the Imperial and Lower Colorado River Valleys. Gusts could reach upwards of 25-30 mph in the aforementioned areas and potentially as high as 40 mph in far SW Imperial County.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Global models are coming into somewhat better agreement with the pattern evolution this weekend. Both the ECMWF and GFS show high pressure strengthening over the southern Plains with the western periphery of the ridge extending over E AZ and NM. This will cause the subtropical jet to shift wwd beginning Saturday, setting up better moisture advection over southeast CA and southwest AZ. NBM PoPs are still not overly impressive, mainly in the 20-30% range on Saturday, however the GEFS/GFS indicates a final slug of moisture from Marie being pulled into southeast CA on Sunday with PWATs rising above 2.0". Therefore we will have to monitor for heavier rainfall potential in portions of SE California including Joshua Tree NP on Sunday. Elsewhere, across southcentral AZ, rain chances look to be meager due to more extensive cloud cover and very low instability. The latest WPC QPF field shows a local minimum in rainfall totals (<0.10") in southcentral AZ including the Phoenix Metro through this weekend. By early next week, there are large discrepancies in the ridge/trough positioning which will complicate the precipitation forecast, but there will still be adequate moisture across our region which will keep low end PoPs in place across eastern and southeastern AZ Monday and Tuesday with potentially better precipitation chances arriving Wednesday.

The temperature forecast this weekend into early next week remains largely unchanged, although there will likely be a gradual increase from near normal temperatures on Saturday to slightly above normal temperatures Sunday into early next week as ridging strengthens over the region. Depending on how strong the ridge gets, NBM temps could climb a few more degrees in subsequent runs and it is not out of the question that we could see lower desert highs approaching 110 degrees as indicated by the NBM 75th percentile on Monday and Tuesday.

AVIATION

Updated at 0520Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation concerns are expected through Thursday evening under FEW-SCT cloud decks around 8-12 kft. Winds will favor diurnal trends with a slower-than-ususal turn to westerly flow, resulting in a window of southerly crosswinds at KPHX and KDVT. There are hints of TS developing in the southern and eastern portions of the airspace by the afternoon hours with perhaps some cells migrating to within the vicinity of the terminals. KIWA is the most likely (20-30% chances) to see VCTS, but nearby convection cannot be ruled out for the other sites. However, chances are too low (<20%) to warrant inclusion of even VCTS at this time for KPHX, KDVT, and KSDL.

Southeast California/Southwest Arizona including KIPL and KBLH: Breezy conditions, once again during the afternoon and evening, hours will be the main aviation concern. Winds overnight will be light, with perhaps some variability being observed at times, especially at KBLH. Flow will contain some degree of a westerly component at KIPL while KBLH switches between southerly and southwesterly directions. Mostly clear skies will be common over the region.

FIRE WEATHER

Isolated to widely scattered showers and storms will be possible in southcentral AZ later today through Friday. Rain chances will expand westward through this weekend, becoming focused over the western districts Saturday and Sunday. The best chances for wetting rainfall will be over the higher terrain areas of eastern and southeastern AZ. Afternoon minimum humidities will range from 7-15% across southeast CA and between 20-35% for the remainder of the region through Friday and will likely increase above 25% areawide this weekend. Overnight recoveries will range from poor across the western deserts and good to excellent across the eastern districts. Daytime winds will remain elevated out of the south to southwest, with the strongest gusts in Southeast CA and along the Lower Colorado River Valley peaking between 20-30 mph during the afternoon/early evening.

PSR WATCHES/WARNINGS/ADVISORIES

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