textproduct: NWS Phoenix

UPDATE

Updated 18z Aviation

KEY MESSAGES

- A low pressure system and lingering showers will exit the region today with a brief period of cooler temperatures.

- High pressure will quickly build into the region the remainder of the week leading to dry weather and record warmth possible by the weekend.

SHORT TERM /Today through Thursday/

A well defined cutoff low continues its slow progression eastward into cntrl/nrn Sonora with several vorticity centers rotating about the larger cyclonic gyre. Upper level divergence fields remain maximized over the forecast area on the northern edge of the cold core with modest theta-e advection importing moisture northward. Several bands of showers will continue to pivot into southern Gila County through the morning before more defined subsidence spreads into the area by late afternoon in response to the cutoff finally accelerating into far west Texas. Thereafter, pronounced height rises will quickly build into the SW Conus as broad subtropical ridging becomes established over the East Pacific. There is excellent forecast confidence H5 heights gradually climb near 585dm resulting in sfc temperatures nearly 15F above normal Thursday.

LONG TERM /Friday through Monday/

Forecast confidence remains excellent through the weekend with resounding ensemble agreement depicting stagnant longwave features settling over the Conus. With trough amplification over the eastern Conus, strong East Pacific ridging will envelop the Southwest with H5 heights oscillating between 582-588dm. Ensemble guidance spread remains extremely narrow and reflects anomalous tropospheric height/thermal measures near the maximum of mid March climatology. High temperatures 20F above normal will become common by the end of the week resulting in widespread minor HeatRisk while also setting daily records (see Climate section). It's becoming inevitable that some the warmer, lower desert communities will experience the first 100F of the season early next week as the NBM 50th percentiles now covers this threshold. Virtually all ensemble members indicate even warmer weather materializing by the middle of next week as H5 heights likely eclipse 590dm. The ensemble guidance envelop is solidly above the 100F threshold for all lower desert communities portending a prolonged period of record setting, and potentially unprecedented warmth.

AVIATION

Updated at 1750Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Winds will generally be out of the west through this evening before shifting out of the east later this evening/overnight. Speeds will generally be under 10 kts, with period of light variability to even calm conditions expected heading into the overnight period. SCT-BKN cloud decks between 4-6 kft will linger through the early afternoon before lifting and scattering out afterwards with clear skies expected later this evening.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns under generally clear skies can be expected throughout the TAF period. At KIPL, winds will generally be light and variable with a period of southerly winds likely this evening through the overnight period. At KBLH, winds will generally be out of the south. Wind speeds will be aob 10 kts.

FIRE WEATHER

Dry weather with unusually warm temperatures and low humidities will return during the latter half of the week with record setting warmth likely by the weekend. Minimum humidity levels in a 25-50% range this afternoon will deteriorate significantly closer to a 7-15% range late in the week. Correspondingly, good to excellent overnight recovery of 60-90% will retreat into a 15-40% poor to fair category. Winds will be fairly light with only modest afternoon upslope gustiness limiting a greater fire weather danger.

PSR WATCHES/WARNINGS/ADVISORIES

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