textproduct: NWS Phoenix

UPDATE

00Z Aviation Discussion.

KEY MESSAGES

- Temperatures will warm well above normal late this week through the weekend, in the nineties for many lower desert locations, resulting in widespread Minor Heat Risk.

- Temperatures are expected to warm further next week, likely reaching the triple digits across the lower deserts and breaking daily and potentially monthly high temperature records.

SHORT TERM /TODAY THROUGH THURSDAY/

A fairly persistent area of light showers E/SE of the Phoenix area has subsided and moved out of the CWA early this afternoon as a well- defined cutoff low progresses eastward over Chihuahua. As flow aloft has turned northerly on the backside of this cutoff low, midlevel moisture is already scouring out, with only lingering low level moisture leading to cumulus development across portions of South- Central AZ. Confidence remains excellent that midlevel heights will now build along the West Coast over the next few days, with mean H5 heights eventually reaching a 585-589 dam range. This will result in rapid warming into the 80s (5F-10F above daily normals) Wednesday and then lower to middle 90s by Thursday (around 15F above daily normals).

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 2335Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation weather concerns are anticipated through the forecast period. Elevated westerly flow with intermittent gusts into the teens will continue over the next couple hours. Winds will diminish below 8 kts after sunset and shift out of the E-SE late tonight with periods of calm conditions at times. FEW to SCT altocumulus with bases around 7-8 kft will dissipate this evening and lead way to clear skies through Wednesday.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns under mostly clear skies can be expected across SE California. At KIPL, winds will generally be light and variable with a period of S-SE winds likely this evening through the overnight period. At KBLH, winds will generally be out of the south. Speeds are expected to remain aob 10 kts at both sites.

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.