textproduct: NWS Phoenix

UPDATE

06Z 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 0505Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation concerns are expected during the TAF period. Winds will follow familiar light and diurnal trends with window of VRB to calm conditions, especially overnight and during directional changes. Other than a FEW high clouds over the region tonight, skies should be mostly clear.

Southeast California/Southwest Arizona including KIPL and KBLH: The only aviation concern over the next 24 hours will be FG potential at KIPL. As of now, too much uncertainty exists to include a prevailing or even TEMPO group for reduced VIS at the terminal, therefore, only VCFG is mentioned in the TAF at this time. Updates may be needed if direct VIS impacts are realized. Otherwise, both terminals will experience light winds with extended periods of VRB to calm conditions and just a FEW passing high clouds early tonight.

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.