textproduct: NWS Phoenix

UPDATE...Updated 06z Aviation Discussion

KEY MESSAGES

- An Extreme Heat Warning has been issued for Phoenix and portions of southeast California on Sunday and Monday.

- Widespread moderate HeatRisk will develop today into Saturday with isolated major HeatRisk early next week.

- Monday should be the warmest day next week with lower desert high temperatures peaking between 105 and 110 degrees.

SHORT TERM /Today through Saturday/

On mid-level WV imagery, an upper level ridge can be seen building over Western CONUS, and a small cut off low continuing to progress eastwards into western Texas. Today, afternoon high temperatures will be between 99-102 in the Phoenix Metro, and between 100-105 in the western deserts as H5 heights are between 581-583 dam. Heights are expected to increase further heading into the weekend with H5 heights between 582-584 dam on Saturday, causing temperatures to warm another 1-3 degrees across the lower deserts. While temperatures in the low to mid 100s aren't completely uncommon for this time of year, they still fall in the 90th percentile of climatology. Otherwise, very dry air associated with this ridge will keep skies clear, which in turn will increase overnight low temperatures to the low to mid 70s across the lower deserts.

LONG TERM /Sunday through Thursday/

A stronger subtropical ridge will also build across the eastern Pacific through Saturday, eventually shifting eastward into our region Sunday into Monday. This will give a quick boost to upper level heights raising H5 heights to 585-588dm Sunday before peaking between 588-591dm Monday, which is near the 99th percentile of climatological records. Even hotter temperatures will occur across the area Sunday into Monday with some Major HeatRisk developing across the lower deserts. Highs Sunday are expected to reach 104-106 degrees in Phoenix to 105-108 degrees across the lower deserts of southeast California and southwest Arizona. With peak heights on Monday, highs are likely to be between 106-108 degrees in Phoenix to 107-110 degrees across the western deserts. Monday's highs should be the closest to records with the forecast only 2-4 degrees shy.

An Extreme Heat Warning has been issued for the Phoenix metro for Sunday and Monday, while the Warning remains in effect for the same time period across western Imperial County. This heat event will bring our hottest temperatures so far this spring, but again the dry conditions will allow for a decent reprieve during the overnight hours with most locations dipping into the upper 60s to the lower 70s.

By Monday night into Tuesday, a weak cut-off low that forms over the weekend just off the coast of southern Baja, is expected to track toward southern California as an open wave. This disturbance is not anticipated to bring much of anything other than some higher level clouds on Tuesday and Wednesday, but it should help to lower heights and temperatures slightly. Although the forecast temperature spread increases starting Tuesday, models still heavily favor a cooling trend into the latter half of next week as the ridge weakens and ejects eastward. High temperatures are shown to drop back closer to 100 degrees by next Wednesday or Thursday.

AVIATION

Updated at 0510Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major weather concerns under clear skies can be expected throughout the TAF period. The overall wind pattern will continue to exhibit the typical diurnal tendencies with speeds aob 12 kts, although occasional gusts near 20 kts will be common once again for Saturday afternoon/early evening.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation weather concerns under clear skies can be expected throughout the TAF period. At KIPL, winds will generally prevail out of the west, with the exception of a period southeasterly winds during the early to mid-afternoon hours. At KBLH, winds will generally fluctuate out of the south to southwest. Overall wind speeds will be aob 12 kts, although some gusts upwards of 20-25 kts will be possible at KIPL once again for Saturday evening.

FIRE WEATHER

High pressure will remain in place leading to hot and dry conditions lasting through at least the first half of next week. Highs are forecast to top 100 degrees across the lower deserts by Saturday with the peak of the heat occurring on Monday. Expect MinRHs from 6-12% each day with poor overnight recoveries mostly between 20-35%. Winds will remain relatively light for much of the period, but some afternoon breeziness with gusts around 20 mph likely. The combination of the hot temperatures, very low RHs, dry fuels, and breezy conditions focused during the late afternoon hours should result in elevated fire weather conditions for portions of the area.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Extreme Heat Warning from 10 AM Sunday to 8 PM MST Monday for AZZ537-540-542>544-546-548-550-551.

CA...Extreme Heat Warning from 10 AM Sunday to 8 PM PDT Monday for CAZ562-563-566.