textproduct: NWS Phoenix

UPDATE

Updated 18Z Aviation Discussion.

KEY MESSAGES

- An Extreme Heat Warning will be in effect for the Phoenix Metro from late this morning through Tuesday and for portions of the western deserts today and Monday. - Moderate HeatRisk will impact the majority of the area through the first half of the week with isolated major HeatRisk through Tuesday.

- Monday will be the hottest day with lower desert high temperatures as hot as 110 degrees.

SHORT TERM /TODAY THROUGH TUESDAY/

Current objective analysis shows a weak shortwave trough tracking through the Four Corners area, while a reinforcing ridge of high pressure is already nudging in behind the trough. As the ridge moves directly overhead later today lasting through Monday, temperatures will continue to heat up. Extreme Heat Warnings go in effect late this morning for the Phoenix metro and across western Imperial County with highs averaging 103-107 degrees across the lower deserts. As heights aloft peak near climatological records tonight into Monday, the air mass will heat up even more with NBM forecast temperatures ticking up another 3 degrees or so, averaging 106-109 degrees. Monday's readings should fall just short of daily records and bring more widespread Major HeatRisk. Additional Extreme Heat Warning areas for Monday include much of the Lower CO River Valley, Yuma, and El Centro. Expect continued clear skies through Monday and seasonably low RHs reaching the single digits during the afternoon hours.

Model guidance continues to show a weak shortwave trough developing west of Baja by Monday before tracking northward Tuesday into Wednesday across California. This disturbance will somewhat push the upper level ridge to our east, but the ridge axis will remain close enough on Tuesday to keep near record high temperatures in place across the eastern half of Arizona. Forecast highs Tuesday for Phoenix do drop off a couple of degrees, but most locations within Phoenix will still reach 105 degrees and the Extreme Heat Warning will remain in place through early Tuesday evening. Southeast California will be much closer to the passing disturbance allowing for a more noticeable cooldown with highs dropping to 102-105 degrees. Winds will also become quite breezy Tuesday afternoon focused across the Lower CO River Valley. Gusts of 25-30 mph and low RHs during the afternoon hours should promote elevated fire weather conditions across the Lower CO River Valley.

LONG TERM /WEDNESDAY THROUGH SATURDAY/

The latter half of the coming week will involve a larger Pacific system moving into northern California on Wednesday displacing the ridge over our region well to the east by Thursday. Wednesday should be a bit of a transition day as heights really start to lower, but daytime highs may react more to the influx of upper level moisture and clouds. Forecast highs are still shown to top 100 degrees, but on average should be between 100-103 degrees across the lower deserts. As the flow turns from the south on Wednesday to more out of the west on Thursday, any moisture and clouds will get pushed to the east out of the region. The Pacific system is then favored to move east northeastward through northern Nevada into Wyoming on Thursday, but it will also help to further depress heights over our region lasting through Friday. Models are now trending slightly cooler late this week with highs potentially dipping into the mid to upper 90s on Friday. The outlook for next weekend favors temperatures warming back up to 100 or just over 100 degrees as a brief ridge moves through the region, while dry conditions and generally clear skies prevail.

AVIATION

Updated at 1744Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation concerns are expected throughout the TAF period. Winds will follow typical diurnal tendencies and speeds will generally be aob 10 kts. However this afternoon/evening could see speeds periodically above 10 kts with gusts near 20 kts. Skies will remain mostly clear for the TAF period.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns are expected through the TAF period. At KIPL, winds will be SE'rly through the afternoon turning W'rly by this evening for the over night hours. At KBLH, winds will be S/SW'rly early this afternoon through the remainder of the period. Overall wind speeds will be aob 10 kts. Skies will remain clear throughout the period.

FIRE WEATHER

Hot and dry conditions will prevail through the first half of this week with lower desert highs averaging 105 degrees. Minimum humidity levels will mostly fall into the single digits each day with only very minimal improvement across the eastern districts going into midweek. Overnight recoveries will remain poor to fair averaging 20-35%. Winds will be light and diurnal today, before elevated easterly winds with gusts to around 25 mph impact the eastern districts Monday morning. Tuesday will bring more of a predominant southerly wind, particularly across the western districts where afternoon gusts of 25-30 mph will be possible. 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 11 AM to 8 PM MST Monday for AZZ530- 532.

Extreme Heat Warning until 8 PM MST Tuesday for AZZ537-540- 542>544-546-548-550-551.

CA...Extreme Heat Warning from 11 AM to 8 PM PDT Monday for CAZ567- 569-570.

Extreme Heat Warning until 8 PM PDT Monday for CAZ562-563-566.