textproduct: NWS Phoenix

KEY MESSAGES

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

- Monday is expected to be the hottest day with lower desert high temperatures peaking between 105 and 110 degrees.

SHORT TERM /TODAY THROUGH MONDAY/

Upper level ridging is now fully in place over Western CONUS, with the axis centered over the Pacific NW states (WA,OR,CA). Throughout this weekend the ridge will move further inland and is expected to be fully over the desert SW by late Sunday into Monday. H5 heights will steadily climb from 582-584 today to between 588-591 by Sunday/Monday, in response temperatures will also steadily warm, with readings today between 102-104 degrees in the Phoenix area to 103-106 degrees across southeast California and southwest Arizona. By Sunday temperatures will increase 1-3 degrees from today, and highs are expected to peak on Monday to be between 106-109 degrees in the Phoenix area to 108-110 degrees across southeast California and southwest Arizona. Both Sunday and Monday will represent a high-end Moderate HeatRisk for nearly all locations across southeast California through southern and central Arizona with Monday having the highest areal coverage (~25%) of Major HeatRisk. With that being said, an Extreme Heat Warning remains in effect for western portions of Imperial County and for the Phoenix metro for Sunday and Monday, with the Imperial Valley and the Lower Colorado River Valley zones included in the warning for just Monday.

LONG TERM /TUESDAY THROUGH FRIDAY/

A gradual change in the upper level pattern will help to bring some modest heat relief by the latter half of next week. The first change will be a weak trough that is forecast to develop just west of southern Baja on Sunday before tracking northward along the California coastline on Tuesday. This feature is not expected to bring big changes to our region, but it will lead to increased southerly flow and moisture while also somewhat displacing the ridge to our east. Models show decent moisture advection mainly above 15K feet into our region starting Monday night, but more so Tuesday night into Wednesday. Tuesday may bring some sparse higher level clouds, before thicker and more cloud coverage is likely to move in on Wednesday.

The track of the shortwave trough across California Tuesday and Wednesday is also expected to lower heights across the Desert Southwest, but any cooling will be slow to occur. Tuesday's forecast highs are very similar to Sunday's expected readings, but by Wednesday highs are likely to fall back to just above 100 degrees. The latest NBM has come in slightly warmer for afternoon highs on Tuesday for the Phoenix metro, resulting in areas of Major HeatRisk continuing. Thus, we have elected to extend the Extreme Heat Warning for the Phoenix metro through Tuesday Evening. A larger, but weakening Pacific low is then expected to reach the California coast sometime Wednesday into Wednesday night before moving east northeast through Nevada and Utah on Thursday and/or Friday of next week. This disturbance should continue to aid in weak height falls across the Desert Southwest late next week potentially dropping daytime highs into the upper 90s, or around five degrees above normal.

AVIATION

Updated at 1730Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation weather concerns under mostly clear skies can be expected throughout the TAF period. The overall wind pattern will continue to exhibit the typical diurnal tendencies with the normal westerly shift anticipated within the next couple hrs. Speeds should remain around 8-10 kts, although occasional gusts near 20 kts will be possible this afternoon through early evening.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather concerns under mostly 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 for the next few hrs. At KBLH, winds will generally fluctuate from S-SW during the day and veer north late tonight. Overall wind speeds will be aob 10 kts, although a brief period of gusts up to 20-25 kts can be anticipated at KIPL for a few hrs this evening.

FIRE WEATHER

Hot and dry conditions will prevail through this weekend and well into next week with the lower desert highs topping 100 degrees through at least Tuesday. With afternoon highs warming 10-15 degrees above normal, minimum humidity levels will mostly fall into the single digits each day. Correspondingly, overnight recovery will only be in a poor to fair 20-35% range. Winds will be very typical for mid May through Monday with some gusts around 20 mph common during mid/late afternoon. 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 from 10 AM Sunday to 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 from 10 AM Sunday to 8 PM PDT Monday for CAZ562-563-566.