textproduct: NWS Phoenix

UPDATE...Updated 00z Aviation Discussion

KEY MESSAGES

- Relatively stable temperatures with afternoon highs 4 to 8 degrees above normal will prevail through Saturday, then cool closer to the daily normals Sunday into early next week.

- Breezy conditions will return to the area over the weekend with the strongest gusts across Southeast California where a Wind Advisory has been issued.

- Critical fire weather conditions will be possible this weekend, particularly on Sunday for the Eastern Arizona higher terrain.

SHORT TERM /TODAY THROUGH FRIDAY/

A shortwave trough can be seen on mid-level water vapor imagery over southern California and beginning to push into the western parts of Arizona. This shortwave will help temperatures trend back towards normal, however, afternoon highs today remain 4-7 degrees above normal, with the forecasted high in the upper 90s with localized areas reaching triple digits in the lower desert areas. This shortwave will continue to progress eastwards over today and Friday, however temperatures will only be affected by 1-2 degrees each day as it shifts over the region. H5 heights today and Friday will float between 580-584 dam, which is near climatological average despite the above normal temperatures. Otherwise, ample dry air aloft will keep skies clear, and allow for effective overnight radiative cooling keeping the morning low temperatures near normal, upper 60s to lower 70s, across the lower deserts.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

The main concern in the long term will be increased winds across the region this weekend leading to elevated to locally critical fire weather conditions. Ensembles show good agreement that a trough in the northern stream will move onshore along the Pacific Northwest Coast early Saturday, followed by a period of amplification and strongly negative midlevel height anomalies becoming established over the Interior West. However, WPC cluster analysis continue to show discrepancies in how strong this trough will be and the precise timing, resulting in some uncertainty in how much regional pressure gradients will tighten, but several disturbances are likely to rotate about this larger scale troughing feature, affecting the Desert Southwest this weekend into early next week. The current timing of the stronger winds (and associated areas of fire weather concerns) favors southeast California and southwest Arizona Saturday, the Eastern AZ higher terrain Sunday, and potentially the Lower CO River Valley on Monday. That being said, a Wind Advisory has been issued for the SW portion of Imperial County starting Saturday afternoon through Sunday night.

Aside from winds and fire weather concerns, the pattern this weekend will promote cooler temperatures by Sunday. Latest NBM probabilistic temperature guidance shows spread increasing, with IQRs of at least 5F Sunday onward. However, Monday is shaping up to be the coolest of the next 7 days, with many lower desert areas struggling to reach the middle 90s. Negative midlevel height anomalies appear to depart to the north and east during the middle of next week, allowing H5 heights to rebound closer to 580 dam. Anticipate afternoon highs to warm in response through the middle of the week, likely nearing 100F once again for the typically warmer spots across the lower desert. However, the overall pattern/flow aloft does not substantially change, with ensembles generally showing ridging off the West coast and broad anticyclonic flow over the Western/Central CONUS.

AVIATION

Updated at 2305Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation weather concerns under generally clear skies can be expected throughout the TAF period. The overall wind pattern will continue to exhibit the typical diurnal tendencies with speeds aob 10 kts. Some occasional afternoon/early evening gusts in the mid to upper teens will be common.

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, westerly winds will be common while at KBLH, winds will fluctuate between the south to southwest. Overall wind speeds will range between 8-12 kts throughout the period. At KIPL, sundowner gusts upwards of 20-25 kts will be possible early this evening.

FIRE WEATHER

Slightly above normal temperatures, dry conditions, and lighter winds with typical afternoon upslope/upvalley breeziness will prevail through Friday. A weather system will move onshore along the Pacific Northwest early Saturday and deepen over the Western US resulting in increased winds across the area this weekend. The strongest winds are anticipated in Southeast CA, where a wind advisory has been issued, and into Southwest AZ on Saturday, then the Eastern AZ high terrain by Sunday. This will likely result in elevated to locally critical fire weather conditions as afternoon minRHs will commonly fall in an 8-15% range through early next week, and overnight recoveries ranging from 25-45% across the area and improving only slightly from there on Saturday and Sunday nights.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...Wind Advisory from 2 PM Saturday to 11 PM PDT Sunday for CAZ562.