textproduct: NWS Phoenix

UPDATE

18Z Aviation Discussion.

KEY MESSAGES

- Dry conditions with temperatures hovering around 5 to 8 degrees above normal will prevail through this weekend.

- A slight cooling trend is anticipated by early next week with lower desert highs falling into the low to mid 70s

SHORT TERM /TODAY THROUGH SUNDAY/

A Rex blocking pattern continues to affect the Western U.S. with the ridge center slowing shifting from northern California to off the coast of Oregon. Deep troughing is also affecting much of the central and eastern U.S. with a strong shortwave currently digging southward through the Central Plains. The shifting of the high center away from our region, the reinforcement of troughing to our east and is leading to lowering heights over our region. Despite H5 heights lowering from 582-584dm yesterday to 576-578dm today, it will have relatively little effect on our temperatures. This brief dip in heights should knock a degree or two off our highs today, but they will stabilize over the weekend as a new high center forms over California. This benign weather pattern will keep dry conditions in place through the weekend with temperatures mostly between 5-8 degrees above normal. Daytime highs this weekend are forecast to top out in the mid 70s for the bulk of the lower deserts under periodic thin high clouds.

LONG TERM /MONDAY THROUGH THURSDAY/

Little change is anticipated for the first half of next week as the Rex block evolves more into an Omega block with upper level ridging persisting across much of the Western U.S. The center of the ridge will remain north of our region, but it should still provide a good amount of influence. Forecast H5 heights are shown to lower a bit further early next week and this should eventually push daily highs more into the lower 70s by Tuesday or Wednesday. A closed low is also likely to become a bit more organized off the West Coast during the first half of next week before potentially approaching our region late next week. Models usually have a difficult time handling the timing of the cut-off low evolution, so it would not be surprising if the timing of this low gets pushed back a few days. A minority of the ensemble members currently show a fairly organized closed low moving near our region by next weekend bringing a return of rain chances, but it is way too early to speculate on any details. If this low does come to fruition, it should be a fairly warm system with higher snow levels and temperatures at most falling back into a normal range.

AVIATION

Updated at 1705Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation weather concerns under generally clear skies can be expected throughout the TAF period. Winds will follow light and diurnal tendencies with speeds aob 8 kts. Extended periods of variable and calm conditions will be common.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather concerns under mostly clear skies can be expected throughout the TAF period. Through early Saturday morning, winds will generally fluctuate between west to north at both sites with speeds under 10 kts, with periods of variable and calm conditions. Wind speeds will pick up late Saturday morning out of the north, with some gusts approaching 20 kts, especially at KBLH.

FIRE WEATHER

Unseasonably strong high pressure will continue to bring above normal temperatures and dry conditions through at least the weekend. Daily MinRH values will mainly fall between 15-20% with overnight recoveries of 30-50%. Winds have also settled down, but some breezy northerly winds will remain possible through Saturday across the Lower CO River Valley and over the Arizona high terrain.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...None.