textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion.

KEY MESSAGES

- A large low pressure system will meander across California through the latter half of the week leading to breezy to locally windy conditions and elevated fire weather conditions across the region.

- Temperatures will cool to below normal levels as early as today across the western deserts and eventually across the rest of Arizona Thursday into Friday.

- Above normal temperatures are forecast to return by early next week with highs topping 100 degrees by Monday.

SHORT TERM /TODAY THROUGH FRIDAY/

An anomalously strong upper level low has settled in across central California and western Nevada over the past 24 hours and is forecast to essentially remain in place through Thursday. The outer expanses of the low also extend well into the Desert Southwest, particularly into southeast California where temperatures will be heavily influenced today. A modestly strong gradient will continue across much of our area today providing a continuation of breezy to locally windy conditions. The strongest winds today will remain across western Imperial County where gusts of over 30 mph are expected. Elsewhere, afternoon wind gusts should most commonly reach between 20-25 mph with some locales reaching 30 mph. The closer proximity of the low to southern California are expected to keep daytime highs only in the mid 80s, whereas the Phoenix area will still easily reach into the lower 90s.

The low is forecast to begin filling later starting tonight and continue into Friday as it slowly shifts northeastward into the Nevada and then Utah by Friday night. The gradient during this weakening phase will slacken off allowing winds to decrease Thursday into Friday. Wind gusts Thursday will primarily top out around 25 mph and mainly be over the Arizona high terrain before winds return to normal on Friday. Temperatures Thursday are forecast to be within a degree on today's highs before areawide highs Friday become more uniform in the upper 80s to around 90 degrees.

LONG TERM /SATURDAY THROUGH TUESDAY/

Once the low ejects northeastward into the Central Rockies on Saturday, height rises and modest warming will spread over our region. A ridge will also begin to develop over the Southern and Central Plains this weekend increasing its influence over the Desert Southwest, especially by early next week. NBM/WPC forecast temperatures reach closer to seasonal normals on Saturday and then within the normal range by Sunday. Model guidance then favors the ridge to shift westward early next week with the ridge axis moving into New Mexico by around Monday or at the latest Tuesday. Due to the shift in the ridge, H5 heights are forecast to reach near 588dm by Tuesday, or just shy of the 90th percentile of climatology. High temperatures are expected to easily top 100 degrees across the lower deserts by Monday with peak readings anywhere from 103-108 degrees on Tuesday and/or next Wednesday. These temperatures will easily push our HeatRisk into the Moderate category, but relatively mild overnight lows in the upper 60s to mid 70s will help to limit the chance of reaching near the Major category.

Dry conditions and clear to mostly clear skies are forecast for the weekend, but there are some signs of increasing moisture first across New Mexico around Monday and then potentially advecting into eastern Arizona as early next Tuesday. If this increase in moisture comes to fruition, shower and thunderstorm chances across the high terrain may come into the picture by Tuesday. There is still a good deal of uncertainty with any rain chances next week, so stay tuned.

AVIATION

Updated at 1115Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Breezy afternoon and evening winds will be the main aviation weather impact through the TAF period. Winds will behave similarly to yesterday with easterly winds continuing through the early morning hours before becoming S-SW around 15Z this morning, resulting in a prolonged period of southerly cross winds. Later the afternoon will bring westerly winds with gusts between 20-25 kts lasting through 02-04Z tonight. FEW high cirrus will pass overhead at times.

Southeast California/Southwest Arizona including KIPL and KBLH: Strong wind gusts will continue to be the primary aviation weather impact through the TAF period, with westerly wind gusts exceeding 30 kts at KIPL and SW-S gusts up to 25-30 kts at KBLH. The gusty winds will pick up again by late this morning peaking by the evening hours. The winds will generate blowing dust regionally, which may reduce slantwise visibility, but the wind orientation will not be ideal for significant surface visibility reductions at the terminals. FEW high cirrus will pass overhead at times.

FIRE WEATHER

A large weather system situated over California and portions of the Desert Southwest will continue to bring breezy to locally windy conditions into Thursday. Elevated fire weather conditions will be a concern during the afternoon/early evening hours with occasional wind gusts of over 25 mph and MinRHs between 12-20%. The strongest gusts of over 30-35 mph will affect portions of southeast California. Temperatures will cool off today across the western districts and eventually across the region of the area by Friday with readings stay at or below normal through Saturday. Winds are expected to diminish Thursday into Friday with overall light winds across the area by Saturday. High pressure is forecast to build across the region over the weekend into early next week leading to quick increase in temperatures and falling RHs, but winds will remain on the lighter side.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...Wind Advisory until 5 AM PDT Thursday for CAZ562.