textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion.

KEY MESSAGES

- A large low pressure system will meander over California over the next few days leading to breezy to locally windy conditions and elevated fire weather conditions across the region.

- Below normal temperatures will be common across the region through at least the start of the weekend.

- Above normal temperatures are forecast to return by early next week with highs reaching around 100 for many locations by Sunday.

SHORT TERM /TODAY THROUGH FRIDAY/

An unseasonably strong area low pressure has settled over Central California and Western Nevada and is expected to remain relatively stationary through at least Thursday. The heaviest influence from this disturbance will be felt over Southeast California and Southwest Arizona, where well below normal temperatures will be felt. Afternoon readings west of Maricopa County will range in the middle to upper 80s, a good 10-15 degrees cooler compared to what we typically see this time of year. Further removed from the cooler air associated with the low, temperatures in and around the Phoenix metro will reach into the lower and middle 90s, still below normal, but closer to what is more common for late May.

After a breezy day regionwide yesterday, thanks to the approach of the previously mentioned system tightening up our regional pressure gradient, winds will be enhanced once again this afternoon and evening. Gusts should hover close to 20-30 mph for most areas, with the exception of the typically windy spots of Southeastern California where gusts may exceed 35+ mph. A Wind Advisory remains in effect for the far Southwestern corner of Imperial County until Thursday morning due to the elevated potential of gusts reaching 45+ mph.

As we transition into the back half of the week, the California low will begin to fill in and slowly begin to lift to the northeast toward Utah. As this occurs, the gradient will begin to weaken, but will take a bit of time to do so, so breezy and locally windy conditions can be expected to continue into Thursday regionwide, before becoming more focused over the eastern portion of our forecast area by Friday as the system migrates. In terms of temperatures, trends will vary depending on your location. Over SE CA, readings will gradually trend upwards, while further east, a downtrend will take place as cooler air spreads further into Southern Arizona. Regardless of your location, below normal temperatures will be common across the region through Friday.

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 1735Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Gusty S-SW winds through early this evening and a prolonged period with a southerly cross-runway component at KPHX will be the main weather issues through the TAF period under mostly clear skies. Winds have already established out of a prevailing southerly direction, with occasional gusts into the upper teens observed. Directions will vary between 160-210 before gaining a more decidedly westerly component between 21-23Z. Gusts will subside between 03-05Z this evening, with moderate confidence in a typical nocturnal E/SE wind switch before sunrise Thursday. A similar evolution to the winds is expected Thursday.

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. Winds will increase through the afternoon, with gusts peaking early this evening (overnight at KIPL). 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.