textproduct: NWS Phoenix

UPDATE

Updated 12Z Aviation Discussion.

KEY MESSAGES

- A large weather system will stall out across California over the next few days leading to breezy to locally windy conditions and elevated fire weather conditions across portions of the Desert Southwest.

- Temperatures will cool to below normal levels starting Wednesday with afternoon highs in the mid to upper eighties across the western deserts to the lower nineties across the south-central Arizona lower deserts.

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

SHORT TERM /TODAY THROUGH WEDNESDAY/

The weather system that brought showers and thunderstorms Sunday and Monday is finally exiting the region to the northeast leaving drier conditions and clear skies. However, another much larger Pacific low is already moving southward along the Pacific Northwest coast with guidance showing it stalling out across the northern half of California later today. Modest height falls will occur across the Desert Southwest today into Wednesday, particularly across southern California. This will lead to increased winds especially starting this afternoon with gusts of 30-45 mph becoming common across portions of southeast California and northwestern Arizona to 20-30 mph across southern and central Arizona. Advisory level winds are likely to occur this evening across the western half of Imperial County with blowing dust becoming a possibility.

As the low gets closer to our region tonight into Wednesday, cooler air will begin to filter into the region. This cooler air mass will lower daytime highs Wednesday into the mid to upper 80s across the western deserts to as low as the lower 90s in the Phoenix area. Breezy to locally windy conditions will persist over much of the area through Wednesday as the low center shifts slightly farther south over central California.

LONG TERM /THURSDAY THROUGH MONDAY/

Model guidance heavily favors the Pacific low staying in place across California into Nevada through Thursday, but it expected to begin filling and lessening the threat for windy conditions. Thursday should be another breezy day, but more muted compared to today and Wednesday. The low is forecast to finally begin shifting more into the Great Basin while continuing to weaken on Friday. NBM forecast temperatures will stay below normal Thursday and Friday with highs anywhere from the mid to upper 80s across the western deserts to around the lower 90s across the south-central Arizona lower deserts.

The upper level weather pattern should weaken across much of the Western U.S. over the weekend with weak ridging to zonal westerly flow taking over across the Desert Southwest. Height rises and warming conditions are expected beginning this weekend, likely persisting through early next week. The latest NBM/WPC forecast temperatures shows highs around 100 degrees by Sunday and as high as 104-108 degrees by next Tuesday.

AVIATION

Updated at 1124Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation concerns are expected throughout the TAF period. Easterly winds will prevail through the early morning hours before a few hours of southerly winds develop ahead of the westerly shift this afternoon. Gusty conditions will pick back up this afternoon with gusts between 15-20kts. Just past midnight winds will relax and begin to switch out of the east while the two northern terminals becoming light and vrb. Skies will remain mostly clear with the exception to few passing cirrus clouds throughout the period.

Southeast California/Southwest Arizona including KIPL and KBLH: Breezy to windy conditions will be the main aviation weather impact during the next 24 hours, with 25-30 kt westerly gusts at KIPL expected again by 20Z this afternoon, lasting through the end of the period. Winds will also increase again to around 30 kts at KBLH by ~18Z through past midnight tonight. Wind directions will be out of the west through the period at KIPL and favor a S-SW at KBLH. The winds will likely generate blowing dust enough to create some slantwise visibility impacts with a low chance for surface visibility reductions. Mostly clear skies will be common through this morning before high clouds move in.

FIRE WEATHER

A much larger weather system will dive southward into the Southwestern U.S. over the next couple of days creating breezy to locally windy conditions. Elevated fire weather conditions will become a concern starting this afternoon as winds pick up and MinRHs stay between 10-20%. The gusty winds will continue through at least Wednesday with the strongest gusts of over 30 mph affecting portions of the western districts, while temperatures dip and MinRHs improve slightly (15-25%). Breezy conditions may persist into Thursday before dying down into Friday as the weather system weakens and moves away from the region. High pressure is then expected to build across the region over the weekend into early next week leading to an increase in temperatures and falling RHs, but winds are forecast to be fairly light.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...Wind Advisory from 3 PM this afternoon to 5 AM PDT Thursday for CAZ562.

Wind Advisory from 5 PM this afternoon to 3 AM PDT Wednesday for CAZ566-567.