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 starting Wednesday with afternoon highs in the mid to upper eighties across the western deserts to the low 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 latest water vapor satellite imagery as well as streamline analysis show a large, potent upper-level low centered near northern CA. Modest height falls and an increasing pressure gradient will lead to increasing winds this afternoon through this evening, particularly across southeast CA through the western third of Arizona, where gusts between 25-35 mph can be expected. Across the western half of Imperial County, mountain rotors will lead to even higher wind gusts in excess of 40 mph where wind advisories are in effect. With the strong winds will also come the potential for blowing dust, resulting in temporarily reductions in visibilities. Afternoon high temperatures today will top out in the mid 90s across most of the lower desert locations.

The aforementioned upper-level low will slightly migrate into central CA on Wednesday. As it does so, 500 mb height fields will decrease into the 568-576dm range and thus cooler surface temperatures into a below normal category can be expected. Afternoon highs across the western deserts are only expected to top out into the mid to upper 80s, which will be a solid 10 degrees below normal for late May. Across the south-central AZ lower deserts, afternoon highs will be warmer, with readings topping out in the low 90s. Breezy to locally windy will extend areawide as the upper-level jet on the southeast periphery of the trough extends into AZ. Widespread afternoon/evening peak gusts are expected to range between 25-35 mph, with locally higher gusts across the western half of Imperial County once again.

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 0003Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Breezy afternoon and evening winds will be the main aviation weather impact through Wednesday. W-SW winds gusting as high as 20-25 kts will continue through 04-05Z this evening before subsiding and diurnal E winds will develop by 07-09Z. Gusty S winds will develop by 15-17Z Wednesday and persist through 00-01Z before shifting more W-SW. Wind gusts Wednesday will be around 20-25 kts again. Gusty southerly crosswinds will be an impact for PHX and DVT for much of the day. FEW to SCT high clouds will clear out tonight.

Southeast California/Southwest Arizona including KIPL and KBLH: Strong wind gusts will be the primary aviation weather impact through Wednesday, with westerly wind gusts exceeding 30 kts at KIPL and SW-S gusts up to 25-30 kts at KBLH. The gusty winds will subside overnight, but pick up again by late morning Wednesday and peak in the evening. The winds will generate blowing dust regionally, which may reduce slantwise visibility, but the wind orientation is not ideal for significant surface visibility reductions at the terminals. High clouds now will clear out later tonight.

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 until 5 AM PDT Thursday for CAZ562.

Wind Advisory until 3 AM PDT Wednesday for CAZ566-567.