Marine Weather and Tide Forecast for Rillito, AZ

DISCUSSION

Low amplitude ridging today is bringing clear skies and above normal temperatures across southeastern Arizona. To the west, a shortwave trough approaches, set to cross the region through Monday. A surface pressure gradient will tighten tonight from east to west in response to the incoming wave. This pressure gradient will increase east to southeast winds across much of southeastern Arizona, especially in east-southeast oriented valleys. That especially includes the Gila River and San Simon valleys and locations immediately downstream of Redington Pass in the Tucson area. Sustained winds of 25 to near 35 mph will be likely in these locations with gusts up to 40 mph. A Wind Advisory has been issued for much of the southeastern Arizona's lower elevation areas, excluding central to western Pima county.
Additionally, a blowing dust threat will accompany these winds, especially across more dust- prone areas within the San Simon Valley which impact portions of Interstate-10 between Willcox and the AZ/NM state line.

The east-southeast flow will also bring an increase in mid-level moisture to southeastern Arizona. The 12Z HRRR suite shows good chances of 0.4-0.7 inches of precipitable water by Sunday afternoon, adequate for at least a slight chance (10-15 percent)
of mainly dry thunderstorms. While the overall chance of measurable precipitation is very low with dry lower levels still in place, a few light showers can't be ruled out with the added support of the crossing shortwave trough. Gusty outflow winds up to 45 mph is the more likely culprit from any shower/thunderstorm given the dry sub- cloud layer and inverted-V forecast soundings for Sunday.

The pressure gradient will loosen Sunday afternoon with winds diminishing through the evening, however southeasterly breezes are likely in the Gila through much of the night. The exiting trough on Monday will be centered over the White Mountains and will bring a chance of afternoon showers and thunderstorms to the high terrain.

Looking at the rest of this upcoming work week, deeper troughing out of the Pacific will make its way over the Great Basin and Rockies, remaining mostly to the north of the desert southwest.
Stronger quasi-zonal flow associated with this pattern will keep southeastern Arizona dry, breezy, and around 2-7 degrees above normal.

AVIATION
Valid through 20/00Z.

SKC through 19/03Z, then increasing mid to high level clouds through the remainder of the forecast period. Ceilings mostly above 20k feet with a few areas of 15k foot ceilings. Surface winds east-southeast 10-15 kts with gust up to 20 kts east of KTUS through 19/05Z, then increasing to 15-20 kts with gusts up to 30 kts after 19/05Z. Areas of the Gila River Valley including KSAD will see the strongest winds through Sunday with southeast winds of 22-26 kts and gusts to 35 kts. KSAD may also see localized BLDU with visibility down to 3-5SM. A period of LLWS possible at KTUS between 19/07Z and 19/11Z before surface winds increase as southeasterly wind at 1500-2000 ft AGL increases to 40 kts. Winds gradually diminish Sunday afternoon and evening, remaining breezy Sunday night at KSAD.

FIRE WEATHER

High pressure building in from the east tonight will bring strengthening east-southeast winds across much of southeastern Arizona through Sunday. Expect winds of 20-30 mph with gusts up to 35 mph, with stronger winds in areas exposed to east- southeast flow (especially through the Gila River Valley). The pressure gradient will loosen with winds diminishing through the late afternoon and evening hours Sunday. Although minimum RHs between 15-20 percent are anticipated in the valleys east and northeast of Tucson Sunday, we may see brief near critical Fire Weather conditions develop. In addition to the winds, a gradual increase in low and mid- level moisture will result in a slight chance (10-15%) chance for cloud buildups or a dry thunderstorm over the higher terrain Sunday afternoon. Little-to-no rainfall is expected. A stray lightning strike combined with gusty and erratic outflow winds could result in a new wildfire start and rapid growth with abundant dry fuel. Much lighter winds are expected Monday with a lingering chance of thunderstorms in the White Mountains in the afternoon. Passing systems to the north will keep southeastern Arizona dry but breezy each day through the remainder of the work week.

TWC WATCHES/WARNINGS/ADVISORIES
Wind Advisory from 3 AM to 1 PM MST Sunday for AZZ503>507.
Wind Advisory from midnight tonight to 1 PM MST Sunday for AZZ508-509.