Area Forecast Discussion

KEY MESSAGES

- Light showers prevail through the afternoon in the Basin into the Yakima/Kittitas Valley.

- Mostly dry conditions continue Wednesday and later through the day.

- Active weather with breezy winds through the late part of the week and into next week.

DISCUSSION

Radar currently advertises light precip across the Columbia Basin into the Yakima/Kittitas Valley that will continue through the afternoon hours. Soundings from OTX taken at 12z show lower level dry air, which will allow little precip to accumulate out of this system. PoPs are tapered up to 15% through the general populated areas north of the Blue Mountains.

Area of low pressure is located right off the coast of California and is expected to move inland (>90% confidence) over southern Oregon and northern California over the next few hours. Rain chances continue to be low (<20% chance) through late Wednesday, but conditions remain mostly dry with ridging developing just north in British Columbia. Ridging will keep the weather dry and slightly warmer going through late Wednesday, but guidance is in great agreement that a shortwave from the Pacific will move inland by late Wednesday/early Thursday. Light precip and locally breezy winds develop with the passage, otherwise not expecting mush of any impacts from this system (50-70% chance).

Looking towards the weekend, EURO and GFS members are hinting of another weather system with a shortwave embedded pushing along the area with periods of high PoPs (50-70% chances) along the Cascades with lower chances (10-30% chances) across east of the Cascades and into the populated centers across the rest of the CWA. That shortwave will then push north and northeastward into Canada by early next week (50-70% confidence), with another system right behind located in the Pacific. Guidance gets shaky after Sunday/Monday with guidance struggling with the strength and timing of the second shortwave. GFS members favors a stronger/wetter system, while Euro members trend towards a weaker/drier system. At this point not seeing meaningful impacts currently, as IVT values are currently <250 kg/ms through Monday. Still plenty of time to monitor for this evolving forecast incase the set-up changes.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

MVFR or lower conditions to impact most sites through tonight, otherwise VFR conditions expected to prevail after 17Z. Sites DLS/RDM/BDN are already seeing either low CIGs or low vsby impact the sites tonight. VSBY 1SM or lower is expected to develop at sites RDM/BDN with CIGS down to 300ft tonight, then clear after 15Z. Site DLS is expected to see vsby remain around 3SM through 17Z. VSBY at sites PDT/YKM are expected to deteriorate to around 3SM after 08Z, with 1SM or lower developing at site PDT around 11Z. Short-term guidance tonight is favoring intermittent MVFR vsby developing at site PSC between 11Z-15Z tomorrow morning, so have included in the TAF tonight. Site ALW is expected to remain VFR through the overnight period, but short-term guidance does indicate a chance (30-40%) of low vsby/CIGs developing around the Walla Walla valley overnight. Winds will be light, 12kts or less, through the period. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 31 52 37 56 / 0 0 50 30 ALW 35 51 40 54 / 0 0 50 40 PSC 31 53 35 59 / 0 0 40 20 YKM 32 54 35 59 / 20 0 30 0 HRI 29 53 36 59 / 0 0 50 20 ELN 27 51 30 53 / 10 0 50 0 RDM 22 57 30 53 / 0 0 20 0 LGD 31 57 34 54 / 0 0 20 50 GCD 31 58 35 53 / 0 0 20 20 DLS 35 55 40 60 / 0 0 50 10

PDT WATCHES / WARNINGS / ADVISORIES

WA...None. OR...None.