textproduct: Pendleton

KEY MESSAGES

- Light to moderate mountain showers across the WA Cascades and Northern Blues today

- Breezy winds through the Columbia Basin and Eastern Columbia River Gorge this afternoon

- Near to above normal temperatures, mostly dry conditions, and light winds develop into early next week

DISCUSSION

Nighttime satellite imagery tonight shows increasing mid to upper level cloud cover from northwest to southeast. Meanwhile radar is showing returns mostly over northwest WA at this time, with returns slowly expanding south and east.

Today and Wednesday: Zonal flow aloft will remain over the forecast area throughout today and Wednesday, however an upper shortwave trough passing through BC will clip the WA Cascades and northern Blue mountains. This will result in light to moderate rain showers developing across these areas. Since 24 hours ago, chances for 0.1 inches of precip in the Northern Blues has fallen quite a bit, with only a 10-25% chance through tonight. Meanwhile, there is a 70-95% chance of 0.25 inches along portions of the WA Cascades and east slopes (highest chances in central WA Cascades, lowest south central WA Cascades). In addition to the shortwave trough, a weak cold front boundary will move across WA during the day. This will result in breezy west to southwest winds (15-25mph with gusts 25-40 mph) in the Columbia Basin and Eastern Gorge developing throughout the day, with light to locally breezy winds elsewhere.

Flat upper level ridging in the eastern Pacific will build into the western CONUS by Wednesday morning, resulting in a return to dry conditions and light winds.

Thursday and Friday: Ensemble guidance are in good agreement that near zonal flow will persist over the PacNW as a flat ridge remains just south of the region. This will allow a subtle shortwave to slide across the PacNW Thursday, with very light showers developing across the WA Cascades during the day (confidence 55-65%).

Friday, ensemble and deterministic guidance are in favor of upper level ridging beginning to build into the PacNW from the south, with a drying and warming trend beginning. However, about 22% of members made up from the ECMWF, GFS, and Canadian ensemble suites favor another shortwave trough quickly sliding across the area, resulting in another round of showers across the Cascade crest/east slopes and the northern Blues Friday. At this time, confidence is low (20%) in this solution developing.

Saturday through Monday: Upper level ridging will continue to build over the PacNW over the weekend and into early next week (confidence 50-70%). Temperatures will be on a gradual warming trend, with a return to 80 degree temps next Monday (50-75% chance). Otherwise, dry conditions with light winds will prevail during this period. Lawhorn/82

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

VFR conditions to prevail through the period. CIGs are expected to remain 5kft AGL or higher as a system moves through the area. Winds will increase to 12-17kts with gusts 20-30kts at sites DLS/PDT/ALW/PSC between 19Z and 1-3Z. Otherwise, winds will be light through the period. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 76 49 72 46 / 0 10 0 0 ALW 75 54 72 50 / 0 10 10 0 PSC 78 49 75 45 / 0 10 0 0 YKM 74 50 71 48 / 10 10 0 0 HRI 77 51 75 45 / 0 10 0 0 ELN 66 44 66 42 / 20 20 0 0 RDM 75 38 74 39 / 0 0 0 0 LGD 75 47 70 44 / 0 0 10 0 GCD 75 43 74 45 / 0 0 0 0 DLS 74 53 76 49 / 0 10 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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