textproduct: Pendleton

KEY MESSAGES

- Warm and dry conditions through the next few days as an upper ridge prevails over the region.

- Cooler, wetter pattern in the midweek with split flow entering the region.

- Light mountain snow showers possible mid to late week (10-20%).

DISCUSSION

Satellite and radar indicate clear and dry conditions across the region as upper level ridge persists and continues to push to the east. High temperatures will continue to get warmer through Wednesday (>90% chance) with MaxTs climbing up to 10 to 15 degrees above climatological average. The upper ridge will keep winds calm and light with just diurnal driven speeds through at least mid-week (70-90% chance).

Weather becomes more active as a trough amplify's from the Gulf of Alaska into the Pacific through the week. Guidance and clusters are in good agreement that the trough will dig south through mid-week and form a cut off low just off the shore of California. It will then move onshore of California (70-80% chance) then continue to push off into the east. Closer to home, another shortwave is moving off the coast of British Colombia and into the PacNW region the same time as the cutoff low is moving across California. This split-flow pattern will bring precip chances up late Wednesday into the rest of the week (40-70% chances) with it being a mostly rain dominant system. Current NBM snow level forecasts over the Wallowas late Thursday through early Friday morning advertise 5500 to 6000 feet with minimum snow heights around 4500 to 5000 feet. A 10-30% chance of light mountain snow showers exists for this scenario, with more areas of a mix of rain/show through the Wallowas and northern Blue Mountains. Depending of the strength of the shortwave above Washington state/British Colombia, a stronger shortwave could bring lighter snow showers to a wider coverage, but not anticipating anything greater than 0.05 inches of QPF (70-90% chance) with dry PWAT values less than 0.25 inches. Looking at the potential for winds, tight pressure gradients developing across the area will be bring breezy to windy conditions across much of the area (with the exception of Central Oregon). Elevated winds with gusts up to 30-35 mph shows 40-70% chances across the region. Upping to wind advisory thresholds (45 mph gusts or greater) secludes chances to the Dalles and other parts of the Cascade gaps with 20-50% chances.

Guidance is in good agreement the weather system will push-off Friday with dry conditions developing with a short-lived ridge entering the region bringing some temporary relief before another shortwave crosses the region Saturday. Agreement is shaky at best going into the weekend with strength all over the place, including the impacts to the area. According to clusters, 22% brings a much weaker solution with a mostly rain dominant solution, while 50% advertise a stronger system with stronger cold air advection. Will need to monitor for snow and rain impacts over the next several days for this evolving forecast.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

VFR conditions currently across all sites, which will stay the course through the period. Light, terrain and diurnally-driven winds are expected to stay below 6 kts. A low chance of light, afternoon rain for KRDM/KBDN (5-10% chance). 75

Preliminary Point Temps/PoPs

PDT 36 62 36 63 / 0 0 0 0 ALW 41 63 39 63 / 0 0 0 0 PSC 36 65 35 68 / 0 0 0 0 YKM 39 63 39 69 / 0 0 0 0 HRI 36 63 35 65 / 0 0 0 0 ELN 35 60 33 65 / 0 0 0 0 RDM 29 59 28 60 / 0 10 10 0 LGD 39 69 36 68 / 0 0 0 0 GCD 39 71 37 71 / 0 0 0 0 DLS 43 66 42 70 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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