textproduct: Pendleton

KEY MESSAGES

- An upper low and trough will move across the region through early Sunday.

- Mountain snow tonight, with the highest amounts over the Cascades.

- Mountain thunderstorms Saturday afternoon.

- Dry weather from Monday onward.

DISCUSSION

An upper level low and trough was moving into the Pacific Northwest. On Saturday, it will be over the region and then by Sunday it will be moving eastward and out of the area.

After the low departs the region, high pressure and dry weather will move in for most of the upcoming week. By the end of the week, high temperatures will average about 5 degrees above normal.

As the low and trough move into the area tonight through Saturday morning, snow levels will drop. By Saturday morning, snow levels will be below 4000 feet across the Cascades and below 3500 feet across the Washington Cascades. Therefore, some snow is likely, with several inches possible even at pass level, especially the higher passes like White Pass where there could be 2 to 4 inches and possibly more. At the highest elevations there could be locations that even more. During the day, there would likely be a mix or a changeover to rain or at least any snow that falls would not accumulate.

Additionally on Saturday, as the upper low moves across the area, there will be enough instability for thunderstorms in the mountains, though overall chances are generally <= 20 percent.

By Sunday, precip chances shift eastward mainly to eastern Oregon, with the trough, and there is still at least low thunderstorm chances.

Saturday looks breezy to windy once again, mainly along the Cascade gaps, Kittitas Valley, Columbia Basin, central Oregon and Blue Mountain Foothills. Wind gusts of 30 to 35 mph wind guts with gusts to 40 mph are possible. Will have to see how things develop to see if any wind headlines are needed, but guidance overperformed today. NBM probabilities of wind gusts >=47 mph is generally < 50 percent in these areas.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Radar shows some rain showers close to PDT and ALW that will slowly dissipate over the next few hours. Not expecting any sites to dip below VFR over the next 24-hours, but the main highlight will be the wind. Winds will decrease going into the early morning hours, but will once again re-strengthen to 20 to 30 knots going into the mid to late morning hours. In ALW, expecting light showers to move-in by 18Z. There is a slight 5 to 10% chance that a moderate shower will bring in MVFR conditions briefly.

Preliminary Point Temps/PoPs

PDT 40 59 36 62 / 20 30 30 0 ALW 43 58 40 62 / 30 70 50 10 PSC 41 65 38 70 / 10 20 20 0 YKM 37 64 37 70 / 10 10 0 0 HRI 39 63 37 67 / 10 20 10 0 ELN 32 56 34 63 / 40 10 10 0 RDM 31 54 26 60 / 10 10 20 0 LGD 37 51 34 54 / 40 70 60 10 GCD 36 52 32 54 / 20 30 60 10 DLS 43 60 40 67 / 80 30 20 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Winter Weather Advisory until 11 PM PDT Saturday for WAZ522. OR...Winter Weather Advisory until 11 PM PDT Saturday for ORZ509.