textproduct: Pendleton

DISCUSSION

An area of surface high pressure remains over Eastern Washington into central Oregon Tonight as visible satellite imagery continues to show widespread stratus across all areas expect for the higher elevations of the eastern mountains. A subtle 500 mb pos vorticity moves northwest to southeast across the area after midnight and through about 00z Friday, offering a slight (localized 20% chances) adjustment to our possible sensible weather. NBM is modeling some very light snow accums (Trace 0.1) across WA694 zone, as well as across the Oregon Cascades. As this system is weak, the surface pattern/cold pool is not anticipated to change. Given this pattern of persistence is expected for another couple of days we extrapolated out probabilities for freezing fog for Tonight. Stratus is likely to remain in place until the weekend when the next approaching system can disrupt the weak pressure gradient we now have and allow the boundary layer winds to develop. Afternoon high temperatures continue to remain well below the NBM values, in the areas under stratus and area closer to NBM 10th or even 5th percentile values. Current forecast continues to reflect a blend of persistence and the 25th percentile NBM through Saturday afternoon.

Air Quality Advisory was reposted/extended though Monday morning for southern Deschutes county. Ensemble 850 mb winds suggests a dominant westerly component and stronger winds speeds in excess of 15kts over a more broad area from the Columbia River Gorge through all of SE WA by Monday, which could be able to mix out some of the areas that have been seeing low stratus and fog for several days in a row. NBM warms temperatures into the upper 30s across ridges to the 40s in the lower elevations and basins.

AVIATION

A range of impacts will persist for the terminals through at least late Friday morning. A blanket of stratus in the 1500 to 2000 ft range persists with a weak shortwave riding nw to southeast overnight, creating orographically lifted snow showers along the Cascades. The system is too weak to impact surface winds Tonight. Lowest visibility and ceilings remain most likely (80%) in the LIFR or VLIFR categories are be expected to return to BDN and RDM.

PRELIMINARY POINT TEMPS/POPS

PDT 22 33 19 35 / 0 0 0 0 ALW 24 32 22 34 / 0 0 0 0 PSC 25 38 20 36 / 0 0 0 0 YKM 23 35 19 33 / 0 0 0 0 HRI 24 34 19 34 / 0 0 0 0 ELN 20 34 17 32 / 0 0 0 0 RDM 19 33 13 37 / 0 10 0 0 LGD 21 35 16 35 / 0 0 0 0 GCD 20 36 16 36 / 10 0 0 0 DLS 27 37 23 38 / 20 10 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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