textproduct: Pendleton

DISCUSSION

Models are in good agreement with the upper level ridge approaching across the region this morning, bringing in a west- southwest flow aloft and light precipitation. Mountain areas will continue to see lingering snow showers (>70% confidence) with accumulations up to 0.30" for portions of the WA Cascades and the Wallowas. The NBM raw ensembles show a 40-60% probability of snow accumulating up to 0.70" for the Northern Blues, but 15-30% prob for snow amounts higher than that. Starting later this morning, our forecast area will be dry through Saturday morning.

Over this weekend, the leading edge of a weak upper level ridge will arrive to the region with the associated frontal system. This system will bring light precipitation mainly over the WA/OR Cascades and could spill into other areas (North Central OR, Simcoe Highlands, and Foothills-Southern Blue Mountains of OR). The NBM and HREF models seem to be aligned together with additional light snow up to 2" for the WA Cascades near I-90 to Snoqualmie Pass and US20 to Santiam Pass for East Slopes of OR Cascades. NBM raw ensembles favor a 40-60% prob or more for snow accumulations of 2 to 5" for the highest peaks of the WA/OR Cascades. Ochoco-John Day Highlands and John Day Basin may see snow totals less than 1" (>50% confidence). Low elevations could have light rain up to 0.10", but with low confidence (10-20%). In addition to this system, sustained winds of 15-25 mph with gusts of 25-45 mph may develop over the eastern mountains through this weekend (50-80% prob). With the models revealing tight surface pressure gradients, these winds will also be driven by the south- southwesterly flow from the high terrain of Central OR to the Wallowas. The NBM probability also suggests >50% prob for gusts exceeding 40 mph over the Grande Ronde Valley near Union, OR.

Models depict an persistent active pattern Monday onward with mountain snow and low elevation rain. The Euro looks to be more wetter with the next round of systems arriving sooner than other models, so timing or the amplitude of incoming system could differ. Otherwise, models and ensembles seems to remain in an agreement with the precipitation and frontal systems through the long term (>50% confidence). Feaster/97

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

VFR conditions will prevail for KDLS/KRDM/KBDN throughout the day. Low to mid clouds will continue for the remaining sites during the morning hours (50% confidence). With that, flight categories may become MVFR or lower for KPDT, KYKM, KALW, and KPSC. Conditions will start to improve starting this afternoon. Feaster/97

Preliminary Point Temps/PoPs

PDT 27 47 32 55 / 0 10 10 30 ALW 29 47 36 54 / 0 10 10 30 PSC 27 47 30 53 / 0 10 10 30 YKM 26 39 28 45 / 10 30 30 50 HRI 27 46 30 54 / 0 10 10 30 ELN 23 36 27 41 / 10 40 30 60 RDM 24 44 30 52 / 20 20 10 40 LGD 24 41 33 48 / 0 10 10 30 GCD 22 43 31 50 / 0 20 10 20 DLS 32 43 32 48 / 20 60 40 70

PDT WATCHES/WARNINGS/ADVISORIES

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