textproduct: Pendleton

KEY MESSAGES

- Precipitation returns today through this weekend.

- Moderate to heavy mountain snow possible Monday onward next week.

DISCUSSION

A synoptic scale upper trough, positive tiled from nrn BC into the eastern Pacific, will shift toward the region through the weekend, with some feature of a cutoff low at 500 mb developing over the nrn CA coast. A swrly flow aloft will promote vort advection and positive lift into wrn WA Tonight, with Mountain snows increasing with time. IVT around the 100-200 kg/ms will limit the amount of snow and overall lowland QPF. Snow levels are already below pass levels. Ahead of the precipitation onset, HREF ensemble members do not show a returning dense fog signal across the Lower Columbia Basin/Tri-Cities area Tonight and Tomorrow morning, like has been seen the previous 48 hours. For this weekends system, the trend will begin with the mountain snows and low land rains to begin across the Washington Cascades with near 100 percent chances for snow. The snow amounts at pass level will not be significant, as the NBM mean shows about 2-3 inches at White and Snoqualmie Pass. Next week, another AR impacts the region as NBMs 25th to 75th members percentile range of outcomes of roughly 1 to 2 feet of snow at the pass levels for the 3 day period ending Saturday morning. With little if any snow (mean is 2 inches) east of Cle Elum into the Yakima Valley. Similar range of outcomes are showing from the NBM members for the other pass levels of the Washington and and Oregon Cascades, as well as the Northern Blue Mountains near Tollgate. Uncertainty is high as to the overall impacts given these range of outcomes but it seems reasonable to expects some headlines going into the midweek period. Russell/71

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

VFR conditions currently for all sites except PSC where IFR stratus has been in place all day. Confidence in persistence of stratus this evening and overnight is low (30 percent). Elsewhere (and including PSC if stratus breaks) CIGs will lower this evening and overnight as a weak system moves over the region. Precipitation through Saturday afternoon is expected to be mostly light, and most likely (80 percent confidence) rain with low (20 percent) confidence of it mixing with snow at RDM/BDN. Sustained winds of 10 kts or less are anticipated for all sites. 86

Preliminary Point Temps/PoPs

PDT 38 46 35 46 / 30 60 70 30 ALW 40 46 37 46 / 50 60 80 50 PSC 36 49 36 50 / 40 30 40 10 YKM 31 46 32 46 / 40 10 20 10 HRI 36 47 36 49 / 30 40 60 20 ELN 30 43 28 42 / 50 10 10 10 RDM 30 44 29 47 / 10 50 40 10 LGD 36 47 36 50 / 30 80 80 60 GCD 35 48 33 50 / 10 60 60 30 DLS 38 47 39 48 / 70 40 50 20

PDT WATCHES/WARNINGS/ADVISORIES

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