textproduct: Pendleton

DISCUSSION

Through This Afternoon, expected snow will be little more than a trace up on the ridge tops in Kittitas County from a few showers. The remainder of the area was under sunny sky with the exception of a narrow band of broken cirrus spreading west to east into central Oregon. Breezy to windy and relatively dry conditions are the focus for the forecast Today as high pressure is anchored over the region. Downsloping surface winds have adiabatically warmed temperatures across the Columbia Basin into the low 60s in spots, with highs in the mid 50s in most of the valleys.

Short term breezy dry conditions will be replaced with a couple of rounds of precipitation late Saturday Night and again around Wednesday. Increasing clouds on Saturday will limit high temperatures to the lower 50s across the Columbia Basin, and 40s across the Lower Slopes of the WA Cascades.

The latest run of the NBM has also backed off intensity of high level snow amounts across the East Slopes of the Oregon Cascades and the Ochoco John Day Highlands, while creating more uncertainty with respect to onset, anywhere from Saturday evening to sometime Sunday. Mean NBM precipitation amounts of a trace up to around 0.10 on Sunday evening followed by a return to dry conditions across the entire forecast area through Tuesday.

As the high pressure weakens and local microclimate pressure gradients begin to become more impacting, we see the NBM showing stronger winds up to 20 knots in that zone and a 90th percentile showing 30 knots sustained could be in the range of outcomes. So far the GFS/GEFS are showing a weak signal not indicative of high winds.

Another wet period is looking more likely (90%) on Tuesday Night into Wednesday as the ensembles bring in a broad trough with a mid level cold pool and a 100-250 kg/ms IVT atmospheric river broadly inland across the Columbia Basin. With the colder air aloft, snow levels will be coming down (to around the 4,000ft AGL level to promote the return of mountain snows for the eastern slopes of WA and OR Cascades as and to below 5000 ft for the Wallowas.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

VFR conditions prevail for all sites. Cloud coverage will begin increasing around 08Z tonight for KDLS, KRDM, and KBDN. KPDT, KYKM, KALW, and KPSC may see clouds develop around 11Z/12Z Sunday morning (40-50% confidence). Sunday will be a cloudy day for all sites with few-ovc clouds at 25.0kft. Winds will be less than 10kts for this TAF period. Feaster/97

Preliminary Point Temps/PoPs

PDT 32 52 34 52 / 0 0 10 10 ALW 35 52 36 52 / 0 0 0 10 PSC 30 53 32 55 / 0 0 0 0 YKM 30 52 32 55 / 0 0 0 0 HRI 31 52 34 54 / 0 0 0 10 ELN 30 49 29 50 / 0 0 0 0 RDM 27 55 33 52 / 0 20 20 30 LGD 32 57 35 57 / 0 0 10 30 GCD 32 56 36 57 / 0 20 30 50 DLS 34 52 36 55 / 0 0 10 20

PDT WATCHES/WARNINGS/ADVISORIES

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