textproduct: Pendleton

KEY MESSAGES

- Isolated showers today and Wednesday, mainly over the mountains

- Breezy to locally windy westerly winds through the Cascade gaps today

- Warming through the week

DISCUSSION

Through Saturday, warming temperatures and mostly dry conditions are forecast region-wide as an upper-level ridge of high pressure will likely (95 percent confidence) build into the region from the Pacific and dominate the weather. A couple weak shortwaves coupled with modest diurnally induced instability (surface-based CAPE of a up to a couple hundred J/kg from forecast soundings) may facilitate some isolated showers, mainly over the mountains through Thursday, but PoPs are low (15 percent or less).

Breezy to locally windy westerly winds are forecast through the Cascade gaps today, but not anticipating a need for any wind headlines. Late Wednesday through Thursday, a reversal to mostly light easterly to northeasterly (offshore) winds is forecast as a shortwave trough digs south across the northern Plains and Rockies, just clipping the edge of our forecast area.

Considerable uncertainty in the 500-hPa pattern is present in ensemble solutions by the weekend and early next week, with the majority of the variance in solutions explained by timing and magnitude differences regarding the arrival of a trough or closed low from the Pacific. Ensemble trends have been towards a closed low for the Pacific Northwest sometime between Monday and Tuesday, but run-to-run and ensemble-to-ensemble differences are still quite significant and forecast confidence is lower than average. Ensemble clustering tools did not run today, so can't provide any more details about scenarios at this time.

The NBM has westerly winds returning to the region by late Friday, persisting through the weekend and into early next week. There are low chances (10-40 percent) of reaching advisory- level winds Saturday and Sunday through wind-prone areas of the lower elevations, primarily the eastern Columbia River Gorge, north-central Oregon, the foothills of the Blue Mountains, and the Kittitas Valley. By Monday, chances increase to 20-60 percent across the same areas. Of course, the magnitude of winds will be tied to the synoptic pattern, and given the uncertainty (see paragraph above), can't really talk about much confidence in forecast details yet.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

VFR conditions to prevail through the period. Breezy winds continue at sites DLS/PDT/PSC for the next couple hours tonight, with light and diurnally driven winds developing after 07-08Z. Otherwise, light winds at all other sites through the period. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 46 73 46 76 / 0 0 0 0 ALW 50 73 49 76 / 0 0 0 0 PSC 49 78 51 81 / 0 0 0 0 YKM 47 79 50 80 / 0 0 0 0 HRI 48 76 49 79 / 0 0 0 0 ELN 43 73 45 75 / 0 0 0 0 RDM 37 73 39 77 / 0 0 0 0 LGD 40 70 41 73 / 0 0 0 0 GCD 39 73 39 75 / 0 0 0 0 DLS 50 77 51 83 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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