textproduct: Pendleton

KEY MESSAGES

- Near to above normal temperatures with dry conditions through Thursday

- Widespread showers and breezy to windy conditions develop late Thursday through Friday

- Split flow emerging Monday bringing light winds and dry conditions

DISCUSSION

Little to talk about across the region tonight, with nighttime satellite imagery only showing decks of cirrus spreading east of the Cascades.

Today through Saturday: Mostly quiet conditions with near to above normal temperatures will prevail today and tomorrow as the PacNW sits underneath a west to southwest flow aloft. During Thursday, flow aloft will increase from the southwest as an upper trough with an attendant surface low swing towards the PacNW. Southerly winds through the Grand Ronde Valley and north/south valleys in Wallowa county will increase to around 15-25 mph with gusts up to 35 mph ahead of the trough/low Thursday afternoon.

Late Thursday, shower activity will increase across the Cascade crest as the upper trough and surface low continue to approach the PacNW. Rain showers will then spread eastward across the remainder of the forecast area early Saturday morning into the afternoon as the trough and remnants of the low continue east. There will be a 60-90% chance of at least measurable rain across much of the forecast area Friday, with a 40-60% chance of 0.25 inches in the northern Blues and a 50-80% chance of 0.5 inches along the Cascade crest and east slopes. In addition to precipitation, the upper trough and surface low passage will bring increasing westerly winds across the forecast area. Winds will be 15-30 mph with gusts 35-50 mph through the Cascade gaps and into the Columbia Basin, with winds 15-20 mph and gusts up to 35 mph elsewhere. Surface winds will be supported by a 40-50kt low level jet that will mix down across portions of the Columbia Basin Friday afternoon, with mod-high confidence (65-80%) that wind advisories will be needed.

Shower activity and windy conditions will diminish overnight Friday into Saturday as the upper trough exits the region to the northeast. Weak broad troughing will develop offshore the PacNW Saturday, placing the region under weak flow aloft. This will result in dry and cool conditions with light winds Saturday (confidence 60-75%). Lawhorn/82

Sunday through Tuesday: Sunday afternoon into Monday has the trough arriving at the coast, centering within California. Model members are in agreement for the timing and position of the trough. After landfall of the trough, a split flow will emerge as trough moves south of the Pacific NW. Impacts will be minimal bringing light winds and dry conditions. Ensemble members are in slight disagreement with the progression of the trough in California, with the Global and Canadian members having it linger till Tuesday afternoon, while the European member has it leave Monday night. Monday into Tuesday ensemble members show increasing mountain showers with offshore troughing, while deterministic forecasts shows a low pressure system with possible cold front passage. Confidence in timing and extent of showers is low (15% Confidence). Near to below normal temperature conditions are expected from Sunday into Tuesday.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

DLS/PDT/RDM/BDN: VFR conditions likely to continue over the TAF period. No risk of high winds, low cloud base, or low visibility present for the TAF period.

YKM/ALW/PSC: VFR conditions to prevail through the period. Winds will be light and diurnally driven. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 74 46 77 52 / 0 0 0 10 ALW 75 52 78 56 / 0 0 0 0 PSC 77 47 78 51 / 0 0 0 20 YKM 74 48 74 53 / 0 0 0 70 HRI 77 47 78 51 / 0 0 0 20 ELN 69 42 69 47 / 0 0 0 80 RDM 73 39 80 44 / 0 0 0 70 LGD 78 47 85 52 / 0 0 0 0 GCD 80 47 87 52 / 0 0 0 0 DLS 76 50 77 54 / 0 0 0 80

PDT WATCHES/WARNINGS/ADVISORIES

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