textproduct: Pendleton

KEY MESSAGES

- Near to above normal temperatures with dry conditions through today

- Widespread showers and breezy to windy conditions develop later tonight through Friday, then a return to dry and quiet conditions with below normal temperatures this weekend

- Light showers for Monday afternoon into Tuesday with moderate confidence in timing and extent(40%) but low confidence in amount(10%).

UPDATE

Model guidance and ensembles show winds to be very breezy tomorrow with 70-90% confidence in winds reaching advisory criteria. With that, a Wind Advisory has been issued for the Eastern Columbia River Gorge of OR & WA, Simcoe Highlands, North Central Oregon, Foothills of the Blue Mountains, Lower Columbia Basin and the Yakima Valley from 8 AM to 11 PM Friday.

DISCUSSION

Nighttime satellite imagery tonight shows scattered decks of cirrus moving across the forecast area, while surface observations show quiet conditions.

Today through Sunday: Mostly quiet conditions with near to above normal temperatures will prevail again today as the PacNW sits underneath a southwest flow aloft. As an upper trough approaches coastal PacNW later this morning, a modest southerly low level jet (25-35kts) will develop over northeast OR. These jet winds will mix down to the surface, resulting in southerly winds (15-25 mph with gusts up to 35 mph) through the Grand Ronde Valley and north/south valleys in Wallowa county through this afternoon.

Later tonight, shower activity will increase across the Cascade crest as the upper trough and an attendant surface low continue to approach the PacNW. Rain showers will then spread eastward across the remainder of the forecast area early Friday 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 only a 30-45% chance of 0.25 inches in the northern Blues and a 65-95% 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 west to southwest winds across the forecast area. Winds will be 20-30 mph with gusts 35-50 mph through the Cascade gaps and into the Columbia Basin and adjacent foothills/valleys, with winds 15-25 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 (75-90%) that gusts 45mph or higher will be observed in wind prone areas.

Shower activity and windy conditions will diminish Friday night into Saturday as the upper trough and surface low exit to the northeast. Weak broad troughing will then develop offshore the PacNW Saturday, then slide across the region through Sunday. Lack of moisture and strong flow aloft with this feature will result in dry conditions with mostly light winds, and temperatures below normal over the weekend. Lawhorn/82

Monday through Wednesday: Monday has split flow conditions still present for the region, with troughing to the south and ridging to the north, bringing low impacts of dry conditions and light winds(40% confidence). Ensemble members are in agreement with timing, strength, and position of the split flow conditions and the trough to the south(93% of members). Monday afternoon into Tuesday, ensemble members are split 50%/50% on the presence of either a shortwave trough or a ridge building over the Basin. Both situations bringing light showers(40% confidence) with low confidence(10% confidence) in rainfall amounts for the Cascade Crest and East Slopes. 35% of the ensemble cluster members show light showers for the CWA around midday Tuesday. Tuesday into Wednesday has similar conditions present with the split changing to favor the ridge pattern building over the region at 52%/48%. Low confidence (10%) in light showers for Tuesday afternoon into Wednesday. Temperatures for the region will be near/ slightly below normal.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

KDLS/KRDM/KBDN:VFR should prevail for most of the forecast period. Rain chances increase around 08Z Friday, ceiling are expected to lower along side this to around 11,000ft.

KYKM/KPSC: VFR conditions prevail through the most of the period. Rain chances inceraes after 07Z Friday, with the rain ceilings are expected to lower to around 10,000ft.

KALW/KPDT: VFR conditions prevail though most of the forecast period. Rain hances incerases after 11Z Friday, ceilings associated with this rain are expected to lower to about 8,000ft.

Toward the end of the forecast period a wind advisory comes into effect for KYKM/KDLS/KPDT. Sustained winds for this advisory are expected to prevail from the SW at 17-26 kts with gusts up to 39-47 kts.

Preliminary Point Temps/PoPs

PDT 79 50 70 41 / 0 0 80 0 ALW 80 55 70 46 / 0 0 90 10 PSC 79 52 73 42 / 0 10 80 0 YKM 74 54 66 40 / 0 60 40 0 HRI 79 52 72 42 / 0 10 80 0 ELN 70 49 61 36 / 0 70 60 10 RDM 84 44 60 31 / 0 60 20 0 LGD 85 52 67 39 / 0 0 50 10 GCD 88 53 67 38 / 0 0 50 0 DLS 78 56 67 45 / 0 70 60 10

PDT WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory from 8 AM to 11 PM PDT Friday for WAZ024-027-521. OR...Wind Advisory from 8 AM to 11 PM PDT Friday for ORZ041-044-507- 508-510.