textproduct: Pendleton

KEY MESSAGES

- Widespread showers and breezy to windy conditions develop Friday morning into Friday night. Wind Advisories in effect from 8 AM Friday through 11 PM Friday.

- Dry and light wind conditions return this weekend with temperatures below normal.

- Mountain showers and at or below seasonal temperatures Monday onward

UPDATE

Have issued additional Wind Advisories for Friday's wind event, in effect for Central Oregon (8AM-5PM) as well as the Lower Columbia Basin of Washington and the Foothills of the Blue Mountains of Washington (11AM-11PM).

DISCUSSION

Current satellite imagery shows high and mid-level clouds moving in over the forecast area which might make temperatures cooler than the forecasted high temperature for the day, while surface observations are relatively calm and quiet.

Friday...As the upper-level trough and attendant low propagate inland from the coastal PacNW, there is a chance (80-90%) of widespread showers across much of Central and northeast Oregon and into central southern WA early Friday morning. As this system moves through the area, model guidance and ensembles show rain showers beginning after midnight near the Cascades with more widespread rain beginning after 8 AM PDT. There will be a (70-90%) chance for measurable rain for most of the forecasted area Friday, with a chance (80-90%) for wetting rain, more so in the mountainous areas near the Cascades, Ochoco Mountains, and Southern/Northern Blues. At least 0.05-0.2 inches are forecasted elsewhere in the forecast area (50-60%). Along with this precipitation, the upper trough and surface low system will bring gusty west-southwesterly winds to much of the forecast area (85-90%). Winds will be 25-30 mph with gusts up to 35-45 mph across the Cascade Gaps and Columbia Basin due to the strong low-level jet moving through and mixing down to the surface, as well as the Rattlesnake Ridge and Horse Heaven Hills (85-90%). Winds will be 15-25 mph with gusts up to 35 mph elsewhere (70-80%). Yakima and Kittitas Valleys could see gusts 45 mph or higher but chances are lower (35-40%) Friday afternoon.

Saturday-Sunday...Showers and windy conditions should diminish late Friday night into Saturday morning as the upper trough and low propagate northeast out of the forecast area. Relatively dry conditions are expected with the upper flow becoming more westerly bringing light winds back into the area Saturday morning. Model guidance shows a weak broad trough begin to develop offshore the PacNW Saturday night, then slide into the region through Sunday, but due to lack of moisture and strong upper-level flow, it will mostly be dry with light wind conditions and temperatures in the low-mid 60s. Ames/01

Monday through Wednesday: Models show the region to be under a weak split flow pattern with a ridge to the north of the region and a trough to the southwest. This will bring continued dry conditions and light winds through Monday night. In house calculations show the temperatures to be nearly 5 degrees below seasonal average Monday with temperatures in the mid to upper 60s with isolated locations in the Basin seeing low 70s.

By Tuesday models are in agreement that the synoptic system will shift more towards zonal flow. Clusters are in good agreement with mainly the strength of the incoming system with mainly timing being the lack of confidence. By Tuesday morning, light mountain showers will begin over the Washington Cascades before shifting to the crests of the Blue Mountains with 40% of the ensembles showing precipitation chances. Temperatures will be slightly warmer than Monday but still at or near normal seasonal temperatures in the low 70s (40-60%).

Wednesday models begin to phase apart with GFS showing northwest flow aloft precipitation along the Cascade crests and a front coming across the area while the Euro shows continued zonal flow with precipitation along the WA Cascade crests. NBM appears to be a bit more in line with the Euro with only showers along the WA Cascade crests. In house calculations show temperatures to be at or near seasonal normal with a few isolated locations seeing slightly above normal temperatures. Temperatures are set to be in the low to mid 70s (50-60%). 90

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

A weather system will track across the area overnight and early Friday, spreading scattered to numerous showers and increasing the pressure gradients through the gaps, for strong westerly winds with gusts into the 30 to 45 knot range late morning Friday and though the afternoon. HREF probabilities show extremely low (less than 20%) chances for any MVFR ceilings an lower (less than 10%) chances for MVFR visibility in the rains.

Preliminary Point Temps/PoPs

PDT 50 70 41 64 / 0 80 0 0 ALW 55 70 46 66 / 0 90 10 0 PSC 52 73 42 68 / 10 80 0 0 YKM 54 66 40 64 / 60 40 0 0 HRI 52 72 42 67 / 10 80 0 0 ELN 49 61 36 59 / 70 60 10 0 RDM 44 60 31 63 / 60 20 0 0 LGD 52 67 39 65 / 0 50 10 0 GCD 53 67 38 67 / 0 50 0 0 DLS 56 67 45 68 / 70 60 10 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory from 8 AM to 11 PM PDT Friday for WAZ024-027-521. Wind Advisory from 11 AM to 11 PM PDT Friday for WAZ028-029. OR...Wind Advisory from 8 AM to 11 PM PDT Friday for ORZ041-044-507- 508-510. Wind Advisory from 8 AM to 5 PM PDT Friday for ORZ511.