textproduct: Pendleton

KEY MESSAGES

- Widespread breezy to windy westerly winds Sunday, strongest through the Kittitas Valley

- Below-normal temperatures, breezy to locally windy westerly winds, and occasional mountain showers through the week

DISCUSSION

Water vapor satellite imagery this afternoon shows the center of an upper low has come onshore, though regional radar imagery so far today has shown shower activity has mostly been focused outside of the forecast area. Shower activity across the Cascade crest/east slopes and across the eastern mountains will develop over the next couple hours as the low continues to push inland. Increasing surface instability and modest low to mid level lapse rates will also allow for a few showers to develop into isolated thunderstorms through this evening. Otherwise, breezy west to northwest winds have developed through the Cascade gaps into the Columbia Basin today.

The upper closed low pushing into the PacNW today will start the prolonged trend of upper level troughing over the PacNW through most the next week. The upper low will track east across the region through Monday, with the main shower activity tied to a series of shortwaves rounding the low both days. That said, shower activity will mainly be confined to portions of the Cascades, Northern Blues, and Wallowas through this period, with best chances over the Wallowa Mountains. Cluster ensemble guidance is in good agreement of shortwave troughs diving down the AK/BC coastlines and across the PacNW Tues/Wed and Thursday, which will bring another round of light mountain rain showers across the forecast area those days (confidence 55-75%).

As mentioned earlier, breezy winds have developed in the lower elevations today, and are expected to persist through much of the week as the troughing pattern holds over the PacNW. The strongest winds of the week will develop tomorrow afternoon as a surface low develops in northern MT, resulting in a tightening cross-Cascade pressure gradient. Winds will generally be 15-30 mph with gusts up to 40 mph, however winds through the Kittitas valley are expected to increase to 25-35 mph and gusts to around 50 mph tomorrow (confidence 75-85%). Otherwise, daily winds will be 15-25 mph with gusts to around 35 mph throughout the week.

Lastly, the persistent trough pattern will keep temperatures much cooler than normal through the week, with afternoon temperatures generally 5 to 15 degrees below normal (confidence 60-75%). This means that afternoon temperatures in the lower elevations will be in the 70s, with locally 80s, throughout much of the week. In the mountains, mid-elevations will generally be in the upper 50s to 60s, with lower to mid 50s in the high- elevations. Lawhorn/82

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

VFR conditions are forecast at all sites for the next 24 hours. Winds will be breezy to windy and gusty through the majority of the period, strongest during the afternoon and evening hours Sunday. There is a low (10-30 percent) chance of rain showers overnight into Sunday morning at PDT/ALW/PSC, but opted to forgo any PROB30 or TEMPO groups for rain showers in the 06Z TAFs due to insufficient confidence in timing/location.

Preliminary Point Temps/PoPs

PDT 49 73 50 72 / 10 20 10 10 ALW 54 74 53 72 / 10 30 20 30 PSC 55 81 54 78 / 10 10 0 10 YKM 51 81 53 81 / 0 0 0 0 HRI 52 77 52 75 / 0 10 0 10 ELN 51 71 52 72 / 0 0 0 10 RDM 41 67 40 70 / 30 0 0 0 LGD 45 65 47 69 / 30 40 20 30 GCD 42 65 44 71 / 50 40 10 0 DLS 54 73 55 72 / 10 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory from 10 AM to 11 PM PDT Sunday for WAZ026. OR...None.