textproduct: Pendleton

KEY MESSAGES

- Dry conditions and warming temperatures into the middle of the week

- Mountain showers and thunderstorms return Wednesday, and again Friday into the weekend

- Breezy winds will redevelop in the lower elevations late Wednesday and persist into the weekend

DISCUSSION

Today through Early Wednesday: Water Vapor satellite imagery tonight shows a broad upper low centered over northern MT, with visible satellite showing thin cirrus extending across portions of eastern WA.

Today, the intermountain PacNW will sit between the upper low over MT and a developing upper level ridge offshore. Tomorrow through early Wednesday, the ridge will slide over the PacNW, bringing temperatures into the upper 70s to mid 80s in the lower elevations. Otherwise, conditions will remain dry with locally breezy afternoon winds.

Wednesday through Sunday: Ensemble guidance is in good agreement of an upper shortwave trough sliding across the PacNW Wednesday, though there remains some uncertainty in the exit timing and strength of this feature. While the main consensus is for a return of mountain showers and breezy lowland winds into Thursday morning, under half the members (~45%) favor a stronger shortwave that will bring area wide showers late Wednesday that will linger across the Blues/Wallowas into Thursday afternoon. Otherwise, this pattern would also favor a return of afternoon/evening isolated thunderstorms over the mountain areas Wednesday.

Dry conditions will return to the area after the shortwave exit sometime Thursday, but breezy to locally gusty Cascade gap winds will persist(confidence 60-70%). Ensemble guidance is in good agreement that an upper low will arrive offshore the PacNW Friday then push inland Saturday morning. Showers will develop along the Cascade crest Friday, then spread along the east slopes and over the northern Blues late Saturday morning (confidence 50-60%). Disagreement grows amongst ensemble guidance Saturday afternoon through Sunday in regards to how quick the trough passes overhead, with the leading solutions (~60% of members) favoring the trough exiting to the eat by Sunday afternoon, while the remaining members favor the trough still over the region. The former solution would favor drier conditions developing by Sunday afternoon, while latter favor s continued mountain showers through Sunday. Overall forecast confidence is low-moderate(35-45%) at this time. Besides precipitation, the upper low arrival and subsequent passage will produce breezy winds across the lower elevations and below normal temperatures through the weekend (confidence 50-60%). Lawhorn/82

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

VFR conditions to prevail through the period. Winds will be light, 12kts or less, and terrain/diurnally driven through the period. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 77 48 80 49 / 0 0 0 0 ALW 77 52 80 54 / 0 0 0 0 PSC 82 52 84 53 / 0 0 0 0 YKM 82 53 83 54 / 0 0 0 0 HRI 81 50 82 51 / 0 0 0 0 ELN 77 49 78 51 / 0 0 0 0 RDM 74 41 80 46 / 0 0 0 0 LGD 73 45 78 46 / 0 0 0 0 GCD 76 42 82 45 / 0 0 0 0 DLS 83 57 86 59 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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