textproduct: Pendleton

KEY MESSAGES

- Dry conditions will remain dry and warm into the midweek

- Another round of breezy conditions will develop Sunday, strongest winds in the Cascade Gaps

- Mountain rain shower and isolated thunderstorm chances return midweek

DISCUSSION

Tonight through Monday: Upper level ridging has redeveloped over the region, with satellite showing cirrus spilling into the northern half of the forecast area this afternoon. Winds have been light, with dry conditions across much of the area.

The upper ridge will keep conditions fairly dry while temperatures remain around 5 to 15 degrees above normal across the much of the region. These conditions will continue through Monday as the upper ridge continues to influence the region. While winds will be light the remainder of today and Monday, a shortwave passing through the ridge on Sunday will bring another round of widespread breezy conditions (15-25mph with gusts 25-40mph). Once again there is growing concern of stronger winds through the Kittitas valley, however confidence is only moderate (55-65%) in wind gusts reaching 45 mph Sunday afternoon.

Tuesday through Friday: Ensemble cluster guidance is in good agreement in the breakdown of upper level ridging over the region Tuesday, with a deeper south to southwest flow developing as well as a signal for thermal troughing to develop into eastern and central OR. This will promote a modest increase in high temperatures over the region, with upper 80s to mid 90s in the lower elevations, and mid 70s to mid 80s in mountain valleys. In addition to warming temperatures, instability across the mountainous terrain will also introduce a slight chance (15-25%) of showers and isolated thunderstorms for Tuesday afternoon into the evening.

Tuesday night through Friday, disagreement grows amongst ensemble guidance in the evolution of the synoptic pattern. The majority consensus (~60 to 70% of members) is that an upper low/trough offshore will kick inland sometime late Tuesday into Wednesday. A northern track of the low feature will bring shower and isolated thunderstorm chances to most mountain areas and the Blue Mountain foothills, while a southern track keeps the best chances across central and eastern OR. Following the trough passage, a quick transient ridge will bring dry conditions across the area Wednesday night into Thursday morning (confidence 45-60%). Thursday afternoon into Friday, ensemble cluster guidance depicts upper level troughing developing offshore, with 50% of members favoring shower chances across the Cascades and eastern mountains, and the other 50% favoring shower chances only along the Cascade crest. Overall forecast confidence in timing and extent of shower chances is low- moderate (25-40%) during the Wednesday through Friday period. Lawhorn/82

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

VFR conditions to prevail through the period. Winds will remain light, 12kts or less, at sites PDT/RDM/BDN/YKM/ALW/PSC through the period. Site DLS will see winds increase to around 20kts with gusts to around 30kts around 17Z. Lawhorn/82

FIRE WEATHER

High pressure will remain over the region with dry and warming conditions persisting at the surface. Breezy west to northwest winds will develop Sunday, with strongest winds through the Cascade gaps. A breakdown in high pressure Tuesday will result in an increasing unstable airmass over portions of central Oregon and the eastern mountains. Afternoon relative humidities will be mostly in the teens to mid 20s, with single digits in central Oregon this afternoon and again Tuesday afternoon.

Preliminary Point Temps/PoPs

PDT 48 78 46 77 / 0 0 0 0 ALW 51 79 50 77 / 0 0 0 0 PSC 50 84 50 81 / 0 0 0 0 YKM 51 83 46 80 / 0 0 0 0 HRI 49 82 48 79 / 0 0 0 0 ELN 48 75 43 76 / 0 0 0 0 RDM 45 81 38 83 / 0 0 0 0 LGD 44 84 43 79 / 0 0 0 0 GCD 43 89 43 84 / 0 0 0 0 DLS 53 77 48 82 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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