textproduct: Pendleton

KEY MESSAGES

- Conditions will remain dry and warm into the midweek

- Breezy conditions today, with strongest winds in the Cascade Gaps

- Mountain rain shower and isolated thunderstorm chances return midweek

UPDATE

Winds have touched advisory criteria through the Kittitas Valley this afternoon, and am anticipating (80 percent confidence) them to remain in the 25-35 mph range with gusts up to 45 mph through evening as a shortwave trough passes over the region and cross- Cascade pressure gradients remain tight (5-7 mb difference between SEA and ELN). Thus, have opted to issue a short- duration Wind Advisory, valid until 8 PM this evening.

DISCUSSION

Tonight through Monday: Satellite imagery this afternoon shows a shortwave flattening a ridge over the PacNW, with mostly cloudy conditions across the forecast area. Breezy winds are developing through the Cascade gaps and along the Cascade east slopes, with winds beginning to push further east into the Basin and adjacent valleys.

The upper ridge will continue to influence the region into Tuesday, keeping conditions dry and warm across the forecast area. The shortwave passage today will continue to produce breezy winds late into this evening, with winds generally 15-25 mph and gusts up to 40 mph. Tomorrow, winds will become light again with clear skies.

Tuesday through Saturday: Ensemble cluster guidance remains 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 central OR and the eastern mountains will result in an increased cumulus field across the OR Cascades and eastern mountains, with a very low chance (<10%) of an isolated shower/thunderstorm.

Tuesday night through Thursday, uncertainty remains around the evolution of an upper low/trough that will shift inland and across the PacNW. While there is good agreement that low will kick inland sometime Wednesday, ensemble members are split on the track of the trough and timing of its passage overhead. Solutions range from a track over the PacNW, which would result in shower chances and isolated thunderstorm chances across our mountain zones and along foothill locations, while a southern track would limit showers and thunderstorms to central and eastern OR. Timing of the trough passage will also impact timing of showers/thunderstorms across the area, with members split on having the trough out of the region by Thursday evening, or the trough still impacting the area through Thursday night. Forecast confidence in shower/thunderstorm extent is moderate (45-55%) while timing is low-moderate (30-40%).

Friday into Saturday, ensemble members are in generally good agreement of upper level troughing developing offshore Friday, then kicking inland through Saturday, though there is uncertainty in exact timing this far out. As the next trough kicks inland, expect another round of mountain rain showers to develop into the weekend. Lawhorn/82

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

VFR conditions to prevail through the period. Winds will increase to 12-18kts with gusts 20-30kts at sites DLS/PDT/RDM/BDN/YKM through this morning and afternoon and persist into the mid to late evening hours. Winds at sites ALW/PSC are expected to increase to around 12kts, but gusts are expected to be less than 18kts and periodic. Otherwise, winds will become light tonight through tomorrow. Lawhorn/82

FIRE WEATHER

High pressure remains over the region with dry and warming conditions into late Tuesday. Breezy west to northwest winds will continue to impact the region today, with strongest winds in the Cascade gaps. There will be increasing unstable conditions across central OR and the eastern mountains Tuesday. Min RHs Tuesday will generally be in the teens to mid 20s, with single digits in Central OR. Isolated to scattered mountain showers and thunderstorms develop Wednesday into the weekend.

Preliminary Point Temps/PoPs

PDT 45 76 47 85 / 0 0 0 0 ALW 49 76 51 88 / 0 0 0 0 PSC 49 80 50 91 / 0 0 0 0 YKM 46 79 49 88 / 0 0 0 0 HRI 47 79 48 88 / 0 0 0 0 ELN 43 75 45 83 / 0 0 0 0 RDM 37 82 45 91 / 0 0 0 0 LGD 42 77 45 91 / 0 0 0 0 GCD 42 83 46 95 / 0 0 0 0 DLS 48 82 52 89 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory until 8 PM PDT this evening for WAZ026. OR...None.