textproduct: Pendleton

KEY MESSAGES

- Temperatures will slowly warm to above normal by the end of the week.

- Slight chance to chance (10-30%) of thunderstorms over the Blue Mountains region Thursday and Friday.

DISCUSSION

Water vapor imagery shows a shortwave trough moving southeast along the BC coast. This system will facilitate our next chances of rain, with a slight chance (15-25%) of showers arriving to the Washington Cascades later this morning. The shortwave will then develop into a closed low over the Pacific Northwest later this afternoon through tonight and provide modest chances (15-40%) of precipitation across central Oregon and the surrounding mountains.

Ensemble NWP guidance is in reasonably good agreement regarding the track of the low, but some uncertainty exists in its location for Wednesday through Friday. In general, ensemble mean 500-hPa heights and vorticity show the low retrograding slightly on Wednesday, tracking from southwest Oregon to northwest California, or just offshore. The forecast area will remain mostly dry on Wednesday, increasingly so the farther southwest the low tracks. The low is then expected to eject northeast across the Pacific Northwest Thursday through Friday, though clusters of ensemble solutions continue to show some differences in timing and magnitude of the low during this period. Over half of members advertise a solution that is conducive to convection Thursday (Blue Mountains region and portions of central Oregon) and Friday (northeast Blue Mountains). Chances of thunderstorms are highest on Thursday (15-30%), especially for the northeast Blue Mountains. Chances drop to 10-15% for Friday, highest over Wallowa County.

All ensemble members indicate the low will exit to the east by Saturday, with transient upper-level ridging replacing it over the Pacific Northwest. This would facilitate above-normal temperatures and dry conditions areawide.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

VFR conditions are forecast through the TAF period. CIGs will lower during the day as low pressure moves toward the region. There is a chance (30-40%) of showers at RDM/BDN late this afternoon and evening, with very low (<20% percent) chances of showers elsewhere. Sustained winds will be predominantly 12 kts or less, with afternoon and evening gusts of 15-25 kts at BDN/RDM.

Preliminary Point Temps/PoPs

PDT 68 44 72 47 / 0 10 0 0 ALW 70 48 75 52 / 0 10 0 0 PSC 71 46 78 48 / 10 10 0 0 YKM 66 47 74 48 / 10 10 0 0 HRI 71 46 76 47 / 0 10 0 0 ELN 60 42 70 45 / 20 10 0 0 RDM 69 39 68 37 / 0 40 10 0 LGD 71 45 74 45 / 0 10 0 0 GCD 74 45 74 45 / 0 20 10 10 DLS 73 54 80 55 / 0 10 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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