textproduct: Pendleton

KEY MESSAGES

- Dry conditions persist into the beginning of the weekend with an upper level ridge of high pressure continues to move overhead.

- Freezing temperatures expected to continue overnight in the Columbia Basin, Cascade gaps, Yakima Valley and Foothills of the Blue Mountains.

- Weather system approaches the area next week with cooler conditions with periods of shower activity early next week. Long term guidance split going into the middle to late next week.

DISCUSSION

A low amplitude ridge is situated across the area, promoting dry and clear conditions through the overnight hours, allowing sub- freezing temperatures through the region. As of 4 am, sub- freezing temperatures have already reached across portions the Columbia Basin, Cascade gaps, Yakima Valley and Foothills of the Blue Mountains. Current confidence is high (70-80% chance) that freezing temperatures will persist long enough and spread through at least 50% of each zone to verify their season ending freeze. If a final assessment later this morning verifies each zone, they will no longer receive Freeze Warnings until Spring 2027.

Guidance is in good agreement that a closed low will develop off the coast of Alaska tracking inland by Tuesday, however clusters aren't quite converged into its strength and timing. Of the clusters by Tuesday night, 38% (mostly consisting of the GFS) result in a drier pattern with a weaker shortwave while the remaining 62% (mostly consisting of the EURO) roughly give a wetter pattern across the area. Ensembles quickly diverge again going into the mid-week after Wednesday with roughly a 70/30 split leaning into a trough situated over the PacNW over a ridge settling in. Periods of showers and cooler temperatures will prevail over the trough scenario while drier and warmer conditions accompany the ridge scenario. Current outlooks suggest Monday and Tuesday will see the best chances of showers (30-50% chance) with light mountain showers in the very highest peaks (10-30% chance).

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

VFR conditions will persist through the forecast period with generally light winds. CIGs will move over the region through the day. No CIG or VIS issues will occur.

Preliminary Point Temps/PoPs

PDT 58 32 59 33 / 0 0 0 20 ALW 59 38 61 38 / 0 0 0 10 PSC 59 29 58 33 / 0 0 0 20 YKM 58 32 58 36 / 0 0 10 20 HRI 57 30 58 32 / 0 0 0 20 ELN 55 25 54 30 / 0 0 10 30 RDM 59 28 64 27 / 0 0 0 30 LGD 59 34 61 37 / 0 0 0 10 GCD 60 30 64 34 / 0 0 0 10 DLS 62 36 60 38 / 0 0 10 40

PDT WATCHES/WARNINGS/ADVISORIES

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