textproduct: Pendleton

DISCUSSION

Little to talk about on satellite and radar tonight as a transient ridge passing to the north is providing mostly clear skies, light winds, and dry conditions.

Today through Thursday: Deterministic and ensemble guidance has come into better agreement of a transient ridge continuing to influence the region through the first half of today. This will result in mostly dry and mild conditions to start off the mid week, though cloud cover will increase from the southwest throughout the day. While conditions remain clear for now, a weak inversion over the Columbia Basin and adjacent valleys may lead (15-25% chance) to patchy stratus/fog developing. However, any fog/stratus that materializes will quickly dissipate by mid-morning. Later today, the ridge will push east as a trough with two defined lows develops offshore. One of the lows will move inland and become an open wave across northern CA and southern OR late tonight through Wednesday. Shortwave impulses swinging out of the low during this period will bring a dusting of light snow to portions of the Ochoco-John Day Highlands, and the Strawberrys/Elkhorns/Wallowas.

By late Wednesday, the trough axis will exit the region, allowing a transient ridge to move over the PacNW with dry conditions prevailing through Thursday.

Friday through Monday: By early Friday, ensemble cluster solutions show a trough dropping out of the Gulf of Alaska with the main low circulation setting up offshore the PacNW. Over the weekend, the trough will deepen as it swings inland with increasing precipitation chances across the forecast area(confidence 60-75%). Secondary lows diving out of the Gulf of Alaska will reinforce the upper trough over western CONUS, however this will keep the trough axis offshore (confidence 55-75%) through early next week. Ensemble cluster solutions, reinforced by the ensemble atmospheric river guidance, indicate weak moisture support with the trough, which translates to mostly light (but persistent) precipitation chances across the forecast area through early Monday. By Sunday though, there is a cluster solution (<15% of ensemble members) that indicate a brief period of moderate to locally heavy snow along the OR Cascade crest, with light snow across the remainder of the mountains. As an idea of how much snow area mountains may see over the weekend, the 48-hr probability of 6 inches or more is 25-40% across the Cascade crest, Blues, Eagle Caps, and Elkhorn Crest. Lastly, in the lower elevations, there is moderate confidence (45-70%) of light rain and/or a rain/snow mix throughout the weekend. Lawhorn/82

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

VFR conditions will persist across all TAF sites through the forecast period with the exception of YKM. YKM will likely (60-80%) see VIS drop to 5SM round 12Z due to BR with a brief chance of seeing VIS as low as 3SM briefly between 16-18Z. Otherwise, all TAF sites will remain VFR through the period with light and variable winds below 6kts. 90

Preliminary Point Temps/PoPs

PDT 28 43 29 47 / 0 0 0 0 ALW 31 43 31 47 / 0 0 0 0 PSC 29 48 30 48 / 0 0 0 0 YKM 28 49 29 45 / 0 0 0 0 HRI 29 46 30 48 / 0 0 0 0 ELN 28 44 28 43 / 0 0 0 0 RDM 23 43 22 51 / 0 0 0 0 LGD 28 48 26 50 / 0 0 0 0 GCD 28 48 27 50 / 10 10 0 0 DLS 33 49 33 50 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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