textproduct: Pendleton

KEY MESSAGES

1. Dry and warm conditions through the end of the week

2. Gusty conditions through the Grande Ronde Valley tomorrow afternoon with elevated fire risk.

3. Trough develops through area beginning Monday with the potential for rainfall along Blue Mountains

DISCUSSION

Clear skies continue to be present over the region thanks to continued upper-level ridging along the US West Coast. Current guidance timing suggests that the ridge will remain present in the region throughout the rest of today and tomorrow, transitioning to zonal flow alongside a shortwave trough tomorrow night into Saturday morning. Said shortwave trough will likely (greater than 50% chance) be positioned along the US- Canada border, limiting precipitation chances through the region (less than 20%). As the primary trough axis continues to move eastward, deterministic guidance highlights a favorable surface pressure gradient across the Blue Mountains for gusty south/southeast winds tomorrow into Saturday morning, especially around the Grande Ronde Valley. NBM ensemble probabilities for this time show a high chance (around 75%) of localized sustained winds in excess of 20 mph, with a moderate chance (up to 50%) of local gusts in excess of 40mph in the Grande Ronde Valley. Given the windy conditions in these regions, as well as RH values around 15-20% for much of the Blue Mountains in the afternoon, an elevated fire risk is present for these regions for Friday afternoon into the evening.

As zonal flow continues throughout the weekend, an upper level trough will begin to develop offshore Sunday night through Monday, moving into the PacNW region Monday night into Tuesday. Ensemble guidance is confident (greater than 75% chance) that a trough will occur, however significant variability still exists regarding trough strength and timing. Because of this uncertainty in trough depth, there is low confidence (around 30-40%) in current rainfall amounts. In scenarios where the trough is deeper, with a closed low developing near California, rainfall is limited to non-wetting amounts along the Blue Mountains. In scenarios with a more northward low or open wave setup, wetting rainfall in these regions is more likely with the improved moisture flow pattern. Lingering rainfall is possible into Wednesday and Thursday as the trough moves eastward and weakens, however the same model variability concerns and low confidence still applies.

Preliminary Point Temps/PoPs

PDT 69 37 74 41 / 0 0 0 0 ALW 69 44 75 49 / 0 0 0 0 PSC 72 38 70 39 / 0 0 0 0 YKM 70 42 70 43 / 0 0 0 0 HRI 70 37 71 41 / 0 0 0 0 ELN 67 38 67 41 / 0 0 0 0 RDM 75 33 79 36 / 0 0 0 0 LGD 70 41 71 46 / 0 0 0 0 GCD 75 36 77 37 / 0 0 0 0 DLS 74 44 76 47 / 0 0 0 0

Preliminary Point Temps/PoPs

PDT 69 37 74 41 / 0 0 0 0 ALW 69 44 75 49 / 0 0 0 0 PSC 72 38 70 39 / 0 0 0 0 YKM 70 42 70 43 / 0 0 0 0 HRI 70 37 71 41 / 0 0 0 0 ELN 67 38 67 41 / 0 0 0 0 RDM 75 33 79 36 / 0 0 0 0 LGD 70 41 71 46 / 0 0 0 0 GCD 75 36 77 37 / 0 0 0 0 DLS 74 44 76 47 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

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