textproduct: Pendleton

KEY MESSAGES

- Areas of dense fog prevailing in the overnight to late morning hours today and Thursday night.

- Pattern favors dry conditions in the short-term through today with breezy winds across the area before another weather system goes through the region.

- Active weather resumes Friday (90% confidence) through the weekend with moderate to heavy showers with embedded gusty winds through the area (50-70% chance).

DISCUSSION

Satellite displays mid to low-level clouds through the area with areas of dense fog in the basins, valleys, and gaps in parts of Northern Oregon and Southern Washington state. Fog is expected to more or less stay put through the overnight hours and into the late morning hours. Guidance points that fog will lift through the afternoon when daytime heating kicks in and kicks the fog out. An overhead ridge persisting through Thursday will stay in place through today and continue the dry conditions we've experienced. Fog will re-develop later tonight also as a result, with less of a chance of the fog extending down into Central Oregon (20-30% confidence).

Active weather resumes Friday with guidance having high confidence (>90% chance) that a low pressure system off the coast will bring widespread moderate to heavy rain PoPs with mountain snow above 5500 feet. Heaviest precip is expected to be along the Cascades and eastern slopes of the Cascades with NBM advertising 70-80% chances of a quarter inch or more rain over a 24-hour period through Saturday morning. Chances of the same QPF drops down to 30-50% in the Yakima/Kittitas Valley and large swaths of the Columbia Basin. Light precip in the Cascades and Wallowas continue through Saturday as a transient ridge moves through and leaves most of the lower elevation areas dry.

Guidance is in good agreement that tight pressure gradients with a strong 50-70 knot jet stream across the area will bring breezy to windy conditions across Central Oregon, Columbia Basin, Eastern Mountains, and Grande Ronde Valley. Wind gusts up to 35 to 50 mph is possible with this system as NBM advertises a 30-50% chance of >45 mph gusts in those mentioned areas. Wouldn't be surprised if wind advisory's would be issued later today as confidence grows that we'll see criteria being met.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

All flight categories are possible. TAF period should be book ended by FG/HZ for most sites. KALW will experience LLWS at 2,000ft with 40kt winds at 170 degrees beginning at 02Z. Sites at KRDM, KBDN, KDLS, KPDT, KYKM, and KPSC should all see an improvement in visibility beginning after 21-22Z for aforementioned sites with PSC seeing improvement after 00Z. Gudience does point to some uncertainty on the timing and if the fog will lift.

Preliminary Point Temps/PoPs

PDT 62 41 68 40 / 0 0 10 90 ALW 62 46 67 44 / 0 0 10 90 PSC 56 35 61 38 / 0 0 20 70 YKM 58 36 56 36 / 0 0 70 50 HRI 56 36 64 38 / 10 0 20 80 ELN 55 33 53 32 / 0 0 60 60 RDM 70 43 57 31 / 0 0 80 20 LGD 61 44 61 37 / 0 0 0 90 GCD 67 39 61 34 / 0 0 40 100 DLS 59 40 55 40 / 0 0 80 30

PDT WATCHES/WARNINGS/ADVISORIES

WA...Dense Fog Advisory until 11 AM PST this morning for WAZ026-029. OR...Dense Fog Advisory until 11 AM PST this morning for ORZ507.