textproduct: Pendleton

KEY MESSAGES

- Weak instability and dry condition present today.

- Critically Windy and dry on Saturday. *Fire Weather Watch Issued*

- Dry conditions return through the first half of week.

DISCUSSION

Current radar and visible satellite imagery shows dry conditions as mid-to high level clouds begin to encroach into Central and North-Central Oregon. This is associated with a passing weak shortwave that is slightly increasing winds and instability across the region. Thunderstorms are not anticipated with this feature, but fire activity may become more active through the afternoon as a result. High pressure slides in behind the passing shortwave by Friday morning, leading to light winds and drier conditions with afternoon humidities between 15-22%.

An approaching upper level trough on Saturday, and an associated dry cold front, will pass through the Pacific Northwest. This feature will increase winds out of the west as sustained winds of 15-30 mph and gusts of 30-40 mph will be possible, with highest winds expected across the Kittitas Valley and the Simcoe Highlands. Chances of wind advisory level gusts being reached is currently 60-80% via the NBM across these areas. Fire weather concerns also arise as a result of the increased winds and antecedent dry conditions. As a result, a Fire Weather Watch has been issued for much of the area on Saturday, including the Lower Columbia Basin, Eastern Mountains, and portions of Central Oregon. Afternoon humidities as low as 17% will be possible, which are more focused to areas of Central Oregon zones.

In the wake of the passing system, the ECMWF and GFS AI ensembles suggest a building upper level ridge along the coast will allow for a thermal trough to develop Monday and Tuesday. Winds will be coming in from the north and east, with afternoon humidities dropping into the low to mid-teens by Tuesday. A warming trend will also commence through the early workweek as highs peak in the low to mid-90s across the Columbia Basin and Central Oregon on Wednesday. 75

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

VFR conditions currently across all sites, which will stay the course through the period. Breezy winds for KDLS are expected to persist until later tonight, subsiding through the overnight period. Elsewhere, light winds below 10kts will extend through Friday morning. 75

FIRE WEATHER

Elevated fire weather concerns persist through the week under a dry and diurnally breezy regime. Winds will become more terrain driven on Friday as a result of increased high pressure in the wake of a passing system today, but humidities will continue to trend downward. Concerns peak on Saturday associated with a passing dry cold front that brings windy conditions through the Columbia Basin, Eastern Mountains, and Central Oregon. As a result, Fire Weather Watches have been extended to these areas to highlight the potential for rapid fire spread and/or spotting related to new and existing fires. Conditions relax Sunday ahead of a thermal trough developing along the coast that will promote significant drying and north/east winds Monday and Tuesday. Poor to moderate overnight humidities are anticipated Monday through Wednesday mornings. 75

Preliminary Point Temps/PoPs

PDT 55 92 62 85 / 0 0 0 0 ALW 60 95 66 88 / 0 0 0 0 PSC 56 95 62 91 / 0 0 0 0 YKM 57 95 61 88 / 0 0 0 0 HRI 57 94 64 86 / 0 0 0 0 ELN 56 92 59 80 / 0 0 0 0 RDM 47 93 51 85 / 0 0 0 0 LGD 55 98 59 89 / 0 0 0 0 GCD 54 100 57 93 / 0 0 0 0 DLS 58 95 63 81 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Fire Weather Watch from Saturday morning through Saturday evening for WAZ691>693. OR...Air Quality Alert until noon PDT Friday for ORZ041-049-050-502- 503-505-506-509>511. Fire Weather Watch from Saturday morning through Saturday evening for ORZ691>700.