textproduct: Pendleton

KEY MESSAGES

- Cooling trend through Thursday.

- Dry and locally breezy conditions through the week.

- Elevated fire weather concerns through Saturday.

DISCUSSION

Current radar and infrared satellite imagery shows light returns lingering across eastern Wallowa county under mostly clear skies. This is in response to the upper level trough that approached the area during the afternoon and evening hours on Tuesday, bringing some strong thunderstorms to areas of Grant and Union counties. The trough axis passed overnight which kept winds breezy across the Kittitas Valley, Columbia Gorge, and the Blue Mountain foothills. Flow aloft has turned more from the west and zonal in the wake of the passing system this morning, leading to slightly cooler temperatures today associated with a weak cold front. High temperatures will reach into the low to mid-90s across the Columbia Basin and Blue Mountain foothills, which is 2-4 degrees above normal. Another dissipating shortwave will bring another weak blast of cooler air on Thursday as high temperatures approach near normal values.

The weak, dissipating shortwaves both today and Thursday will allow daily pressure gradients to develop along the Cascades, keeping winds breezy through the afternoon hours across the Columbia Basin. The GFS and NAM advertise a gradient of 8-10mb between Portland and Spokane today, which correlates to sustained winds of 15-25 mph with gusts up to 35 mph out of the west. Peak winds are expected to occur after 5 PM and subside late in the evening. Northwest sustained winds of 20-30 mph and gusts up to 40 mph are expected in the Kittitas Valley, and will peak earlier around 3 PM and extend through the evening. Advisory-level winds are not expected as the NBM suggests only a 30-35% chance of sustained winds of 30 mph or greater, or gusts of 45 mph or greater over the Kittitas Valley. Advisory level wind chances are much lower in the Columbia Basin, 10% or less.

An upper level low will continue dropping along the British Columbia coast through the remainder of the week, stalling just north of Vancouver Island Saturday morning. Weak, shortwaves will spin off this parent low to bring similar afternoon winds through the remainder of the week. The ECMWF AI ensembles and GFS AI ensembles are in good agreement with a strong high pressure center developing across the 4 corners region Saturday as the low stalls off the British Columbia coast. This enhances southwest flow aloft and increasing high temperatures into the mid-90s across the Columbia Basin, Blue Mountain foothills, and Central Oregon through the weekend. The high shifts northeast and into the Plains as the low offshore weakens and lifts northeast into Central British Columbia, northern Alberta, and northern Saskatchewan early next week - effectively riding up and over the central CONUS ridge. Winds across the area will subside on Sunday into Monday, but humidities are expected to dry as the large ridge infiltrates its influence into the area from the southeast. 75

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

VFR conditions currently across all sites, which will stay the course through the period. Widespread breezy winds through the morning and afternoon with sustained wind of 10-20kts and gusts of 20-25kts. 25kft ceilings this morning will clear late in the afternoon through early evening. 75

FIRE WEATHER

Elevated fire weather concerns will persist through the week for WA690, WA691, OR691, and OR703, peaking through the afternoon hours associated with the incoming weak shortwaves. Afternoon humidities will also hover in the upper teens to mid-20s each day, with moderate to good overnight recoveries between 40-60%. Thursday is expected to be the most concerning day as minimum humidities of 15-20% and west northwest winds between 15-20 mph with gusts up to 30 mph will be possible. Higher winds of 15-25 mph with gusts up to 35 mph are likely across the Kittitas Valley Thursday. Very low afternoon humidities dropping near single digit values are also forecast for OR700 and OR696 on Thursday. These concerns on Thursday will be further analyzed, but no fire weather product is anticipated at this time. 75

Preliminary Point Temps/PoPs

PDT 88 55 87 55 / 0 0 0 0 ALW 90 60 88 60 / 0 0 0 0 PSC 93 57 91 58 / 0 0 0 0 YKM 92 57 91 57 / 0 0 0 0 HRI 91 58 90 59 / 0 0 0 0 ELN 82 54 83 54 / 0 0 0 0 RDM 86 48 86 47 / 0 0 0 0 LGD 88 53 87 52 / 0 0 0 0 GCD 90 51 89 51 / 0 0 0 0 DLS 85 58 87 60 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...OR...None.