textproduct: Pendleton

KEY MESSAGES

1. Dry, warm and breezy conditions will persist through the weekend and beginning of the week

2. Pattern shift mid-week could bring precipitation and thunderstorm chances

DISCUSSION

Current satellite shows mostly clear skies with smoke lingering in some areas around the wildfires. Smoke will continue to linger through the period but with the increased winds, will not settle to heavily at the surface except overnight. AQAs are still in effect for most counties except Sherman, Gilliam, Morrow and Umatilla and will remain through at least Wednesday before being reevaluated.

Dry and warm conditions will persist through mid-week as westerly flow aloft continues over the region. Westerly flow will continue through mid week-with temperatures becoming slightly cooler. In house calculations shows much of the region to still be above seasonal average near 5 degrees above normal today. As the temperatures begin to decrease, relative humidity will begin to increase. This will bring the area out of critical fire weather conditions but will still remain elevated. Winds are expected to remain 10 to 15 mph and gusting between 25 to 35 mph through at least tomorrow with 80% of the NBM raw ensembles in agreement.

Wednesday models show an upper level low beginning to slip into the PacNW. This will bring southwest flow aloft as well as some mid level moisture. Looking at NBM ensembles, there is a 15-20% chance of the northern Cascades seeing thunderstorms. Looking at GFS forecast soundings, there is MUCAPE values of between 250-500 J/kg , lapse rates of over 10 C/km, LIs of -2 and shear of 24 kts. These storms will likely provide a strike or two as well as producing some measurable rainfall.

Thursday appears to be a lull in activity before picking back up Friday. Models show the region to be wedged between the upper level trough to the north and the Four Corner high to the south. The high will usher in some monsoonal moisture into central and eastern OR. By Friday afternoon the moisture will be over central Or and the eastern mountains with NBM ensembles showing 20-0% chances. As this remains five days out, we will continue to monitor as the event draws near.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

VFR conditions currently across all sites, which will stay the course for most terminals through the period. KRDM/KBDN will be the exception as smoke from nearby wildfires is expected to drop visibilities the 5SM. Breezy winds are also anticipated for KDLS/KPDT with gusts of 20-30kts through the afternoon. 75

FIRE WEATHER

Westerly flow has brought cooler temperature and increasing relative humidity. While there are breezy conditions expected across the region, especially through the Cascade Gaps and along the southern Blue foothills, wind and relative humidity thresholds are below critical. Fire weather remains elevated and will remain elevated through the week.

Wednesday could see chances (15-20%) of thunderstorms along the norther Cascades in Kittitas Valley. While we don't expect them to be strong in nature, we can not rule out a strike or two and gusty outflows. As we move into Friday, models show monsoonal moisture moving into the southern portion of the region through Deschutes, Crook, Grant and Wallowa counties has 20-30% chances of seeing thunderstorms. Otherwise the remainder of the region will be under unstable conditions.

Preliminary Point Temps/PoPs

PDT 53 88 54 84 / 0 0 0 0 ALW 60 89 60 86 / 0 0 0 0 PSC 56 91 57 89 / 0 0 0 0 YKM 58 92 59 88 / 0 0 0 0 HRI 57 90 58 87 / 0 0 0 0 ELN 55 85 55 82 / 0 0 0 0 RDM 46 88 45 84 / 0 0 0 0 LGD 52 90 53 87 / 0 0 0 0 GCD 52 92 52 89 / 0 0 0 0 DLS 60 88 61 83 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Air Quality Alert until 11 AM PDT Thursday for WAZ024-026>030- 521>523. OR...Air Quality Alert until noon PDT Wednesday for ORZ041-049-050- 502-503-505-506-508>511.