textproduct: Pendleton

KEY MESSAGES

- Breezy afternoon winds continue through Saturday.

- Fire weather concerns Saturday. *Fire Weather Watch Issued*

- Warming and drying trend peaks Monday-Tuesday.

DISCUSSION

Current radar and visible satellite imagery shows dry conditions under clear to mostly clear skies. This is in response to the presence of a transient upper level ridge that is between two shortwaves, with one departing to our east and the second approaching the coast. The pattern has allowed for the northwest flow aloft, that brought below normal temperatures to the area, to become more from the west. Winds will increase this afternoon and evening as the shortwave approaches and a pressure gradient develops along the Cascades, allowing west-northwest winds of 17-22 mph with gusts up to 37 mph through the Columbia Gorge, Simcoe Highlands, and Kittitas Valley. The shortwave stalls and dissipates on Friday, which again leads to a pressure gradient developing along the Cascades, albeit much weaker. West winds of 15-20 mph with gusts up to 32 mph will be possible across the Columbia Gorge, Simcoe Highlands, and Kittitas Valley on Friday.

A stronger upper level shortwave approaches the coast on Saturday as an upper level ridge builds inland. These features will enhance the warming and drying trend, dropping afternoon humidities into the mid-teens as sustained west winds of 15 to 25 mph and gusts up to 35 mph are possible. These values, and the added confidence of guidance agreement, has warranted the issuance of a FIRE WEATHER WATCH over the Lower Columbia Basin of Oregon (OR691) on Saturday between noon and 10 PM. Low humidities will be widespread on Saturday, including near single digit values across Central Oregon and low 20s through the Kittitas Valley, but winds look to subside in these areas - unlike across the Lower Columbia Basin of Oregon. These areas will continue to be analyzed as the event nears, but only a 10-25% chance of red flag wind and humidity conditions are currently forecast. Fire weather concerns materialize Monday and Tuesday across Central and Eastern Oregon due to abundant dry lightning, but current confidence is low due to the inconsistency in guidance.

The upper level ridge continues to build through the weekend into the early part of the week. Weekend high temperatures in the low to mid-90s across the Lower Columbia Basin and Central Oregon will increase into the mid-to upper 90s Monday and Tuesday. The NBM suggests a 50-60% chance of high temperatures both days reaching 95 degrees or above for the Tri-Cities and Yakima areas, and a 35-45% chance for Hermiston. The upper level ridge suppresses and southwest flow aloft becomes more from the west Wednesday and Thursday, allowing high temperatures to slowly cool into the low 90s. 75

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

VFR conditions are expected (99 percent confidence) for the next 24 hours at all TAF sites. Winds will be diurnally breezy at DLS with winds of mostly 10 kts or less, aside from PM gusts, elsewhere.

FIRE WEATHER

Diurnally breezy conditions continue today through Saturday as the drying and warming trend persists. Critical values look to be reached on Saturday associated with a building upper level ridge from our south, but winds do begin to slacken due to the present high pressure. However, the Lower Columbia Basin does hold onto those increased winds longer as both critical winds and afternoon humidities align, reaching Red Flag Warning criteria. Thus, a FIRE WEATHER WATCH has been issued for OR691 on Saturday between 12 PM and 10 PM. There are some portions of isolated concern over OR690 (Kittitas Valley), but is confined to the east section of the zone between 1700-1900.

The presence of the upper level ridge will effectively dry conditions through the weekend and into the early part of the week. Guidance suggests a couple systems approaching from the southwest and passing through Central Oregon, which may result in abundant dry thunderstorms across OR693, OR694, OR695, OR697, PR698, OR699, OR700, and OR705 both Monday and Tuesday. At this time, Monday looks to have better dry thunderstorm chances (10-20%) than Tuesday (10-15%), but this will have to be further analyzed as the event nears. 75

Preliminary Point Temps/PoPs

PDT 52 85 54 88 / 0 0 0 0 ALW 57 86 60 89 / 0 0 0 0 PSC 54 89 56 92 / 0 0 0 0 YKM 54 88 55 91 / 0 0 0 0 HRI 54 88 57 91 / 0 0 0 0 ELN 51 82 52 83 / 0 0 0 0 RDM 43 86 48 88 / 0 0 0 0 LGD 49 85 52 88 / 0 0 0 0 GCD 47 87 51 92 / 0 0 0 0 DLS 56 86 57 88 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...Fire Weather Watch from Saturday afternoon through Saturday evening for ORZ691.