textproduct: Pendleton

KEY MESSAGES

- Heat Advisories remain in effect through 10 PM.

- Very low to slight chance (5-20 percent) of high-based showers and thunderstorms today and Saturday. Red Flag Warnings in effect for several fire weather zones.

- Widespread breezy to windy westerly winds coupled with low relative humidity Saturday. Red Flag Warnings in effect for numerous fire weather zones. Wind Advisories in effect.

DISCUSSION

Water vapor imagery shows a large, closed low offshore in the Pacific, just west of the OR/CA border. Meanwhile, an upper- level ridge of high pressure extends from the Four Corners into the Pacific Northwest. The interaction of these two synoptic- scale features will drive the bulk of our weather over the next couple days.

Under the ridge, widespread hot conditions are in place with afternoon high temperatures already in the 90s to lower 100s this afternoon. Temperatures are expected to continue climbing in areas bereft of significant mid/high cloud. Clouds draped over the western half of our forecast area will suppress daytime highs relative to yesterday. Heat Advisories remain in effect through 10 PM this evening due to widespread Moderate (level 2 of 4) to Major (level 3 of 4) HeatRisk. This level of heat affects anyone without cooling/hydration.

Ensemble NWP guidance is in concensus that the upper low will slowly track north-northeast through the day, remaining just offshore. This places the forecast area under southerly to southwesterly flow aloft. Synoptic-scale forcing coupled with increasing mid-level moisture may facilitate some high-based showers and thunderstorms this afternoon, tonight, and into Saturday morning, but probabilities are quite low (5-15 percent), highest for the Cascades.

The low is then expected (95 percent confidence) to track inland across northern Oregon and Washington during the day Saturday, morphing into an open-wave trough as it moves inland. Its attendant cold frontal passage during the day will help drive breezy to windy westerly winds through the Cascade gaps as well as across the Columbia Basin and portions of the Blue Mountains. Wind Advisories were issued for many public forecast zones across north-central Oregon and south-central Washington, and may be expanded should confidence increase in windy conditions extending farther east across the Columbia Basin and Blue Mountain foothills.

While confidence was "only" medium-high (50-90%) in reaching rh thresholds across fire weather zones, due to the magnitude of the forecast winds (10-25 mph with gusts of 25-40 mph, locally higher through especially wind-prone areas), have issued Red Flag Warnings for wind and low relative humidity for the majority of our non-mountain fire weather zones for later Saturday morning (OR/WA693) or Saturday afternoon (WA690, WA691, OR691, OR696, OR698, OR700, and OR703).

In addition to Red Flag Warnings for wind/rh, the potential for abundant lightning and gusty outflow winds prompted Red Flag Warnings for WA695 (tonight through Saturday morning) and OR/WA692 (late Saturday morning through Saturday evening).

Some breezy conditions are forecast to linger Sunday as the trough exits to the east.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Conditions initialize at VFR. Elevated smoke prevails across the region with 6 to 8 SM visibilities across sites in Central OR through the Foothills of the Blues, which will not take much to put into MVFR over the next few hours. Conditions will improve when daytime mixing lifts the smoke by the later morning to the early afternoon hours. Breezy winds develop in the Cascade gaps in DLS by 07Z with 20 to 30 knot gusts developing.

Preliminary Point Temps/PoPs

PDT 63 91 50 84 / 10 0 0 0 ALW 70 94 59 85 / 10 0 0 0 PSC 67 96 58 87 / 10 10 0 0 YKM 71 95 58 87 / 10 20 0 0 HRI 69 93 58 86 / 10 10 0 0 ELN 66 88 54 79 / 10 20 0 0 RDM 55 89 45 85 / 10 0 0 0 LGD 65 95 52 87 / 10 20 10 0 GCD 64 95 54 89 / 10 0 0 0 DLS 67 86 60 85 / 10 10 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Heat Advisory until 10 PM PDT this evening for WAZ024-026>030- 521-523. Air Quality Alert until noon PDT Monday for WAZ026-522-523. Wind Advisory from 11 AM to 11 PM PDT Saturday for WAZ024-521. Red Flag Warning from noon to 10 PM PDT Saturday for WAZ690- 691. Red Flag Warning from 11 AM to 11 PM PDT Saturday for WAZ692. Red Flag Warning from 10 AM to 8 PM PDT Saturday for WAZ693. Wind Advisory from 2 PM to 10 PM PDT Saturday for WAZ026. Red Flag Warning from 11 PM this evening to noon PDT Saturday for WAZ695. OR...Heat Advisory until 10 PM PDT this evening for ORZ041-044-049- 050-502-503-505>508-510-511. Air Quality Alert until noon PDT Monday for ORZ041-044-049-050- 502-503-505>507-509>511. Wind Advisory from 11 AM to 11 PM PDT Saturday for ORZ041-044- 508-510. Red Flag Warning from noon to 10 PM PDT Saturday for ORZ691- 696-698-700-703. Red Flag Warning from 11 AM to 11 PM PDT Saturday for ORZ692. Red Flag Warning from 10 AM to 8 PM PDT Saturday for ORZ693.