textproduct: Pendleton

KEY MESSAGES

- Warmer temperatures continue through Tuesday, with cooler temperatures to follow by a cold frontal passage in the midweek.

- Widespread 10-25% chances of thunderstorms with isolated to scattered development Tuesday, with much less coverage through the early Wednesday morning hours.

- Breezy to locally windy conditions possible going into Wednesday as the cold frontal system passes through the region.

DISCUSSION

Monday will be the warmest day of the 7 day forecast as NBM mean highs reach around 80 degrees across the Lower Columbia Basin, the John Day Basin, Central Oregon and the Yakima Valley. Ensemble clustering still shows the upper low setting up off the CA coast by Day 3 (Tuesday) with a diffluent upper pattern across the Interior NW. The clusters show some variance in how much instability will develop across the Mountains zones on Tuesday afternoon, ranging from fairly low (under 100 J/kg to as much as 400 J/kg CAPE), leaving still uncertainty with respect to how isolated or scattered the convection may be. Wetting rain chances however is an area of ever increasing confidence as overall pops increase from 70 to 90 percent late Tuesday afternoon through the nighttime hours. The ESAT shows the event is not extreme with about a 1-2 standardized anomaly for IVT into southern Oregon Tuesday. A limited area of the northern Blue Mountains has 40 to 50% chances to meet or exceed 2 inches of rainfall by Thursday overnight. That same 40 to 50% threshold lowered to one inch extends more broadly across the entire eastern Mountains as well as much of the Oregon Cascades crest. Along with the incoming wet system, the temperatures will then become moderated beginning Tuesday across Central Oregon into the Columbia Basin and then farther north on Wednesday as the rains overspread the broader region. Wednesday is shaping up to be the coolest day of the 7 day forecast where NBM means printing 50s from Central Oregon into the Lower Columbia Basin, and 60s farther north into the Yakima and northern Benton counties. Wednesday also may be pointing toward potential wind advisories for parts of the Oregon Columbia Basin and Simcoe Highlands as models hint at gusts in excess of 40 mph. Russell/71

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

VFR conditions currently across all sites, which will stay the course through the period. Sustained afternoon winds between 10- 15kts expected for KRDM/KBDN, subsiding later in the evening as ceilings drop to around 10kft. Light winds elsewhere below 10kts as ceilings of 25kft become overcast in the evening. 75

HYDROLOGY

Within bank rises on some area rivers are expected heading into the middle of the week in response to runoff. The Naches river is forecast to reach and exceed the action stage at Naches Tuesday morning and then at Cliffdell Tuesday Night before beginning a gradual fall. The Grande Ronde River at Troy is forecast to reach about 1 foot below minor flood stage late Wednesday. No scenarios in the HEFS exceedance probabilities suggest flooding is possible (less than 10% chances). Russell/71

Preliminary Point Temps/PoPs

PDT 44 76 48 71 / 0 0 10 30 ALW 49 76 52 73 / 0 0 10 30 PSC 44 80 49 78 / 0 0 10 10 YKM 47 79 49 75 / 0 0 10 10 HRI 44 79 49 74 / 0 0 10 10 ELN 44 75 47 68 / 0 0 10 20 RDM 40 75 42 62 / 0 10 20 30 LGD 41 75 44 72 / 0 0 10 40 GCD 44 77 44 70 / 0 0 10 60 DLS 52 78 52 67 / 0 10 20 20

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...None.