textproduct: Pendleton

KEY MESSAGES

- Rain and mainly mountain thunderstorm chances begin today in central Oregon and increase Friday and Saturday.

- Cooler, more seasonal temperatures next week.

- Elevated river levels on the Naches and portions of the Grande Ronde with certain other rivers having in-banks rises.

DISCUSSION

An upper low off of northern California will move eastward and weaken as it moves inland as an open trough later today. Another upper low will move toward northern California and move inland Saturday night or Sunday morning. The combination of these two lows will help keep a broad upper trough over the western states and keep the weather unsettled through the weekend.

Precipitation and thunder chances will develop mainly across central Oregon today then become more widespread on Friday with the best (20-30 percent) chances of thunder across central Oregon and the John Day Highlands and Rain chances spreading across much of Oregon. By Saturday, rain chances spread everywhere, with thunder spreading north and eastward as well.

There still remains good CAPE and LIs but some CIN as well. Thunderstorms could be more widespread on Saturday, even though overall percentages are lower (generally <20 percent). There still also remains a question as to if there will be too much cloud cover, especially Saturday to inhibit widespread thunderstorm development, and will there be breaks where convection can form.

By Sunday the whole trough begins to move north and eastward with rain and some limited thunder chances lingering. Monday will see improving conditions as high pressure build in. The flow becomes more zonal on Tuesday, and this will usher in another system and another shot of rain by later Tuesday into Wednesday, with drier weather returning for Thursday.

The rain over the weeknight will cause some rivers to rise, with the Naches and some points on the Grande Ronde forecast to reach Action Stage. Others will see in-banks rises but are not forecast to reach action stage at this time.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

VFR conditions expected through most of the period. Scattered showers and thunderstorms have develop across southern and central OR this afternoon. This activity is expected to continue into the evening hours, with a prob30 of showers at site RDM, and periodic showers/thunderstorms at site BDN through 04Z. Tomorrow, shower chances are expected to return to these sites around or after 19Z. Prevailing winds will remain light, 12kts or less, and diurnally driven through the period. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 42 66 46 68 / 0 30 30 60 ALW 45 67 49 68 / 0 20 30 70 PSC 42 71 48 73 / 0 10 30 40 YKM 43 70 47 69 / 0 10 20 30 HRI 41 69 47 71 / 0 10 30 40 ELN 40 67 44 64 / 0 10 20 40 RDM 39 67 40 63 / 30 60 60 50 LGD 41 68 44 63 / 0 40 50 80 GCD 45 64 43 63 / 10 70 60 70 DLS 48 72 51 69 / 10 10 40 50

PDT WATCHES/WARNINGS/ADVISORIES

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