textproduct: Pendleton

KEY MESSAGES

- An upper low moving onshore will bring precipitation mainly to central and southern Oregon through Monday.

- An upper trough will bring better chances for precipitation later Tuesday into Thursday.

- Gusty winds are possibly with the trough Wednesday into Thursday.

DISCUSSION

An upper low off the coast will move eastward today. As it does, precipitation will move onshore ahead of the low in southwest flow. The low mill move onshore in northern California tonight and more precipitation is expected. This low will move eastward and out of the area on Monday.

Snow levels will be quite high...generally higher than 6500 feet as this low moves through, so little, if any snow is expected, except for the highest elevations. Liquid QPF values will range from a few hundredths to around 0.25 inches, with some of the higher elevations receiving between 0.25 to 0.50 inches.

A ridge will build in behind the departing low for Monday into much of Tuesday, bringing dry weather. Across western sections of the area and the mountains, precipitation will begin to move in on Tuesday but will hold off over most locations until Tuesday night.

By later Tuesday and into Tuesday night an upper trough will move across the Pacific Northwest and bring more widespread precipitation chances that will continue into Wednesday before being more confined to the mountains on Thursday.

Snow levels will start off relatively high, with values between 5000 and 5500 feet in the north and 5500 and 6500 feet in the south and east. However, snow levels will fall and by later Wednesday will be between 4000 and 5000 feet across the region and will fall to between 3000 and 3500 feet in many areas by Thursday morning. This would put snow levels below the higher passes by Thursday morning.

Liquid equivalent precipitation ranges from a few hundredths to around 0.10 inches in the lower elevations to over 1 inch along the crests of the Blue Mountains, Wallowas and Cascades. However, given the time of year it is difficult for any snow to accumulate on road surfaces during the day unless it falls hard or it is exceptionally cold. At night, accumulation is possible, but it would still require cold road surfaces. It would still be dependent on what time most of the precipitation were to occur, and in this case some is definitely going to occur during the daytime hours. Timing is still a bit of a question, and that leads to uncertainty in the accumulation amounts. So while some accumulation is possible, how much is the big question. The greatest chances are above 5000 feet, but below that it is a lot more. The NBM probabilities of snow accumulations >=4 inches along the Cascade Crest in the Wednesday-Thursday timeframe ranges from 30 to 70 percent. However, the NBM probabilities of snow accumulations >=6 inches decreases in most areas to under 30 percent with some higher values at the higher elevations.

As the trough moves across the area, Wednesday into THursday, winds will increase and become gusty. Wind gusts on Wednesday, especially for the normally breezier locations like the Cascade gaps, Columbia Basin and foothills of the Blue Mountains will see gusts in the 25 to 35 mph range, with gusts as high as 40 mph. Breezy conditions will linger into Thursday but look to be a tad lower. NBM probability of wind gusts >= 39 mph on Wednesday in these areas range from about 60 to 80 percent. NBM probabilities of wind gusts >=47 mph are generally less than 50 percent.

High temperatures look to be above normal Monday and Tuesday then close to normal from Wednesday onward.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

VFR conditions and light winds are expected at all TAF sites except for RDM and BDN. RDM and BDN will see some MVFR conditions late tonight and into into Monday in -RA.

Preliminary Point Temps/PoPs

PDT 53 36 57 37 / 10 20 10 0 ALW 53 37 56 40 / 0 10 10 0 PSC 56 33 60 38 / 0 0 0 0 YKM 55 32 59 36 / 0 0 0 0 HRI 55 35 60 38 / 0 10 0 0 ELN 51 30 55 34 / 0 0 0 0 RDM 53 36 55 32 / 40 60 20 0 LGD 56 40 57 34 / 20 40 30 0 GCD 56 41 53 34 / 60 70 50 0 DLS 56 39 61 42 / 10 10 10 0

PDT WATCHES/WARNINGS/ADVISORIES

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