textproduct: Pendleton

DISCUSSION

Key Points...

1. Freezing Rain for portions of the area today through tonight.

2. Additional precipitation, into the weekend, mainly for the mountains...with lower elevation rain and mountain snow.

A complex forecast for today into tonight. As the area of high pressure that had been over the west moves eastward, moisture from California will move northward into Oregon today.

While there is not a lot of moisture, QPF (liquid equivalent) values across the lower elevations are mainly less than 0.10 inches, with higher amounts over 0.50 inches and some areas even over 1.00 inch in the mountains through today and Friday in the mountains.

Where the problem arises, especially across lower elevations, is that temperatures will remain steady or slowly rise today and then will finally rise more Friday and Saturday.

With temperatures in the 20s in many areas, as the precipitation moves in, freezing rain looks to be the result. The other issue that remains, is guidance still disagrees on exactly how much QPF there will be with some guidance suggesting not very much and others suggesting more, but of course with freezing rain even a few hundredths can be enough to cause impacts.

Winter Weather advisories are in effect and while it will ultimately end up being dependent on temperatures and QPF, a few hundredths of an inch to a tenth of an inch of freezing rain is possible across the advisory area.

Beyond tonight/early Friday, the precipitation should end everywhere but the mountains during the morning on Friday and temperatures will rebound nicely. Then, an area of low pressure is expected to move northward up the coast into Saturday and precipitation chances will return Friday night into early Saturday, with the highest chances in the mountains. There will then be another shot Saturday night into Sunday as a trough moves onshore. FInally, by later Monday, it looks like drier conditions should result.

Snow levels will initially be quite high, everywhere but the Washington Cascades. Across the Washington Cascades today they will be below 2000 feet but 3500 to 4500 feet in the Blue Mountains early and over 7500 feet in the Oregon Cascades. By afternoon, snow levels will be 6500-7500 feet everywhere, so any precipitation in the mountains will be rain except at the crests, though even in the Washington Cascades there could be some freezing rain accumulation before the transition to rain.

By Sunday, snow levels will fall to around 400-4500 feet in the Washington Cascades and 5000-5500 feet elsewhere. During this time there could be 2 to 4 inches of snow at pass level in the Washington Cascades, less in the Blue Mountains and Oregon Cascades, though the could be higher amounts at the higher elevations.

AVIATION

12Z TAFS...Conditions range from VFR to LIFR currently. Expect all sites to deteriorate during the day and into the evening as FZRA impacts all TAF sites. Most sites are expected to be IFR/LIFR.

Winds are expected to be light.

PRELIMINARY POINT TEMPS/POPS

PDT 34 29 47 34 / 70 80 40 10 ALW 34 31 45 37 / 60 90 70 10 PSC 33 28 43 32 / 50 70 30 20 YKM 35 29 42 32 / 40 60 20 30 HRI 33 28 43 34 / 60 80 30 20 ELN 33 28 39 32 / 40 60 40 40 RDM 43 34 53 35 / 70 60 0 10 LGD 41 35 46 38 / 80 90 70 10 GCD 43 38 51 37 / 90 90 40 10 DLS 36 33 45 37 / 70 90 50 40

PDT WATCHES/WARNINGS/ADVISORIES

OR...Winter Weather Advisory until 1 AM PST Friday for ORZ041-510.

Air Stagnation Advisory until noon PST today for ORZ044-507-508- 510-511.

Winter Weather Advisory from 7 AM this morning to 1 AM PST Friday for ORZ044-507-508.

Winter Weather Advisory until 1 PM PST this afternoon for ORZ511.

WA...Winter Weather Advisory until 1 AM PST Friday for WAZ024.

Air Stagnation Advisory until noon PST today for WAZ026>029.

Winter Weather Advisory from 10 AM this morning to 4 AM PST Friday for WAZ026>029.

Freezing Fog Advisory until noon PST today for WAZ028.

Winter Weather Advisory until 4 AM PST Friday for WAZ521>523.