textproduct: Pendleton

DISCUSSION

Key Messages:

1. More rain Monday into early Wednesday will bring additional hydro concerns.

2. Breezy conditions Monday, then widespread windy conditions Wednesday.

3. Significant snow for the Cascades and lower snow levels Wednesday through the end of the week.

After a couple of days of dry weather, precipitation is set to return.

The first system will begin to move in late tonight into Monday, with the greatest impacts over the mountains. However, even lower elevations could see some light precipitation. There will likely be some drying over the lower elevation areas Monday night into Tuesday before a second, system affects the region Tuesday night into Wednesday.

This second system will be a decent short wave trough and strong cold front which will move across the Pacific Northwest. Snow levels will fall sharply behind the front and winds are expected to become gusty on Wednesday. Additionally, there will be about a 10 degree drop in temperatures, between Tuesday and Wednesday, even though temperatures will still remain above normal.

Behind the front, significant snow is expected in the Washington Cascades, and along the crest of the Oregon Cascades and Blue Mountains. This system exits the region Wednesday night and there is another lull, before more precipitation roll in Thursday into Friday, with drying looking to be in store for next weekend.

Monday's system will bring upwards of one inch of rain to the Cascades and this rain will make it into the rivers that feed into the Cascades (Naches, Yakima). This system is supplied by an atmospheric river. All rivers in this area are currently running high with the Yakima at Kiona still above flood stage but falling. However, as this new water makes its way down, the rivers will respond and some additional flooding is anticipated later in the week.

When the second system moves through, snow levels will drop from 8000 to 9000 feet on Monday to 2000-2500 feet by Wednesday morning and below 2000 feet by Wednesday afternoon. Any precipitation will turn to snow in the mountains. Pass level snow could easily by 6 plus inches Wednesday and potentially even more Thursday. The Blue Mountains could see 2 to 4 inches Wednesday and again, significantly higher on Thursday, depending on how things play out. Winter Weather headlines will likely be needed for a portion of the Wednesday through Friday time frame.

With the Wednesday system also comes the potential for strong winds and a high wind watch has been issued for a large part of north-central and northeastern Oregon and south-central and southeastern Washington. On Wednesday, the NBM probabilities of wind gusts >=47 mph are >70 percent over a large portion of the region. NBM probabilities of wind gusts >=55 mph are >60 percent over portions of the Columbia Basin, Simcoe Highlands, Foothills of the Blue Mountains, Yakima and Kittitas Valleys.

AVIATION

00z TAFS...VFR conditions to prevail through the period. CIGs are expected to remain above 4kft AGL through the period, with vsby remaining 6 miles or above as well. A system coming early tomorrow will bring light rain impacts at sites DLS, with PROB30 groups for sites PDT/ALW/PSC. Chances at site YKM have come down, so have removed the PROB30 group for the site. Precip impacts will linger at site DLS towards the end of the period, with impacts ending around 18Z for sites PDT/ALW/PSC. Breezy winds 12-17kts with gusts to around 25kts will develop at sites RDM/BDN between 13Z-15Z, and at sites PDT/YKM/ALW between 18Z-21Z. Winds at site PSC will increase at the tail end of the TAF period. Lawhorn/82

PRELIMINARY POINT TEMPS/POPS

PDT 43 64 43 60 / 10 70 40 20 ALW 45 62 46 58 / 10 80 60 40 PSC 42 64 43 60 / 20 60 20 20 YKM 40 62 38 56 / 30 70 20 50 HRI 40 62 42 60 / 10 60 30 20 ELN 38 55 34 49 / 40 80 40 70 RDM 38 64 38 58 / 10 60 30 10 LGD 38 50 39 54 / 10 80 60 30 GCD 37 56 41 55 / 10 60 50 20 DLS 45 60 44 58 / 40 90 70 70

PDT WATCHES/WARNINGS/ADVISORIES

OR...High Wind Watch from Tuesday evening through Wednesday afternoon for ORZ041-044-507-508-510.

WA...High Wind Watch from Tuesday evening through Wednesday afternoon for WAZ024-026>029-521.

Flood Watch from late tonight through Wednesday morning for WAZ522-523.