textproduct: Pendleton

KEY MESSAGES

- Dry much of today, then rain developing late this afternoon/early this evening. Isolated thunderstorms this evening.

- Widespread rain tonight into Sunday.

- Breezy to windy across the Columbia Gorge, Columbia Basin, Kittitas Valley and Blue Mountain Foothills this evening through Sunday morning.

- Dry Monday through the rest of the upcoming week.

DISCUSSION

An area of low pressure off the coast of Oregon and Washington is moving southeastward, This low move onshore late this evening/overnight.

As the low moves closer, rain is expected to develop from west to east during the evening hours. Rain will become widespread overnight into Sunday morning before decreasing from west to east during the afternoon and evening on Sunday as the low moves northeastward towards southern Canada.

The rain should be over by early Monday. Dry weather is then expected for the remainder of the week, though a second trough dropping down Tuesday night into Wednesday will have to be watched, it has little moisture with it.

Model guidance is still not in great agreement with respect to rainfall amounts. However, there is solid agreement that the mountains will get the highest amounts, and most, if not all areas will receive decent rains and should get wetting rains. It does appear that the higher amounts will be over the Washington Cascades and nearby areas, but exactly how much the models are in disagreement over, though there is agreement on 1 inch plus. Over the Blue Mountains, there is a bit more variability with amounts ranging from 0.50 inch to over an inch. NBM probabilities of 24 hour rainfall amounts >=0.50 inches are high across much of the region, generally greater than 60%, though current QPF amounts across the Basin are less than 0.50 inches. Across the mountain areas they are >80%. NBM probabilities >=1 inch are highest in the Washington Cascades (>80 percent), though more variability is shown across the Blue Mountains and other eastern mountains where percentages vary from 30 to about 50 percent.

There is also a low (<20%) chance of thunderstorms this evening and overnight. Depending on thunderstorm development, the potential exists for flooding over the burn scars associated with the Paradise and Hagen fires so flood watches are in effect for these areas.

Winds will also increase this evening and become gusty and continue through Sunday across the Columbia Gorge, Basin, Kittitas Valley and Foothills of the Blue Mountains. Winds gusts will be in the 25 to 30 mph range with gusts possibly as high as 40 mph. NBM probabilities of wind gusts >=25 mph are 90% across much of the region. However, wind gusts >=39 mph are 50% or higher across portions of the Basin and Blue Mountain Foothills. Wind gusts >=48 mph are 20 to 40 percent.

The combination of the gusty winds and rain will create wind swept rain at times across portions of the area.

High temperatures today will be a couple of degrees below normal. However, on Sunday, highs will be 15 to 20 degrees below normal, and will struggle in the lower 60s...and in some areas may not get out of the 50s. Highs will slowly warm up through the week, into the 70s, (but will still be below normal), but by Friday and Saturday will be close to normal.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

TAFS will start out dry and VFR across the region, but as an area of low pressure approaches later today and moves across the region tonight, CIGS will decrease. RA will overspread the area this evening/overnight and continue through Sunday before ending from west to east. MVFR CIGS potentially VSBYS are forecast in any moderate to heavier rain. Additionally, there is a low (<20%) chance of thunderstorms this evening and tonight, but due to the low chances, will not include in any individual terminal at this time. The only TAF sites not likely to see reduced conditions are BDN and RDM.

Winds will also increase and become gusty. Wind gusts 25 to 35 kts are expected at all sites and 20 to 25 kts at BDN and RDM.

Preliminary Point Temps/PoPs

PDT 76 45 61 45 / 0 90 80 50 ALW 79 49 60 50 / 0 90 90 80 PSC 80 47 63 45 / 0 90 90 20 YKM 76 50 63 44 / 10 90 100 0 HRI 79 46 63 45 / 0 100 80 30 ELN 72 44 59 41 / 0 100 100 10 RDM 71 36 60 32 / 10 80 10 0 LGD 81 44 59 42 / 0 90 80 70 GCD 81 43 59 40 / 0 100 40 10 DLS 77 51 66 49 / 20 90 60 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Flash Flood Watch from this afternoon through Sunday evening for WAZ030. OR...Flash Flood Watch from this afternoon through Sunday evening for ORZ502.