textproduct: Pendleton

DISCUSSION

The windy conditions have panned out to be about what was expected with widespread gusts to up to 50 mph in the Grande Ronde and Northern Blues Foothills, although with a lack of higher end 60 mph gusts. From that aspect, the High Wind Headlines will be canceled balance of the day.

An Atmospheric River wrapping around the closed low at 48.75 and 134.31 late This Morning was analyzed by the GFS/EC as spreading 200-300 kg/ms IVT with about 18-20mm IVW spreading to the Lower Columbia Basin later Today and overnights. This reflects in the HREF showing a sustained period of orographic/weakly synoptic lifted precipitation cross the Cascades, and lower elevations rains increasing to 70-80% chances for most of the WA and OR Columbia Basin through the day Monday. The SLRs are 10-12:1 in the highest elevations of the Upper slopes of the WA Cascade crest, and largely above about about 5,000ft and falling off rapidly to about 5-6-1 below that level with snow levels around 4500 ft. Metro Road data also shows warm melting conditions for I-90 though the daytime hours, and road temps/sub road temps running between 24F and 42F overnight, which should limit travel impacts. Still with persistent moisture availability, the highest elevation should rack up snow accums through Tuesday, tapering off completely on Wednesday. The Winter weather advisory across the Upper Slopes was extended into Monday afternoon, although highest impacts would probably occur during the overnights given the aforementioned road conditions and overall lack of cold advection.

Drier and increasingly uncertain temperatures are anticipated heading into the middle and latter half of the week. The clusters show development of a general zonal westerly flow with gradually diminishing 500 mb heights and 1000-500 mb thickness Wednesday through Friday in a dry low land pattern but high mountain snow showers pattern.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

VFR conditions to prevail through most of the night, with MVFR or lower conditions increasing across the area with incoming precipitation. An atmospheric river aimed at the region will continue to bring rain chances along the Cascade crest and immediate east slopes, with light rain prevailing at sites DLS/YKM. CIGs are expected to steadily lower at site DLS through the period, with MVFR CIGs as early as 12Z. Sites PSC/ALW/PDT have a Prob30 chance of seeing light rain impacts late tonight through tomorrow morning. At sites PDT/ALW, prevailing rain is now expected to develop after 15Z, with heavier precip producing MVFR vsby/CIGs after 00Z. Sites RDM/BDN/PSC are expected to see prevailing rain develop after 00Z, though CIGs are favored (confidence 60-70%) to stay above 3kft AGL. Winds will increase to 12-15kts with gusts to around 25kts at sites RDM/BDN between 17Z-2Z. Otherwise, light winds, 12kts or less, will prevail through the period. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 40 55 40 48 / 50 80 90 90 ALW 41 53 41 48 / 60 90 90 90 PSC 37 54 39 50 / 70 80 70 70 YKM 35 47 35 46 / 80 80 70 60 HRI 38 54 40 49 / 60 80 80 80 ELN 32 42 30 41 / 80 80 50 60 RDM 36 53 37 49 / 60 60 90 80 LGD 38 50 38 48 / 40 70 100 90 GCD 38 52 39 50 / 20 40 90 100 DLS 38 47 40 48 / 90 90 90 80

PDT WATCHES/WARNINGS/ADVISORIES

WA...Winter Weather Advisory until 1 PM PST Monday for WAZ522. OR...None.