textproduct: Pendleton

DISCUSSION

The region is undergoing strong cold advection which will drive down snow levels with time as a weak westerly moisture belt gets channeled inland over the next 24 hours. Winter Weather Advisory is in effect from This morning through Tuesday Afternoon for the Upper Slopes of the WA Cascade Crest. Road temperatures at pass levels have fallen to 32 and as road cams begin to show more snow transitioning from the wet roads to slick with deteriorating visibility. Likewise, the hourly version of WSSI (weather storm severity index) was hitting in the moderate category already on the snow rate element, as of around midnight, so the winter wx advisory was started right now. A Winter Storm Watch is in effect for late Tuesday though Friday morning for which the current expected snow at the pass level is around 2-feet of snow for the 2 day total (NBM mean). The Experimental Winter Storm Outlook is pegging the entire Upper Eastern Slope of WA Cascade in WA are 65 to greater than 80% confidence in criteria, measured in feet of snow. Many river forecast point hydrographs indicate within bank rises late week and through the weekend. None of these are being shown to flood at this time.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

VFR conditions currently area-wide with limited concerns the next 24-hrs. Latest satellite shows stratocu across much of central and northeast OR with high clouds overhead under a zonal 80kt mid-level jet positioned across the WA/OR border. Radar depicts post-frontal upslope snow in the northern Blues and showers largely west of the WA Cascades with limited spillover. Gusts largely 20 kts or more across much of the lower elevations and foothills outside of parts of the WA Lower Basin.

A embedded disturbance in the mid-level flow will track into the region late today reinforcing shower activity west and along the Cascades. Of which, some showers cannot be ruled out at KDLS as they make it into the gorge, however, confidence in sub-MVFR conditions is low (less than 30%). Meantime, 10-30% chance any precip activity affecting the KPDT and KALW terminal today thus no mention in their TAFs. Once the disturbance moves through, a lower sky cover trend will take hold late tonight across most of the terminals outside central OR. Otherwise, moderate winds with gusts 20-30 kts will prevail today with winds lessening late this evening.

Preliminary Point Temps/PoPs

PDT 47 28 47 32 / 10 20 10 10 ALW 48 31 47 35 / 30 50 30 20 PSC 54 29 52 35 / 10 10 0 10 YKM 48 25 48 30 / 10 10 10 40 HRI 51 30 51 34 / 0 10 0 10 ELN 43 24 42 28 / 30 30 10 50 RDM 45 22 43 28 / 0 0 0 10 LGD 43 25 42 27 / 30 40 40 20 GCD 43 24 41 27 / 20 10 20 10 DLS 50 32 49 36 / 40 30 30 50

PDT WATCHES/WARNINGS/ADVISORIES

WA...Winter Weather Advisory until 5 PM PDT Tuesday for WAZ522. Winter Storm Watch from late Tuesday night through Friday morning for WAZ522. OR...None.