textproduct: Pendleton

DISCUSSION

Current satellite and radar imagery show a frontal system moving across our forecast area, bringing light showers over the WA/OR Cascades first. Observed from webcams and surface observations, visibilities have improved to 2SM or higher for Kittitas Valley extending through the Columbia Basin of OR/WA from earlier. However, patchy fog may continue to linger in some localized areas. The weather for the remaining day will become quiet as the upper ridge passes through the PacNW. Fog development will happen overnight into early Saturday morning for Columbia Basin and Yakima/Kittitas Valleys. NBM and HREF suggest a 15-30% probability for visibilities to reach 3SM or lower, but can't exactly rule out on the strength and longevity due to the models being low-bias with the fog. However if things were to further materializes, then Dense Fog advisories will be considered for those areas.

Light mountain rain will develop over this weekend when the another frontal system arrive to our region, impacting the WA/OR Cascades and Northwest Blues. With PoP chances at a 40-70%, the Cascades may get less than a 0.10 inch Saturday but increases up to 0.15 inch or more Sunday. Since snow levels will be above 4 kft, this precip event will most likely be rain-driven. In addition to this, winds could become slightly breezy over the southern part of Wallowa County up to 15-25 mph from tighten surface pressure gradients (30- 40% confidence). Models and ensembles are in good agreement with this pattern and the timing as well.

Starting Monday onwards, an upper ridge will build over the PacNW again. Light mountain rain may linger across the Cascades and Northwest Blues Monday from the initial system. This could bring in QPF amounts up to 0.20 inch, but with slight chances (15-30%). Fog and air stagnation may raise some concerns with this ridge, but confidence is low (<20%) at this time. Feaster/97

UPDATED AVIATION

06Z TAFs..Fog, mist and incoming low CIGs will be the primary areas of concern this forecast period. YKM is at 1/4SM and is likely to stay at LIFR through much of the period. DLS will see a steady decrease in VIS as well through the period with <30% chance of seeing 1/4SM after 16Z. PDT will likely see VIS as low as 1/2SM after 08Z through 22Z, and both ALW and PSC will see a <30% chance of also seeing VIS als low as 1/4SM after 13Z ands persisting a few hours before lifting after 19X for PSC and 00Z for ALW. CIGs will vary from 300 feet at YKM/DLS/ALW/PSC increasing to 5000 feet later in the day. Winds will be light and variable which will assist in keeping the fog in place. Only RDM/BDN will remain VFR through the period. 90

Preliminary Point Temps/PoPs

PDT 39 56 35 51 / 20 0 0 10 ALW 42 55 37 52 / 30 10 0 20 PSC 35 50 33 53 / 20 10 0 10 YKM 34 48 34 50 / 10 10 0 20 HRI 37 51 34 52 / 20 10 0 10 ELN 34 44 33 45 / 10 20 10 30 RDM 33 57 33 53 / 10 0 0 10 LGD 37 51 38 51 / 20 0 0 10 GCD 37 55 35 53 / 10 0 0 10 DLS 41 54 39 52 / 20 10 0 50

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...None.