textproduct: Pendleton

AVIATION...18Z TAFs

VFR conditions will prevail throughout the period for most sites. KPDT is currently experiencing haze, bringing VSBY to MVFR conditions. Should be brief as VSBY improves around this late morning. While the webcams show VSBY over KALW slowly improving as well, freezing fog/mist may remain lingering for the next few hours. However, the low cloud decks and light winds might help keep the fog/mist around longer if conditions further materializes.

Guidance are hinting potential light freezing rain for KALW during Wednesday morning hours, but confidence was too low (<20%) to mention it in the TAF. KDLS may see low clouds arrive early Wednesday morning with a weak frontal system (40-50% confidence). Winds will be less than 10kts. Feaster/97

DISCUSSION

A progressive negatively tilted mid level trough with an attendant surface cold front will bring a low chance (10%) of minor impacts in the form of freezing rain across the Eastern Columbia River Gorge Columbia Basin and possible he Kittitas and Yakima Valleys. later Today and Tonight. Lingering through Wednesday morning. The low risk is due to the speed of the system, the initially dry mid levels and then the warming of the near surface layer once the profile saturates. Snow ratios begin late Tuesday afternoon around 1800-2400 ft and increase to around 3500ft by mid morning Wednesday.

Another fast moving tough moves thorough Wednesday Night and Thursday morning, in a continuing attempt to flatten the mean ridge over the western US into the Interior NW. This episode is more likely to bring mountain snow and lowland rain as the surface temperatures should be modified enough to preclude a freezing rain impact. Thursday mornings NBM expected forecast minimum temperatures are largely above 32 degrees across the Columbia Basin, Gorge areas and into central Oregon to the Foothills of the Blues. So high confidence exists in a prolonged period for precipitation for the Upper Slopes of the WA cascade crest through the end of the weekend (80%).

Thursday Afternoon in to Friday afternoon, expected temperatures moderate into the mid and upper 40s for the afternoon over much of the area, although some colder trapped air in the 30s might still be found in the Kittitas Valley.

PRELIMINARY POINT TEMPS/POPS

PDT 38 26 48 35 / 0 30 30 20 ALW 38 29 47 37 / 0 30 50 20 PSC 38 27 46 34 / 0 20 20 30 YKM 38 26 40 32 / 0 20 20 40 HRI 37 26 45 34 / 0 20 20 30 ELN 33 25 37 31 / 0 20 30 60 RDM 47 28 48 33 / 0 20 10 20 LGD 42 31 45 32 / 0 40 50 10 GCD 46 29 45 32 / 0 50 20 20 DLS 39 30 44 38 / 0 50 50 80

PDT WATCHES/WARNINGS/ADVISORIES

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